TabLayout：另一种Tab的实现方式
来源：互联网 发布：mac怎么重置系统 编辑：程序博客网 时间：2024/05/07 11:26
转载于：http://blog.csdn.net/aigestudio/article/details/47155769
在5.0以前我们想要实现像网易新闻客户端那样的的Tab可以有很多种选择：
比如古老的TabHost，3.0后ActionBar所提供的Tab，以及各种成熟的Tab开源控件等，都可以直接或间接地实现Tab的效果。然而，对于这样一种使用极多的控件，Android是不会放弃将它纳入麾下的打算的，于是乎在5.0后放出的design包中Android就厚颜无耻地推出了自家官方的TabLayout控件来方便地实现类似的效果。其实这玩意跟ActionBar的Tab没什么卵的区别，只是说它更符合谷歌自家的MD设计理念，不过在实际使用中这玩意略显蛋疼，废话不多说，我们还是直接切入主题，要想使用TabLayout你就得导入Android的design包：
<code class="hljs matlab has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">dependencies <span class="hljs-cell" style="box-sizing: border-box;">{ compile <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'com.android.support:design:22.2.0'</span>}</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>然后在你的布局里加入TabLayout就行了：
<code class="hljs xml has-numbering" style="display:block; padding:0px; color:inherit; font-family:'Source Code Pro',monospace;font-size:undefined; white-space:pre; word-wrap:normal; background:transparent"><span class="hljs-pi" style="color:rgb(0,102,102)"><?xml version="1.0" encoding="utf-8"?></span><span class="hljs-tag" style="color:rgb(0,102,102)"><<span class="hljs-title" style="color:rgb(0,0,136)">RelativeLayout</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">xmlns:android</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"http://schemas.android.com/apk/res/android"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_width</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"match_parent"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_height</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"match_parent"</span>></span> <span class="hljs-tag" style="color:rgb(0,102,102)"><<span class="hljs-title" style="color:rgb(0,0,136)">android.support.design.widget.TabLayout</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:id</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"@+id/ac_tab_layout"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_width</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"match_parent"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_height</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"wrap_content"</span> /></span><span class="hljs-tag" style="color:rgb(0,102,102)"></<span class="hljs-title" style="color:rgb(0,0,136)">RelativeLayout</span>></span></code><ul class="pre-numbering" style="position:absolute; width:50px; top:0px; left:0px; margin:0px; padding:6px 0px 40px; border-right-width:1px; border-right-style:solid; border-right-color:rgb(221,221,221); list-style:none; text-align:right; background-color:rgb(238,238,238)"><li style="padding:0px 5px">1</li><li style="padding:0px 5px">2</li><li style="padding:0px 5px">3</li><li style="padding:0px 5px">4</li><li style="padding:0px 5px">5</li><li style="padding:0px 5px">6</li><li style="padding:0px 5px">7</li><li style="padding:0px 5px">8</li><li style="padding:0px 5px">9</li><li style="padding:0px 5px">10</li><li style="padding:0px 5px">11</li></ul>
这里需要注意的是design包中有些资源依赖于5.0，这是不是说我们就不能使用了呢，不是的，我们可以从AppCompat获得这些资源，将当前Activity的主题设置为Theme.AppCompat或其子类即可：
<code class="hljs xml has-numbering" style="display:block; padding:0px; color:inherit; font-family:'Source Code Pro',monospace;font-size:undefined; white-space:pre; word-wrap:normal; background:transparent"><span class="hljs-tag" style="color:rgb(0,102,102)"><<span class="hljs-title" style="color:rgb(0,0,136)">activity</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:name</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"tablayout.TabLayoutActivity"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:theme</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"@style/Theme.AppCompat"</span> /></span></code><ul class="pre-numbering" style="position:absolute; width:50px; top:0px; left:0px; margin:0px; padding:6px 0px 40px; border-right-width:1px; border-right-style:solid; border-right-color:rgb(221,221,221); list-style:none; text-align:right; background-color:rgb(238,238,238)"><li style="padding:0px 5px">1</li><li style="padding:0px 5px">2</li><li style="padding:0px 5px">3</li></ul>
当然现在你运行不会看到任何东西，因为我们没往里面家东西嘛，与ActionBar类似的是TabLayout添加Tab也很方便，只需要调用其addTab方法即可：
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">TabLayoutActivity</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Activity</span> {</span> <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onCreate</span>(Bundle savedInstanceState) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.onCreate(savedInstanceState); setContentView(R.layout.ac_tab_layout); TabLayout tabLayout = (TabLayout) findViewById(R.id.ac_tab_layout); TabLayout.Tab tab1 = tabLayout.newTab().setText(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Tab1"</span>); tabLayout.addTab(tab1); TabLayout.Tab tab2 = tabLayout.newTab().setText(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Tab2"</span>); tabLayout.addTab(tab2); TabLayout.Tab tab3 = tabLayout.newTab().setText(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Tab3"</span>); tabLayout.addTab(tab3); }}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li></ul>运行效果如下：
非常简单，不过需要注意的是，这里的Tab类是TabLayout的一个静态内部类，并且其构造方法是包内可访问的，也就是说你无法在外部构造其实例，只能通过TabLayout的newTab方法：
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">TabLayout</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">HorizontalScrollView</span> {</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// ......省去很多代码......</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Tab</span> {</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// ......省去很多代码......</span> Tab(TabLayout parent) { mPosition = -<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>; mParent = parent; } } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> Tab <span class="hljs-title" style="box-sizing: border-box;">newTab</span>() { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Tab(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>); } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// ......省去很多代码......</span>}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li></ul>addTab方法有四个不同的实现，拿参数最多的addTab(Tab tab, int position, boolean setSelected)方法来说，第一个参数tab就不说了，第二个参数position表示当前Tab需要插入的位置，其值必须小于当前TabLayout所拥有的Tab总数减一，如果大于则会报出数组下标溢出异常，这点很好理解，最后的boolean参数setSelected与其名意义一样，表示当前添加的Tab是否为选中状态，拿上面代码中的第三个tab3来说，我们修改其代码如下：
<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">TabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Tab</span> tab3 = tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.newTab</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setText</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Tab3"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.addTab</span>(tab3, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>, true)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>
运行后tab3默认就会是被选中状态：
TabLayout中的公共方法不算多，大多都很好理解，不过有一个方法爱哥表示对其极度不爽，setScrollPosition从名字上来看它是用来设置滚动位置的，大家注意我们的TabLayout中被选中的Tab下方不是有根线么，我们可以通过这个方法来设置它的位置。首先我们在布局中添加一个按钮：
<code class="hljs xml has-numbering" style="display:block; padding:0px; color:inherit; font-family:'Source Code Pro',monospace;font-size:undefined; white-space:pre; word-wrap:normal; background:transparent"><span class="hljs-pi" style="color:rgb(0,102,102)"><?xml version="1.0" encoding="utf-8"?></span><span class="hljs-tag" style="color:rgb(0,102,102)"><<span class="hljs-title" style="color:rgb(0,0,136)">RelativeLayout</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">xmlns:android</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"http://schemas.android.com/apk/res/android"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_width</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"match_parent"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_height</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"match_parent"</span>></span> <span class="hljs-tag" style="color:rgb(0,102,102)"><<span class="hljs-title" style="color:rgb(0,0,136)">android.support.design.widget.TabLayout</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:id</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"@+id/ac_tab_layout"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_width</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"match_parent"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_height</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"wrap_content"</span> /></span> <span class="hljs-tag" style="color:rgb(0,102,102)"><<span class="hljs-title" style="color:rgb(0,0,136)">Button</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:id</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"@+id/ac_tab_btn"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_width</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"wrap_content"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_centerInParent</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"true"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_height</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"wrap_content"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:text</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"Move"</span> /></span><span class="hljs-tag" style="color:rgb(0,102,102)"></<span class="hljs-title" style="color:rgb(0,0,136)">RelativeLayout</span>></span></code><ul class="pre-numbering" style="position:absolute; width:50px; top:0px; left:0px; margin:0px; padding:6px 0px 40px; border-right-width:1px; border-right-style:solid; border-right-color:rgb(221,221,221); list-style:none; text-align:right; background-color:rgb(238,238,238)"><li style="padding:0px 5px">1</li><li style="padding:0px 5px">2</li><li style="padding:0px 5px">3</li><li style="padding:0px 5px">4</li><li style="padding:0px 5px">5</li><li style="padding:0px 5px">6</li><li style="padding:0px 5px">7</li><li style="padding:0px 5px">8</li><li style="padding:0px 5px">9</li><li style="padding:0px 5px">10</li><li style="padding:0px 5px">11</li><li style="padding:0px 5px">12</li><li style="padding:0px 5px">13</li><li style="padding:0px 5px">14</li><li style="padding:0px 5px">15</li><li style="padding:0px 5px">16</li><li style="padding:0px 5px">17</li></ul>
然后呢为这个按钮绑定一个点击事件监听并在其中调用setScrollPosition方法：
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">Button btnAdd = (Button) findViewById(R.id.ac_tab_btn);btnAdd.setOnClickListener(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> View.OnClickListener() { <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onClick</span>(View v) { tabLayout.setScrollPosition(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.5</span>F, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>); }});</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul>setScrollPosition方法的三个参数根据官方文档给出的解释如下：
第一个参数表示当前Tab的位置，第二个参数是偏移值，从文档中看到该值的取值范围是0到1的一个半开区间，最后一个参数很好理解表示是否置移动后位置所对应的Tab为选中状态，打个比方，如果我从0移动到1的位置，如果updateSelectedText为true，那么1这个位置上的文本就会是一个选中状态。上面的代码中我们只是简单地让下方的横条从0的Tab位置移动到一个0.5F的位置，效果如下：
可能大家会觉得纳闷，这个0.5F是个吊毛意思，其实positionOffset这个参数是一个倍数值，它的计算逻辑有些复杂，从源码中看setScrollPosition的逻辑，大致分为两步：
<code class="hljs java has-numbering" style="display:block; padding:0px; color:inherit; font-family:'Source Code Pro',monospace;font-size:undefined; white-space:pre; word-wrap:normal; background:transparent"><span class="hljs-keyword" style="color:rgb(0,0,136)">public</span> <span class="hljs-keyword" style="color:rgb(0,0,136)">void</span> <span class="hljs-title" style="">setScrollPosition</span>(<span class="hljs-keyword" style="color:rgb(0,0,136)">int</span> position, <span class="hljs-keyword" style="color:rgb(0,0,136)">float</span> positionOffset, <span class="hljs-keyword" style="color:rgb(0,0,136)">boolean</span> updateSelectedText) { <span class="hljs-keyword" style="color:rgb(0,0,136)">if</span> (isAnimationRunning(getAnimation())) <span class="hljs-keyword" style="color:rgb(0,0,136)">return</span>; <span class="hljs-keyword" style="color:rgb(0,0,136)">if</span> (position < <span class="hljs-number" style="color:rgb(0,102,102)">0</span> || position >= mTabStrip.getChildCount()) <span class="hljs-keyword" style="color:rgb(0,0,136)">return</span>; mTabStrip.setIndicatorPositionFromTabPosition(position, positionOffset); scrollTo(calculateScrollXForTab(position, positionOffset), <span class="hljs-number" style="color:rgb(0,102,102)">0</span>); <span class="hljs-keyword" style="color:rgb(0,0,136)">if</span> (updateSelectedText) setSelectedTabView(Math.round((<span class="hljs-keyword" style="color:rgb(0,0,136)">float</span>) position + positionOffset));}</code><ul class="pre-numbering" style="position:absolute; width:50px; top:0px; left:0px; margin:0px; padding:6px 0px 40px; border-right-width:1px; border-right-style:solid; border-right-color:rgb(221,221,221); list-style:none; text-align:right; background-color:rgb(238,238,238)"><li style="padding:0px 5px">1</li><li style="padding:0px 5px">2</li><li style="padding:0px 5px">3</li><li style="padding:0px 5px">4</li><li style="padding:0px 5px">5</li><li style="padding:0px 5px">6</li><li style="padding:0px 5px">7</li><li style="padding:0px 5px">8</li><li style="padding:0px 5px">9</li><li style="padding:0px 5px">10</li></ul>首先是
<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">mTabStrip<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setIndicatorPositionFromTabPosition</span>(position, positionOffset)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>
这段的调用，其目的很简单，就是设置Tab下方的那个横条的位置，先是调用SlidingTabStrip的setIndicatorPositionFromTabPosition方法赋值：
<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> setIndicatorPositionFromTabPosition(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> position, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> positionOffset) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (TabLayout.isAnimationRunning(getAnimation())) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span>; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { mSelectedPosition = position; mSelectionOffset = positionOffset; updateIndicatorPosition(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span>; }}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul>然后又调用了updateIndicatorPosition来做具体的位置更新操作：
<code class="hljs vbscript has-numbering" style="display:block; padding:0px; color:inherit; font-family:'Source Code Pro',monospace;font-size:undefined; white-space:pre; word-wrap:normal; background:transparent"><span class="hljs-keyword" style="color:rgb(0,0,136)">private</span> void updateIndicatorPosition() { View selectedTitle = getChildAt(mSelectedPosition); <span class="hljs-built_in" style="color:rgb(102,0,102)">int</span> <span class="hljs-built_in" style="color:rgb(102,0,102)">left</span>; <span class="hljs-built_in" style="color:rgb(102,0,102)">int</span> <span class="hljs-built_in" style="color:rgb(102,0,102)">right</span>; <span class="hljs-keyword" style="color:rgb(0,0,136)">if</span> (selectedTitle != <span class="hljs-literal" style="color:rgb(0,102,102)">null</span> && selectedTitle.getWidth() > <span class="hljs-number" style="color:rgb(0,102,102)">0</span>) { <span class="hljs-built_in" style="color:rgb(102,0,102)">left</span> = selectedTitle.getLeft(); <span class="hljs-built_in" style="color:rgb(102,0,102)">right</span> = selectedTitle.getRight(); <span class="hljs-keyword" style="color:rgb(0,0,136)">if</span> (mSelectionOffset > <span class="hljs-number" style="color:rgb(0,102,102)">0.0</span>F && mSelectedPosition < getChildCount() - <span class="hljs-number" style="color:rgb(0,102,102)">1</span>) { View nextTitle = getChildAt(mSelectedPosition + <span class="hljs-number" style="color:rgb(0,102,102)">1</span>); <span class="hljs-built_in" style="color:rgb(102,0,102)">left</span> = (<span class="hljs-built_in" style="color:rgb(102,0,102)">int</span>) (mSelectionOffset * (float) nextTitle.getLeft() + (<span class="hljs-number" style="color:rgb(0,102,102)">1.0</span>F - mSelectionOffset) * (float) <span class="hljs-built_in" style="color:rgb(102,0,102)">left</span>); <span class="hljs-built_in" style="color:rgb(102,0,102)">right</span> = (<span class="hljs-built_in" style="color:rgb(102,0,102)">int</span>) (mSelectionOffset * (float) nextTitle.getRight() + (<span class="hljs-number" style="color:rgb(0,102,102)">1.0</span>F - mSelectionOffset) * (float) <span class="hljs-built_in" style="color:rgb(102,0,102)">right</span>); } } <span class="hljs-keyword" style="color:rgb(0,0,136)">else</span> { <span class="hljs-built_in" style="color:rgb(102,0,102)">left</span> = <span class="hljs-built_in" style="color:rgb(102,0,102)">right</span> = -<span class="hljs-number" style="color:rgb(0,102,102)">1</span>; } setIndicatorPosition(<span class="hljs-built_in" style="color:rgb(102,0,102)">left</span>, <span class="hljs-built_in" style="color:rgb(102,0,102)">right</span>);}</code><ul class="pre-numbering" style="position:absolute; width:50px; top:0px; left:0px; margin:0px; padding:6px 0px 40px; border-right-width:1px; border-right-style:solid; border-right-color:rgb(221,221,221); list-style:none; text-align:right; background-color:rgb(238,238,238)"><li style="padding:0px 5px">1</li><li style="padding:0px 5px">2</li><li style="padding:0px 5px">3</li><li style="padding:0px 5px">4</li><li style="padding:0px 5px">5</li><li style="padding:0px 5px">6</li><li style="padding:0px 5px">7</li><li style="padding:0px 5px">8</li><li style="padding:0px 5px">9</li><li style="padding:0px 5px">10</li><li style="padding:0px 5px">11</li><li style="padding:0px 5px">12</li><li style="padding:0px 5px">13</li><li style="padding:0px 5px">14</li><li style="padding:0px 5px">15</li><li style="padding:0px 5px">16</li><li style="padding:0px 5px">17</li></ul>首先是得到当前Tab左右的坐标值，然后尝试获取下一个Tab，如果有，那么根据相对位置计算最终的左右坐标，没有则不改变使用当前的左右坐标，这很好理解，最后通过setIndicatorPosition放啊分设置最终的横条位置：
<code class="hljs vbscript has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> void setIndicatorPosition(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">int</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">left</span>, <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">int</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">right</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">left</span> != mIndicatorLeft || <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">right</span> != mIndicatorRight) { mIndicatorLeft = <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">left</span>; mIndicatorRight = <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">right</span>; ViewCompat.postInvalidateOnAnimation(this); }}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul>回到setScrollPosition方法中再看看第二步滚动TabLayout到指定位置：
<code class="hljs scss has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-function" style="box-sizing: border-box;">scrollTo(<span class="hljs-function" style="box-sizing: border-box;">calculateScrollXForTab(position, positionOffset)</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>)</span>;</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>
这一步在默认模式下不会被执行，TabLayout提供两种模式，一种是填充模式，也就是默认模式，表示TabLayout不可滚动，其宽度有一个最大值，所有的Tab则会挤在这个宽度中：
该模式的常量值为MODE_FIXED = 1，而我们可以通过TabLayout的setTabMode方法来设置其模式，这里我们将TabLayout的模式改为可滚动：
<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setTabMode</span>(TabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.MODE</span>_SCROLLABLE)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>
TabLayout.MODE_SCROLLABLE的常量值为0，这时候再看看效果：
这时候TabLayout变为可滚动而所有的Tab均显示完整。好我们现在回过头来看看
<code class="hljs scss has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-function" style="box-sizing: border-box;">scrollTo(<span class="hljs-function" style="box-sizing: border-box;">calculateScrollXForTab(position, positionOffset)</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>)</span>;</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>
这段代码，scrollTo这个方法相信大家做过滑动都不会太陌生，其会将当前视图滚动至指定的坐标位置，TabLayout是一个水平滚动视图，因此其Y坐标滚动至恒为0，而X坐标则通过calculateScrollXForTab这个方法来计算：
<code class="hljs cs has-numbering" style="display:block; padding:0px; color:inherit; font-family:'Source Code Pro',monospace;font-size:undefined; white-space:pre; word-wrap:normal; background:transparent"><span class="hljs-keyword" style="color:rgb(0,0,136)">private</span> <span class="hljs-keyword" style="color:rgb(0,0,136)">int</span> <span class="hljs-title" style="">calculateScrollXForTab</span>(<span class="hljs-keyword" style="color:rgb(0,0,136)">int</span> position, <span class="hljs-keyword" style="color:rgb(0,0,136)">float</span> positionOffset) { <span class="hljs-keyword" style="color:rgb(0,0,136)">if</span> (mMode == <span class="hljs-number" style="color:rgb(0,102,102)">0</span>) { View selectedChild = mTabStrip.getChildAt(position); View nextChild = position + <span class="hljs-number" style="color:rgb(0,102,102)">1</span> >= mTabStrip.getChildCount() ? <span class="hljs-keyword" style="color:rgb(0,0,136)">null</span> : mTabStrip.getChildAt(position + <span class="hljs-number" style="color:rgb(0,102,102)">1</span>); <span class="hljs-keyword" style="color:rgb(0,0,136)">int</span> selectedWidth = selectedChild == <span class="hljs-keyword" style="color:rgb(0,0,136)">null</span> ? <span class="hljs-number" style="color:rgb(0,102,102)">0</span> : selectedChild.getWidth(); <span class="hljs-keyword" style="color:rgb(0,0,136)">int</span> nextWidth = nextChild == <span class="hljs-keyword" style="color:rgb(0,0,136)">null</span> ? <span class="hljs-number" style="color:rgb(0,102,102)">0</span> : nextChild.getWidth(); <span class="hljs-keyword" style="color:rgb(0,0,136)">return</span> (<span class="hljs-keyword" style="color:rgb(0,0,136)">int</span>) (((<span class="hljs-keyword" style="color:rgb(0,0,136)">float</span>) selectedChild.getLeft() + (<span class="hljs-keyword" style="color:rgb(0,0,136)">float</span>) (selectedWidth + nextWidth) * positionOffset * <span class="hljs-number" style="color:rgb(0,102,102)">0.5</span>F + (<span class="hljs-keyword" style="color:rgb(0,0,136)">float</span>) selectedChild.getWidth() * <span class="hljs-number" style="color:rgb(0,102,102)">0.5</span>F) - (<span class="hljs-keyword" style="color:rgb(0,0,136)">float</span>) getWidth() * <span class="hljs-number" style="color:rgb(0,102,102)">0.5</span>F); } <span class="hljs-keyword" style="color:rgb(0,0,136)">else</span> { <span class="hljs-keyword" style="color:rgb(0,0,136)">return</span> <span class="hljs-number" style="color:rgb(0,102,102)">0</span>; }}</code><ul class="pre-numbering" style="position:absolute; width:50px; top:0px; left:0px; margin:0px; padding:6px 0px 40px; border-right-width:1px; border-right-style:solid; border-right-color:rgb(221,221,221); list-style:none; text-align:right; background-color:rgb(238,238,238)"><li style="padding:0px 5px">1</li><li style="padding:0px 5px">2</li><li style="padding:0px 5px">3</li><li style="padding:0px 5px">4</li><li style="padding:0px 5px">5</li><li style="padding:0px 5px">6</li><li style="padding:0px 5px">7</li><li style="padding:0px 5px">8</li><li style="padding:0px 5px">9</li><li style="padding:0px 5px">10</li><li style="padding:0px 5px">11</li></ul>这里可以看到先做了一个判断，如果模式为填充也就是MODE_FIXED的情况下是不需要滚动的，只有当模式为MODE_SCROLLABLE时才会去滚动，X坐标的计算逻辑与updateIndicatorPosition方法中的计算逻辑类似，都是通过当前Tab与下一个Tab的相对关系来计算的。那么为什么爱哥会对setScrollPosition这个方法表示极度不爽呢？首先，这个方法调用的前提根据官方文档和源码来看是需要相邻的两个Tab共同计算的，打个比方，如果我想从第0个Tab跳转至第1个Tab那么我就可以这么干：
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">TabLayoutActivity</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Activity</span> {</span> <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onCreate</span>(Bundle savedInstanceState) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.onCreate(savedInstanceState); setContentView(R.layout.ac_tab_layout); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> TabLayout tabLayout = (TabLayout) findViewById(R.id.ac_tab_layout); TabLayout.Tab tab1 = tabLayout.newTab().setText(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Tab1"</span>); tabLayout.addTab(tab1); TabLayout.Tab tab2 = tabLayout.newTab().setText(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Tab2"</span>); tabLayout.addTab(tab2); TabLayout.Tab tab3 = tabLayout.newTab().setText(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Tab3"</span>); tabLayout.addTab(tab3); tabLayout.setTabMode(TabLayout.MODE_SCROLLABLE); Button btnAdd = (Button) findViewById(R.id.ac_tab_btn); btnAdd.setOnClickListener(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> View.OnClickListener() { <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onClick</span>(View v) { tabLayout.setScrollPosition(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>F, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>); }); }}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li></ul>从第0个Tab开始，偏移值为一个单位，效果如下：
注意到这里的一个BUG没有，淡定，好戏在后头，大家想想虽说官方文档建议第二个参数的取值区间在0到1，但是我们完全可以考虑将该值设置大于1对吧，假设，仅仅是个假设，我们将其设为2，那么是否可以表示我们能直接从第0个Tab直接跳转到第2个Tab呢？答案好像是肯定的：
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">btnAdd.setOnClickListener(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> View.OnClickListener() { <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onClick</span>(View v) { tabLayout.setScrollPosition(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>F, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>);});</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>运行效果如下：
是不是有点意外？但是注意，这种想法是错误的！！！这里之所以能够直接跳转到第2个Tab是因为在这个例子中我们的每个Tab宽度都是一样的，如果我们将Tab稍作修改：
<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">TabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Tab</span> tab1 = tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.newTab</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setText</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Aige"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.addTab</span>(tab1)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>TabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Tab</span> tab2 = tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.newTab</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setText</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"AigeStudio"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.addTab</span>(tab2)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>TabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Tab</span> tab3 = tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.newTab</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setText</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Studio"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.addTab</span>(tab3)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li></ul>
这时候你就会看到错误的计算显示了：
当然如果仅仅是相邻的滚动，这样做是没问题的，比如我们从第1个Tab滚动至第2个Tab：
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">TabLayoutActivity</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Activity</span> {</span> <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onCreate</span>(Bundle savedInstanceState) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.onCreate(savedInstanceState); setContentView(R.layout.ac_tab_layout); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> TabLayout tabLayout = (TabLayout) findViewById(R.id.ac_tab_layout); TabLayout.Tab tab1 = tabLayout.newTab().setText(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Aige"</span>); tabLayout.addTab(tab1); TabLayout.Tab tab2 = tabLayout.newTab().setText(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"AigeStudio"</span>); tabLayout.addTab(tab2, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>); TabLayout.Tab tab3 = tabLayout.newTab().setText(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Studio"</span>); tabLayout.addTab(tab3); tabLayout.setTabMode(TabLayout.MODE_SCROLLABLE); Button btnAdd = (Button) findViewById(R.id.ac_tab_btn); btnAdd.setOnClickListener(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> View.OnClickListener() { <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onClick</span>(View v) { tabLayout.setScrollPosition(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>F, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>); } }); }}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li></ul>这样就没问题：
使用setScrollPosition的另一个问题是，滚动时Tab底部那个横条切换生硬，不知道大家注意到没，没注意到往上看之前的一些切换动图，非常生硬，然而如果我们用另外一种方式来做这种切换就显得很带感了，Tab类中提供了一个select方法来设置当前Tab被选中：
<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> final <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> Tab { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// ......省去很多代码......</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">select</span>() { mParent.selectTab(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>); } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// ......省去很多代码......</span>}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul>这个方法所带来的效果就很不一样了，比如我们点击设置第三个Tab被选中：
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">TabLayoutActivity</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Activity</span> {</span> <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onCreate</span>(Bundle savedInstanceState) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.onCreate(savedInstanceState); setContentView(R.layout.ac_tab_layout); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> TabLayout tabLayout = (TabLayout) findViewById(R.id.ac_tab_layout); TabLayout.Tab tab1 = tabLayout.newTab().setText(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Aige"</span>); tabLayout.addTab(tab1); TabLayout.Tab tab2 = tabLayout.newTab().setText(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"AigeStudio"</span>); tabLayout.addTab(tab2); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> TabLayout.Tab tab3 = tabLayout.newTab().setText(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Studio"</span>); tabLayout.addTab(tab3); tabLayout.setTabMode(TabLayout.MODE_SCROLLABLE); Button btnAdd = (Button) findViewById(R.id.ac_tab_btn); btnAdd.setOnClickListener(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> View.OnClickListener() { <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onClick</span>(View v) { tab3.select(); } }); }}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li></ul>效果是不是要动感的多呢：
从源码里可以看到select方法本质是调用了TabLayout中的selectTab方法：
<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> selectTab(Tab tab) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mSelectedTab == tab) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mSelectedTab != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mOnTabSelectedListener != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) mOnTabSelectedListener.onTabReselected(mSelectedTab); animateToTab(tab.getPosition()); } } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> newPosition = tab == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> ? -<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span> : tab.getPosition(); setSelectedTabView(newPosition); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> ((mSelectedTab == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> || mSelectedTab.getPosition() == -<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>) && newPosition != -<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>) setScrollPosition(newPosition, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.0</span>F, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> animateToTab(newPosition); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mSelectedTab != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> && mOnTabSelectedListener != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) mOnTabSelectedListener.onTabUnselected(mSelectedTab); mSelectedTab = tab; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mSelectedTab != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> && mOnTabSelectedListener != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) mOnTabSelectedListener.onTabSelected(mSelectedTab); }}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li></ul>在该方法中比较重要的就是一个animateToTab方法的调用，该方法是产生动画效果的关键：
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">animateToTab</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> newPosition) { clearAnimation(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (newPosition == -<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (getWindowToken() == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> || !ViewCompat.isLaidOut(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>)) { setScrollPosition(newPosition, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.0</span>F, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span>; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> startScrollX = getScrollX(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> targetScrollX = calculateScrollXForTab(newPosition, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.0</span>F); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> duration = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">300</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (startScrollX != targetScrollX) { ValueAnimatorCompat animator = ViewUtils.createAnimator(); animator.setInterpolator(AnimationUtils.FAST_OUT_SLOW_IN_INTERPOLATOR); animator.setDuration(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">300</span>); animator.setIntValues(startScrollX, targetScrollX); animator.setUpdateListener(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ValueAnimatorCompat.AnimatorUpdateListener() { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onAnimationUpdate</span>(ValueAnimatorCompat animator) { scrollTo(animator.getAnimatedIntValue(), <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> TabLayout <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>$<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>$<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span> = TabLayout.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>(); } } ); animator.start(); } mTabStrip.animateIndicatorToPosition(newPosition, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">300</span>);}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li></ul>如果你不需要设置Tab的一些监听的话那么完全可以通过反射的方式调用该方法滚动Tab至指定位置：
<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">public class TabLayoutActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.onCreate</span>(savedInstanceState)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> setContentView(R<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.layout</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ac</span>_tab_layout)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> final TabLayout tabLayout = (TabLayout) findViewById(R<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.id</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ac</span>_tab_layout)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> TabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Tab</span> tab1 = tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.newTab</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setText</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Aige"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.addTab</span>(tab1)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> TabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Tab</span> tab2 = tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.newTab</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setText</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"AigeStudio"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.addTab</span>(tab2)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> TabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Tab</span> tab3 = tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.newTab</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setText</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Studio"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.addTab</span>(tab3)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> TabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Tab</span> tab4 = tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.newTab</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setText</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Fuck You"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.addTab</span>(tab4)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> TabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Tab</span> tab5 = tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.newTab</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setText</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Some of bitch"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.addTab</span>(tab5)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> TabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Tab</span> tab6 = tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.newTab</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setText</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Android"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.addTab</span>(tab6)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setTabMode</span>(TabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.MODE</span>_SCROLLABLE)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> Button btnAdd = (Button) findViewById(R<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.id</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ac</span>_tab_btn)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> btnAdd<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setOnClickListener</span>(new View<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.OnClickListener</span>() { @Override public void onClick(View v) { Class <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">clz</span> = tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getClass</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> try { Method animateToTab = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">clz</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getDeclaredMethod</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"animateToTab"</span>, new Class[]{int<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.class</span>})<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> animateToTab<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setAccessible</span>(true)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> animateToTab<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.invoke</span>(tabLayout, new Object[]{<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>})<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> } catch (Exception e) { e<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.printStackTrace</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> } } })<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> }}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li></ul>运行效果如下：
Tab中还有些其它的方法比如setIcon设置图标、setTag设置一个Tag标签还有setCustomView设置一个自定义视图作为一个Tab等，这些都比较简单不多说了：
TabLayout还有个setTabGravity方法可以用来设置TabLayout的布局方式，该方法只有两个可选参数GRAVITY_FILL = 0和GRAVITY_CENTER = 1，默认值是GRAVITY_FILL，setTabGravity方法只有在Mode为MODE_FIXED的情况下才有用，比如现在我们有两个Tab且这两个Tab的宽度比TabLayout小，默认情况下Tab的显示如下：
如果我们将Gravity设置为GRAVITY_CENTER：
<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setTabMode</span>(TabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.MODE</span>_FIXED)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setTabGravity</span>(TabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.GRAVITY</span>_CENTER)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>
那么它就会是这个样子：
不难理解吧。我们还可以通过setOnTabSelectedListener方法为Tab切换设置监听器，OnTabSelectedListener接口中有三个方法onTabSelected、onTabUnselected和onTabReselected，前两个都很好理解不多说，不过要注意的是onTabUnselected总会在onTabSelected前被触发，而onTabReselected则会在你重复点击Tab的时候会被触发。你也可以调用setTabTextColors方法来更改显示文本的颜色，setTabTextColors接收两个颜色值分别表示普通状态的颜色和选中状态的颜色，当然你也可以提供一个ColorStateList对象：
<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">tabLayout<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setTabTextColors</span>(Color<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.RED</span>, Color<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.GREEN</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>
效果如下：
这里要注意的是setTabTextColors方法必须在你添加Tab也就是调用addTab前调用，否则无效，这也是一个bug。还有一点是你无法通过代码的方式修改指示器也就是Tab下方的那根横线，因为那玩意由TabLayout的一个私有内部类SlidingTabStrip控制，其中的方法全TM是non-public的，不过值得欣慰的是你可以在xml中通过属性来改变它，当然上面我们说到的文本颜色也可以通过这种方式修改：
<code class="hljs xml has-numbering" style="display:block; padding:0px; color:inherit; font-family:'Source Code Pro',monospace;font-size:undefined; white-space:pre; word-wrap:normal; background:transparent"><span class="hljs-pi" style="color:rgb(0,102,102)"><?xml version="1.0" encoding="utf-8"?></span><span class="hljs-tag" style="color:rgb(0,102,102)"><<span class="hljs-title" style="color:rgb(0,0,136)">RelativeLayout</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">xmlns:android</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"http://schemas.android.com/apk/res/android"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">xmlns:app</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"http://schemas.android.com/apk/res-auto"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_width</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"match_parent"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_height</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"match_parent"</span>></span> <span class="hljs-tag" style="color:rgb(0,102,102)"><<span class="hljs-title" style="color:rgb(0,0,136)">android.support.design.widget.TabLayout</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:id</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"@+id/ac_tab_layout"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_width</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"match_parent"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_height</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"wrap_content"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">app:tabIndicatorColor</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"#FFFFFF"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">app:tabSelectedTextColor</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"#00FF00"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">app:tabTextColor</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"#FF0000"</span> /></span><span class="hljs-tag" style="color:rgb(0,102,102)"></<span class="hljs-title" style="color:rgb(0,0,136)">RelativeLayout</span>></span></code><ul class="pre-numbering" style="position:absolute; width:50px; top:0px; left:0px; margin:0px; padding:6px 0px 40px; border-right-width:1px; border-right-style:solid; border-right-color:rgb(221,221,221); list-style:none; text-align:right; background-color:rgb(238,238,238)"><li style="padding:0px 5px">1</li><li style="padding:0px 5px">2</li><li style="padding:0px 5px">3</li><li style="padding:0px 5px">4</li><li style="padding:0px 5px">5</li><li style="padding:0px 5px">6</li><li style="padding:0px 5px">7</li><li style="padding:0px 5px">8</li><li style="padding:0px 5px">9</li><li style="padding:0px 5px">10</li><li style="padding:0px 5px">11</li><li style="padding:0px 5px">12</li><li style="padding:0px 5px">13</li><li style="padding:0px 5px">14</li><li style="padding:0px 5px">15</li></ul>
效果如下：
大部分情况下TabLayout都不会单独使用，一般我们会配合ViewPager来实现一个完整的Tab切换效果，而TabLayout也提供了几个很简便的方法来与ViewPager进行关联交互，先在我们的布局里加一个ViewPager：
<code class="hljs xml has-numbering" style="display:block; padding:0px; color:inherit; font-family:'Source Code Pro',monospace;font-size:undefined; white-space:pre; word-wrap:normal; background:transparent"><span class="hljs-pi" style="color:rgb(0,102,102)"><?xml version="1.0" encoding="utf-8"?></span><span class="hljs-tag" style="color:rgb(0,102,102)"><<span class="hljs-title" style="color:rgb(0,0,136)">LinearLayout</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">xmlns:android</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"http://schemas.android.com/apk/res/android"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_width</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"match_parent"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_height</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"match_parent"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:orientation</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"vertical"</span>></span> <span class="hljs-tag" style="color:rgb(0,102,102)"><<span class="hljs-title" style="color:rgb(0,0,136)">android.support.design.widget.TabLayout</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:id</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"@+id/ac_tab_layout"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_width</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"match_parent"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_height</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"wrap_content"</span> /></span> <span class="hljs-tag" style="color:rgb(0,102,102)"><<span class="hljs-title" style="color:rgb(0,0,136)">android.support.v4.view.ViewPager</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:id</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"@+id/ac_tab_vp"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_width</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"match_parent"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_height</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"0dp"</span> <span class="hljs-attribute" style="color:rgb(102,0,102)">android:layout_weight</span>=<span class="hljs-value" style="color:rgb(0,136,0)">"1"</span> /></span><span class="hljs-tag" style="color:rgb(0,102,102)"></<span class="hljs-title" style="color:rgb(0,0,136)">LinearLayout</span>></span></code><ul class="pre-numbering" style="position:absolute; width:50px; top:0px; left:0px; margin:0px; padding:6px 0px 40px; border-right-width:1px; border-right-style:solid; border-right-color:rgb(221,221,221); list-style:none; text-align:right; background-color:rgb(238,238,238)"><li style="padding:0px 5px">1</li><li style="padding:0px 5px">2</li><li style="padding:0px 5px">3</li><li style="padding:0px 5px">4</li><li style="padding:0px 5px">5</li><li style="padding:0px 5px">6</li><li style="padding:0px 5px">7</li><li style="padding:0px 5px">8</li><li style="padding:0px 5px">9</li><li style="padding:0px 5px">10</li><li style="padding:0px 5px">11</li><li style="padding:0px 5px">12</li><li style="padding:0px 5px">13</li><li style="padding:0px 5px">14</li><li style="padding:0px 5px">15</li><li style="padding:0px 5px">16</li><li style="padding:0px 5px">17</li><li style="padding:0px 5px">18</li></ul>
然后，然后，然后还是看代码吧，TabLayout与ViewPager结合的逻辑有点绕：
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">TabLayoutActivity</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Activity</span> {</span> <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/** * 数据源 */</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> String[] DATA = {<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"AigeStudio"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Aige"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Studio"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Android"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Java"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Design"</span>}; <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onCreate</span>(Bundle savedInstanceState) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.onCreate(savedInstanceState); setContentView(R.layout.ac_tab_layout); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 获取ViewPager</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> ViewPager viewPager = (ViewPager) findViewById(R.id.ac_tab_vp); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 构造一个TabPagerAdapter对象</span> TabPagerAdapter adapter = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> TabPagerAdapter(); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 获取ViewPager</span> TabLayout tabLayout = (TabLayout) findViewById(R.id.ac_tab_layout); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 设置TabLayout模式</span> tabLayout.setTabMode(TabLayout.MODE_SCROLLABLE); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 设置从PagerAdapter中获取Tab</span> tabLayout.setTabsFromPagerAdapter(adapter); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 设置Tab的选择监听</span> tabLayout.setOnTabSelectedListener(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> TabLayout.OnTabSelectedListener() { <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onTabSelected</span>(TabLayout.Tab tab) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 每当我们选择了一个Tab就将ViewPager滚动至对应的Page</span> viewPager.setCurrentItem(tab.getPosition(), <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>); } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onTabUnselected</span>(TabLayout.Tab tab) { } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onTabReselected</span>(TabLayout.Tab tab) { } }); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 构造一个TabLayoutOnPageChangeListener对象</span> TabLayout.TabLayoutOnPageChangeListener listener = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> TabLayout.TabLayoutOnPageChangeListener(tabLayout); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 设置ViewPager页面改变后的监听</span> viewPager.addOnPageChangeListener(listener); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 设置ViewPager的适配器</span> viewPager.setAdapter(adapter); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">TabPagerAdapter</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">PagerAdapter</span> {</span> <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">getCount</span>() { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> DATA.length; } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> <span class="hljs-title" style="box-sizing: border-box;">isViewFromObject</span>(View view, Object object) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> view == object; } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> Object <span class="hljs-title" style="box-sizing: border-box;">instantiateItem</span>(ViewGroup container, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> position) { TextView tvContent = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> TextView(TabLayoutActivity.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>); tvContent.setText(DATA[position]); tvContent.setGravity(Gravity.CENTER); container.addView(tvContent, ViewPager.LayoutParams.MATCH_PARENT, ViewPager.LayoutParams.WRAP_CONTENT); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> tvContent; } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">destroyItem</span>(ViewGroup container, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> position, Object object) { container.removeView((View) object); } <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> CharSequence <span class="hljs-title" style="box-sizing: border-box;">getPageTitle</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> position) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> DATA[position]; } }}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li><li style="box-sizing: border-box; padding: 0px 5px;">64</li><li style="box-sizing: border-box; padding: 0px 5px;">65</li><li style="box-sizing: border-box; padding: 0px 5px;">66</li><li style="box-sizing: border-box; padding: 0px 5px;">67</li><li style="box-sizing: border-box; padding: 0px 5px;">68</li><li style="box-sizing: border-box; padding: 0px 5px;">69</li><li style="box-sizing: border-box; padding: 0px 5px;">70</li><li style="box-sizing: border-box; padding: 0px 5px;">71</li><li style="box-sizing: border-box; padding: 0px 5px;">72</li><li style="box-sizing: border-box; padding: 0px 5px;">73</li><li style="box-sizing: border-box; padding: 0px 5px;">74</li><li style="box-sizing: border-box; padding: 0px 5px;">75</li><li style="box-sizing: border-box; padding: 0px 5px;">76</li><li style="box-sizing: border-box; padding: 0px 5px;">77</li><li style="box-sizing: border-box; padding: 0px 5px;">78</li><li style="box-sizing: border-box; padding: 0px 5px;">79</li><li style="box-sizing: border-box; padding: 0px 5px;">80</li><li style="box-sizing: border-box; padding: 0px 5px;">81</li><li style="box-sizing: border-box; padding: 0px 5px;">82</li><li style="box-sizing: border-box; padding: 0px 5px;">83</li><li style="box-sizing: border-box; padding: 0px 5px;">84</li><li style="box-sizing: border-box; padding: 0px 5px;">85</li></ul>运行效果如下：
其它的不多说，大家注意到我们的代码中并没有添加Tab的具体逻辑，但是从运行的结果来看却实实在在地把我们的Tab标题显示上去了，这里主要还是要归功于TabLayout的setTabsFromPagerAdapter方法，在该方法中TabLayout会通过PagerAdapter的getPageTitle方法获得Page中的标题并将其封装成一个Tab添加至TabLayout中：
<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">setTabsFromPagerAdapter</span>(PagerAdapter adapter){ removeAllTabs(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> count = adapter.getCount(); i < count; i++) addTab(newTab().setText(adapter.getPageTitle(i)));}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li></ul>这也是为什么我们会在PagerAdapter中重写getPageTitle方法返回数据的原因。同时我们为TabLayout设置了一个Tab选择监听，在Tab被选择后可以让滚动至对应的Page，这一步就完成了Tab到Page的事件绑定，那么当Page改变后又如何影响Tab呢？这时候我们就得为ViewPager添加一个PageChangeListener，而这个PageChangeListener当然你可以自己去实现，但是TabLayout提供了一个方便的实现类TabLayoutOnPageChangeListener，我们只需构造一个添加到ViewPager即可。是不是觉得逻辑有点乱？一会TabLayout一会ViewPager的，确实，我也觉的，不过TabLayout提供了一个更超级简便的方法setupWithViewPager来完成与ViewPager的结合，使用方法很简单，先把ViewPager的相关参数什么的设置好，比如Adapter什么的，然后直接调用TabLayout的setupWithViewPager方法设置即可：
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onCreate</span>(Bundle savedInstanceState) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.onCreate(savedInstanceState); setContentView(R.layout.ac_tab_layout); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 获取ViewPager</span> ViewPager viewPager = (ViewPager) findViewById(R.id.ac_tab_vp); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 构造一个TabPagerAdapter对象</span> TabPagerAdapter adapter = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> TabPagerAdapter(); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 获取ViewPager</span> TabLayout tabLayout = (TabLayout) findViewById(R.id.ac_tab_layout); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 设置TabLayout模式</span> tabLayout.setTabMode(TabLayout.MODE_SCROLLABLE); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 设置ViewPager的适配器</span> viewPager.setAdapter(adapter); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 设置ViewPager</span> tabLayout.setupWithViewPager(viewPager);}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li></ul>是不是感觉瞬间就简单了很多…………Fuck。好了TabLayout就啰嗦到这里，总结就一句话，这货一定是程序猿心情不好的时候写的，很多逻辑好奇葩啊有木有~~~~
Demo项目源码在Github可下载：AndroidViewDemo
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