android ViewSwitcher详解 .

来源：互联网发布：windows xp 安装盘编辑：程序博客网时间：2024/05/22 02:29

ViewSwitcher 的作用简单来说就是：在两个视图间转换时显示动画

它的两个子类应该很熟悉，ImageSwitcher：转换图片时增加动画效果;TextSwitcher：转换文字时增加动画效果;其实例见apidemos中ImageSwitcher实例和TextSwitcher实例

但不要忽略ViewSwicher,在一些场合还是很有用的

在android里视图切换是一个很常见的需求，比如说加载view和后台背景，当后台加载数据时，loding view显示，数据View隐藏，加载完成，反向此过程。使用ViewSwicher提供了简单的逻辑，产生更可读的代码。

举个最常见的例子，列表底部加载

Button more

01<?xmlversion="1.0"encoding="utf-8"?>
02<Buttonxmlns:android="http://schemas.android.com/apk/res/android"
03    android:id="@+id/btn_loadmorecontacts"
04    android:text="Load More Items"
05    android:layout_width="fill_parent"
06    android:layout_height="wrap_content"
07    android:textAppearance="?android:attr/textAppearanceLarge"
08    android:minHeight="?android:attr/listPreferredItemHeight"
09    android:textColor="#FFFFFF"
10    android:background="<a href="http://my.oschina.net/asia"rel="nofollow"target="_blank">@android</a> :drawable/list_selector_background"
11    android:clickable="true"
12    android:onClick="onClick" />

大致是这样子

加载中视图：

01<?xmlversion="1.0"encoding="utf-8"?>
02<RelativeLayoutxmlns:android="http://schemas.android.com/apk/res/android"
03    android:layout_width="wrap_content"
04    android:layout_height="wrap_content"
05    android:gravity="center_horizontal"
06    android:minHeight="?android:attr/listPreferredItemHeight">
07 
08    <ProgressBar
09        android:id="@+id/progressbar"
10        android:layout_width="wrap_content"
11        android:layout_height="wrap_content"
12        android:layout_centerVertical="true"/>
13 
14    <TextView
15        android:text="Loading…"
16        android:textAppearance="?android:attr/textAppearanceLarge"
17        android:layout_height="wrap_content"
18        android:layout_width="wrap_content"
19        android:layout_toRightOf="@+id/progressbar"
20        android:layout_centerVertical="true"
21        android:gravity="center"
22        android:padding="10dip"
23        android:textColor="#FFFFFF"/>
24</RelativeLayout>

01public class ViewSwitcherExample extendsListActivity
02                 implementsOnClickListener {
03    
04    //sample list items
05    staticfinal String[] ITEMS =new String[]
06          {"List Item 1", "List Item 2", 
07            "List Item 3","List Item 4", 
08            "List Item 5","List Item 6", 
09            "List Item 7","List Item 8", 
10            "List Item 9","List Item 10" };
11    
12    //the ViewSwitcher
13    privateViewSwitcher switcher;
14    
15    /** Called when the activity is first created. */
16    @Override
17    publicvoid onCreate(Bundle savedInstanceState) {
18      super.onCreate(savedInstanceState);
19      
20      //no window title
21      requestWindowFeature(Window.FEATURE_NO_TITLE);
22      
23      //create the ViewSwitcher in the current context
24      switcher =new ViewSwitcher(this);
25      
26      //底部 Button: see XML1
27      Button footer = (Button)View.inflate(this, R.layout.btn_loadmore,null);
28      
29      //进度条View: see XML2
30      View progress = View.inflate(this, R.layout.loading_footer,null);
31      
32      //向viewSwitcher加入view (first added will show first)
33      switcher.addView(footer);
34      switcher.addView(progress);
35      
36      //listview底部加入swicher
37      getListView().addFooterView(switcher);
38      
39      //add items to the ListView
40      setListAdapter(newArrayAdapter(this,
41              android.R.layout.simple_list_item_1, ITEMS));
42    }
43 
44    @Override/* Load More Button Was Clicked */
45    public void onClick(View arg0) {
46        //first view is showing, show the second progress view
47        switcher.showNext();
48        //and start background work
49        new getMoreItems().execute();
50    }
51    
52    /** Background Task To Get More Items**/
53    private class getMoreItems extends AsyncTask {
54        @Override
55        protected Object doInBackground(Void… params) {
56            //code to add more items
57            //...
58            try {
59                Thread.sleep(3000); //only to demonstrate
60            } catch (InterruptedException e) {
61                e.printStackTrace();
62            }
63            return null;
64        }
65 
66        @Override /* Background Task is Done */
67        protectedvoid onPostExecute(Object result) {
68            //go back to the first view
69            switcher.showPrevious();
70                        //update the ListView
71        }
72    }
73}

1switcher.showNext();  // Switches to the next view
2switcher.showPrevious();  // Switches to the previous view

当然你也可以使用xml形式构造ViewSwicher,这里加上了系统自带的切换效果@android:anim/slide_in_left和@android:anim/slide_out_right

01<?xmlversion="1.0"encoding="utf-8"?>
02<ViewSwitcherxmlns:android="http://schemas.android.com/apk/res/android"
03    android:id="@+id/profileSwitcher"
04    android:layout_width="fill_parent"
05    android:layout_height="fill_parent"
06    android:inAnimation="@android:anim/slide_in_left"
07    android:outAnimation="@android:anim/slide_out_right">
08<RelativeLayout
09    android:layout_width="wrap_content"
10    android:layout_height="wrap_content">
11    <ProgressBar
12        android:id="@+id/progressbar"
13        android:layout_width="wrap_content"
14        android:layout_height="wrap_content"
15        android:layout_centerVertical="true"/>
16    <TextView
17        android:text="Loading…"
18        android:layout_height="wrap_content"
19        android:layout_width="wrap_content"
20        android:layout_toRightOf="@+id/progressbar"
21        android:gravity="center"/>
22</RelativeLayout>
23 
24<RelativeLayout
25    android:layout_width="wrap_content"
26    android:layout_height="wrap_content"
27    android:gravity="center_horizontal">
28    <TextView
29        android:text="Finished!"
30        android:layout_height="wrap_content"
31        android:layout_width="wrap_content"
32        android:layout_centerVertical="true"/>
33</RelativeLayout>
34 
35</ViewSwitcher>

你喜欢的话可以加入动画效果，使用View gone、Visible方式还是ViewSwicher还是看自己喜好了