Android Design Support Library之TabLayout

TabLayout是Android Design Support Library库中的控件。Google在2015年的IO大会上，给我们带来了更加详细的Material Design设计规范，同时也给我们带来了全新的Android Design Support Library，在这个support库中,Google给我们提供了更加规范的MD设计风格的控件。最重要的是，Android Design Support Library可以向下兼容到Android 2.2。

接下来，我们开始熟悉TabLayout的使用，并完成一个类似网易新闻客户端滑动标签的效果，它的滑动标签由Toolbar+TabLayout实现，内容显示由ViewPager+Fragment实现。

1.配置build.gradle

dependencies {    compile fileTree(include: ['*.jar'], dir: 'libs')    testCompile 'junit:junit:4.12'    compile 'com.android.support:appcompat-v7:23.1.1'    compile 'com.android.support:recyclerview-v7:23.1.1'    compile 'com.android.support:support-v4:23.1.1'    compile 'com.android.support:cardview-v7:23.1.1'    compile 'com.android.support:design:23.2.0'}

com.android.support:design:23.2.0就是我们需要引入的Android Design Support Library，其次我们还引入了RecyclerView和CardView两个Android 5.X的新控件。

2.主界面的布局

主界面的布局由AppBarLayout、Toolbar和TabLayout，以及ViewPager组成，主界面布局文件activity_main.xml如下:

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:fitsSystemWindows="true"    android:orientation="vertical">    <android.support.design.widget.AppBarLayout        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:theme="@style/AppTheme.AppBarOverlay">        <android.support.v7.widget.Toolbar            android:id="@+id/toolbar"            android:layout_width="match_parent"            android:layout_height="?attr/actionBarSize"            android:background="?attr/colorPrimary"            app:layout_scrollFlags="scroll|enterAlways"            app:popupTheme="@style/AppTheme.PopupOverlay" />        <android.support.design.widget.TabLayout            android:id="@+id/tabs"            android:layout_width="match_parent"            android:layout_height="wrap_content"            app:tabIndicatorColor="#ADBE107E"            app:tabMode="scrollable">        </android.support.design.widget.TabLayout>    </android.support.design.widget.AppBarLayout>    <android.support.v4.view.ViewPager        android:id="@+id/viewpager"        android:layout_width="match_parent"        android:layout_height="match_parent"        app:layout_behavior="@string/appbar_scrolling_view_behavior">    </android.support.v4.view.ViewPager></LinearLayout>

这里用到AppBarLayout和Toolbar，AppBarLayout是Android Design Support Library新加的空间继承自LinearLayout，它用来将Toolbar和TabLayout组合起来成为一个整体。ViewPager用来实现Fragment页面的切换

布局文件中最关键的一点是android.support.design.widget.TabLayout的app:tabMode=”scrollable”，它表示tab标签的模式是可滑动的，如果不设置次模式的话，标签将不可滑动。

3.主界面的实现

1. 实例化TabLayout，给TabLayout标签设置文字
2. 实例化FragmentAdapter，加载Fragment
3. 实例化ViewPager，并设置ViewPager的适配器FragmentAdapter
4. TabLayout与ViewPager关联
5. TabLayout设置适配器FragmentAdapter

MainActivity.java如下所示

package com.deason.library.mytablayout;import android.os.Bundle;import android.support.design.widget.TabLayout;import android.support.v4.app.Fragment;import android.support.v4.view.ViewPager;import android.support.v7.app.AppCompatActivity;import android.support.v7.widget.Toolbar;import android.view.Menu;import android.view.MenuItem;import java.util.ArrayList;import java.util.List;public class MainActivity extends AppCompatActivity {    private ViewPager mViewPager;    private TabLayout mTabLayout;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);        setSupportActionBar(toolbar);        mViewPager = (ViewPager) findViewById(R.id.viewpager);        initViewPager();    }    private void initViewPager() {        mTabLayout = (TabLayout) findViewById(R.id.tabs);        List<String> titles = new ArrayList<String>();        titles.add("新闻");        titles.add("财经");        titles.add("娱乐");        titles.add("体育");        titles.add("军事");        titles.add("科技");        titles.add("教育");        titles.add("历史");        titles.add("文化");        titles.add("校园");        for(int i= 0;i < titles.size();i++) {            //设置TabIndicator文字            mTabLayout.addTab(mTabLayout.newTab().setText(titles.get(i)));        }        List<Fragment> fragments = new ArrayList<Fragment>();        for (int i = 0; i < titles.size(); i++) {            fragments.add(new TabFragment());        }        //实例化适配器        FragmentAdapter mAdapter = new FragmentAdapter(getSupportFragmentManager(),fragments,titles);        //给ViewPager设置适配器        mViewPager.setAdapter(mAdapter);        //将TabLayout和ViewPager关联起来        mTabLayout.setupWithViewPager(mViewPager);        //给TabLayout设置适配器        mTabLayout.setTabsFromPagerAdapter(mAdapter);     }}

3.1 实例化FragmentAdapter

FragmentAdapter.java

package com.deason.library.mytablayout;import android.support.v4.app.Fragment;import android.support.v4.app.FragmentManager;import android.support.v4.app.FragmentPagerAdapter;import java.util.List;/** * Created by liuguoquan on 2016/2/24. */public class FragmentAdapter extends FragmentPagerAdapter {    private List<Fragment>  mFragments;    private List<String>    mTitles;    public FragmentAdapter(FragmentManager fm,List<Fragment> fragments,List<String> titles) {        super(fm);        this.mFragments = fragments;        this.mTitles = titles;    }    @Override    public Fragment getItem(int position) {        return mFragments.get(position);    }    @Override    public int getCount() {        return mFragments.size();    }    //Tabs标签名称    @Override    public CharSequence getPageTitle(int position) {        return mTitles.get(position);    }}

3.2 TabFragment

package com.deason.library.mytablayout;import android.os.Bundle;import android.support.v4.app.Fragment;import android.support.v7.widget.LinearLayoutManager;import android.support.v7.widget.RecyclerView;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;/** * A simple {@link Fragment} subclass. */public class TabFragment extends Fragment {    private RecyclerView mRecyclerView;    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container,                             Bundle savedInstanceState) {        // Inflate the layout for this fragment        View view = inflater.inflate(R.layout.fragment_list,container,false);        return view;    }    @Override    public void onActivityCreated(Bundle savedInstanceState) {        super.onActivityCreated(savedInstanceState);    }}

4 运行效果