前言
在谷歌发布Android Design Support Library之前，app底部tab布局的实现方法就有很多种，其中有RadioGroup+FrameLayout、TabHost+Fragment、FragmentPagerAdapter+ViewPager等方法，虽然这些方法虽然能达到同样的效果，但我个人总觉得有些繁琐。然而，Google在2015的IO大会上，给开发者们带来了全新的Android Design Support Library，里面包含了许多新控件，这些新控件有许多是把以前的一些第三方开源库官方化，实现起来更为简便，简直是开发者的福音。其中的TabLayout控件让我想到了app底部的tab布局，而且TabLayout用法更加简单，为何不试试用TabLayout实现简单的实现呢？好了，话不多说，先看看效果：
底部tab布局.png
是不是和以前的方法实现的效果一样呢？下面我们来看看怎么简单实现。
过程
因为TabLayout和ViewPager分别是属于design和v4包下的，所以我们先在app的build.gradle中添加：
compile 'com.android.support:design:23.1.1'
compile 'com.android.support:support-v4:23.1.1'
然后在主布局文件activity_main.xml中添加布局控件：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity">
<android.support.v4.view.ViewPager
android:id="@+id/viewPager"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:scrollbars="none">
</android.support.v4.view.ViewPager>
<android.support.design.widget.TabLayout
android:id="@+id/tabLayout"
android:layout_width="match_parent"
android:layout_height="50dp"
app:tabGravity="fill"
app:tabIndicatorHeight="0dp"
app:tabMode="fixed"
app:tabSelectedTextColor="#FF4081"
app:tabTextColor="#000">
</android.support.design.widget.TabLayout>
</LinearLayout>
就仅一个ViewPager和TabLayout就可以实现，是不是比以前的方法繁琐的布局简便很多？上面TabLayout中app:tabIndicatorHeight="0dp"是为了不显示tab底部的横线，app:tabMode="fixed"是让底部tab布局不可滑动。
接下来就和往常一样在MainActivity.java中初始化布局，设置适配器：
private void initViews() {
mTablayout= (TabLayout) findViewById(R.id.tabLayout);
mViewPager= (ViewPager) findViewById(R.id.viewPager);
mViewPager.setAdapter(new FragmentPagerAdapter(getSupportFragmentManager()) {
private String[] mTitles = new String[]{"唐僧", "大师兄", "二师兄","沙师弟"};
@Override
public Fragment getItem(int position) {
if (position == 1) {
return new TwoFragment();
} else if (position == 2) {
return new ThreeFragment();
}else if (position==3){
return new FourFragment();
}
return new OneFragment();
}
@Override
public int getCount() {
return mTitles.length;
}
@Override
public CharSequence getPageTitle(int position) {
return mTitles[position];
}
});
mTablayout.setupWithViewPager(mViewPager);
one = mTablayout.getTabAt(0);
two = mTablayout.getTabAt(1);
three = mTablayout.getTabAt(2);
four = mTablayout.getTabAt(3);
one.setIcon(getResources().getDrawable(R.drawable.ic_favorite_black_18dp));
two.setIcon(getResources().getDrawable(R.mipmap.ic_launcher));
three.setIcon(getResources().getDrawable(R.mipmap.ic_launcher));
four.setIcon(getResources().getDrawable(R.mipmap.ic_launcher));
}
上面要注意的地方是别忘了在FragmentPagerAdapter中手动添加：
@Override
public CharSequence getPageTitle(int position) {
return mTitles[position];
}
不然不显示底部的文字。
mTablayout.setupWithViewPager(mViewPager);将TabLayout和ViewPager关联起来。
one = mTablayout.getTabAt(0);获取底部单个tab，用来添加初始化图片，注意下标都是从0开始的。
初始化监听事件
private void initEvents() {
mTablayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
if (tab == mTablayout.getTabAt(0)) {
one.setIcon(getResources().getDrawable(R.drawable.ic_favorite_black_18dp));
mViewPager.setCurrentItem(0);
} else if (tab == mTablayout.getTabAt(1)) {
two.setIcon(getResources().getDrawable(R.drawable.ic_favorite_black_18dp));
mViewPager.setCurrentItem(1);
} else if (tab == mTablayout.getTabAt(2)) {
three.setIcon(getResources().getDrawable(R.drawable.ic_favorite_black_18dp));
mViewPager.setCurrentItem(2);
}else if (tab == mTablayout.getTabAt(3)){
four.setIcon(getResources().getDrawable(R.drawable.ic_favorite_black_18dp));
mViewPager.setCurrentItem(3);
}
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
if (tab == mTablayout.getTabAt(0)) {
one.setIcon(getResources().getDrawable(R.mipmap.ic_launcher));
} else if (tab == mTablayout.getTabAt(1)) {
two.setIcon(getResources().getDrawable(R.mipmap.ic_launcher));
} else if (tab == mTablayout.getTabAt(2)) {
three.setIcon(getResources().getDrawable(R.mipmap.ic_launcher));
}else if (tab == mTablayout.getTabAt(3)){
four.setIcon(getResources().getDrawable(R.mipmap.ic_launcher));
}
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
}
在onTabSelected中设置选中tab时切换的图片，onTabUnselected中设置没有被选中时的图片。别忘了mViewPager.setCurrentItem(0);这句，这是用来点击tab时切换ViewPager，如果不加这一句的话滑动ViewPager底部tab可以切换，但是点击tab而ViewPager不会切换。
Fragment中的简单布局
fragment_one.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="唐僧"
android:layout_marginTop="100dp"
android:layout_gravity="center"
android:textSize="30sp"/>
</LinearLayout>
OneFragment.java
public class OneFragment extends Fragment{
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_one,container,false);
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
}
}
MainActivity.java完整代码：
public class MainActivity extends AppCompatActivity {
private TabLayout mTablayout;
private ViewPager mViewPager;
private TabLayout.Tab one;
private TabLayout.Tab two;
private TabLayout.Tab three;
private TabLayout.Tab four;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initViews();
initEvents();
}
private void initEvents() {
mTablayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
if (tab == mTablayout.getTabAt(0)) {
one.setIcon(getResources().getDrawable(R.drawable.ic_favorite_black_18dp));
mViewPager.setCurrentItem(0);
} else if (tab == mTablayout.getTabAt(1)) {
two.setIcon(getResources().getDrawable(R.drawable.ic_favorite_black_18dp));
mViewPager.setCurrentItem(1);
} else if (tab == mTablayout.getTabAt(2)) {
three.setIcon(getResources().getDrawable(R.drawable.ic_favorite_black_18dp));
mViewPager.setCurrentItem(2);
}else if (tab == mTablayout.getTabAt(3)){
four.setIcon(getResources().getDrawable(R.drawable.ic_favorite_black_18dp));
mViewPager.setCurrentItem(3);
}
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
if (tab == mTablayout.getTabAt(0)) {
one.setIcon(getResources().getDrawable(R.mipmap.ic_launcher));
} else if (tab == mTablayout.getTabAt(1)) {
two.setIcon(getResources().getDrawable(R.mipmap.ic_launcher));
} else if (tab == mTablayout.getTabAt(2)) {
three.setIcon(getResources().getDrawable(R.mipmap.ic_launcher));
}else if (tab == mTablayout.getTabAt(3)){
four.setIcon(getResources().getDrawable(R.mipmap.ic_launcher));
}
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
}
private void initViews() {
mTablayout= (TabLayout) findViewById(R.id.tabLayout);
mViewPager= (ViewPager) findViewById(R.id.viewPager);
mViewPager.setAdapter(new FragmentPagerAdapter(getSupportFragmentManager()) {
private String[] mTitles = new String[]{"唐僧", "大师兄", "二师兄","沙师弟"};
@Override
public Fragment getItem(int position) {
if (position == 1) {
return new TwoFragment();
} else if (position == 2) {
return new ThreeFragment();
}else if (position==3){
return new FourFragment();
}
return new OneFragment();
}
@Override
public int getCount() {
return mTitles.length;
}
@Override
public CharSequence getPageTitle(int position) {
return mTitles[position];
}
});
mTablayout.setupWithViewPager(mViewPager);
one = mTablayout.getTabAt(0);
two = mTablayout.getTabAt(1);
three = mTablayout.getTabAt(2);
four = mTablayout.getTabAt(3);
one.setIcon(getResources().getDrawable(R.drawable.ic_favorite_black_18dp));
two.setIcon(getResources().getDrawable(R.mipmap.ic_launcher));
three.setIcon(getResources().getDrawable(R.mipmap.ic_launcher));
four.setIcon(getResources().getDrawable(R.mipmap.ic_launcher));
}
}
结束语
以上就是简单用TabLayout+ViewPager实现app底部Tab布局的整个过程，如果你有更好的方法，或者文章中存在错误或不足的地方，欢迎在文章下面评论交流！
