今天新建Android Studio项目的时候，发现一个微妙的变化： 看完心情是这样的：
这个什么东西：
BottomNavigationView 来看看吧，小伙伴们：
先看它的布局文件：
<android.support.design.widget.BottomNavigationView android:id="@+id/navigation" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_gravity="bottom" android:background="?android:attr/windowBackground" app:menu="@menu/navigation" />app:menu 一定是我们的菜单，来看看：
<?xml version="1.0" encoding="utf-8"?> <menu xmlns:android="http://schemas.android.com/apk/res/android"> <item android:id="@+id/navigation_home" android:icon="@drawable/ic_home_black_24dp" android:title="@string/title_home" /> <item android:id="@+id/navigation_dashboard" android:icon="@drawable/ic_dashboard_black_24dp" android:title="@string/title_dashboard" /> <item android:id="@+id/navigation_notifications" android:icon="@drawable/ic_notifications_black_24dp" android:title="@string/title_notifications" /> </menu>果然如此。那么在MainActivity中，它是怎么使用的呢？
public class MainActivity extends AppCompatActivity { private TextView mTextMessage; private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener = new BottomNavigationView.OnNavigationItemSelectedListener() { @Override public boolean onNavigationItemSelected(@NonNull MenuItem item) { switch (item.getItemId()) { case R.id.navigation_home: mTextMessage.setText(R.string.title_home); return true; case R.id.navigation_dashboard: mTextMessage.setText(R.string.title_dashboard); return true; case R.id.navigation_notifications: mTextMessage.setText(R.string.title_notifications); return true; } return false; } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mTextMessage = (TextView) findViewById(R.id.message); BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation); navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener); } }哈哈，以后底部导航栏就可以放大招啦！
