android studio tabhost基础 多功能时钟app tabhost

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:orientation="vertical"
tools:context="com.example.jowang.clock.MainActivity">

<TabHost
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/tabHost"
android:layout_gravity="center_horizontal">

<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">

<TabWidget
android:id="@android:id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"></TabWidget>

<FrameLayout
android:id="@android:id/tabcontent"
android:layout_width="match_parent"
android:layout_height="match_parent">

<LinearLayout
android:id="@+id/tabTime"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"></LinearLayout>

<LinearLayout
android:id="@+id/tabAlarm"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"></LinearLayout>

<LinearLayout
android:id="@+id/tabTimer"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"></LinearLayout>
<LinearLayout
android:id="@+id/tabStopwatch"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"></LinearLayout>
</FrameLayout>
</LinearLayout>
</TabHost>
</LinearLayout>

public class MainActivity extends AppCompatActivity {
private TabHost tabHost;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tabHost=(TabHost)findViewById(R.id.tabHost);
tabHost.setup();
tabHost.addTab(tabHost.newTabSpec("tabTime").setIndicator("时钟").setContent(R.id.tabTime));
tabHost.addTab(tabHost.newTabSpec("tabAlarm").setIndicator("闹钟").setContent(R.id.tabAlarm));
tabHost.addTab(tabHost.newTabSpec("tabTimer").setIndicator("计时器").setContent(R.id.tabTimer));
tabHost.addTab(tabHost.newTabSpec("tabStopwatch").setIndicator("秒表").setContent(R.id.tabStopwatch));

}
}