使用TabHost添加选项卡时出错

Question

我正在尝试使用下面的标签主机创建标签式视图，但应用程序被强制关闭...我正在尝试使用标签主机创建标签式视图，如下面但应用程序被强制关闭...我正在尝试创建标签式视图使用下面的标签主机，但应用程序被强制关闭...

MainActivity.java

package darpan.slider;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TabHost;


public class MainActivity extends Activity {

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.TabSpec tab1 = tabHost.newTabSpec("First");
    TabHost.TabSpec tab2 = tabHost.newTabSpec("Second");
    TabHost.TabSpec tab3 = tabHost.newTabSpec("Third");

    tab1.setIndicator("First");
    tab1.setContent(new Intent(this, FirstTab.class));

    tab2.setIndicator("Second");
    tab2.setContent(new Intent(this, SecondTab.class));

    tab3.setIndicator("Third");
    tab3.setContent(new Intent(this, ThirdTab.class));

    tabHost.addTab(tab1);
    tabHost.addTab(tab2);
    tabHost.addTab(tab3);

    tabHost.setCurrentTab(1);
    }
}

logcat的：

02-10 15:54:00.061  23783-23783/darpan.slider W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41c7c700)
02-10 15:54:00.061  23783-23783/darpan.slider E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{darpan.slider/darpan.slider.MainActivity}: java.lang.NullPointerException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2295)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2349)
        at android.app.ActivityThread.access$700(ActivityThread.java:159)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:176)
        at android.app.ActivityThread.main(ActivityThread.java:5419)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:525)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.NullPointerException
        at android.widget.TabHost.addTab(TabHost.java:253)
        at darpan.slider.MainActivity.onCreate(MainActivity.java:36)
        at android.app.Activity.performCreate(Activity.java:5372)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2257)