嗨，我是这个“标签活动”概念的新手。我搜索了这个，最后我知道我应该实现“片段”。我完成了以下代码，但它显示错误。请指导我解决这个问题。
public class VendorActivity extends FragmentActivity
{
private FragmentTabHost mTabHost;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_vendor);
mTabHost = (FragmentTabHost)findViewById(android.R.id.tabhost);
// Tab for Photos
TabSpec photospec = mTabHost.newTabSpec("Photos");
// setting Title and Icon for the Tab
photospec.setIndicator("Photos");
Intent photosIntent = new Intent(this, Simple.class);
photospec.setContent(photosIntent);
System.out.println("b4 fragment");
TabSpec songspec = mTabHost.newTabSpec("Songs");
songspec.setIndicator("Songs");
Intent songsIntent = new Intent(this, Contacts.class);
songspec.setContent(songsIntent);
System.out.println("bafter fragment");
System.out.println("1");
mTabHost.addTab(photospec); // Error comes here.android
System.out.println("2");
mTabHost.addTab(songspec);
System.out.println("3");
// mTabHost.addTab(mTabHost.newTabSpec("simple").setIndicator("Simple"),
// FragmentStackSupport.sim.class, null);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_vendor, menu);
return true;
}
}
我的 XML：
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.app.FragmentTabHost
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@android:id/tabhost"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TabWidget
android:id="@android:id/tabs"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
<FrameLayout
android:id="@android:id/tabcontent"
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>
</LinearLayout>
</android.support.v4.app.FragmentTabHost>
我的日志猫：
03-29 23:44:09.245: I/Process(447): Sending signal. PID: 447 SIG: 9
03-29 23:46:17.304: I/System.out(474): b4 fragment
03-29 23:46:17.304: I/System.out(474): bafter fragment
03-29 23:46:17.304: I/System.out(474): 1
03-29 23:46:17.444: D/AndroidRuntime(474): Shutting down VM
03-29 23:46:17.444: W/dalvikvm(474): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
03-29 23:46:17.584: E/AndroidRuntime(474): FATAL EXCEPTION: main
03-29 23:46:17.584: E/AndroidRuntime(474): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.vegetable/com.vegetable.VendorActivity}: java.lang.NullPointerException
03-29 23:46:17.584: E/AndroidRuntime(474): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
03-29 23:46:17.584: E/AndroidRuntime(474): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
03-29 23:46:17.584: E/AndroidRuntime(474): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
03-29 23:46:17.584: E/AndroidRuntime(474): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
03-29 23:46:17.584: E/AndroidRuntime(474): at android.os.Handler.dispatchMessage(Handler.java:99)
03-29 23:46:17.584: E/AndroidRuntime(474): at android.os.Looper.loop(Looper.java:123)
03-29 23:46:17.584: E/AndroidRuntime(474): at android.app.ActivityThread.main(ActivityThread.java:4627)
03-29 23:46:17.584: E/AndroidRuntime(474): at java.lang.reflect.Method.invokeNative(Native Method)
03-29 23:46:17.584: E/AndroidRuntime(474): at java.lang.reflect.Method.invoke(Method.java:521)
03-29 23:46:17.584: E/AndroidRuntime(474): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
03-29 23:46:17.584: E/AndroidRuntime(474): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
03-29 23:46:17.584: E/AndroidRuntime(474): at dalvik.system.NativeStart.main(Native Method)
03-29 23:46:17.584: E/AndroidRuntime(474): Caused by: java.lang.NullPointerException
03-29 23:46:17.584: E/AndroidRuntime(474): at android.widget.TabHost.addTab(TabHost.java:209)
03-29 23:46:17.584: E/AndroidRuntime(474): at com.vegetable.VendorActivity.onCreate(VendorActivity.java:50)
03-29 23:46:17.584: E/AndroidRuntime(474): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-29 23:46:17.584: E/AndroidRuntime(474): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
03-29 23:46:17.584: E/AndroidRuntime(474): ... 11 more