android - 为什么每次启动使用支持 fragment 的 Activity 时都会出现 IllegalStateException？

Question

我使用 Android 支持库在 Honeycomb 之前的应用程序中使用 fragment 。

如果我在 Activity 的 onCreate 方法中添加一个 fragment ，Activity 就会因 IllegalStateException 而崩溃。

08-04 10:19:49.100: ERROR/AndroidRuntime(18501): FATAL EXCEPTION: main  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501): java.lang.RuntimeException: Unable to start activity ComponentInfo{net..../net.....homescreen...Main}: java.lang.IllegalStateException: Activity has been destroyed  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at android.app.ActivityThread.access$1500(ActivityThread.java:117)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at android.os.Handler.dispatchMessage(Handler.java:99)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at android.os.Looper.loop(Looper.java:123)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at android.app.ActivityThread.main(ActivityThread.java:3691)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at java.lang.reflect.Method.invokeNative(Native Method)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at java.lang.reflect.Method.invoke(Method.java:507)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:847)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at dalvik.system.NativeStart.main(Native Method)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501): Caused by: java.lang.IllegalStateException: Activity has been destroyed  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at android.support.v4.app.FragmentManagerImpl.enqueueAction(FragmentManager.java:1257)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at android.support.v4.app.BackStackRecord.commitInternal(BackStackRecord.java:535)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at android.support.v4.app.BackStackRecord.commit(BackStackRecord.java:519)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at net.....AbstractActivity.onCreate(AbstractActivity.java:103)   
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at net.....homescreen...Main.onCreate(..Main.java:51)   
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)  
08-04 10:19:49.100: ERROR/AndroidRuntime(18501):     ... 11 more  

AbstractActivity 的 onCreate 看起来像这样:

protected void onCreate(Bundle savedInstanceState) {
    if (menuEnabled) {
        FragmentManager fragmentManager = getCompatibleFragmentManager();
        FragmentTransaction transaction = fragmentManager
                .beginTransaction();
        transaction.add(new OptionsMenuFragment(), OPTIONS_MENU_IDENTIFIER);
        transaction.commit();
    }
    super.onCreate(savedInstanceState);
}

如果我调试调用，我会看到 fragmentmanager 抛出此异常，因为 Activity 为空。似乎 fragmentmanager 根本没有初始化。

我做错了什么？

Answer 1

事实证明，兼容包中的 FragmentActivity 在 onCreate 方法本身中初始化 fragment 管理器。

如果我将对 super 的调用移至 onCreate 方法的开头，一切正常。