Android片段和方向更改导致:IllegalStateException:在onSaveInstanceState之后无法执行此操作

Question

每当我加载片段的主要活动并且用户启动新活动,切换设备的方向并返回主活动时,我就会收到此错误.

@Override
public void onCreate(Bundle savedInstanceState) {
    setContentView(R.layout.home_layout);
    super.onCreate(savedInstanceState);
    fragmentManager = getSupportFragmentManager();
    fragment = fragmentManager.findFragmentById(R.id.layFragment);

    initialize();
}

@Override
public void onConfigurationChanged(Configuration newConfig) {
    setContentView(R.layout.home_layout);
    initialize();
    super.onConfigurationChanged(newConfig);
}

private void initialize() {
    layStatus = (LinearLayout) findViewById(R.id.layStatus);
    txtStatus = (TextView) findViewById(R.id.txtStatus);
    ....
    handleFragments(lastFragmentId);
}

public void handleFragments(int fragmentId) {
        if (fragment == null) {
            FragmentTransaction ft = fragmentManager.beginTransaction();
            if (fragmentId==someFragmentId){
                ft.replace(R.id.layFragment, new FragmentSomeFragment());
            }
            else
            ....

            ft.commit();
        }
}

在我的android清单中,活动被声明为:

 <activity
        android:name=".HomeActivity"
        android:configChanges="keyboardHidden|orientation" />
<activity

在另一个关于SO的问题中,我发现这可能是由支持库中的一个错误造成的,我添加没有任何运气:

// needed as a workaround for a bug in the Support library
@Override
protected void onSaveInstanceState(Bundle outState) {
    outState.putString("WORKAROUND_FOR_BUG_19917_KEY", "WORKAROUND_FOR_BUG_19917_VALUE");
    super.onSaveInstanceState(outState);
}

我的应用程序从Android 2.2运行,我正在使用android-support-v4.jar支持库来获取片段.

日志看起来像:

07-27 11:56:20.399: E/AndroidRuntime(16021): FATAL EXCEPTION: main
07-27 11:56:20.399: E/AndroidRuntime(16021): java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState
07-27 11:56:20.399: E/AndroidRuntime(16021):    at android.support.v4.app.FragmentManagerImpl.checkStateLoss(FragmentManager.java:1299)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at android.support.v4.app.FragmentManagerImpl.enqueueAction(FragmentManager.java:1310)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at android.support.v4.app.BackStackRecord.commitInternal(BackStackRecord.java:541)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at android.support.v4.app.BackStackRecord.commit(BackStackRecord.java:525)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at com.rightcab.driver.core.HomeActivity.handleFragments(HomeActivity.java:341)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at com.rightcab.driver.core.HomeActivity.initialize(HomeActivity.java:128)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at com.rightcab.driver.core.HomeActivity.onConfigurationChanged(HomeActivity.java:153)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at android.app.ActivityThread.performConfigurationChanged(ActivityThread.java:3618)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at android.app.ActivityThread.handleActivityConfigurationChanged(ActivityThread.java:3771)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1328)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at android.os.Handler.dispatchMessage(Handler.java:99)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at android.os.Looper.loop(Looper.java:137)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at android.app.ActivityThread.main(ActivityThread.java:4745)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at java.lang.reflect.Method.invokeNative(Native Method)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at java.lang.reflect.Method.invoke(Method.java:511)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
07-27 11:56:20.399: E/AndroidRuntime(16021):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

首先,正如我所看到的,您希望自己处理配置更改.为了让事情与API等级13+正常工作,你有一个更大的价值添加到configChanges参数,如所描述这里.

接下来,当用户离开你的主要活动,onSaveInstanceState以及onPause方法被调用它.当用户旋转设备并返回主要活动时.onConfigurationChanged方法之前 被调用onResume().因此,您的活动仍然暂停,您无法执行FragmentTransaction.

此外,如果我们看一下源代码,我们可以看到以下onResume方法注释:

将onResume()发送到片段.请注意,为了更好地与平台的旧版本进行互操作,在此调用时,不会 恢复附加到活动的片段.这意味着在某些情况下,仍可以保存先前的状态,不允许修改状态的片段事务.要正确地与处于正确状态的片段进行交互,您应该覆盖{@link #onResumeFragments()}.

因此,在您的活动中操作片段的正确位置是重写onResumeFragments方法,因为我们可以在源代码中阅读此方法的注释:

这是{@link #onResume()}的片段定向版本,您可以覆盖它以在其片段恢复的同一点执行Activity中的操作.一定要经常打电话给超级班级.

protected void onResumeFragments() {
    super.onResumeFragments();

    // YOUR STUFF IS HERE
}

Answer 2

如果StenaviN建议onConfigurationChange()在resume()返回您的活动之前返回:

这是生命周期:

onCreate()
onResume()
// Move away from you're Activity
onPause()
// Move back to your Activity
onConfigurationChange()
onResume()

但重要的是这个:

如果恢复的Activity还是你改变Orientation的Activity你Fragments将被罚款!你不需要用新副本替换旧的副本,事实上你不应该!如果您只是删除此行,则不会出现问题:

handleFragments(lastFragmentId);

但是,如果您这样做是因为您需要Fragment加载新的布局资源(layout/frag.xml=> layout-land/frag.xml),那么您将需要执行以下操作:

boolean mResumed = false;
onPause() {
    mResumed = false;
}

onResume() {
    mResumed = true;
} 

...

    if(mResumed) handleFragments(lastFragmentId);