那些遇到过的问题

java.lang.IllegalStateException:无法在onSaveInstanceState之后执行此操作

sam*_*amo 131 android exception android-asynctask illegalstateexception android-fragments

我正在为我的应用程序使用支持库.在我的FragmentActivity中,我使用AsyncTask从Internet下载数据.在onPreExecute()方法中我添加了一个Fragment,在onPostExecute()方法中我再次删除它.当两者之间的方向发生变化时,我得到了上述异常.请看一下细节:

private class onFriendAddedAsyncTask extends AsyncTask<String, Void, String> {
    DummyFragment dummyFragment; 
    FragmentManager fm;
    FragmentTransaction ft;

@Override
protected void onPreExecute() {
    Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPreExecute");
    dummyFragment = DummyFragment.newInstance();
    fm = getSupportFragmentManager();
    ft = fm.beginTransaction();
    ft.add(dummyFragment, "dummy_fragment");
    ft.commit();
}

@Override
protected void onPostExecute(String result) {
    Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPostExecute");
    ft = fm.beginTransaction();
    ft.remove(dummyFragment);
    ft.commit();
}

@Override
protected String doInBackground(String... name) {
    Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/doInBackground");
    ...
}
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我得到了以下LogCut:

01-05 23:54:19.958: V/MyFragmentActivity(12783): onFriendAddedAsyncTask/onPreExecute
01-05 23:54:19.968: V/DummyFragment(12783): onAttach
01-05 23:54:19.968: V/DummyFragment(12783): onCreate
01-05 23:54:19.968: V/MyFragmentActivity(12783): onFriendAddedAsyncTask/doInBackground
01-05 23:54:19.973: V/DummyFragment(12783): onCreateView
01-05 23:54:19.973: V/DummyFragment(12783): onActivityCreated
01-05 23:54:19.973: V/DummyFragment(12783): onStart
01-05 23:54:19.973: V/DummyFragment(12783): onResume
01-05 23:54:21.933: V/MyFragmentActivity(12783): onSaveInstanceState
01-05 23:54:21.933: V/DummyFragment(12783): onSaveInstanceState
01-05 23:54:21.933: V/MyFragmentActivity(12783): onPause
01-05 23:54:21.933: V/DummyFragment(12783): onPause
01-05 23:54:21.938: V/MyFragmentActivity(12783): onStop
01-05 23:54:21.938: V/DummyFragment(12783): onStop
01-05 23:54:21.938: V/MyFragmentActivity(12783): onDestroy
01-05 23:54:21.938: V/DummyFragment(12783): onDestroyView
01-05 23:54:21.938: V/DummyFragment(12783): onDestroy
01-05 23:54:21.938: V/DummyFragment(12783): onDetach
01-05 23:54:21.978: V/MyFragmentActivity(12783): onCreate
01-05 23:54:21.978: V/DummyFragment(12783): onAttach
01-05 23:54:21.978: V/DummyFragment(12783): onCreate
01-05 23:54:22.263: V/MyFragmentActivity(12783): onStart
01-05 23:54:22.313: V/DummyFragment(12783): onCreateView
01-05 23:54:22.313: V/DummyFragment(12783): onActivityCreated
01-05 23:54:22.313: V/DummyFragment(12783): onStart
01-05 23:54:22.323: V/MyFragmentActivity(12783): onResume
01-05 23:54:22.323: V/MyFragmentActivity(12783): onPostResume
01-05 23:54:22.323: V/MyFragmentActivity(12783): onResumeFragments
01-05 23:54:22.323: V/DummyFragment(12783): onResume
01-05 23:54:27.123: V/MyFragmentActivity(12783): onFriendAddedAsyncTask/onPostExecute
01-05 23:54:27.123: D/AndroidRuntime(12783): Shutting down VM
01-05 23:54:27.123: W/dalvikvm(12783): threadid=1: thread exiting with uncaught exception (group=0x4001d7d0)
01-05 23:54:27.138: E/AndroidRuntime(12783): FATAL EXCEPTION: main
01-05 23:54:27.138: E/AndroidRuntime(12783): java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState
01-05 23:54:27.138: E/AndroidRuntime(12783):    at android.support.v4.app.FragmentManagerImpl.checkStateLoss(FragmentManager.java:1314)
01-05 23:54:27.138: E/AndroidRuntime(12783):    at android.support.v4.app.FragmentManagerImpl.enqueueAction(FragmentManager.java:1325)
01-05 23:54:27.138: E/AndroidRuntime(12783):    at android.support.v4.app.BackStackRecord.commitInternal(BackStackRecord.java:548)
01-05 23:54:27.138: E/AndroidRuntime(12783):    at android.support.v4.app.BackStackRecord.commit(BackStackRecord.java:532)
01-05 23:54:27.138: E/AndroidRuntime(12783):    at com.xyz.dummy.MyFragmentActivity$onFriendAddedAsyncTask.onPostExecute(MyFragmentActivity.java:447)
01-05 23:54:27.138: E/AndroidRuntime(12783):    at com.xyz.dummy.MyFragmentActivity$onFriendAddedAsyncTask.onPostExecute(MyFragmentActivity.java:1)
01-05 23:54:27.138: E/AndroidRuntime(12783):    at android.os.AsyncTask.finish(AsyncTask.java:417)
01-05 23:54:27.138: E/AndroidRuntime(12783):    at android.os.AsyncTask.access$300(AsyncTask.java:127)
01-05 23:54:27.138: E/AndroidRuntime(12783):    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:429)
01-05 23:54:27.138: E/AndroidRuntime(12783):    at android.os.Handler.dispatchMessage(Handler.java:99)
01-05 23:54:27.138: E/AndroidRuntime(12783):    at android.os.Looper.loop(Looper.java:123)
01-05 23:54:27.138: E/AndroidRuntime(12783):    at android.app.ActivityThread.main(ActivityThread.java:4627)
01-05 23:54:27.138: E/AndroidRuntime(12783):    at java.lang.reflect.Method.invokeNative(Native Method)
01-05 23:54:27.138: E/AndroidRuntime(12783):    at java.lang.reflect.Method.invoke(Method.java:521)
01-05 23:54:27.138: E/AndroidRuntime(12783):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)
01-05 23:54:27.138: E/AndroidRuntime(12783):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
01-05 23:54:27.138: E/AndroidRuntime(12783):    at dalvik.system.NativeStart.main(Native Method)
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在关于类似问题的其他线程中,原因似乎是在调用onResume()方法之前调用onPostExecute方法.但是我得到了异常,即使之前调用了onResume().

有人知道什么是错的吗？

活动看起来像这样:

public class MyFragmentActivity extends FragmentActivity implements OnFriendSelectedListener, OnFriendAddedListener, OnFriendOptionSelectedListener, LoaderCallbacks<Cursor> {

@Override
public void onCreate(Bundle savedInstanceState) {
    Log.v("MyFragmentActivity", "onCreate");
    super.onCreate(savedInstanceState);
    setContentView(R.layout.fragment_activity_layout);
    FragmentManager fm = getSupportFragmentManager();
    FragmentTransaction ft = fm.beginTransaction();
    FriendListFragment friendListFragment = (FriendListFragment)fm.findFragmentById(R.id.friend_list_fragment_layout);
    if (friendListFragment == null) {
        friendListFragment = new FriendListFragment(); 
        ft.add(R.id.friend_list_fragment_layout, friendListFragment);
        ft.commit();
        fm.executePendingTransactions();
        startService(new Intent(this, MyIntentService.class));
        getSupportLoaderManager().initLoader(CHECK_EMPTY_DATABASE, null, this);
    }
}

    @Override
public boolean onCreateOptionsMenu(Menu menu) {
    super.onCreateOptionsMenu(menu);
    getMenuInflater().inflate(R.menu.fragment_activity_options_menu, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    super.onOptionsItemSelected(item);
    switch (item.getItemId()) {
    case R.id.add_friend_menu_item:
        AddFriendDialogFragment addFriendDialogFragment = AddFriendDialogFragment.newInstance();
        addFriendDialogFragment.show(getSupportFragmentManager(), "add_friend_dialog_fragment");
        return true;
    default:
        return false;
    }
}

@Override
public void onFriendAdded(String name) {
    name = name.trim();
    if (name.length() > 0) {
        new onFriendAddedAsyncTask().execute(name);
    }
}
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使用commitAllowingStateLoss()时,我得到以下异常:

01-06 14:54:29.548: E/AndroidRuntime(18020): FATAL EXCEPTION: main
01-06 14:54:29.548: E/AndroidRuntime(18020): java.lang.IllegalStateException: Activity has been destroyed
01-06 14:54:29.548: E/AndroidRuntime(18020):    at android.support.v4.app.FragmentManagerImpl.enqueueAction(FragmentManager.java:1329)
01-06 14:54:29.548: E/AndroidRuntime(18020):    at android.support.v4.app.BackStackRecord.commitInternal(BackStackRecord.java:548)
01-06 14:54:29.548: E/AndroidRuntime(18020):    at android.support.v4.app.BackStackRecord.commitAllowingStateLoss(BackStackRecord.java:536)
01-06 14:54:29.548: E/AndroidRuntime(18020):    at com.xyz.dummy.FadiaFragmentActivity$onFriendAddedAsyncTask.onPostExecute(FadiaFragmentActivity.java:461)
01-06 14:54:29.548: E/AndroidRuntime(18020):    at com.xyz.dummy.FadiaFragmentActivity$onFriendAddedAsyncTask.onPostExecute(FadiaFragmentActivity.java:1)
01-06 14:54:29.548: E/AndroidRuntime(18020):    at android.os.AsyncTask.finish(AsyncTask.java:417)
01-06 14:54:29.548: E/AndroidRuntime(18020):    at android.os.AsyncTask.access$300(AsyncTask.java:127)
01-06 14:54:29.548: E/AndroidRuntime(18020):    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:429)
01-06 14:54:29.548: E/AndroidRuntime(18020):    at android.os.Handler.dispatchMessage(Handler.java:99)
01-06 14:54:29.548: E/AndroidRuntime(18020):    at android.os.Looper.loop(Looper.java:123)
01-06 14:54:29.548: E/AndroidRuntime(18020):    at android.app.ActivityThread.main(ActivityThread.java:4627)
01-06 14:54:29.548: E/AndroidRuntime(18020):    at java.lang.reflect.Method.invokeNative(Native Method)
01-06 14:54:29.548: E/AndroidRuntime(18020):    at java.lang.reflect.Method.invoke(Method.java:521)
01-06 14:54:29.548: E/AndroidRuntime(18020):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)
01-06 14:54:29.548: E/AndroidRuntime(18020):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
01-06 14:54:29.548: E/AndroidRuntime(18020):    at dalvik.system.NativeStart.main(Native Method)
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I get the same IllegalStateExeption when I implement the AsynTask as follows, because the findFragmentById() method returns a null pointer.

private class onFriendAddedAsyncTask extends AsyncTask<String, Void, String> {

    protected void onPreExecute() {
        Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPreExecute");
        FragmentManager fm = getSupportFragmentManager();
        FragmentTransaction ft = fm.beginTransaction();
        DummyFragment dummyFragment = DummyFragment.newInstance();
        ft.add(R.id.dummy_fragment_layout, dummyFragment);
        ft.commit();
    }

    protected void onPostExecute(String result) {
        Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPostExecute");
        FragmentManager fm = getSupportFragmentManager();
        FragmentTransaction ft = fm.beginTransaction();
        DummyFragment dummyFragment = (DummyFragment) fm.findFragmentById(R.id.dummy_fragment_layout);
        ft.remove(dummyFragment);
        ft.commitAllowingStateLoss();
    }
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In the next step I use a handler for the adding and removing the DummyFragment. Additionally I've added some more debug output.

private class onFriendAddedAsyncTask extends AsyncTask<String, Void, String> {

    @Override
    protected void onPreExecute() {
        Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPreExecute " + getSupportFragmentManager());
        Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPreExecute " + getSupportFragmentManager().findFragmentById(R.id.dummy_fragment_layout));
        Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPreExecute " + getSupportFragmentManager().findFragmentById(R.id.friend_list_fragment_layout));

        new Handler().post(new Runnable() {
            public void run() {
                Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPreExecute " + getSupportFragmentManager());
                Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPreExecute " + getSupportFragmentManager().findFragmentById(R.id.dummy_fragment_layout));
                Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPreExecute " + getSupportFragmentManager().findFragmentById(R.id.friend_list_fragment_layout));
                FragmentManager fm = getSupportFragmentManager();
                FragmentTransaction ft = fm.beginTransaction();
                DummyFragment dummyFragment = DummyFragment.newInstance();
                ft.add(R.id.dummy_fragment_layout, dummyFragment);
                ft.commit();
            }
        });

    @Override
    protected void onPostExecute(String result) {
        Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPostExecute " + getSupportFragmentManager());
        Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPostExecute " + getSupportFragmentManager().findFragmentById(R.id.dummy_fragment_layout));
        Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPostExecute " + getSupportFragmentManager().findFragmentById(R.id.friend_list_fragment_layout));

        new Handler().post(new Runnable() {
            public void run() {
                Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPostExecute " + getSupportFragmentManager());
                Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPostExecute " + getSupportFragmentManager().findFragmentById(R.id.dummy_fragment_layout));
                Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPostExecute " + getSupportFragmentManager().findFragmentById(R.id.friend_list_fragment_layout));
                FragmentManager fm = getSupportFragmentManager();
                FragmentTransaction ft = fm.beginTransaction();
                DummyFragment dummyFragment = (DummyFragment) fm.findFragmentById(R.id.dummy_fragment_layout);
                ft.remove(dummyFragment);
                ft.commitAllowingStateLoss();
            }
        });
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I get following LogCut:

01-07 19:00:17.273: V/MyFragmentActivity(4124): onFriendAddedAsyncTask/onPreExecute FragmentManager{45e384a8 in MyFragmentActivity{45e38358}}
01-07 19:00:17.273: V/MyFragmentActivity(4124): onFriendAddedAsyncTask/onPreExecute null
01-07 19:00:17.273: V/MyFragmentActivity(4124): onFriendAddedAsyncTask/onPreExecute FriendListFragment{45e38ab0 #0 id=0x7f0a0002}
01-07 19:00:17.283: V/MyFragmentActivity(4124): onFriendAddedAsyncTask/onPreExecute FragmentManager{45e384a8 in MyFragmentActivity{45e38358}}
01-07 19:00:17.288: V/MyFragmentActivity(4124): onFriendAddedAsyncTask/doInBackground
01-07 19:00:17.288: V/MyFragmentActivity(4124): onFriendAddedAsyncTask/onPreExecute null
01-07 19:00:17.288: V/MyFragmentActivity(4124): onFriendAddedAsyncTask/onPreExecute FriendListFragment{45e38ab0 #0 id=0x7f0a0002}
01-07 19:00:17.308: V/DummyFragment(4124): onAttach DummyFragment{45dd7498 #2 id=0x7f0a0004}
01-07 19:00:17.308: V/DummyFragment(4124): onCreate DummyFragment{45dd7498 #2 id=0x7f0a0004}
01-07 19:00:17.308: V/DummyFragment(4124): onCreateView DummyFragment{45dd7498 #2 id=0x7f0a0004}
01-07 19:00:17.308: V/DummyFragment(4124): onActivityCreated DummyFragment{45dd7498 #2 id=0x7f0a0004}
01-07 19:00:17.308: V/DummyFragment(4124): onStart DummyFragment{45dd7498 #2 id=0x7f0a0004}
01-07 19:00:17.313: V/DummyFragment(4124): onResume DummyFragment{45dd7498 #2 id=0x7f0a0004}
01-07 19:00:18.098: V/MyFragmentActivity(4124): onSaveInstanceState DummyFragment{45dd7498 #2 id=0x7f0a0004}
01-07 19:00:18.098: V/DummyFragment(4124): onSaveInstanceState DummyFragment{45dd7498 #2 id=0x7f0a0004}
01-07 19:00:18.098: V/MyFragmentActivity(4124): onPause DummyFragment{45dd7498 #2 id=0x7f0a0004}
01-07 19:00:18.098: V/DummyFragment(4124): onPause DummyFragment{45dd7498 #2 id=0x7f0a0004}
01-07 19:00:18.103: V/MyFragmentActivity(4124): onStop DummyFragment{45dd7498 #2 id=0x7f0a0004}
01-07 19:00:18.103: V/DummyFragment(4124): onStop DummyFragment{45dd7498 #2 id=0x7f0a0004}
01-07 19:00:18.103: V/MyFragmentActivity(4124): onDestroy DummyFragment{45dd7498 #2 id=0x7f0a0004}
01-07 19:00:18.103: V/DummyFragment(4124): onDestroyView DummyFragment{45dd7498 #2 id=0x7f0a0004}
01-07 19:00:18.108: V/DummyFragment(4124): onDestroy DummyFragment{45dd7498 #2 id=0x7f0a0004}
01-07 19:00:18.113: V/DummyFragment(4124): onDetach DummyFragment{45dd7498 #2 id=0x7f0a0004}
01-07 19:00:18.138: V/MyFragmentActivity(4124): onCreate
01-07 19:00:18.138: V/FriendListFragment(4124): FriendListFragment
01-07 19:00:18.138: V/FriendListFragment(4124): onAttach FriendListFragment{45e4a7f8 #0 id=0x7f0a0002}
01-07 19:00:18.138: V/FriendListFragment(4124): onCreate FriendListFragment{45e4a7f8 #0 id=0x7f0a0002}
01-07 19:00:18.148: V/DummyFragment(4124): onAttach DummyFragment{45d7d1a0 #2 id=0x7f0a0004}
01-07 19:00:18.153: V/DummyFragment(4124): onCreate DummyFragment{45d7d1a0 #2 id=0x7f0a0004}
01-07 19:00:18.523: V/MyFragmentActivity(4124): onStart DummyFragment{45d7d1a0 #2 id=0x7f0a0004}
01-07 19:00:18.543: V/FriendListFragment(4124): onActivityCreated FriendListFragment{45e4a7f8 #0 id=0x7f0a0002}
01-07 19:00:18.548: V/DummyFragment(4124): onCreateView DummyFragment{45d7d1a0 #2 id=0x7f0a0004}
01-07 19:00:18.548: V/DummyFragment(4124): onActivityCreated DummyFragment{45d7d1a0 #2 id=0x7f0a0004}
01-07 19:00:18.548: V/FriendListFragment(4124): onLoadFinished FragmentManager{45d8e478 in MyFragmentActivity{45e4a6d8}}
01-07 19:00:18.548: V/FriendListFragment(4124): onLoadFinished FriendListFragment{45e4a7f8 #0 id=0x7f0a0002}
01-07 19:00:18.553: V/DummyFragment(4124): onStart DummyFragment{45d7d1a0 #2 id=0x7f0a0004}
01-07 19:00:18.553: V/FriendListFragment(4124): onLoadFinished FragmentManager{45d8e478 in MyFragmentActivity{45e4a6d8}}
01-07 19:00:18.553: V/FriendListFragment(4124): onLoadFinished FriendListFragment{45e4a7f8 #0 id=0x7f0a0002}
01-07 19:00:18.558: V/MyFragmentActivity(4124): onResume DummyFragment{45d7d1a0 #2 id=0x7f0a0004}
01-07 19:00:18.558: V/MyFragmentActivity(4124): onPostResume DummyFragment{45d7d1a0 #2 id=0x7f0a0004}
01-07 19:00:18.558: V/MyFragmentActivity(4124): onResumeFragments DummyFragment{45d7d1a0 #2 id=0x7f0a0004}
01-07 19:00:18.558: V/FriendListFragment(4124): onResume FriendListFragment{45e4a7f8 #0 id=0x7f0a0002}
01-07 19:00:18.563: V/FriendListFragment(4124): onCreateLoader FriendListFragment{45e4a7f8 #0 id=0x7f0a0002}
01-07 19:00:18.563: V/DummyFragment(4124): onResume DummyFragment{45d7d1a0 #2 id=0x7f0a0004}
01-07 19:00:18.723: V/FriendListFragment(4124): onLoadFinished FragmentManager{45d8e478 in MyFragmentActivity{45e4a6d8}}
01-07 19:00:18.723: V/FriendListFragment(4124): onLoadFinished FriendListFragment{45e4a7f8 #0 id=0x7f0a0002}
01-07 19:00:18.893: V/MyFragmentActivity(4124): onFriendAddedAsyncTask/onPostExecute FragmentManager{45e384a8 in null}}
01-07 19:00:18.893: V/MyFragmentActivity(4124): onFriendAddedAsyncTask/onPostExecute null
01-07 19:00:18.893: V/MyFragmentActivity(4124): onFriendAddedAsyncTask/onPostExecute null
01-07 19:00:18.923: V/MyFragmentActivity(4124): onFriendAddedAsyncTask/onPostExecute FragmentManager{45e384a8 in null}}
01-07 19:00:18.923: V/MyFragmentActivity(4124): onFriendAddedAsyncTask/onPostExecute null
01-07 19:00:18.923: V/MyFragmentActivity(4124): onFriendAddedAsyncTask/onPostExecute null
01-07 19:00:18.928: D/AndroidRuntime(4124): Shutting down VM
01-07 19:00:18.928: W/dalvikvm(4124): threadid=1: thread exiting with uncaught exception (group=0x4001d7d0)
01-07 19:00:18.938: E/AndroidRuntime(4124): FATAL EXCEPTION: main
01-07 19:00:18.938: E/AndroidRuntime(4124): java.lang.IllegalStateException: Activity has been destroyed
01-07 19:00:18.938: E/AndroidRuntime(4124):     at android.support.v4.app.FragmentManagerImpl.enqueueAction(FragmentManager.java:1329)
01-07 19:00:18.938: E/AndroidRuntime(4124):     at android.support.v4.app.BackStackRecord.commitInternal(BackStackRecord.java:548)
01-07 19:00:18.938: E/AndroidRuntime(4124):     at android.support.v4.app.BackStackRecord.commitAllowingStateLoss(BackStackRecord.java:536)
01-07 19:00:18.938: E/AndroidRuntime(4124):     at com.xyz.dummy.MyFragmentActivity$onFriendAddedAsyncTask$2.run(MyFragmentActivity.java:476)
01-07 19:00:18.938: E/AndroidRuntime(4124):     at android.os.Handler.handleCallback(Handler.java:587)
01-07 19:00:18.938: E/AndroidRuntime(4124):     at android.os.Handler.dispatchMessage(Handler.java:92)
01-07 19:00:18.938: E/AndroidRuntime(4124):     at android.os.Looper.loop(Looper.java:123)
01-07 19:00:18.938: E/AndroidRuntime(4124):     at android.app.ActivityThread.main(ActivityThread.java:4627)
01-07 19:00:18.938: E/AndroidRuntime(4124):     at java.lang.reflect.Method.invokeNative(Native Method)
01-07 19:00:18.938: E/AndroidRuntime(4124):     at java.lang.reflect.Method.invoke(Method.java:521)
01-07 19:00:18.938: E/AndroidRuntime(4124):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)
01-07 19:00:18.938: E/AndroidRuntime(4124):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
01-07 19:00:18.938: E/AndroidRuntime(4124):     at dalvik.system.NativeStart.main(Native Method)
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In onPreExecute() the FriendListFragment has the id=0x7f0a0002. Inside the handler the DummyFragment is created with id=0x7f0a0004. In onPostExecute() both IDs are null. In onPreExecute() the address of MyFragmentActivity is 45e38358. but in onPostExecute() it's null. But in both methods the FragmentManager address is 45e384a8. I guess onPostExecute uses an invalid FragmentManager. But why?

Ole*_*ich 97

您应该Handler按如下方式进行交易:

@Override
protected void onPostExecute(String result) {
    Log.v("MyFragmentActivity", "onFriendAddedAsyncTask/onPostExecute");
    new Handler().post(new Runnable() {
            public void run() {
                fm = getSupportFragmentManager();
                ft = fm.beginTransaction();
                ft.remove(dummyFragment);
                ft.commit();
            }
        });
}
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  • 对于那些仍在寻找解决方案的人...请参阅[**博客文章**](http://www.androiddesignpatterns.com/2013/08/fragment-transaction-commit-state-loss.html )有关此主题的更多信息. (105认同)
  • 它没有帮助.行为和以前一样. (11认同)
  • 请考虑以下代码:`private static WeakReference <FragmentActivity> mActivity = null;` (3认同)
  • 简而言之,"WeakReference"会阻止您泄漏活动......您需要调用`mActivity.get()`来实际获取实例,如果活动被销毁,它将为null.要更新它,你需要编写`mActivity = new WeakReference <FragmentActivity>(this);` - 一个好的地方在`onCreate()` - 它将更新引用. (2认同)

sam*_*amo 53

谢谢Oleg Vaskevich.使用WeakReference中的FragmentActivity问题解决了.我的代码现在看起来如下:

public class MyFragmentActivity extends FragmentActivity implements OnFriendAddedListener {

    private static WeakReference<MyFragmentActivity> wrActivity = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        wrActivity = new WeakReference<MyFragmentActivity>(this);
        ...

    private class onFriendAddedAsyncTask extends AsyncTask<String, Void, String> {

        @Override
        protected void onPreExecute() {
            FragmentManager fm = getSupportFragmentManager();
            FragmentTransaction ft = fm.beginTransaction();
            DummyFragment dummyFragment = DummyFragment.newInstance();
            ft.add(R.id.dummy_fragment_layout, dummyFragment);
            ft.commit();
        }

        @Override
        protected void onPostExecute(String result) {
            final Activity activity = wrActivity.get();
            if (activity != null && !activity.isFinishing()) {
                FragmentManager fm = activity.getSupportFragmentManager();
                FragmentTransaction ft = fm.beginTransaction();
                DummyFragment dummyFragment = (DummyFragment) fm.findFragmentById(R.id.dummy_fragment_layout);
                ft.remove(dummyFragment);
                ft.commitAllowingStateLoss();
            }
        }
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ale*_*lex 36

我相信这个问题的正确答案是以下方法.

public abstract int commitAllowingStateLoss ()
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与commit()类似,但允许在保存活动状态后执行提交.这很危险,因为如果活动需要稍后从其状态恢复,则提交可能会丢失,因此这应该仅用于UI状态可以在用户上意外更改的情况.

以上描述涉及该方法.

protected void onSaveInstanceState(android.os.Bundle outState)
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当设备进入睡眠状态时,会出现此问题.

http://developer.android.com/reference/android/app/FragmentTransaction.html

Bas*_*ous 24

短而有效的解决方案:

遵循简单步骤:

步骤1:覆盖onSaveInstanceState相应片段中的状态.并从中删除超级方法.

@Override
public void onSaveInstanceState(Bundle outState) {
}
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第2步:使用CommitAllowingStateLoss();而不是commit();片段操作.

fragmentTransaction.commitAllowingStateLoss();
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  • 谢谢.这对我有用,但我知道这不是最好的解决方案. (2认同)
  • 删除超级方法，还会禁用保存片段状态。 (2认同)

Nas*_*kov 10

isFinishing()在显示片段之前检查活动是否存在.

例:

if(!isFinishing()) {
FragmentManager fm = getSupportFragmentManager();
            FragmentTransaction ft = fm.beginTransaction();
            DummyFragment dummyFragment = DummyFragment.newInstance();
            ft.add(R.id.dummy_fragment_layout, dummyFragment);
            ft.commitAllowingStateLoss();
}
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Ale*_*lex 5

我有类似的问题,我固定通过从移动一些片段交易码onResume()成onStart().

更确切地说:我的应用程序是一个启动器.按下Android主页按钮后,用户可以选择启动器,直到他/她的决定被记住.当此时"返回"(例如,通过点击灰色区域)应用程序崩溃.

也许这有助于某人.

Fel*_*idh 5

使用commitAllowingStateLoss()代替 commit()。

当您使用commit()它时，如果发生状态丢失，它会抛出异常，但commitAllowingStateLoss()会在没有状态丢失的情况下保存事务，以便在发生状态丢失时不会抛出异常。

Waj*_*Ali 5

这解决了我的问题：Kotlin 代码：

val fragmentTransaction = activity.supportFragmentManager.beginTransaction()
fragmentTransaction.add(dialogFragment, tag)
fragmentTransaction.commitAllowingStateLoss()
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与 有何commitAllowingStateLoss()不同commit()？

根据文档：

类似commit()，但允许在保存活动状态后执行提交。 https://developer.android.com/reference/android/app/FragmentTransaction#commitAllowingStateLoss()

PS：您可以通过此方法显示片段对话框或加载片段。两者都适用。

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