我在manager.popBackStack的行下面收到此错误。有没有解决的办法?它恰好发生了。
public void updateView(Fragment fragment) {
IFragment currentFragment = (IFragment)fragment;
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = manager.beginTransaction();
fragmentTransaction.replace(R.id.content_frame, fragment);
if(currentFragment != null)
{
if(currentFragment.isRoot())
{
manager.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
}
else
{
fragmentTransaction.addToBackStack("test");
}
}
fragmentTransaction.commitAllowingStateLoss();
if(drawerManager.DrawerLayout != null) {
drawerManager.DrawerLayout.closeDrawer(drawerManager.DrawerList);
}
}
致命异常:java.lang.IllegalStateException:无法在android.support.v4.app.FragmentManagerImpl.enqueueAction(FragmentManager)的android.support.v4.app.FragmentManagerImpl.checkStateLoss(FragmentManager.java:2044)的onSaveInstanceState之后执行此操作。 java:2067)在android.support.v4.app.FragmentManagerImpl.popBackStack(FragmentManager.java:799)的com.exposure.activities.BaseActivity.updateView(BaseActivity.java:239)com.exposure.activities.events.EventActivity .setupEvent(EventActivity.java:204)位于com.exposure下com.exposure.utilities.ActivityContainer.getData(ActivityContainer.java:83)的com.exposure.activities.events.EventActivity.getData(EventActivity.java:117)。在android.os.AsyncTask的android.O.AsyncTask.finish(AsyncTask.java:695)上的utilities.DataTask.onPostExecute(DataTask.java:37)android.os.AsyncTask $ InternalHandler.handleMessage上的android.os.AsyncTask.-wrap1(未知来源) (AsyncTask.java:712)在android.os.Looper.loop上的android.os.Handler.dispatchMessage(Handler.java:105) (Looper.java:164)位于android.app.ActivityThread.main(ActivityThread.java:6938)的java.lang.reflect.Method.invoke(Method.java)位于com.android.internal.os.Zygote $ MethodAndArgsCaller。在com.android.internal.os.ZygoteInit.main上运行(Zygote.java:327)(ZygoteInit.java:1374)
正如Fragment Transactions & Activity State Loss在子弹点“避免在异步回调方法中执行事务”中所解释的那样:
避免在异步回调方法中执行事务。这包括常用的方法,如
AsyncTask#onPostExecute()
和LoaderManager.LoaderCallbacks#onLoadFinished()
。在这些方法中执行事务的问题是,在调用它们时,它们不知道Activity生命周期的当前状态。
这似乎是你从异步任务调用updateView()
时遇到的问题,但让我们测试一下这个假设。
以下演示应用程序创建一个片段,模拟后台处理和模仿异步回调的回调。代码中有一个标志,当设置为true时mFixIt
会使应用程序正常运行(不会爆炸),而当false时,应用程序会失败。
使用mFixIt == false。触发器是主页按钮,导致应用程序进入停止状态:
这是堆栈跟踪:
14967-15003 E/AndroidRuntime: FATAL EXCEPTION: Thread-2
Process: com.example.illegalstatepopbackstack, PID: 14967
java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState
at android.support.v4.app.FragmentManagerImpl.checkStateLoss(FragmentManager.java:2080)
at android.support.v4.app.FragmentManagerImpl.enqueueAction(FragmentManager.java:2106)
at android.support.v4.app.FragmentManagerImpl.popBackStack(FragmentManager.java:832)
at com.example.illegalstatepopbackstack.MainActivity.updateView(MainActivity.java:70)
at com.example.illegalstatepopbackstack.ui.main.MainFragment$1.run(MainFragment.java:63)
at java.lang.Thread.run(Thread.java:764)
现在用mFixIt
== true。这次的不同之处在于,当活动处于停止状态时,应用会识别异步回调,记录已发生这种情况,并在重新启动应用时完成处理。视觉效果只是按下主页按钮并从“最近”恢复。应用程序只是在开始时放置片段,重新启动时更改顶部TextView
文本并从backstack弹出片段。
可以看出,处理按预期完成。
这是一个微不足道的例子。如果您的处理涉及更多,或者您只是想要一种更正式的方式来处理这种情况,我建议您查看this solution。
以下是演示应用的代码:
main activity.Java
public class MainActivity extends AppCompatActivity {
// Set to true to fix the problem; false will cause the IllegalStateException
private boolean mFixIt = false;
private MainFragment mFragment;
private TextView mTextView;
private boolean mIsPaused;
private boolean mUpdateViewNeeded;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_activity);
mTextView = findViewById(R.id.textView);
FragmentManager fm = getSupportFragmentManager();
if (savedInstanceState == null) {
// Create out fragment
mFragment = MainFragment.newInstance();
fm.beginTransaction()
.replace(R.id.container, mFragment)
.addToBackStack(FRAGMENT_TAG)
.commit();
} else {
// Find the restored fragment.
mFragment = (MainFragment) fm.findFragmentByTag(FRAGMENT_TAG);
}
}
@Override
protected void onStop() {
super.onStop();
// Simulate a background task that does something useful. This one just waits a few
// second then does a callback to updateView(). The activity will be fully paused by then.
mFragment.doSomethingInBackground();
mIsPaused = true;
Log.d("MainActivity","<<<< stopped");
}
@Override
protected void onStart() {
super.onStart();
mIsPaused = false;
if (mUpdateViewNeeded) {
// Execute delayed processing now that the activity is resumed.
updateView(getSupportFragmentManager().findFragmentByTag(FRAGMENT_TAG));
}
}
public void updateView(Fragment fragment) {
if (mIsPaused && mFixIt) {
// Delay processing
mUpdateViewNeeded = true;
} else {
// Do out update work. If we are paused, this will get an IllegalStateException. If
// we are resumed, this will work as intended.
mTextView.setText("Replaced...");
getSupportFragmentManager().popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
mUpdateViewNeeded = false;
}
}
public static final String FRAGMENT_TAG = "MyFragment";
}
main fragment.Java
public class MainFragment extends Fragment {
MainActivity mMainActivity;
public static MainFragment newInstance() {
return new MainFragment();
}
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
@Nullable Bundle savedInstanceState) {
return inflater.inflate(R.layout.main_fragment, container, false);
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
mMainActivity = (MainActivity) context;
}
@Override
public void onDetach() {
super.onDetach();
mMainActivity = null;
}
@Override
public void onStart() {
super.onStart();
}
public void doSomethingInBackground() {
new Thread(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
if (mMainActivity != null) {
mMainActivity.updateView(MainFragment.this);
}
}
}).start();
}
}
main_activity.xml
<TextView
android:id="@+id/textView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@android:color/holo_blue_light"
android:gravity="center"
android:text="To be replaced..."
android:textSize="36sp"
android:textStyle="bold" />
<FrameLayout
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" />
main_fragment.xml
<android.support.constraint.ConstraintLayout
android:id="@+id/main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/holo_green_light"
tools:context=".ui.main.MainFragment">
<TextView
android:id="@+id/message"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="MainFragment"
android:textSize="36sp"
android:textStyle="bold"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>
只需调用popBackStackImmediate(),因为常规popBackStack()是异步的...
问题基本上是:
IllegalStateException:无法在onSaveInstanceState之后执行此操作。
因此,请查看!isFinishing() && !isDestroyed()
中的.updateView()
因为这会在true
上返回onSaveInstanceState()
...
同样,这种情况可以减轻,防止崩溃。