我在项目中遇到此错误，我无法理解问题，我所知道的只是它是NPE，但我在崩溃日志中看不到任何Java文件。
我到处都在搜索这种错误，但是我找不到具体的解决方案。
请有人帮我解决这个错误。
我正在下面的logcat中发布崩溃日志。
Crashed: main
at android.view.ViewGroup.removeViewInternal(ViewGroup.java:5270)
at android.view.ViewGroup.removeViewAt(ViewGroup.java:5233)
at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1771)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1827)
at android.support.v4.app.FragmentManagerImpl.dispatchStateChange(FragmentManager.java:3244)
at android.support.v4.app.FragmentManagerImpl.dispatchPause(FragmentManager.java:3216)
at android.support.v4.app.Fragment.performPause(Fragment.java:2527)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1485)
at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1759)
at android.support.v4.app.BackStackRecord.executePopOps(BackStackRecord.java:851)
at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2593)
at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2383)
at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2338)
at android.support.v4.app.FragmentManagerImpl.popBackStackImmediate(FragmentManager.java:854)
at android.support.v4.app.FragmentManagerImpl.popBackStackImmediate(FragmentManager.java:797)
at ca.dataready.smartparent.HomeActivity.onBackPressed(HomeActivity.java:724)
at android.app.Activity.onKeyUp(Activity.java:3150)
at android.view.KeyEvent.dispatch(KeyEvent.java:2779)
at android.app.Activity.dispatchKeyEvent(Activity.java:3481)
at android.support.v7.app.AppCompatActivity.dispatchKeyEvent(AppCompatActivity.java:534)
at android.support.v7.view.WindowCallbackWrapper.dispatchKeyEvent(WindowCallbackWrapper.java:58)
at android.support.v7.app.AppCompatDelegateImplBase$AppCompatWindowCallbackBase.dispatchKeyEvent(AppCompatDelegateImplBase.java:316)
at android.support.v7.view.WindowCallbackWrapper.dispatchKeyEvent(WindowCallbackWrapper.java:58)
at com.android.internal.policy.DecorView.dispatchKeyEvent(DecorView.java:415)
at android.view.ViewRootImpl$ViewPostImeInputStage.processKeyEvent(ViewRootImpl.java:5191)
at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:5063)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4581)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4634)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4600)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4727)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4608)
at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:4784)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4581)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4634)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4600)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4608)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4581)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4634)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4600)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4760)
at android.view.ViewRootImpl$ImeInputStage.onFinishedInputEvent(ViewRootImpl.java:4921)
at android.view.inputmethod.InputMethodManager$PendingEvent.run(InputMethodManager.java:2599)
at android.view.inputmethod.InputMethodManager.invokeFinishedInputEventCallback(InputMethodManager.java:2160)
at android.view.inputmethod.InputMethodManager.finishedInputEvent(InputMethodManager.java:2151)
at android.view.inputmethod.InputMethodManager$ImeInputEventSender.onInputEventFinished(InputMethodManager.java:2574)
at
android.view.InputEventSender.dispatchInputEventFinished(InputEventSender.java:141)
at android.os.MessageQueue.nativePollOnce(MessageQueue.java)
at android.os.MessageQueue.next(MessageQueue.java:379)
at android.os.Looper.loop(Looper.java:144)
at android.app.ActivityThread.main(ActivityThread.java:7425)
at java.lang.reflect.Method.invoke(Method.java)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:245)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:921)
编辑-
我已经查看了崩溃日志，发现它正在onBackpressed中发生
这是代码
@Override
public void onBackPressed() {
FragmentManager fm = getSupportFragmentManager();
if (drawerLayout.isDrawerOpen(GravityCompat.START)) {
drawerLayout.closeDrawer(GravityCompat.START);
} else if (fm.getBackStackEntryCount() > 0) {
Log.i("MainActivity", "popping backstack");
getSupportFragmentManager().popBackStackImmediate();
} else {
Log.i("MainActivity", "nothing on backstack, calling super");
super.onBackPressed();
}
}
答案 0 :(得分：0)
我认为您不见了，尝试尝试更改
@Override
public void onBackPressed() {
Fragment fragment = null;
if(view == findViewById(R.id.YOURID)){
fragment = new SOMEFragmentOne();
} else {
fragment = new SOMEFragmentTwo();
}
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction transaction = fm.beginTransaction();
transaction.replace(R.id.output, fragment);
transaction.commit();
if (drawerLayout.isDrawerOpen(GravityCompat.START)) {
drawerLayout.closeDrawer(GravityCompat.START);
} else if (fm.getBackStackEntryCount() > 0) {
Log.i("MainActivity", "popping backstack");
getSupportFragmentManager().popBackStackImmediate();
} else {
Log.i("MainActivity", "nothing on backstack, calling super");
super.onBackPressed();
}
}
SOMEFragmentOne 和 SOMEFragmentTwo 是扩展Fragment的两个类。