在 setUserVisibleHint() 上调试时启动应用程序崩溃

Question

如果我正常运行该应用程序，它会正常工作，当我在setUserVisibleHint()中的 if 语句上放置断点时，它会崩溃并出现异常：java.lang.IllegalStateException: No activity.

那么问题出在哪里呢？

public class MyFragment extends Fragment 

public MyFragment() {
// Required empty public constructor
}
public static CommunityFragment newInstance() {
Bundle args = new Bundle();
MyFragment fragment = new MyFragment();
fragment.setArguments(args);
return fragment;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment     
return inflater.inflate(R.layout.fragment_community, container, false);
}

@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
if (getActivity() != null && isVisibleToUser) {
// fragment is visible
}
} else if (getActivity() != null) {
// fragment is invisible
}
}
} 
}

日志猫：

E/AndroidRuntime: FATAL EXCEPTION: main
    PID: 8669
   java.lang.IllegalStateException: No activity
       at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1578)
       at android.support.v4.app.FragmentManagerImpl.dispatchCreate(FragmentManager.java:2883)
       at android.support.v4.app.Fragment.onCreate(Fragment.java:1268)
       at android.support.v4.app.Fragment.performCreate(Fragment.java:2177)
       at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1244)
       at android.support.v4.app.FragmentTransition.addToFirstInLastOut(FragmentTransition.java:1080)
       at android.support.v4.app.FragmentTransition.calculateFragments(FragmentTransition.java:971)
       at android.support.v4.app.FragmentTransition.startTransitions(FragmentTransition.java:95)
       at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2143)
       at android.support.v4.app.FragmentManagerImpl.optimizeAndExecuteOps(FragmentManager.java:2098)
       at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:1979)
       at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:626)
       at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:143)
       at android.support.v4.view.ViewPager.populate(ViewPager.java:1268)
       at android.support.v4.view.ViewPager.populate(ViewPager.java:1116)
       at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1642)
       at android.view.View.measure(View.java:18788)
       at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
       at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:714)
       at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:786)
       at android.view.View.measure(View.java:18788)
       at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:715)
       at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:461)
       at android.view.View.measure(View.java:18788)
       at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
       at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
       at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:139)
       at android.view.View.measure(View.java:18788)
       at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
       at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
       at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
       at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
       at android.view.View.measure(View.java:18788)
       at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
       at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
       at android.view.View.measure(View.java:18788)
       at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
       at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
       at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
       at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
       at android.view.View.measure(View.java:18788)
       at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
       at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
       at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2643)
       at android.view.View.measure(View.java:18788)
       at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2100)
       at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1216)
       at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1452)
       at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1107)
       at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6013)
       at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
       at android.view.Choreographer.doCallbacks(Choreographer.java:670)
       at android.view.Choreographer.doFrame(Choreographer.java:606)
       at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
      at android

Answer 1

而不是

if (getActivity() != null && isVisibleToUser) {
// fragment is visible
}
} else if (getActivity() != null) {
// fragment is invisible
}

尝试使用

if (getView() != null) {
// fragment is visible
}

它对我有用。