FragmentManager IllegalStateException: No host

Question

UPDATE: Crashes gone when i put nullcheks (fragment != null, getActivity() != null) whereever i could.

My app is using ViewPager (offscreen limit 5) with FragmentStatePagerAdapter initialized with getSupportFragmentManager(). Each page has it's own fragments and backstack.

App crashes on startup. Problem occurs only on preLollipop devices and emulator. Using latest support lbrary (tried 24.0.0 also - same result) Stacktrace:

java.lang.IllegalStateException: No host at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1273) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1268) at android.support.v4.app.FragmentManagerImpl.dispatchCreate(FragmentManager.java:2138) at android.support.v4.app.Fragment.onCreate(Fragment.java:1254) at android.support.v4.app.Fragment.performCreate(Fragment.java:2062) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1051) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1286) at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:758) at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:1632) at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:637) at android.support.v4.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:166) at android.support.v4.view.ViewPager.populate(ViewPager.java:1237) at android.support.v4.view.ViewPager.populate(ViewPager.java:1085) at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1611) at android.view.View.measure(View.java:16497) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404) at android.widget.LinearLayout.measureVertical(LinearLayout.java:695) at android.widget.LinearLayout.onMeasure(LinearLayout.java:588) at android.view.View.measure(View.java:16497) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) at android.view.View.measure(View.java:16497) at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:719) at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:455) at android.view.View.measure(View.java:16497) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135) at android.view.View.measure(View.java:16497) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) at android.view.View.measure(View.java:16497) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) at android.view.View.measure(View.java:16497) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404) at android.widget.LinearLayout.measureVertical(LinearLayout.java:695) at android.widget.LinearLayout.onMeasure(LinearLayout.java:588) at android.view.View.measure(View.java:16497) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2291) at android.view.View.measure(View.java:16497) at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1912) at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1109) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1291) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:996) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5600) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761) at android.view.Choreographer.doCallbacks(Choreographer.java:574) at android.view.Choreographer.doFrame(Choreographer.java:544) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747) at android.os.Handler.handleCallback(Handler.java:733) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:136)

Answer 1

If you have nested Fragment (extends FragmentActivity), then use getChildFragmentManager() instead of getFragmentManager().

may be it will help you ..

Answer 2

In my case, I am using viewpager inside fragment and was using getChildFragmentManager() while setting viewpager adapter. It is also recommended to use this I guess.

There is also an issue, java.lang.IllegalStateException: No host exception was not showing everytime but it was showing too often when I called a method of viewpager containing Activity or coming back from another Activity class before setting viewpager.setCurrentItem(POSITION);

I tried in many ways and finally I changed getChildFragmentManager() to getActivity().getSupportFragmentManager();

After changing this java.lang.IllegalStateException: No host exception is not showing any more.

I think its related to Activity state issue which contains viewpager.