问题记录：java.lang.IllegalStateException: Fragment has not been attached yet.

java.lang.IllegalStateException: Fragment has not been attached yet.
        at android.support.v4.app.Fragment.instantiateChildFragmentManager(Fragment.java:2383)
        at android.support.v4.app.Fragment.getChildFragmentManager(Fragment.java:845)
        at com.zxycloud.zxwl.fragment.service.patrol.task.TaskDetailsFragment.onHiddenChanged(TaskDetailsFragment.java:175)
        at android.support.v4.app.FragmentManagerImpl.completeShowHideFragment(FragmentManager.java:1763)
        at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1822)
        at android.support.v4.app.BackStackRecord.executePopOps(BackStackRecord.java:856)
        at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2622)
        at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2411)
        at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2366)
        at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2273)
        at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:733)
        at android.os.Handler.handleCallback(Handler.java:888)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:213)
        at android.app.ActivityThread.main(ActivityThread.java:8147)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1101)

问题原因：快速切换fragment，重复调用getChildFragmentManager
解决方式：添加isAdd()做为判断条件