FragmentManager IllegalStateException：没有主机

Question

更新： 当我把nullcheks（片段！= null，getActivity（）！= null）放进去的时候，崩溃就消失了。

我的应用正在使用 ViewPager （屏幕外限制5），并使用 getSupportFragmentManager（）初始化 FragmentStatePagerAdapter 。每个页面都有自己的片段和后台堆栈。

应用程序在启动时崩溃。问题仅出现在 preLollipop 设备和模拟器上。使用最新的支持lbrary（试过24.0.0也 - 同样的结果） 堆栈跟踪：

  

java.lang.IllegalStateException：没有主持人   android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1273）                                                                              在   android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1268）                                                                              在   android.support.v4.app.FragmentManagerImpl.dispatchCreate（FragmentManager.java:2138）                                                                              在android.support.v4.app.Fragment.onCreate（Fragment.java:1254）                                                                              在android.support.v4.app.Fragment.performCreate（Fragment.java:2062）                                                                              在   android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1051）                                                                              在   android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1286）                                                                              在   android.support.v4.app.BackStackRecord.run（BackStackRecord.java:758）                                                                              在   android.support.v4.app.FragmentManagerImpl.execSingleAction（FragmentManager.java:1632）                                                                              在   android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss（BackStackRecord.java:637）                                                                              在   android.support.v4.app.FragmentStatePagerAdapter.finishUpdate（FragmentStatePagerAdapter.java:166）                                                                              在android.support.v4.view.ViewPager.populate（ViewPager.java:1237）                                                                              在android.support.v4.view.ViewPager.populate（ViewPager.java:1085）                                                                              在android.support.v4.view.ViewPager.onMeasure（ViewPager.java:1611）                                                                              在android.view.View.measure（View.java:16497）                                                                              在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5125）                                                                              在   android.widget.LinearLayout.measureChildBeforeLayout（LinearLayout.java:1404）                                                                              在android.widget.LinearLayout.measureVertical（LinearLayout.java:695）                                                                              在android.widget.LinearLayout.onMeasure（LinearLayout.java:588）                                                                              在android.view.View.measure（View.java:16497）                                                                              在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5125）                                                                              在android.widget.FrameLayout.onMeasure（FrameLayout.java:310）                                                                              在android.view.View.measure（View.java:16497）                                                                              在   android.widget.RelativeLayout.measureChildHorizo​​ntal（RelativeLayout.java:719）                                                                              在android.widget.RelativeLayout.onMeasure（RelativeLayout.java:455）                                                                              在android.view.View.measure（View.java:16497）                                                                              在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5125）                                                                              在android.widget.FrameLayout.onMeasure（FrameLayout.java:310）                                                                              在   android.support.v7.widget.ContentFrameLayout.onMeasure（ContentFrameLayout.java:135）                                                                              在android.view.View.measure（View.java:16497）                                                                              在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5125）                                                                              在android.widget.FrameLayout.onMeasure（FrameLayout.java:310）                                                                              在android.view.View.measure（View.java:16497）                                                                              在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5125）                                                                              在android.widget.FrameLayout.onMeasure（FrameLayout.java:310）                                                                              在android.view.View.measure（View.java:16497）                                                                              在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5125）                                                                              在   android.widget.LinearLayout.measureChildBeforeLayout（LinearLayout.java:1404）                                                                              在android.widget.LinearLayout.measureVertical（LinearLayout.java:695）                                                                              在android.widget.LinearLayout.onMeasure（LinearLayout.java:588）                                                                              在android.view.View.measure（View.java:16497）                                                                              在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5125）                                                                              在android.widget.FrameLayout.onMeasure（FrameLayout.java:310）                                                                              在   com.android.internal.policy.impl.PhoneWindow $ DecorView.onMeasure（PhoneWindow.java:2291）                                                                              在android.view.View.measure（View.java:16497）                                                                              在android.view.ViewRootImpl.performMeasure（ViewRootImpl.java:1912）                                                                              在android.view.ViewRootImpl.measureHierarchy（ViewRootImpl.java:1109）                                                                              在android.view.ViewRootImpl.performTraversals（ViewRootImpl.java:1291）                                                                              在android.view.ViewRootImpl.doTraversal（ViewRootImpl.java:996）                                                                              在   android.view.ViewRootImpl $ TraversalRunnable.run（ViewRootImpl.java:5600）                                                                              在   android.view.Choreographer $ CallbackRecord.run（Choreographer.java:761）                                                                              在android.view.Choreographer.doCallbacks（Choreographer.java:574）                                                                              在android.view.Choreographer.doFrame（Choreographer.java:544）                                                                              在   android.view.Choreographer $ FrameDisplayEventReceiver.run（Choreographer.java:747）                                                                              在android.os.Handler.handleCallback（Handler.java:733）                                                                              在android.os.Handler.dispatchMessage（Handler.java:95）                                                                              在android.os.Looper.loop（Looper.java:136）

Answer 1

如果你有嵌套的Fragment（扩展FragmentActivity），那么使用getChildFragmentManager（）而不是getFragmentManager（）。

可能会帮助你..

Answer 2

就我而言，我在使用viewpager inside fragment并在设置viewpager适配器时使用getChildFragmentManager()。我猜也建议使用它。

还有一个问题，java.lang.IllegalStateException: No host异常没有每次都显示但是当我在设置viewpager.setCurrentItem(POSITION);之前调用包含Activity的viewpager方法或从另一个Activity类返回时，它常常显示p>

我尝试了多种方式，最后我将getChildFragmentManager()更改为getActivity().getSupportFragmentManager();

更改后，java.lang.IllegalStateException: No host异常不再显示。

我认为它与包含viewpager的活动状态问题有关。

Answer 3

使用viewPager时，请确保遵循这些做法

1. 在构造函数中调用super（fragmentManager）
2. 如果您在片段中使用Viewpager，请将getChildFragmentManager传递给适配器