android - FragmentManager 在使用方法 setOffscreenPageLimit() 后已经在执行事务

Question

我有一个带有多个 fragment 的抽屉导航，其中一个是带有两个 recyclerview fragment 的 tablayout，在抽屉导航 fragment 之间切换后 RecyclerView 项目消失，我找到了一个解决方案，我需要使用方法 setOffscreenPageLimit() ViewPager 但它给了我问题标题中提到的错误

这是我的日志

java.lang.IllegalStateException: FragmentManager is already executing transactions
                                                                               at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:1626)
                                                                               at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:679)
                                                                               at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:143)
                                                                               at android.support.v4.view.ViewPager.populate(ViewPager.java:1240)
                                                                               at android.support.v4.view.ViewPager.populate(ViewPager.java:1088)
                                                                               at android.support.v4.view.ViewPager.setOffscreenPageLimit(ViewPager.java:852)
                                                                               at com.amir.ahmed.EELUStudentUnion.SelectionFragment.setupViewPager(SelectionFragment.java:59)
                                                                               at com.amir.ahmed.EELUStudentUnion.SelectionFragment.onActivityCreated(SelectionFragment.java:40)
                                                                               at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:2089)
                                                                               at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1133)
                                                                               at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1290)
                                                                               at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:801)
                                                                               at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1677)
                                                                               at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:536)
                                                                               at android.os.Handler.handleCallback(Handler.java:739)
                                                                               at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                               at android.os.Looper.loop(Looper.java:158)
                                                                               at android.app.ActivityThread.main(ActivityThread.java:7225)
                                                                               at java.lang.reflect.Method.invoke(Native Method)
                                                                               at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
                                                                               at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)

标签布局 fragment 代码

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    viewPager = (ViewPager) getActivity().findViewById(R.id.viewpager);
    setupViewPager(viewPager);

    viewPager.setOffscreenPageLimit(2);

    tabLayout = (TabLayout) getActivity().findViewById(R.id.tabs);
    tabLayout.setupWithViewPager(viewPager);
    setupTabIcons();
}



private void setupViewPager(ViewPager viewPager) {
    ViewPagerAdapter adapter = new ViewPagerAdapter(getFragmentManager());
    adapter.addFrag(new Courses(), "IT");
    adapter.addFrag(new CoursesBussiness(), "Business");
    viewPager.setAdapter(adapter);
}

Answer 1

我遇到了和你类似的问题，经过几个小时的研究，我发现了这个问题。如果您的 ViewPager 是在 Fragment 内部创建的，则需要为 FragmentPagerAdapter 使用 getChildFragmentManager()，而不是 getFragmentManager()。

因此您的 setupViewPager() 方法应如下所示。

private void setupViewPager(ViewPager viewPager) {
    ViewPagerAdapter adapter = new ViewPagerAdapter(getChildFragmentManager());
    adapter.addFrag(new Courses(), "IT");
    adapter.addFrag(new CoursesBussiness(), "Business");
    viewPager.setAdapter(adapter);
}

问题的根本原因是你在 fragment 中嵌入了 fragment ，这就是它会抛出异常的原因。

java.lang.IllegalStateException: FragmentManager is already executing transactions

根据 Google 的文档:

You can now embed fragments inside fragments. This is useful for a variety of situations in which you want to place dynamic and re-usable UI components into a UI component that is itself dynamic and re-usable. For example, if you use ViewPager to create fragments that swipe left and right and consume a majority of the screen space, you can now insert fragments into each fragment page. To nest a fragment, simply call getChildFragmentManager() on the Fragment in which you want to add a fragment. This returns a FragmentManager that you can use like you normally do from the top-level activity to create fragment transactions.