android - 删除 fragment 时崩溃

Question

我在平板电脑上崩溃了，这对我来说很奇怪:

java.lang.NullPointerException: Attempt to read from field 'int android.support.v4.app.Fragment.mContainerId' on a null object reference                                                                          
   at android.support.v4.app.FragmentTransition.addToFirstInLastOut(FragmentTransition.java:1012)                                                                          
   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.execPendingActions(FragmentManager.java:2008)                                                                          
   at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:710)                                                                          
   at android.os.Handler.handleCallback(Handler.java:751)                                                                          
   at android.os.Handler.dispatchMessage(Handler.java:95)                                                                          
   at android.os.Looper.loop(Looper.java:154)                                                                          
   at android.app.ActivityThread.main(ActivityThread.java:6077)                                                                          
   at java.lang.reflect.Method.invoke(Native Method)                                                                          
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)                                                                          
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)

它只发生在我的 api 24 Pixel C 上。 Debug模式无法帮助我找出位置。当我点击一个删除 fragment 的按钮时，它发生了，但是代码的“fragment 删除”部分得到了正确执行，在我的 OnClickListener 执行之后发生了一些事情。

我删除了交易动画并遇到了同样的崩溃。

以前有人经历过吗？

谢谢

Answer 1

似乎解决方案不是保留 fragment 的引用而是使用标签找到它:

之前:

FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
courseLauncherFragment = CourseLauncherFragment.newInstance(courseId);
fragmentTransaction.replace(R.id.launcher_finish_frame_layout, courseLauncherFragment);
fragmentTransaction.commit();
getSupportFragmentManager().executePendingTransactions();

然后删除它:

FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.setCustomAnimations(R.anim.slide_in_left, R.anim.slide_out_left);
fragmentTransaction.remove(courseLauncherFragment);
fragmentTransaction.commit();

现在:

FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.launcher_finish_frame_layout, CourseLauncherFragment.newInstance(courseId), LAUNCHER_FRAGMENT_TAG);
fragmentTransaction.commit();
getSupportFragmentManager().executePendingTransactions();

然后:

FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.setCustomAnimations(R.anim.slide_in_left, R.anim.slide_out_left);
Fragment fragment = fragmentManager.findFragmentByTag(LAUNCHER_FRAGMENT_TAG);
fragmentTransaction.remove(fragment);
fragmentTransaction.commit();