android - 在orrientation之后更改对话框片段中的目标片段更改

Question

我有一个片段,它为选项菜单添加了一个选项.单击此选项时,将打开一个对话框片段.该对话框将原始片段设置为其目标片段.如果在对话框片段打开时没有发生方向改变,则目标片段与预期一样,但是在方向改变之后,目标片段被设置为对话框片段本身而不是先前设置的片段.因此,当我尝试将目标片段转换为设置为目标片段的片段时,我得到了一个classCastException.我需要在对话框中获取目标片段,因为它实现了一个回调(OnStartOrRestartLoader).我一直试图解决这个问题超过一个星期,如果有人能指出我正确的方向,我真的很感激.由于这是我的第一个问题,如果我排除了一些必要的信息,或者这不是一个合适的问题,我会道歉.

在实现OnStartOrRestartLoader的片段(VirsārstsFragment)中,我创建了如下对话框:

FragmentManager fm = getChildFragmentManager();
SearchDialogFragment dialog = new SearchDialogFragment();
dialog.show(fm, "searchDialog");
dialog.setTargetFragment(this, DIALOGFRAGMENT);

然后在SearchDialogFragment中,我执行以下操作来设置回调:

OnStartOrRestartLoader callback = (OnStartOrRestartLoader) getTargetFragment();

logcat的:

08-25 12:15:55.087: E/AndroidRuntime(10057): FATAL EXCEPTION: main
08-25 12:15:55.087: E/AndroidRuntime(10057): Process: com.example, PID: 10057
08-25 12:15:55.087: E/AndroidRuntime(10057): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example/com.example.MainActivity}: java.lang.ClassCastException: com.example.SearchDialogFragment cannot be cast to com.example.OnStartOrRestartLoader
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2224)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2273)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3759)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.app.ActivityThread.access$900(ActivityThread.java:141)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1208)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.os.Handler.dispatchMessage(Handler.java:102)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.os.Looper.loop(Looper.java:136)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.app.ActivityThread.main(ActivityThread.java:5052)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at java.lang.reflect.Method.invokeNative(Native Method)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at java.lang.reflect.Method.invoke(Method.java:515)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:132)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at dalvik.system.NativeStart.main(Native Method)
08-25 12:15:55.087: E/AndroidRuntime(10057): Caused by: java.lang.ClassCastException: com.example.SearchDialogFragment cannot be cast to com.example.OnStartOrRestartLoader
08-25 12:15:55.087: E/AndroidRuntime(10057):    at com.example.SearchDialogFragment.onCreateDialog(SearchDialogFragment.java:59)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.support.v4.app.DialogFragment.getLayoutInflater(DialogFragment.java:307)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:942)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1121)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1103)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1901)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:1518)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:962)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1121)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1103)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1901)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:567)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1171)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.app.Activity.performStart(Activity.java:5322)
08-25 12:15:55.087: E/AndroidRuntime(10057):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2187)
08-25 12:15:55.087: E/AndroidRuntime(10057):    ... 13 more

Answer 1

setTargetFragment不应用于建立父/子片段之间的关系。它应该只用于链接同级片段（即存在于同一个 中的那些FragmentManager）。

它在父/子片段之间不起作用的原因是片段的目标被保存并恢复为它自己的 FragmentManager. 因此，在框架恢复 Activity 之前，例如，方向更改后，一切都将是笨拙的。那时FragmentManager将在其自身而不是父片段中寻找目标片段FragmentManager。