Android 在UI片段重新创建期间，是否不再需要对headless片段调用setTargetFragment？

使用无头片段技术（fragment with

setRetainedInstance（true）

）让长时间运行的任务处理UI更新是很常见的

我正在使用支持库

许多年前，当重新创建

UIFragment

时，以下代码片段是必不可少的，以确保headless fragment引用了最新的

UIFragment

实例

// UIFragment is having configuration change.
// UIFragment is being re-created.
// Make sure headlessFragment is having latest instance of UIFragment.
headlessFragment.setTargetFragment(this, 0);

然而，今天当我使用最新的支持库

v7:25.0.0

重新测试代码时，我意识到这样的代码不再是必需的。我可以用英文写

public class UIFragment extends Fragment {
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        headlessFragment = (HeadlessFragment)fm.findFragmentByTag(HEADLESS_FRAGMENT);

        if (headlessFragment == null) {
            // This happens during UIFragment first-time creation.

            headlessFragment = HeadlessFragment.newInstance();
            headlessFragment.setTargetFragment(this, 0);
            fm.beginTransaction().add(headlessFragment , HEADLESS_FRAGMENT).commitAllowingStateLoss();
        } else {
             // UIFragment is being created.
             //
             // Event without calling headlessFragment.setTargetFragment,
             // headlessFragment.getTargetFragment will *magically* 
             // return latest instance of UIFragment.
        }
    }
}

首先，我怀疑，在最新的支持库中，

headlessFragment.setTargetFragment

在重新创建

UIFragment

的过程中被自动调用

但是，当我尝试通过使用一些日志覆盖

headlessFragment.setTargetFragment

进行确认时，我意识到在

UIFragment

重新创建期间没有调用它

请问，

headlessFragment

如何才能神奇地获得最新的重新创建的

UIFragment

，

public class UIFragment extends Fragment {
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        headlessFragment = (HeadlessFragment)fm.findFragmentByTag(HEADLESS_FRAGMENT);

        if (headlessFragment == null) {
            // This happens during UIFragment first-time creation.

            headlessFragment = HeadlessFragment.newInstance();
            headlessFragment.setTargetFragment(this, 0);
            fm.beginTransaction().add(headlessFragment , HEADLESS_FRAGMENT).commitAllowingStateLoss();
        } else {
             // UIFragment is being created.
             //
             // Event without calling headlessFragment.setTargetFragment,
             // headlessFragment.getTargetFragment will *magically* 
             // return latest instance of UIFragment.
        }
    }
}