片段视图的状态由FragmentManager打破

Question

我想通过片段替换操作保留视图，并注意到一个奇怪的错误：

片段的View通过替换操作销毁后，它仍然有一个父节点，但是，父节点在其子节点之间没有视图。

private View view;

@Override 
public View onCreateView(...) {
  if (view == null) {
      view = // ... inflate view
  } else {
      // at this point, view has mParent, but can't be removed
      // because the parent does not have it among its children
  }
  return view;
}

@Override 
public void onDestroyView() {
    // I could remove the view from its parent here manually, 
    // however, it will cause fragment's content to disappear before
    // the replace animation ends
}

请注意视图如何通过mParent引用其父级，但父级为mChildrenCount。

这会导致片段事务在尝试重用视图时因异常而崩溃： java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first。我发现这种行为异常错误，因为它使片段的视图处于不可用状态。

如果有人遇到此问题，请分享您的解决方法。我想出了一个临时的反思解决方案：

@Override 
public View onCreateView(...) {
  if (view == null) {
      view = // ... inflate view
  } else {
      // clear parent reference (because SDK fails to do it)
      Field f = View.class.getDeclaredField("mParent");
      f.setAccessible(true);
      f.set(view, null);
  }
  return view;
}