在 Activity onRestoreInstanceState() 之前调用 Fragment 的 onCreateView()

Question

所以我有一个附加到活动的片段，我试图确保在屏幕旋转时事情顺利进行（或任何会中断活动的事情）。为此，我在我的活动中使用了 onSaveInstanceState 和 onRestoreInstanceState 方法来保存我的活动存储的信息。

当我的片段的视图被创建时，片段向 Activity 询问信息（这是片段的 onCreateView() ）：

ArrayList<String> picList = mListener.getPics();
ArrayList<String> descripList = mListener.getDescriptions();

为了让片段创建视图，它需要访问 picList 和 descripList，它们是活动的成员变量。这些成员变量在 onSaveInstanceState 和 onRestoreInstanceState 中存储和恢复。

protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    if(photoFile != null)
        outState.putString("photoFile", photoFile.getAbsolutePath());
    outState.putString("currentFragTag", currentFragTag);
    outState.putStringArrayList("picList", picList);
    outState.putStringArrayList("descripList", descripList);
}

@Override
protected void onRestoreInstanceState(Bundle saved) {
    super.onRestoreInstanceState(saved);
    if(saved.getString("photoFile") != null)
        photoFile = new File(saved.getString("photoFile"));
    currentFragTag = saved.getString("currentFragTag");
    picList = saved.getStringArrayList("picList");
    descripList = saved.getStringArrayList("descripList");
    currentFrag = getFragmentManager().findFragmentByTag(currentFragTag);
    changeFrag(currentFrag, currentFragTag);
}

问题是，在活动中调用 onRestoreInstanceState() 之前调用了 onCreateView()。我尝试在片段中使用 onActivityCreated()，但这也是在 onRestoreInstanceState() 之前调用的。附加调试器后，当屏幕旋转时，始终最后调用 onRestoreInstanceState()。这意味着片段在创建视图时无法访问活动的信息。

这应该发生吗？恢复 Activity 时，如何让 Fragment 的视图使用来自 Activity 的信息？

Answer 1

我认为最简单的方法是使用 EventBus。
您可以在重新创建 Activity 时发送“msg”，您的 Fragment 的“目标方法”将获取此 msg（该 msg 是 Object，它可以是一个 bundle）。

Answer 2

更新回复：

阅读替代方案Passing data between a fragment and its container activity。另见this。

修改了之前的回复：

请参阅 this 并尝试将您的代码放在 onResume() 中并使视图无效或 detach/attach the fragment 作为快速解决方案，但不是 the best solution 正如 Alex Lockwood 所说：

片段是可重复使用的 UI 组件。他们有自己的生命周期， 展示自己的观点，定义自己的行为。你通常 不需要让您的活动与内部混乱 片段的工作，因为片段的行为应该是 独立于任何特定活动。

如果确实需要之前的代码，重写next方法，直接在fragment中保存/恢复需要的数据：

/**
 * Called when the fragment's activity has been created and this
 * fragment's view hierarchy instantiated.  It can be used to do final
 * initialization once these pieces are in place, such as retrieving
 * views or restoring state.  It is also useful for fragments that use
 * {@link #setRetainInstance(boolean)} to retain their instance,
 * as this callback tells the fragment when it is fully associated with
 * the new activity instance.  This is called after {@link #onCreateView}
 * and before {@link #onViewStateRestored(Bundle)}.
 *
 * @param savedInstanceState If the fragment is being re-created from
 * a previous saved state, this is the state.
 */
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    if (savedInstanceState != null) {
        restoreInstanceState(savedInstanceState);
    }
}

/**
 * Called to ask the fragment to save its current dynamic state, so it
 * can later be reconstructed in a new instance of its process is
 * restarted.  If a new instance of the fragment later needs to be
 * created, the data you place in the Bundle here will be available
 * in the Bundle given to {@link #onCreate(Bundle)},
 * {@link #onCreateView(LayoutInflater, ViewGroup, Bundle)}, and
 * {@link #onActivityCreated(Bundle)}.
 *
 * <p>This corresponds to {@link Activity#onSaveInstanceState(Bundle)
 * Activity.onSaveInstanceState(Bundle)} and most of the discussion there
 * applies here as well.  Note however: <em>this method may be called
 * at any time before {@link #onDestroy()}</em>.  There are many situations
 * where a fragment may be mostly torn down (such as when placed on the
 * back stack with no UI showing), but its state will not be saved until
 * its owning activity actually needs to save its state.
 *
 * @param outState Bundle in which to place your saved state.
 */
@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.put...;
}

并创建这个，用于从包中检索所需的数据：

public void restoreInstanceState(Bundle savedInstanceState) {
    ... = savedInstanceState.get...
}

或使用getActivity() 方法从此处直接访问某些方法或字段，如果您出于某种原因需要有关活动的代码。

/**
 * Return the {@link FragmentActivity} this fragment is currently associated with.
 * May return {@code null} if the fragment is associated with a {@link Context}
 * instead.
 */
final public FragmentActivity getActivity() {
    return mHost == null ? null : (FragmentActivity) mHost.getActivity();
}

例如：((YourActivity) getActivity()).getPics();

并将getPics() 方法添加到活动中。

更多信息here 和定义接口here 的替代解决方案。