android - 为什么 onCreate Bundle 和 onSaveInstanceState Bundle 在 Fragment 中不同？

Question

我环顾四周，但找不到这个确切问题的答案。

在一个 Activity 中这个简单的程序:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    if(savedInstanceState!=null)Log.e("SaveInstanceState", "onCreate Bundle " + savedInstanceState.hashCode()+" " + this.getClass().getSimpleName());
}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    Log.e("SaveInstanceState", "onSaveInstanceState Bundle " + outState.hashCode()+" " + this.getClass().getSimpleName());

}

将产生以下输出(当我转动手机方向时):

E/SaveInstanceState﹕ onSaveInstanceState Bundle 1110617176 MainActivity
E/SaveInstanceState﹕ onCreate Bundle 1110617176 MainActivity

相同的 Bundle，因此我可以轻松地传递和恢复数据。

但在 fragment 中，这段代码:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if(savedInstanceState!=null)Log.e("SaveInstanceState", "onCreate Bundle " + savedInstanceState.hashCode()+" " + this.getClass().getSimpleName());
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    super.onCreateView(inflater,container, savedInstanceState);
    if(savedInstanceState!=null)Log.e("SaveInstanceState", "onCreateView Bundle " + savedInstanceState.hashCode()+" " + this.getClass().getSimpleName());
    return inflater.inflate(R.layout.fragment_b, container, false);
}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    Log.e("SaveInstanceState", "onSaveInstanceState Bundle " + outState.hashCode()+" " + this.getClass().getSimpleName());

}

此输出结果:

E/SaveInstanceState﹕ onSaveInstanceState Bundle 1110622064 FragmentB
E/SaveInstanceState﹕ onCreate Bundle 1110623448 FragmentB
E/SaveInstanceState﹕ onCreateView Bundle 1110623448 FragmentB

onSaveInstanceState Bundle 和 onCreate 不同，因此我丢失了存储在 onSaveInstanceState Bundle 中的数据。

你知道我做错了什么吗？

更新

好的，谢谢@Sascha Kolberg，Bundle Hashcode 不同的事实并不意味着 Bundle 是空的。那么问题就变成了:

为什么我无法从 Fragment onCreate Bundle 检索我的数据？

这就是我所做的:

    public class FragmentB extends Fragment {

        public static final String USER_TEXT = "user_text";
        EditText userText;

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            super.onCreateView(inflater, container, savedInstanceState);
            View layout = inflater.inflate(R.layout.fragment_b, container, false);
            userText = (EditText) layout.findViewById(R.id.userText);

            if (savedInstanceState != null) {
                Log.e("SaveInstanceState",
                      "onCreateView savedInstanceState " + savedInstanceState + " " + this.getClass().getSimpleName());
                Log.e("SaveInstanceState",
                      "onCreateView savedInstanceState.getString(USER_TEXT) " + savedInstanceState.getString(USER_TEXT) +
                      " " + this.getClass().getSimpleName());
                userText.setText(savedInstanceState.getString(USER_TEXT));
            }
            return layout;
        }

        @Override
        public void onSaveInstanceState(Bundle outState) {
            super.onSaveInstanceState(outState);
            outState = new Bundle();
            outState.putString(USER_TEXT, String.valueOf(userText.getText()));
            Log.e("SaveInstanceState", "onSaveInstanceState outState " + outState + " " + this.getClass().getSimpleName());
            Log.e("SaveInstanceState",
                  "onSaveInstanceState outState.getString(USER_TEXT) " + outState.getString(USER_TEXT) + " " +
                  this.getClass().getSimpleName());
        }
    }

现在，我打开手机，写下“你好!”在 EditText 中，然后清除 logcat，并将手机的方向从纵向更改为横向。

输出如下:

E/SaveInstanceState﹕ onSaveInstanceState outState Bundle[{user_text=Hello! }] FragmentB
E/SaveInstanceState﹕ onSaveInstanceState outState.getString(USER_TEXT) Hello!  FragmentB
E/SaveInstanceState﹕ onCreateView savedInstanceState Bundle[{android:view_state={2131492945=TextView.SavedState{423430e0 start=5 end=5 text=Hello!  locale=fr-FR}}}] FragmentB
E/SaveInstanceState﹕ onCreateView savedInstanceState.getString(USER_TEXT) null FragmentB

旋转手机后EditText为空。我想我可以通过执行以下操作来检索数据:

SparseArray p=savedInstanceState.getSparseParcelableArray("android:view_state");

在 onCreate 方法中，但这看起来真的很复杂。

有什么想法吗？

Answer 1

Activity outState Bundle 还包含其子 fragment 的所有状态。

因此，当 bundle 在 onSaveInstanceState() 中传递一个 fragment 时，它可能会在之后传递它的同级 fragment ，并且在“onCreate()”中包含的不仅仅是它自己的状态。