android – Fragment在旋转设备两次时失去状态

我有一个显示两个片段的活动：

>创建活动时,它会显示Fragment1.
>当用户按下Fragment1上的按钮时,它会显示Fragment2,添加到BACkstack.

碎片很简单. Fragment1包含checkBox和EditText. Fragment2包含简单的TextView.我也在片段的onCreate(…)方法中调用setRetainInstance@R_801_6334@.

问题：如果显示Fragment2并且设备旋转两次,Fragment1将失去其状态.但是,如果设备只旋转一次,一切都按预期工作.

重现步骤：

>启动应用程序.
>选中checkBox并在EditText中键入一些文本
>按Button启动Fragment2
>旋转设备
>再次旋转设备
>按设备上的后退按钮(或模拟器上的ESC)返回Fragment1

Fragment1失去了状态(复选框未选中,EditText为空).
但是,如果在步骤#4之后返回Fragment1 – Fragment1将按预期保持其状态.

问题出在哪儿？所有代码都在下面,包括布局.

@H_658_5@main.xml中：

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://@R_197_10906@mas.android.com/apk/res/android"
    android:id="@+id/placeholder"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

fragment1.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://@R_197_10906@mas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <checkBox
        android:id="@+id/checkBox1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="checkBox" />

    <EditText
        android:id="@+id/editText1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
    </EditText>

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Start Fragment2" />

</LinearLayout>

fragment2.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://@R_197_10906@mas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Fragment #2" />

</LinearLayout>

FragmentTestActivity.java：

package fragmenttest.example.com;

import android.app.Activity;
import android.app.FragmentManager;
import android.os.bundle;

public class FragmentTestActivity extends Activity implements FragmentListener {
    @Override
    public void onCreate(Bundle savedInstanceStatE) {
        super.onCreate(savedInstanceStatE);
        setContentView(R.layout.main);

        FragmentManager fm = getFragmentManager();
        if (fm.findFragmentByTag(Fragment1.TAG) == null) {
            fm.begintransaction().replace(R.id.placeholder,new Fragment1(),Fragment1.TAG).commit();
        }
    }

    @Override
    public void onButtonClick() {
        FragmentManager fm = getFragmentManager();
        if (fm.findFragmentByTag(Fragment2.TAG) == null) {
            fm.begintransaction().replace(R.id.placeholder,new Fragment2(),Fragment2.TAG).addToBACkStack(Fragment2.TAG).commit();
        }
    }
}

Fragment1.java：

package fragmenttest.example.com;

import android.app.Activity;
import android.app.Fragment;
import android.os.bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.onClickListener;
import android.view.ViewGroup;
import android.widget.button;

public class Fragment1 extends Fragment {
    public static final String TAG = Fragment1.class.getName();
    private FragmentListener mListener;

    @Override
    public void onCreate(Bundle savedInstanceStatE) {
        super.onCreate(savedInstanceStatE);
        setRetainInstance@R_801_6334@;
    }

    @Override
    public View onCreateView(LayoutInflater inflater,ViewGroup container,Bundle savedInstanceStatE) {
        View root = inflater.inflate(R.layout.fragment1,container,falsE);

        Button button = (Button) root.findViewById(R.id.button1);
        button.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                mlistener.onButtonClick();
            }
        });

        return root;
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);

        mListener = (FragmentListener) activity;
    }
}

Fragment2.java：

package fragmenttest.example.com;

import android.app.Fragment;
import android.os.bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class Fragment2 extends Fragment {
    public static final String TAG = Fragment2.class.getName();

    @Override
    public void onCreate(Bundle savedInstanceStatE) {
        super.onCreate(savedInstanceStatE);
        setRetainInstance@R_801_6334@;
    }

    @Override
    public View onCreateView(LayoutInflater inflater,Bundle savedInstanceStatE) {
        View root = inflater.inflate(R.layout.fragment2,falsE);
        return root;
    }
}

FragmentListener.java：

package fragmenttest.example.com;

public interface FragmentListener {
    public void onButtonClick();
}