在Android上使用片段无法保存状态的保存捆绑

我有一个具有两个片段的android应用程序，这些片段将数据从fragmentA传递到fragmentB。我可以正确加载所有数据，但是当我改变屏幕方向时，它们都会重新加载。我已经在要保留状态的片段中设置了onSaveInstanceState和onViewStateRestored方法，但是当屏幕方向改变时，什么也不会停留。

The main problem that needs to be fixed is when text is loaded into the TextView in FragmentB - it needs to stay there when the screen orientation is changed.

MainActivity.Java

package com.example.tourguide;

import android.os.Bundle;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.FragmentTransaction;

public class MainActivity extends AppCompatActivity implements FragmentA.FragmentAListener, FragmentB.FragmentBListener {
    private FragmentA fragmentA;
    private FragmentB fragmentB;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        fragmentA = new FragmentA();
        fragmentB = new FragmentB();

        if(savedInstanceState == null) {
            FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
            ft.replace(R.id.container_a, new FragmentA());
            ft.replace(R.id.container_b, new FragmentB());
            ft.commitNow();
        }

    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);

    }

    @Override
    protected void onRestoreInstanceState(@NonNull Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);

    }

    @Override
    public void onInputASent(CharSequence input) {
        fragmentB.updateEditText(input);
    }

    @Override
    public void onInputBSent(CharSequence input) {
        fragmentA.updateEditText(input);
    }
}```
片段Java

package com.example.tourguide;

import android.content.Context; import android.os.Bundle;

import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.AdapterView; import android.widget.ArrayAdapter; import android.widget.ListView; import androidx.annotation.NonNull; import androidx.annotation.Nullable; import androidx.fragment.app.ListFragment;

public class FragmentA extends ListFragment implements AdapterView.OnItemClickListener { private FragmentAListener listener;

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

    String[] locationList = getActivity().getResources().getStringArray(R.array.location_list);
    updateEditText(locationList[position]);
    listener.onInputASent(locationList[position]);
}

public interface FragmentAListener {
    void onInputASent(CharSequence input);
}

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.fragment_a, container, false);

    return v;
}


@Override
public void onListItemClick(@NonNull ListView l, @NonNull View v, int position, long id) {
    super.onListItemClick(l, v, position, id);
}

public void updateEditText(CharSequence newText) {
    //editText.setText(newText);
}

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    if (context instanceof FragmentAListener) {
        listener = (FragmentAListener) context;
    } else {
        throw new RuntimeException(context.toString()
                + " must implement FragmentAListener");
    }
}

@Override
public void onDetach() {
    super.onDetach();
    listener = null;
}

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    ArrayAdapter arrayAdapter = ArrayAdapter.createFromResource(getActivity(), R.array.location_list, android.R.layout.simple_list_item_1);

    setListAdapter(arrayAdapter);

    getListView().setOnItemClickListener(this);
}

}``` FragmentB.Java-这是片段，当旋转屏幕时，需要将该字符串保留在TextView中

package com.example.tourguide;

import android.content.Context;
import android.content.res.Resources;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;


public class FragmentB extends Fragment {
    private FragmentBListener listener;

    private TextView resultsFrag;

    private static final String KEY_TITLE = "title_key";

    private String stateObject;

    public interface FragmentBListener {
        void onInputBSent(CharSequence input);
    }


    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_b, container, false);

        resultsFrag = v.findViewById(R.id.tvFragmentB);

        //I used the same if block in three different locations and none of them worked
        if (savedInstanceState != null) {
            String itemTo = savedInstanceState.getString(KEY_TITLE);
            resultsFrag.setText(itemTo);
        } else {
            Toast.makeText(getActivity(), "Error 1", Toast.LENGTH_SHORT).show();
        }

        return v;
    }

    public void updateEditText(CharSequence newText) {

        String newOption = newText.toString();
        stateObject = newText.toString();

        Resources res = getResources();
        String[] locationDesc = res.getStringArray(R.array.location_description);

        if (newOption.equals("Calgary")) {
            resultsFrag.setText(locationDesc[0]);
        } else if (newOption.equals("Victoria")) {
            resultsFrag.setText(locationDesc[1]);
        } else if (newOption.equals("Vancouver")) {
            resultsFrag.setText(locationDesc[2]);
        } else if (newOption.equals("Toronto")) {
            resultsFrag.setText(locationDesc[3]);
        }

    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        if (context instanceof FragmentBListener) {
            listener = (FragmentBListener) context;
        } else {
            throw new RuntimeException(context.toString()
                    + " must implement FragmentBListener");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        listener = null;
    }

    @Override
    public void onSaveInstanceState(@NonNull Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putString(KEY_TITLE, resultsFrag.getText().toString());
    }

    @Override
    public void onViewStateRestored(@Nullable Bundle savedInstanceState) {
        super.onViewStateRestored(savedInstanceState);

        //I used the same if block in three different locations and none of them worked
        if (savedInstanceState != null) {
            String itemTo = savedInstanceState.getString(KEY_TITLE);
            resultsFrag.setText(itemTo);
        } else {
            Toast.makeText(getActivity(), "Error 2", Toast.LENGTH_SHORT).show();
        }
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

        //I used the same if block in three different locations and none of them worked
        if (savedInstanceState != null) {
            String itemTo = savedInstanceState.getString(KEY_TITLE);
            resultsFrag.setText(itemTo);
        } else {
            Toast.makeText(getActivity(), "Error 3", Toast.LENGTH_SHORT).show();
        }
    }

}```
fragment_b.xml

<resources>
    <string name="app_name">Tour Guide</string>

    <string-array name="location_list">
        <item>Calgary</item>
        <item>Victoria</item>
        <item>Vancouver</item>
        <item>Toronto</item>
    </string-array>

    <!-- Descriptions for the locations -->
    <string-array name="location_description">
        <item>This is a big description for CALGARY - THIS needs to load in for more information regarding CALGARY</item>
        <item>This is a big description for VICTORIA - THIS needs to load in for more information regarding VICTORIA</item>
        <item>This is a big description for VANCOUVER - THIS needs to load in for more information regarding VANCOUVER</item>
        <item>This is a big description for TORONTO - THIS needs to load in for more information regarding TORONTO</item>
    </string-array>

</resources>

fragment_a.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@android:color/holo_green_light"
    android:gravity="center_horizontal"
    android:orientation="vertical"
    android:padding="16dp">

    <ListView
        android:id="@android:id/list"
        android:layout_width="wrap_content"
        android:layout_height="206dp" />

</LinearLayout>```
activity_main.xml

问题来源：Stack Overflow