如何在片段中保存此 TextView 的实例状态？

Question

I have the text inputted by the user in an EditText replace the text of a TextView upon a button press. Once the TextView text has been changed, when I navigate to another fragment or activity and come back, the TextView has reverted back to its original text. I have tried multiple solutions to save the instance state to no avail.

Edit2: The is the latest code from the fragment

public class TeamFragment extends Fragment {

private TextView testTextView;
private EditText testEditText;
private SharedPreferences pref;
private SharedPreferences.Editor editor;


@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);


    View v = inflater.inflate(R.layout.fragment_team, container, false);


    Button button = (Button)v.findViewById(R.id.recordBtn);
    testEditText = v.findViewById(R.id.testEditText);
    pref = this.getActivity().getSharedPreferences("my_pref",
            Context.MODE_PRIVATE);
    editor = pref.edit();

    testTextView = (TextView) v.findViewById(R.id.testTextView);
    final EditText testEditText = (EditText) v.findViewById(R.id.testEditText);

    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            testTextView.setText(testEditText.getText().toString());
            editor.putString("val", testEditText.getText().toString());
            editor.apply();

        }
    });
    return v;

}

@Override
public void onStart() {
    super.onStart();
    String val = this.getActivity().getSharedPreferences("my_pref",
            Context.MODE_PRIVATE).getString("val", "n/a");
    if(val.equals("n/a")) {
        testTextView.setText(val);
    }

}

}

This is my layout file

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/background_light"
android:padding="8dp">

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Record"
    android:layout_centerHorizontal="true"
    android:layout_below="@+id/tresEditText"
    android:id="@+id/recordBtn"
    android:onClick="displayEditText"/>
<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/testTextView"
    android:text="Test"
    android:layout_marginTop="20dp"
    android:layout_marginLeft="30dp"/>
<EditText
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_marginTop="20dp"
    android:layout_marginLeft="100dp"
    android:id="@+id/testEditText"/>

</RelativeLayout>

Answer 1

Your app crashes because you have not initialized EditText and TextView .

Instead of overriding onSaveInstanceState() , consider using SharedPreferences() as onSaveInstanceState() is used to save the state when the device orientation is changed. In your case, what you can do is to save textView data in SharedPreference and when you come back to the fragment, you can check in 'onStart()' whether the SharedPreferences() contain the saved value, then populate your textView accordingly.

You can do something like following:

public class TeamFragment extends Fragment {

private TextView testTextView;
private EditText testEditText;
private SharedPreferences pref;
private SharedPreferences.Editor editor;

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable 
ViewGroup container, @Nullable Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

View v = inflater.inflate(R.layout.fragment_team, container, false);

Button button = (Button)v.findViewById(R.id.recordBtn);
textTextView = v.findViewById(R.id.your_id);
testEditText = v.findViewById(R.id.your_id);
pref = this.getActivity().getSharedPreferences("my_pref", 
Context.MODE_PRIVATE);
editor = pref.edit();

testTextView = (TextView) v.findViewById(R.id.testTextView);
final EditText testEditText = (EditText) 
v.findViewById(R.id.testEditText);

button.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {

        testTextView.setText(testEditText.getText().toString());
        editor.putString("val", testEditText.getText().toString());
        editor.apply();

    }
});
return v;

}

@Override
protected void onStart() {
    super.onStart();
    String val = this.getActivity().getSharedPreferences("my_pref", 
    Context.MODE_PRIVATE).getString("val", "n/a");
    if(val.equals("n/a")) {
      testTextView.setText(val);
    }
 }
}