Android SavedInstanceState - 如何从不同类型的方法中保存变量

Question

I am implementing a simple app (tennis score), and I want to save the set variables before they can be destroyed by the methods when rotating the screen:

public class MainActivity extends AppCompatActivity {
int scorePlayerOne = 0;    // Tracks the score for Player One
int scorePlayerTwo = 0;    // Tracks the score for Player Two
int set1PlayerOne = 0;     // Track the score set for Player One
int set2PlayerOne = 0;
int set3PlayerOne = 0;
int set1PlayerTwo = 0;     // Track the score set for Player Two
int set2PlayerTwo = 0;
int set3PlayerTwo = 0;
int setOfTheGame = 1;      // Tracks the current set of the game

// Declaring and initializing KEY_INDEX to serve as NVP (Name-Value Pair).
private static final String KEY_INDEX = "index";
private static final String KEY_INDEX2 = "index2";

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

    if (savedInstanceState != null) {
        scorePlayerOne = savedInstanceState.getInt(KEY_INDEX, scorePlayerOne);
    }
    if (savedInstanceState != null) {
        scorePlayerTwo = savedInstanceState.getInt(KEY_INDEX2, scorePlayerTwo);
    }
    setContentView(R.layout.activity_main);
    displayForPlayerOne(scorePlayerOne);
    displayForPlayerTwo(scorePlayerTwo);
}

@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
    super.onSaveInstanceState(savedInstanceState);
      /*
    *Save UI state changes to the savedInstanceState.
    * This bundle will be passed to onCreate if the process is
    * killed and restarted.
    * Storing a NVP ("Name-Value Pair") map, and it will get
    * passed in to onCreate () method.
    */
    savedInstanceState.putInt(KEY_INDEX, scorePlayerOne);
    savedInstanceState.putInt(KEY_INDEX2, scorePlayerTwo);
}

}

What I want to do next is to be able to save the remaining (set's variables), I can't do this because the set's variables have the different type of methods (View) and i can't call them onCreate(Bundle savedInstanceState) method

example:

 /**
 * Increase the score of the set for Player One by 1 point.
 */
public void addSetScoreForPlayerOne(View v) {

    if (setOfTheGame == 1) {
        if ((set1PlayerOne == 6 && set1PlayerOne - set1PlayerTwo >= 2)
                || (set1PlayerOne == 7)) {
            setOfTheGame = 2;
            set2PlayerOne++;
            TextView scoreView = findViewById(R.id.player_one_score_set_2);
            scoreView.setText(String.valueOf(set2PlayerOne));
        } else {
            set1PlayerOne++;
        }

Is there a way to figure out this kind of problem? Thx!

Answer 1

By default, when the screen is rotated your Activity is killed and restarted. To make sure no data is lost, you need to properly save and restore your data using the lifecycle methods.

This is how to save.

protected void onSaveInstanceState (Bundle outState) {

    super.onSaveInstanceState(outState);
    outState.putCharSequence(EDIT_TEXT_VALUE, mTextView.getText()); //<-- Saving operation, change the values to what ever you want.

}

This is how to obtain.

protected void onCreate(Bundle savedInstanceState) {
    
    super.onCreate(savedInstanceState);
    mTextView = (TextView) findViewById(R.id.editText);
    
    // Retrieving logic
    if (savedInstanceState != null) {
        CharSequence savedText = savedInstanceState.getCharSequence(EDIT_TEXT_VALUE);
        mTextView.setText(savedText);
    }
    
}