Question

在android中的onPause()方法中，确保Activity恢复到以前的状态的正确方法是什么？

例如，如果我想暂停并恢复此Activity：

/**
 * Class containing an activity where the user enters an answer for each sum
 * within the times tables
 * 
 * @author Ross
 * 
 */
public class PracticeTest extends Activity implements View.OnClickListener {

    // declare variables
    int multiplier;
    int[] results = new int[12];
    int numberPassed;
    TextView question;
    EditText answer;
    ImageView image;
    int score;
    String[] questions = new String[12];
    MediaPlayer correctNoise;
    MediaPlayer incorrectNoise;

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

        setContentView(R.layout.practicetest);

        // / Setting int equal to int passed from previous activity (defaulted
        // to zero)
        numberPassed = getIntent().getIntExtra("convertedNumber2", 0);

        // Initialising variables
        correctNoise = MediaPlayer
                .create(PracticeTest.this, R.raw.correctnoise);
        incorrectNoise = MediaPlayer.create(PracticeTest.this,
                R.raw.incorrectnoise);
        Button submit = (Button) findViewById(R.id.btnGoPractice2);
        answer = (EditText) findViewById(R.id.etEnterNumberPractice2);
        question = (TextView) findViewById(R.id.tvTopPractice2);
        image = (ImageView) findViewById(R.id.imageViewPracticeTest);

        // Setting on click listener for submit button
        submit.setOnClickListener(this);
        // update the question
        updateQuestion();

    }

    public void onClick(View view) {

        // sets text view equal to what is entered in editText
        final String entry = answer.getText().toString();

        // convert from string value to int
        int a = Integer.parseInt(entry); // note: maybe change name

        results[multiplier - 1] = a;

        // Displaying image and noise dependent on user answer
        if (a == numberPassed * multiplier) {

            correctNoise.start();
            image.setImageResource(R.drawable.thumbsup);
            score++;

        } else {
            incorrectNoise.start();
            image.setImageResource(R.drawable.thumbsdown);

        }

        if (multiplier < 12) {

            // called after an answer is given
            updateQuestion();

        } else {
            Intent intent = new Intent(this, PracticeResults.class);
            // Pass variables to next activity
            intent.putExtra("results", results);
            intent.putExtra("numberPassed", numberPassed);
            intent.putExtra("questions", questions);
            intent.putExtra("score", score);
            // Start new activity via intent
            this.startActivity(intent);
        }

    }

    /**
     * Method that updates question
     */
    public void updateQuestion() {
        // increase multiplier (i.e. 7x1 to 7x2 etc)
        multiplier++;
        // string to hold question
        String q = numberPassed + "x" + multiplier + "=";
        // Setting question equal to correct place in questions array
        questions[multiplier - 1] = q;
        // Set text in textView equal to the question
        question.setText(questions[multiplier - 1]);
        // change editText to be blank so a new answer can be entered
        answer.setText("");

    }

}

Answer 1

请参阅此处http://developer.android.com/training/basics/activity-lifecycle/recreating.html

Activity Lifecycle

保存您的活动

static final String STATE_SCORE = "playerScore";
static final String STATE_LEVEL = "playerLevel";
...

@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
    // Save the user's current game state
    savedInstanceState.putInt(STATE_SCORE, mCurrentScore);
    savedInstanceState.putInt(STATE_LEVEL, mCurrentLevel);

    // Always call the superclass so it can save the view hierarchy state
    super.onSaveInstanceState(savedInstanceState);
}

恢复

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState); // Always call the superclass first

    // Check whether we're recreating a previously destroyed instance
    if (savedInstanceState != null) {
        // Restore value of members from saved state
        mCurrentScore = savedInstanceState.getInt(STATE_SCORE);
        mCurrentLevel = savedInstanceState.getInt(STATE_LEVEL);
    } else {
        // Probably initialize members with default values for a new instance
    }
    ...
}

Answer 2

您可以执行以下操作：

1）定义您的活动状态。状态是完整描述您的活动在任何给定时刻的外观和行为的所有数据。

在您的情况下，您需要保存question和answer以及multiplier以及其他您从其他数据无法计算的内容。

2）覆盖onSaveInstanceState()并将您的状态保存在捆绑参数

中

3）在onCreate中，如果savedState参数不为null，则从包中恢复状态，并根据恢复状态填充Activity的视图以及应该初始化的其他任何内容

通过这种方式，您可以保证如果您的活动在暂停时被销毁，数据永远不会丢失。

除此之外，暂停onPause中的所有正在运行的流程，然后继续onResume

Android：暂停，正确方法恢复任何活动？

2 个答案: