Question

I have created a Quiz app for Android using the tutorial here: http://automateddeveloper.blogspot.co.uk/2011/06/getting-started-complete-android-app.html

For each question, the user will only have 20 seconds to answer it. If he/she fails to answer in 20 seconds, an AlertDialog will popup and the game will terminate.

To do this, I have added a counter in the OnCreate method of QuestionActivity class:

final TextView myCounter = (TextView) findViewById(R.id.countdown);
    new CountDownTimer(20000, 1000) {

        @Override
        public void onFinish() {
            timeUp();
        }

        @Override
        public void onTick(long millisUntilFinished) {
            myCounter.setText("Time left: "
                    + String.valueOf(millisUntilFinished / 1000));
        }

    }.start();


public void timeUp() {

    AlertDialog.Builder builder = new AlertDialog.Builder(
            QuestionActivity.this);
    builder.setTitle("Times up!")
            .setMessage("Game over")
            .setCancelable(false)
            .setNeutralButton(android.R.string.ok,
                    new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int id) {
                            QuestionActivity.this.finish();
                        }
                    });
    AlertDialog alert = builder.create();
    alert.show();
}

The counter works displays and functions on screen correctly. After answering a question, the activity moves to the next question and the counter resets itself to 20 seconds again.

The problem

The quiz has 15 questions, after answering 3 or 4 questions, the app crashes and I get the following error:

07-18 00:49:05.530: E/AndroidRuntime(4867): android.view.WindowManager$BadTokenException: Unable to add window -- token android.os.BinderProxy@41533a80 is not valid; is your activity running?

I believe this relates to the AlertDialog. I have looked up this error code on Stackoverflow and the popular solution is to pass ActivityName.this as the context when building the AlertDialog.

Unfortunately this does not solve the problem.

I believe the counter is setting a time limit of 20 seconds for the whole activity. My requirement is 20 seconds for each question.

However, the counter resets to 20 seconds when the user press the’ Next button and the activity moves to the next question.

Should I be resetting the counter when the user presses the Next button? Here is the OnClickListener code for the Next button

if (currentGame.isGameOver()) {
        Intent i = new Intent(this, EndgameActivity.class);
        startActivity(i);
        finish();
    } else {
        Intent i = new Intent(this, QuestionActivity.class);
        startActivity(i);
                    SHOULD I ADD SOMETHING HERE?
        finish();

Can anyone help me code a solution to my problem?

Here is all the code in QuestionActivity.class

public class QuestionActivity extends SherlockActivity implements
    OnClickListener {

private Question currentQ;
private GamePlay currentGame;
private Context context;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.question);

    getSupportActionBar().hide();
    /**
     * Configure current game and get question
     */
    currentGame = ((ChuckApplication) getApplication()).getCurrentGame();
    currentQ = currentGame.getNextQuestion();

    Button nextBtn = (Button) findViewById(R.id.nextBtn);
    nextBtn.setOnClickListener(this);

    Button quitBtn = (Button) findViewById(R.id.quitBtn);
    quitBtn.setOnClickListener(new OnClickListener() {
        public void onClick(View arg0) {
            finish();
        }
    });

    //Update the question and answer options..
    setQuestions();

    final TextView myCounter = (TextView) findViewById(R.id.countdown);
    new CountDownTimer(20000, 1000) {

        @Override
        public void onFinish() {
            // myCounter.setText("Time up!");
            timeUp(context);
        }

        @Override
        public void onTick(long millisUntilFinished) {
            myCounter.setText("Time left: "
                    + String.valueOf(millisUntilFinished / 1000));
        }
    }.start();
}

public void timeUp(Context context) {

    AlertDialog.Builder builder = new AlertDialog.Builder(
            QuestionActivity.this);
    builder.setTitle("Times up!")
            .setMessage("Game over")
            .setCancelable(false)
            .setNeutralButton(android.R.string.ok,
                    new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int id) {
                            QuestionActivity.this.finish();
                        }
                    });
    AlertDialog alert = builder.create();
    alert.show();
}

/**
 * Method to set the text for the question and answers from the current
 * games current question
 */
private void setQuestions() {
    // set the question text from current question
    String question = Utility.capitalise(currentQ.getQuestion()) + "?";
    TextView qText = (TextView) findViewById(R.id.question);
    qText.setText(question);

    // set the available options
    List<String> answers = currentQ.getQuestionOptions();
    TextView option1 = (TextView) findViewById(R.id.answer1);
    option1.setText(Utility.capitalise(answers.get(0)));

    TextView option2 = (TextView) findViewById(R.id.answer2);
    option2.setText(Utility.capitalise(answers.get(1)));

    TextView option3 = (TextView) findViewById(R.id.answer3);
    option3.setText(Utility.capitalise(answers.get(2)));

    TextView option4 = (TextView) findViewById(R.id.answer4);
    option4.setText(Utility.capitalise(answers.get(3)));
}

public void onClick(View arg0) {
    //validate a checkbox has been selected
    if (!checkAnswer())
        return;

    //check if end of game
    if (currentGame.isGameOver()) {
        Intent i = new Intent(this, EndgameActivity.class);
        startActivity(i);
        finish();
    } else {
        Intent i = new Intent(this, QuestionActivity.class);
        startActivity(i);
        finish();
    }
}

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    switch (keyCode) {
    case KeyEvent.KEYCODE_BACK:
        return true;
    }

    return super.onKeyDown(keyCode, event);
}

/**
 * Check if a checkbox has been selected, and if it has then check if its
 * correct and update gamescore
 */
private boolean checkAnswer() {
    String answer = getSelectedAnswer();
    if (answer == null) {
        // Log.d("Questions", "No Checkbox selection made - returning");
        return false;
    } else {
        // Log.d("Questions",
        // "Valid Checkbox selection made - check if correct");
        if (currentQ.getAnswer().equalsIgnoreCase(answer)) {
            // Log.d("Questions", "Correct Answer!");
            currentGame.incrementRightAnswers();
        } else {
            // Log.d("Questions", "Incorrect Answer!");
            currentGame.incrementWrongAnswers();
        }
        return true;
    }
}

private String getSelectedAnswer() {
    RadioButton c1 = (RadioButton) findViewById(R.id.answer1);
    RadioButton c2 = (RadioButton) findViewById(R.id.answer2);
    RadioButton c3 = (RadioButton) findViewById(R.id.answer3);
    RadioButton c4 = (RadioButton) findViewById(R.id.answer4);
    if (c1.isChecked()) {
        return c1.getText().toString();
    }
    if (c2.isChecked()) {
        return c2.getText().toString();
    }
    if (c3.isChecked()) {
        return c3.getText().toString();
    }
    if (c4.isChecked()) {
        return c4.getText().toString();
    }

    return null;
}

Answer 1

I think the activity doesn’t exist anymore at a certain point when you try to make the dialog(probably when the CountDownTimer is near the end?!?).

Anyway I think finishing and starting the same activity for each question isn’t such a good idea, instead you could use the current activity and simply restart the timer. For example:

public class QuestionActivity extends SherlockActivity implements
    OnClickListener {

   private CountDownTimer mCountDown;

   @Override
   public void onCreate(Bundle savedInstanceState) {
      // ...
      mCountDown = new CountDownTimer(20000, 1000) {

        @Override
        public void onFinish() {
            // myCounter.setText("Time up!");
            timeUp(context);
        }

        @Override
        public void onTick(long millisUntilFinished) {
            myCounter.setText("Time left: "
                    + String.valueOf(millisUntilFinished / 1000));
        }
      }.start();
      // ... 

and in the onClick callback do the same to setup a new question, stop the old timer and restart the new timer:

//check if end of game
if (currentGame.isGameOver()) {
    Intent i = new Intent(this, EndgameActivity.class);
    startActivity(i);
    finish();
} else {
    if (mCountDown != null) { 
       mCountDown.cancel();
    }  
    currentQ = currentGame.getNextQuestion();
    setQuestions();
    mCountDown = new CountDownTimer(20000, 1000) {

        @Override
        public void onFinish() {
            // myCounter.setText("Time up!");
            timeUp(context);
        }

        @Override
        public void onTick(long millisUntilFinished) {
            myCounter.setText("Time left: "
                    + String.valueOf(millisUntilFinished / 1000));
        }
    }.start();  
}

Also, in the callback for the Dialog‘s Button I would first close the Dialog before finishing the Activity:

((AlertDialog) dialog).dismiss();
QuestionActivity.this.finish();