如何在Android Quiz App中更改计时器？

我的测验android应用程序有20个多项选择题。每个问题的计时器为30秒。我不想为每个问题分别运行计时器。我希望所有20个问题的倒计时计时器总共运行20分钟，而不是每个问题30秒。怎么做？请帮忙。

private void startCountDown() {
    countDownTimer = new CountDownTimer(timeLeftInMillis, 1000) {
        @Override
        public void onTick(long millisUntilFinished) {
            timeLeftInMillis = millisUntilFinished;
            updateCountDownText();
        }

        @Override
        public void onFinish() {
            timeLeftInMillis = 0;
            updateCountDownText();
            checkAnswer();
        }
    }.start();
}

private void updateCountDownText() {
    int minutes = (int) (timeLeftInMillis / 1000) / 60;
    int seconds = (int) (timeLeftInMillis / 1000) % 60;

    String timeFormatted = String.format(Locale.getDefault(), "%02d:%02d", minutes, seconds);

    textViewCountDown.setText(timeFormatted);

    if (timeLeftInMillis < 10000) {
        textViewCountDown.setTextColor(Color.RED);
    } else {
        textViewCountDown.setTextColor(textColorDefaultCd);
    }
}

private void checkAnswer() {
    answered = true;

    countDownTimer.cancel();

    RadioButton rbSelected = findViewById(rbGroup.getCheckedRadioButtonId());
    int answerNr = rbGroup.indexOfChild(rbSelected) + 1;

    if (answerNr == currentQuestion.getAnswerNr()) {
        score++;
        textViewScore.setText("Score: " + score);
    }

    showSolution();
}

private void showSolution() {
    rb1.setTextColor(Color.RED);
    rb2.setTextColor(Color.RED);
    rb3.setTextColor(Color.RED);
    rb4.setTextColor(Color.RED);

    switch (currentQuestion.getAnswerNr()) {
        case 1:
            rb1.setTextColor(Color.GREEN);
            textViewQuestion.setText("Option 1 is correct");
            break;
        case 2:
            rb2.setTextColor(Color.GREEN);
            textViewQuestion.setText("Option 2 is correct");
            break;
        case 3:
            rb3.setTextColor(Color.GREEN);
            textViewQuestion.setText("Option 3 is correct");
            break;
        case 4:
            rb4.setTextColor(Color.GREEN);
            textViewQuestion.setText("Option 4 is correct");
            break;
    }

    if (questionCounter < questionCountTotal) {
        buttonConfirmNext.setText("Next");
    } else {
        buttonConfirmNext.setText("Finish");
    }
}

private void finishQuiz() {

    finish();
}

@Override
public void onBackPressed() {
    if (backPressedTime + 2000 > System.currentTimeMillis()) {
        finishQuiz();
    } else {
        Toast.makeText(this, "Press back again to finish", Toast.LENGTH_SHORT).show();
    }

    backPressedTime = System.currentTimeMillis();
}

@Override
protected void onDestroy() {
    super.onDestroy();
    if (countDownTimer != null) {
        countDownTimer.cancel();
    }

}