如何在Android中有效使用計時器？

Question

我在問答游戲中使用倒數計時器，我想在計時結束時將分數遞減。 如果有人在計時之前回答了問題，那么分數就會增加。 所以我在計時器onFinsh（）方法中添加了對currentGame.decrementScore（）方法的調用。 但是，當我在計時之前正確回答我的問題時，其仍在減少的計時分數加上正確答案的遞增分數。 我還在onFinsih（）方法中的一個方法中添加了調用，以設置時間上的下一個問題，並再次啟動計時器，但此方法不起作用。 Sommeone可以告訴我如何編碼此問題嗎？

碼：-

public class QuestionActivity extends Activity implements OnClickListener{

    private Question currentQ;
    private GamePlay currentGame;


     @Override
        public void onResume() {
            setTimer();
            super.onResume();
        }


         @Override
            public void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.question);
                /**
         * Configure current game and get question
         */
        currentGame = ((CYKApplication)getApplication()).getCurrentGame();
        currentQ = currentGame.getNextQuestion();
        Button nextBtn1 = (Button) findViewById(R.id.answer1);
        nextBtn1.setOnClickListener(this);
        Button nextBtn2 = (Button) findViewById(R.id.answer2);
        nextBtn2.setOnClickListener(this);
        Button nextBtn3 = (Button) findViewById(R.id.answer3);
        nextBtn3.setOnClickListener(this);
        Button nextBtn4 = (Button) findViewById(R.id.answer4);
        nextBtn4.setOnClickListener(this);
        Button nextBtn5 = (Button) findViewById(R.id.answer5);
        nextBtn5.setOnClickListener(this);
        /**
         * Update the question and answer options..
         */
        setQuestions();

    }


    /**
     * 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)));

        int score = currentGame.getScore();
        String scr = String.valueOf(score);
        TextView score1 = (TextView) findViewById(R.id.score);
        score1.setText(scr);
               }


    public void setTimer() {
        final long finishTime = 15;
        // NOTE: use the member, instead of a local
        CountDownTimer counterTimer = new CountDownTimer(finishTime * 1000, 1000) {
            public void onFinish() {
                currentGame.decrementScore();
                setQuestions();
             }

            public void onTick(long millisUntilFinished) {

                TextView time = (TextView) findViewById(R.id.timers);
                time.setText( " "+millisUntilFinished/1000);
                                }
        };
        counterTimer.start();
    }



    @Override
    public void onClick(View arg0) {
        //Log.d("Questions", "Moving to next question");
        if(arg0.getId()==R.id.answer5)
        {
        new AlertDialog.Builder(this)
        .setMessage("Are you sure?")
        .setCancelable(true)
        .setPositiveButton("Yes",
         new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog,
         int id) {
                finish();
                 }
             }).setNegativeButton("No", null).show();

                }

        else
        {
            if(!checkAnswer(arg0)) return;  

        /**
         * check if end of game
         */
        if (currentGame.isGameOver()){
            //Log.d("Questions", "End of game! lets add up the scores..");
            //Log.d("Questions", "Questions Correct: " + currentGame.getRight());
            //Log.d("Questions", "Questions Wrong: " + currentGame.getWrong());
            Intent i = new Intent(this, EndgameActivity.class);
            startActivity(i);
            finish();
        }
        else{
            Intent i = new Intent(this, QuestionActivity.class);
                        finish();
                        startActivity(i);
        }
        }
      }



    @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(View v) {

        Button b=(Button) v;
        String answer = b.getText().toString();

            //Log.d("Questions", "Valid Checkbox selection made - check if correct");
            if (currentQ.getAnswer().equalsIgnoreCase(answer))
            {
                b.setBackgroundResource(R.drawable.answercolor);
                //Log.d("Questions", "Correct Answer!");
                currentGame.incrementScore();
            }
            else{
                b.setBackgroundResource(R.drawable.answercolorr);
                //Log.d("Questions", "Incorrect Answer!");
                currentGame.decrementScore();
            }
            return true;
        }

}

Answer 1

您需要使用

 CountDownTimer.cancel();

您希望計時器停止遞增或遞減。

http://developer.android.com/reference/android/os/CountDownTimer.html#cancel%28%29

另外，我建議您將CountDownTimer設為成員變量，以便可以從任何地方取消它：

public class QuestionActivity extends Activity implements OnClickListener {

    private CountDownTimer counterTimer;
    // ...


    public void setTimer() {
        final long finishTime = 15;

        counterTimer = new CountDownTimer(finishTime * 1000, 1000) {
            public void onFinish() {
                currentGame.decrementScore();
                setQuestions();
             }

            public void onTick(long millisUntilFinished) {

                TextView time = (TextView) findViewById(R.id.timers);
                time.setText( " "+millisUntilFinished/1000);
            }
        };
        counterTimer.start();
    }
}

Answer 2

在方法checkAnswer（）中，應取消計時器。 否則，當計時器到期時，將調用#onFinish（），從而導致額外的decrementScore（）。