CountDown Timer App Android

Question

我正在Android平台上创建一个倒计时器。

当用户按下“停止”按钮时，我不知道如何将剩余时间存储在计时器上（计时器上的5分钟）。按钮（暂停）。因此，如果用户稍后按下“开始”按钮，再次按下按钮，它将从停止的位置继续倒计时。这是我到目前为止所做的。

public class Timer_App extends Activity {


Button btn_Start, btn_Stop, btn_Reset;
TextView timer_text;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_timer_app);

    //NEVER SLEEP!
    getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);


    //Buttons
    btn_Start = (Button) findViewById(R.id.Start);
    btn_Stop = (Button) findViewById(R.id.Stop);
    btn_Reset = (Button) findViewById(R.id.Reset);

    //FONT
    Typeface typeface = Typeface.createFromAsset(getAssets(), "Digital_Font.TTF");
    timer_text = (TextView) findViewById(R.id.timer_view);
    timer_text.setTypeface(typeface);

    //Timer
    timer_text.setText("05:00);

    final CounterClass timer = new CounterClass(300000, 1000);

    //Start btn
    btn_Start.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            timer.start();
        }
    });

    //Stop btn
    btn_Stop.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            timer.cancel();
        }
    });

    //Reset btn
    btn_Reset.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

        }
    });
}


//TIMER CLASS
public class CounterClass extends CountDownTimer{

    public CounterClass(long millisInFuture, long countDownInterval) {
        super(millisInFuture, countDownInterval);
    }

    @Override
    public void onTick(long millisUntilFinished) {

        String hms = String.format("%02d:%02d",
                TimeUnit.MILLISECONDS.toMinutes(millisUntilFinished) - TimeUnit.HOURS.toMinutes(TimeUnit.MILLISECONDS.toHours(millisUntilFinished)),
                TimeUnit.MILLISECONDS.toSeconds(millisUntilFinished) - TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(millisUntilFinished)));
        timer_text.setText(hms);
    }

    @Override
    public void onFinish() {

    }
}

}