private int minute = 1;//这是分钟
    private int second = 0;//这是分钟后面的秒数。这里是以30分钟为例的，所以，minute是30，second是0
    private TextView tvname;
    private Timer timer;
    private TimerTask timerTask;
 //这是接收回来处理的消息
    private Handler handler = new Handler() {
        public void handleMessage(Message msg) {
            if (minute == 0) {
                if (second == 0) {
                    tvname.setText("结束");
                    if (timer != null) {
                        timer.cancel();
                        timer = null;
                    }
                    if (timerTask != null) {
                        timerTask = null;
                    }
                } else {
                    second--;
                    if (second >= 10) {
                        tvname.setText("0" + minute + ":" + second);
                    } else {
                        tvname.setText("0" + minute + ":0" + second);
                    }
                }
            } else {
                if (second == 0) {
                    second = 59;
                    minute--;
                    if (minute >= 10) {
                        tvname.setText(minute + ":" + second);
                    } else {
                        tvname.setText("0" + minute + ":" + second);
                    }
                } else {
                    second--;
                    if (second >= 10) {
                        if (minute >= 10) {
                            tvname.setText(minute + ":" + second);
                        } else {
                            tvname.setText("0" + minute + ":" + second);
                        }
                    } else {
                        if (minute >= 10) {
                            tvname.setText(minute + ":0" + second);
                        } else {
                            tvname.setText("0" + minute + ":0" + second);
                        }
                    }
                }
            }
        }

    };
//在oncreate中
  tvname = (TextView) findViewById(R.id.tvname);
        if (minute == 0 && second == 30) {
            tvname.setText("" + minute + ":" + second);
            tvname.setTextColor(getResources().getColor(R.color.red));

        } else {
            tvname.setText(minute + ":" + second);
        }

        timerTask = new TimerTask() {
            @Override
            public void run() {
                Message msg = new Message();
                msg.what = 0;
                handler.sendMessage(msg);
            }
        };
        timer = new Timer();
        timer.schedule(timerTask, 0, 1000);

    }

    @Override
    protected void onDestroy() {
        if (timer != null) {
            timer.cancel();
            timer = null;
        }
        if (timerTask != null) {
            timerTask = null;
        }
        minute = -1;
        second = -1;
        super.onDestroy();
    }