Android系统自带的一个倒计时类，可作为验证码倒计时等。

public class TimeCount extends CountDownTimer {
    private static final int TIME_TASCK = 1000;
    private Button button;
    private Context context;
    public TimeCount(Context context, long millisInFuture, Button view) {
        super(millisInFuture, TIME_TASCK);
        button = view;
        this.context = context;
    }

    @Override
    public void onFinish() {// 计时完毕
        button.setTextColor(context.getResources().getColor(R.color.text_white));
        button.setBackgroundResource(R.drawable.button_background);
        button.setText("发送验证码");
        button.setClickable(true);
    }

    @Override
    public void onTick(long millisUntilFinished) {// 计时过程
        button.setTextColor(context.getResources().getColor(R.color.home_item_count));
        button.setClickable(false);//防止重复点击
        button.setBackgroundResource(R.drawable.gray_button_background);
        button.setText(context.getString(R.string.send_count_down, millisUntilFinished / TIME_TASCK));
    }
}