docs: public void start(long millisecond) {
          if (millisecond <= 0) return;
  
          mPreviousIntervalCallbackTime = 0;
  
          if (null != mCustomCountDownTimer) {
              mCustomCountDownTimer.stop();
              mCustomCountDownTimer = null;
          }
  
          long countDownInterval;
          if (mCountdown.isShowMillisecond) {
              countDownInterval = 10;
              updateShow(millisecond);
          } else {
              countDownInterval = 1000;
          }
  
          mCustomCountDownTimer = new CustomCountDownTimer(millisecond, countDownInterval) {
              @Override
              public void onTick(long millisUntilFinished) {
                  updateShow(millisUntilFinished);
              }
  
              @Override
              public void onFinish() {
                  // countdown end
                  allShowZero();
                  // callback
                  if (null != mOnCountdownEndListener) {
                      mOnCountdownEndListener.onEnd(CountdownView.this);
                  }
              }
          };
          mCustomCountDownTimer.start();
      }