//在向服务端发送获取验证码成功的回调函数中，开始发消息：
mHandler.obtainMessage();
mHandler.sendEmptyMessage(MSG_CODE);

//消息的处理：
 private static final int MSG_CODE = 0;
 private int limitTime = 121;
 private Handler mHandler = new Handler(new Handler.Callback() {
    @Override
    public boolean handleMessage(Message msg) {
      if(msg.what==MSG_CODE){
        limitTime--;
        if(limitTime>0){
          mHandler.sendEmptyMessageDelayed(MSG_CODE,1000);
          mBtnVerify.setText("倒计时："+limitTime+"s");

        }else{
          mBtnVerify.setText("获取验证码");
        }
        return true;
      }
      return false;
    }
  });

//在向服务端发送获取验证码成功的回调函数中，开始发消息：
mHandler.post(myRunnale);

//消息的处理：
 private int time = 11;

  private Handler mHandler = new Handler();
  private Runnable myRunnale = new Runnable() {
    @Override
    public void run() {
      time--;
      if(time>0){
        mHandler.postDelayed(myRunnale,1000);
        mTvChange.setText("剩余"+time+"s");
      }else{
        mTvChange.setText("完毕");
      }
    }
  };