CountDownTimer timer = new CountDownTimer(10000, 1000) {
            @Override
            public void onTick(long millisUntilFinished) {
                tv_yzm.setEnabled(false);
                tv_yzm.setText("已发送(" + millisUntilFinished / 1000 + ")");
            }

            @Override
            public void onFinish() {
                tv_yzm.setEnabled(true);
                tv_yzm.setText("获取验证码");
            }
        }.start();

  @Override
    protected void onDestroy() {
        super.onDestroy();
        if (timer!=null){
            timer.cancel();
        }

    }

详细说明参考：https://blog.csdn.net/weixin_42564441/article/details/80967482