//参数一为总时间60s，参数二为间隔时间1s
private CountDownTimer timer = new CountDownTimer(60000, 1000) {
@Override
public void onTick(long millisUntilFinished) {
tv.setText((millisUntilFinished / 1000) + "秒后可重发");
}
@Override
public void onFinish() {
tv.setEnabled(true);
tv.setText("获取验证码");
}};
timer.start()启动
timer.cancel()取消
