使用Android提供的CountDownTimer类实现短信验证码倒计时

android.os.CountDownTimer
public abstract class CountDownTimer {

/**
 * Millis since epoch when alarm should stop:定时时间
 */
private final long mMillisInFuture;
/**
 * The interval in millis that the user receives callbacks:回调间隔时间
 */
private final long mCountdownInterval;

 public CountDownTimer(long millisInFuture, long countDownInterval) {
    mMillisInFuture = millisInFuture;
    mCountdownInterval = countDownInterval;
}

具体代码:
public class MainActivity extends AppCompatActivity {

private TimeCount timeCount;
private Button button;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    button = (Button) findViewById(R.id.btn);

    timeCount = new TimeCount(11000,1000);

    timeCount.setCountListener(new TimeCount.CountListener() {
        @Override
        public void onTick(Long time) {
            button.setText(String.valueOf(time/1000).concat("s"));
            button.setEnabled(false);//设置不可点击
        }

        @Override
        public void onFinish() {
            button.setText("重新发送");
            button.setEnabled(true);
        }
    });
}
public void click(View view){
    Toast.makeText(MainActivity.this,"click",Toast.LENGTH_SHORT).show();
    timeCount.start();

}

}

class TimeCount extends CountDownTimer {

private CountListener countListener;
  /**
   * @param millisInFuture    The number of millis in the future from the call
   *                          to {@link #start()} until the countdown is done and {@link #onFinish()}
   *                          is called.
   * @param countDownInterval The interval along the way to receive
   *                          {@link #onTick(long)} callbacks.
   */
  public TimeCount(long millisInFuture, long countDownInterval) {
      super(millisInFuture, countDownInterval);
  }

  @Override
  public void onTick(long millisUntilFinished) {
      countListener.onTick(millisUntilFinished);

  }

  @Override
  public void onFinish() {
      countListener.onFinish();
  }

public void setCountListener(CountListener countListener){
    this.countListener = countListener;

}
public interface CountListener{
    public void onTick(Long time);
    public void onFinish();
}

}