要点
1.通过计时器Timer TimerTask 设置每秒执行一次递减任务
2.通过handler 在UI线程中修改秒数
3.设置开关，对Timer TimerTask 停止消除任务
4.设置初始按钮样式，和倒计时按钮样式。（自行设置）

import android.os.Handler;  
import android.util.AttributeSet;  
import android.widget.Button;  
import java.util.Timer;  
import java.util.TimerTask;  
  
/** 
 * 倒计时时间控件 
 */  
public class TimeButton extends Button {  
    private long length = 60 * 1000;// 倒计时长度,这里给了默认60秒  
    private String text_after = "s";  
    private String text_before = "获取验证码";  
  
  
    private Timer timer;  
    private TimerTask timerTask;  
    private long time;  
  
    public TimeButton(Context context) {  
        super(context);  
    }  
  
    public TimeButton(Context context, AttributeSet attrs) {  
        super(context, attrs);  
    }  
  
    public TimeButton(Context context, AttributeSet attrs, int defStyleAttr) {  
        super(context, attrs, defStyleAttr);  
    }  
  
    /** 
     * 倒计时 
     */  
   private Handler handler = new Handler() {  
        public void handleMessage(android.os.Message msg) {  
            TimeButton.this.setText(time / 1000 + text_after);  
            time -= 1000;  
            if (time < 0) {  
                TimeButton.this.setEnabled(true);  
                TimeButton.this.setText(text_before);  
                clearTimer();  
            }  
        }  
    };  
  
    private void initTimer() {  
        time = length;  
        if(timer==null) {  
            timer = new Timer();  
        }  
        if(timerTask==null) {  
            timerTask = new TimerTask() {  
                @Override  
                public void run() {  
                    handler.sendEmptyMessage(0x01);  
                }  
            };  
        }  
    }  
  
    private void clearTimer() {  
        try {  
            if (timerTask != null) {  
                timerTask.cancel();  
                timerTask = null;  
            }  
            if (timer != null) {  
                timer.cancel();  
                timer = null;  
            }  
            //还原样式  
            setBackgroundResource(R.drawable.shape_btn_round_corner_orange);  
            setTextColor(getResources().getColor(R.color.common_background_white));  
        }catch (Exception e){  
  
        }  
    }  
  
    /** 
     * 开始倒计时 
     */  
    public void start_count_down(){  
        this.setEnabled(false);  
        initTimer();  
        timer.schedule(timerTask, 0, 1000);  
        //设置倒计时样式  
        setBackgroundResource(R.drawable.shape_common_radius_corner_line);  
        setTextColor(getResources().getColor(R.color.common_top_bar_color_in_orange));  
    }  
  
    /** 
     * 停止倒计时 
     */  
    public void stop_count_down(){  
        clearTimer();  
    }  
  
  
    /** 
     * 设置到计时长度 
     * 
     * @param length 
     *            时间 默认毫秒 
     * @return 
     */  
    public TimeButton setLength(long length) {  
        this.length = length;  
        return this;  
    }  
}