<com.example.anticlockwisedemo.Anticlockwise 
 android:id="@+id/id_timer" 
 android:layout_width="wrap_content" 
 android:layout_height="wrap_content" 
 android:textSize="66sp" /> 

package com.example.anticlockwisedemo; 
 
import java.text.SimpleDateFormat; 
import java.util.Date; 
import android.annotation.SuppressLint; 
import android.content.Context; 
import android.util.AttributeSet; 
import android.widget.Chronometer; 
 
 
/*** 
 * 
 * @author 张小_懒 2015/02/07 
 * 
 */ 
@SuppressLint( 
{ "ViewConstructor", "SimpleDateFormat" }) 
public class Anticlockwise extends Chronometer 
{ 
 public Anticlockwise(Context context, AttributeSet attrs) 
 { 
 super(context, attrs); 
 // TODO 自动生成的构造函数存根 
 mTimeFormat = new SimpleDateFormat("mm:ss"); 
 this.setOnChronometerTickListener(listener); 
 } 
 
 private long mTime; 
 private long mNextTime; 
 private OnTimeCompleteListener mListener; 
 private SimpleDateFormat mTimeFormat; 
 
 public Anticlockwise(Context context) 
 { 
 super(context); 
 
 } 
 
 /** 
 * 重新启动计时 
 */ 
 public void reStart(long _time_s) 
 { 
 if (_time_s == -1) 
 { 
 mNextTime = mTime; 
 } else 
 { 
 mTime = mNextTime = _time_s; 
 } 
 this.start(); 
 } 
 
 public void reStart() 
 { 
 reStart(-1); 
 } 
 
 /** 
 * 继续计时 
 */ 
 public void onResume() 
 { 
 this.start(); 
 } 
 
 /** 
 * 暂停计时 
 */ 
 public void onPause() 
 { 
 this.stop(); 
 } 
 
 /** 
 * 设置时间格式 
 * 
 * @param pattern 
 * 计时格式 
 */ 
 public void setTimeFormat(String pattern) 
 { 
 mTimeFormat = new SimpleDateFormat(pattern); 
 } 
 
 public void setOnTimeCompleteListener(OnTimeCompleteListener l) 
 { 
 mListener = l; 
 } 
 
 OnChronometerTickListener listener = new OnChronometerTickListener() 
 { 
 @Override 
 public void onChronometerTick(Chronometer chronometer) 
 { 
 if (mNextTime <= 0) 
 { 
 if (mNextTime == 0) 
 { 
 Anticlockwise.this.stop(); 
 if (null != mListener) 
 mListener.onTimeComplete(); 
 } 
 mNextTime = 0; 
 updateTimeText(); 
 return; 
 } 
 
 mNextTime--; 
 
 updateTimeText(); 
 } 
 }; 
 
 /** 
 * 初始化时间 
 * @param _time_s 
 */ 
 public void initTime(long _time_s) 
 { 
 mTime = mNextTime = _time_s; 
 updateTimeText(); 
 } 
 
 private void updateTimeText() 
 { 
 this.setText(mTimeFormat.format(new Date(mNextTime * 1000))); 
 } 
 
 interface OnTimeCompleteListener 
 { 
 void onTimeComplete(); 
 } 
 
}