////  StopWatch.h//  ShowTime////  Created by YouXianMing on 14-10-16.//  Copyright (c) 2014年 YouXianMing. All rights reserved.//#import <Foundation/Foundation.h>@protocol StopWatchDelegate <NSObject>- (void)stopWatchDate:(NSDate *)date;@end// 说明：此秒表类是基于CADisplayLink所写，每一帧刷新一次@interface StopWatch : NSObject@property (nonatomic, assign) id<StopWatchDelegate> delegate;- (void)start;        // 开始- (void)stop;         // 停止- (void)reset;        // 复位- (NSDate *)gainDate; // 获取时间（只有在start的时候获取时间才有意义，stop之后返回值为0）@end

////  StopWatch.m//  ShowTime////  Created by YouXianMing on 14-10-16.//  Copyright (c) 2014年 YouXianMing. All rights reserved.//#import "StopWatch.h"@interface StopWatch ()@property (nonatomic, strong) CADisplayLink *countDownTimer;@property (nonatomic, strong) NSDate        *startDate;@property (nonatomic, strong) NSDate        *pausedDate;@property (nonatomic, assign) BOOL           startFlag;@end@implementation StopWatch- (void)start {    _startFlag = YES;        if (_countDownTimer) {        [_countDownTimer invalidate];        _countDownTimer = nil;    }        if (_countDownTimer == nil) {        if(_startDate == nil) {            _startDate = [NSDate date];        }                if(_pausedDate != nil){            NSTimeInterval countedTime = [_pausedDate timeIntervalSinceDate:_startDate];            _startDate = [[NSDate date] dateByAddingTimeInterval:-countedTime];            _pausedDate = nil;        }                _countDownTimer               = [CADisplayLink displayLinkWithTarget:self selector:@selector(timerRunEvent)];        _countDownTimer.frameInterval = 1;        [_countDownTimer addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];    }}- (void)stop {    _startFlag = NO;    if (_countDownTimer) {        [_countDownTimer invalidate];        _countDownTimer = nil;        _pausedDate     = [NSDate date];    }}- (void)reset {    _pausedDate = nil;    _startDate  = [NSDate date];        if (_delegate) {        NSTimeInterval currentToSpecifyDuration = [[[NSDate alloc] init] timeIntervalSinceDate:_startDate];        NSDate *date = [NSDate dateWithTimeIntervalSince1970:currentToSpecifyDuration];        [_delegate stopWatchDate:date];    }}- (NSDate *)gainDate {    if (_startFlag) {        NSTimeInterval currentToSpecifyDuration = [[[NSDate alloc] init] timeIntervalSinceDate:_startDate];        NSDate *date = [NSDate dateWithTimeIntervalSince1970:currentToSpecifyDuration];        return date;    } else {        return nil;    }}- (void)timerRunEvent {    if (_delegate) {        NSTimeInterval currentToSpecifyDuration = [[[NSDate alloc] init] timeIntervalSinceDate:_startDate];        NSDate *date = [NSDate dateWithTimeIntervalSince1970:currentToSpecifyDuration];        [_delegate stopWatchDate:date];    }}- (void)dealloc {    NSLog(@"xxxxxx");}@end