ios NSTimer做的计时器（精确到微妙）

自己在学习过程中用到过NSTimer，当时在网上找了不少资料。现在自己做一个简单的demo跟大家分享。

我就直接在下面粘贴代码，希望能帮到一些初学iOS的朋友。

ViewController.h：

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController{

    UIButton *startButton;

    UIButton *stopButton;

    UILabel *timeLabel;

    UILabel *detailLabel;

    NSTimer *mytimer;

}

@property (nonatomic) BOOL isOn;

@property (nonatomic) int myTimerecord,hour,min,scd,mscd;

@property (nonatomic) NSString *hourText,*minText,*scdText,*mscdText,*timeLabelText;

@end

ViewController.m：

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

_hour = 0;

_min = 0;

_scd = 0;

_mscd = 0;

_myTimerecord = 0;

- (void)viewDidLoad {

    [super viewDidLoad];

    

    detailLabel = [[UILabel alloc]initWithFrame:CGRectMake(60, 30, 200, 70)];

    detailLabel.text = @"计时器";

    [detailLabel setTextAlignment:NSTextAlignmentCenter];

    [self.view addSubview:detailLabel];

    

    startButton = [[UIButton alloc]initWithFrame:CGRectMake(60, 320, 60, 40)];

    [startButton setBackgroundColor:[UIColor blueColor]];

    [startButton setTitle:@"开始" forState:UIControlStateNormal];

    [startButton addTarget:self action:@selector(startBtAction) forControlEvents:UIControlEventTouchUpInside];

    [self.view addSubview:startButton];

    

    stopButton = [[UIButton alloc]initWithFrame:CGRectMake(200, 320, 60, 40)];

    [stopButton setBackgroundColor:[UIColor blackColor]];

    [stopButton setTitle:@"停止" forState:UIControlStateNormal];

    [stopButton addTarget:self action:@selector(stopBtAction) forControlEvents:UIControlEventTouchUpInside];

    [self.view addSubview:stopButton];

    

    timeLabel = [[UILabel alloc]initWithFrame:CGRectMake(0, 100, 320, 120)];

    [timeLabel setTextAlignment:NSTextAlignmentCenter];

    [timeLabel setText:@"00  :  00  :  00  :  00"];

    timeLabel.font = [UIFont boldSystemFontOfSize:32.0];

    [timeLabel setBackgroundColor:[UIColor blackColor]];

    [timeLabel setTextColor:[UIColor whiteColor]];

    [self.view addSubview:timeLabel];

    

    //这里0.01表示设置时间间隔是0.01秒

    mytimer = [NSTimer scheduledTimerWithTimeInterval:0.01 target:self selector:@selector(timerFired) userInfo:nil repeats:YES];

    // Do any additional setup after loading the view.

}

//根据上面的设定，这个方法每隔0.01秒执行一次

-(void)timerFired

{

    if (_isOn) {

        _myTimerecord++;                      //记录累计微妙的值，根据这个值计算出相对应的秒，分钟，小时

        _hour = _myTimerecord / 360000;

        _min = (_myTimerecord%360000)/6000;

        _scd = (_myTimerecord%6000)/100;

        _mscd = _myTimerecord%100;

    }

    [self updateUI];

}

-(void)startBtAction

{

    if (_isOn) {

        _isOn = NO;

    } else {

        _isOn = YES;

    }

}

-(void)stopBtAction

{

    _isOn = NO;//暂停

    [self realStop];

}

-(void)realStop

{

    _hour = 0;

    _min = 0;

    _scd = 0;

    _mscd = 0;

    _myTimerecord = 0;

    _isOn = NO;

}

//这个方法实现数据（_myTimerecord）和页面中显示的值是统一的

-(void)updateUI

{

    if (_hour < 10) {

        _hourText = [[NSString alloc]initWithFormat:@"0%d",_hour];

    }else {

        _hourText = [[NSString alloc]initWithFormat:@"%d",_hour];

    }

    

    if (_min < 10) {

        _minText = [[NSString alloc]initWithFormat:@"0%d",_min];

    }else {

        _minText = [[NSString alloc]initWithFormat:@"%d",_min];

    }

    

    if (_scd < 10) {

        _scdText = [[NSString alloc]initWithFormat:@"0%d",_scd];

    }else {

        _scdText = [[NSString alloc]initWithFormat:@"%d",_scd];

    }

    

    if (_mscd < 10) {

        _mscdText = [[NSString alloc]initWithFormat:@"0%d",_mscd];

    } else {

        _mscdText = [[NSString alloc]initWithFormat:@"%d",_mscd];

    }

    

    _timeLabelText = [[NSString alloc]initWithFormat:@"%@  :  %@  :  %@  :  %@",_hourText,_minText,_scdText,_mscdText];

    [timeLabel setText:_timeLabelText];

    

    if (_isOn) {

        [startButton setTitle:@"暂停" forState:UIControlStateNormal];

    }else {

        [startButton setTitle:@"开始" forState:UIControlStateNormal];

    }

}

@end