1.NSUserDefaults是应用程序实现过程中只会存在单独一个的对象，故可以用它记录小型的数据如系统偏好设置等

2.初始化：

    self.myuserDefaults = [NSUserDefaults standardUserDefaults];

3.取值：

    [_myuserDefaults objectForKey:KMaxScore];

4.赋值：

    [_myuserDefaults setObject:[NSNumber numberWithInt:0] forKey:KMaxScore];

5.NSDate是日期的数据类型

    self.startDate = [NSDate date];//记录当前时间

6.计算间隔时间

    self.timeUse = [_gameTimer.fireDate timeIntervalSinceDate:_startDate];

7.初始化计时器

    self.gameTimer = [NSTimer scheduledTimerWithTimeInterval:_timeBetween
target:self selector:@selector(timerFired:) userInfo:nil repeats:YES];

8.计时器响应时间

    self.timeUse = [_gameTimer.fireDate timeIntervalSinceDate:_startDate];

一个简单的计时器小游戏

#define KMaxScore @"KMaxScore"@interface ViewController ()<UIAlertViewDelegate>@property (nonatomic, strong) UILabel *timeLabel;
@property (nonatomic, strong) UILabel *scoreLabel;
@property (nonatomic, strong) UILabel *animationLabel;
@property (nonatomic, strong) UIButton *aButton;
@property (nonatomic, strong) UIAlertView *myAlertView;@property (nonatomic, strong) NSDate *startDate;
@property (nonatomic, strong) NSTimer *gameTimer;@property (nonatomic, assign) NSInteger timeBetween;//button出现的时间间隔@property (nonatomic, assign) NSInteger buttonX;
@property (nonatomic, assign) NSInteger buttonY;@property (nonatomic, assign) NSInteger score;
@property (nonatomic, assign) NSInteger timeUse;@property (nonatomic, strong) NSUserDefaults *myuserDefaults;@end@implementation ViewController- (void)viewDidLoad {[super viewDidLoad];[self initTheData];[self initTheGame];
}- (void)initTheData{//判断是否第一次启动游戏if ([_myuserDefaults objectForKey:KMaxScore] == nil) {NSLog(@"%@", [_myuserDefaults objectForKey:KMaxScore]);self.myuserDefaults = [NSUserDefaults standardUserDefaults];[_myuserDefaults setObject:[NSNumber numberWithInt:0] forKey:KMaxScore];
//        NSLog(@"haha");}NSLog(@"%@", [_myuserDefaults objectForKey:KMaxScore]);//0
}- (void) initTheGame{UIImageView *bgImageView = [[UIImageView alloc] initWithFrame:self.view.bounds];[bgImageView setImage:[UIImage imageNamed:@"djfoj.jpg"]];[self.view addSubview:bgImageView];
//    NSLog(@"haha");
//    self.timeUse = 0;self.animationLabel = [[UILabel alloc] init];self.timeBetween = 1;self.startDate = [NSDate date];self.gameTimer = [NSTimer scheduledTimerWithTimeInterval:_timeBetween target:self selector:@selector(timerFired:) userInfo:nil repeats:YES];self.score = 0;self.scoreLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 40, 320, 40)];[_scoreLabel setText:[NSString stringWithFormat:@"得分:%d", _score]];[_scoreLabel setTextAlignment:NSTextAlignmentCenter];[self.view addSubview:_scoreLabel];self.timeLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 400, 320, 60)];[_timeLabel setTextAlignment:NSTextAlignmentCenter];[self.view addSubview:_timeLabel];self.aButton = [UIButton buttonWithType:UIButtonTypeCustom];
}- (void)timerFired:(NSTimer *) timer{[_aButton setBackgroundImage:[UIImage imageNamed:@"Unlock_DotLock1_Selected"] forState:UIControlStateNormal];self.buttonX = arc4random_uniform(220) + 50;self.buttonY = arc4random_uniform(360) + 50;[_aButton setFrame:CGRectMake(_buttonX, _buttonY, 52, 52)];[_aButton addTarget:self action:@selector(buttonTouch:) forControlEvents:UIControlEventTouchUpInside];[self.view addSubview:_aButton];self.timeUse = [_gameTimer.fireDate timeIntervalSinceDate:_startDate];[_timeLabel setText:[NSString stringWithFormat:@"剩余时间: %d", 61 - _timeUse]];if (_timeUse >= 56) {[_timeLabel setAlpha:1];[_timeLabel setTextColor:[UIColor redColor]];[_timeLabel setFont:[UIFont fontWithName:_timeLabel.font.fontName size:_timeLabel.font.pointSize + 3]];[UIView animateWithDuration:0.8 animations:^{[_timeLabel setAlpha:0];}];}if (_timeUse == 61) {if (_score > [[_myuserDefaults objectForKey:KMaxScore] intValue]) {[_myuserDefaults setObject:[NSNumber numberWithInt:_score] forKey:KMaxScore];}self.myAlertView = [[UIAlertView alloc] initWithTitle:@"游戏结束" message:
[NSString stringWithFormat:@"您的最高得分为:%d, 您本次的得分为:%d",
[[_myuserDefaults objectForKey:KMaxScore] intValue], _score]
delegate:self cancelButtonTitle:@"再玩一次" otherButtonTitles:@"退出游戏", nil];[_myAlertView show];[_gameTimer invalidate];}
}- (void)buttonTouch:(UIButton *)thisButton{_score++;[_scoreLabel setText:[NSString stringWithFormat:@"得分:%d", _score]];[_animationLabel setAlpha:1];[_animationLabel setFrame:CGRectMake(thisButton.frame.origin.x, thisButton.frame.origin.y, 40, 40)];[_animationLabel setBackgroundColor:[UIColor greenColor]];[_animationLabel setText:@"恭喜"];[_animationLabel setTextAlignment:NSTextAlignmentCenter];[_animationLabel setTextColor:[UIColor redColor]];[self.view addSubview:_animationLabel];[UIView animateWithDuration:1.0 animations:^{[_animationLabel setAlpha:0];}];
}-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{if (buttonIndex == 0) {[self initTheGame];}else{NSLog(@"已经退出游戏");}
}@end