IOS NSTimer 定时器

NSTimer 的初始化

初始化方法：有五种初始化方法

(NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)ti invocation:(NSInvocation *)invocation repeats:(BOOL)yesOrNo;
//例如:
NSTimer * timer = [NSTimer scheduledTimerWithTimeInterval:1 invocation:invo repeats:YES];

(NSTimer *)timerWithTimeInterval:(NSTimeInterval)ti target:(id)aTarget selector:(SEL)aSelector userInfo:(id)userInfo repeats:(BOOL)yesOrNo;
//例如:
NSTimer * timer = [NSTimer timerWithTimeInterval:1 target:self selector:@selector(timerAction) userInfo:nil repeats:NO];

(NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)ti target:(id)aTarget selector:(SEL)aSelector userInfo:(id)userInfo repeats:(BOOL)yesOrNo;
//例如:
NSTimer * timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timerAction:) userInfo:@"123" repeats:YES];

(instancetype)initWithFireDate:(NSDate *)date interval:(NSTimeInterval)ti target:(id)t selector:(SEL)s userInfo:(id)ui repeats:(BOOL)repeats:(BOOL)yesOrNo;
//例如:
NSTimer * timer = [[NSTimer alloc]initWithFireDate:[NSDate distantPast] interval:1 target:self selector:@selector(timerAction:) userInfo:nil repeats:YES];
[[NSRunLoop mainRunLoop]addTimer:timer forMode:NSDefaultRunLoopMode];

它的属性

@property (copy) NSDate *fireDate;//这是设置定时器的启动时间，常用来管理定时器的启动与停止

//启动定时器
timer.fireDate = [NSDate distantPast];
//停止定时器
timer.fireDate = [NSDate distantFuture];

@property (readonly) NSTimeInterval timeInterval;//这个是一个只读属性，获取定时器调用间隔时间

@property NSTimeInterval tolerance;//这是7.0之后新增的一个属性，因为NSTimer并不完全精准，通过这个值设置误差范围

@property (readonly, getter=isValid) BOOL valid;//获取定时器是否有效

@property (readonly, retain) id userInfo;//获取参数信息

释放,销毁定时器

[timer invalidate];//是唯一的方法将定时器从循环池中移除

timer=nil;//同时置空