iOS中定时器NSTimer的使用

1、初始化

+ (NSTimer *)timerWithTimeInterval:(NSTimeInterval)ti target:(id)aTarget selector:(SEL)aSelector userInfo:(id)userInfo repeats:(BOOL)yesOrNo;

+ (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)ti target:(id)aTarget selector:(SEL)aSelector userInfo:(id)userInfo repeats:(BOOL)yesOrNo;

注：不用scheduled方式初始化的，需要手动addTimer:forMode: 将timer添加到一个runloop中。

　　而scheduled的初始化方法将以默认mode直接添加到当前的runloop中.

举例：

NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:10.0 target:self selector:@selector(timerFired:) userInfo:nil repeats:NO];

或

NSTimer *myTimer = [NSTimer  timerWithTimeInterval:3.0 target:selfselector:@selector(timerFired:)userInfo:nilrepeats:NO];

[[NSRunLoop  currentRunLoop] addTimer:myTimerforMode:NSDefaultRunLoopMode];

2、触发（启动）

当定时器创建完（不用scheduled的，添加到runloop中后，该定时器将在初始化时指定的timeInterval秒后自动触发。

可以使用-(void)fire;方法来立即触发该定时器；

注：You can use this method to fire a repeating timer without interrupting its regular firing schedule. If the timer is non-repeating, it is automatically invalidated after firing, even if its scheduled fire date has not arrived.

在重复执行的定时器中调用此方法后立即触发该定时器，但不会中断其之前的执行计划；

在不重复执行的定时器中调用此方法，立即触发后，就会使这个定时器失效。

3、停止

- (void)invalidate;

这个是唯一一个可以将计时器从runloop中移出的方法。

注：

NSTimer可以精确到50-100毫秒.

NSTimer不是绝对准确的,而且中间耗时或阻塞错过下一个点,那么下一个点就pass过去了.

延时函数和Timer的使用

//延时函数：
[NSThread sleepForTimeInterval:5.0]； //暂停5s.

//Timer的使用：
NSTimer *connectionTimer;  //timer对象

//实例化timer
self.connectionTimer=[NSTimer scheduledTimerWithTimeInterval:1.5 target:self selector:@selector(timerFired:) userInfo:nil repeats:NO];
[[NSRunLoop currentRunLoop]addTimer:self.connectionTimer forMode:NSDefaultRunLoopMode];
//用timer作为延时的一种方法
do{
[[NSRunLoopcurrentRunLoop]runUntilDate:[NSDatedateWithTimeIntervalSinceNow:1.0]];
}while(!done); 

//timer调用函数
-(void)timerFired:(NSTimer *)timer{
done =YES;
}

转自：http://magicalboy.com/objective_c_nstimer_usage/#comment-45

创建 NSTimer

1. 1. Scheduled Timers & Using Selector

- (IBAction)startOneOffTimer:sender {

    [NSTimer scheduledTimerWithTimeInterval:2.0

             target:self

             selector:@selector(targetMethod:)

             userInfo:[self userInfo]

             repeats:NO];

}

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1. 1. 如上，如果没有重复执行的timer相当于 

[self performSelector:@selector(targetMethod:) withObject:nil afterDelay:2.0];

// declcare

@property (assign) NSTimer *repeatingTimer;

// implements

- (IBAction)startRepeatingTimer:sender {

    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:0.5

                              target:self selector:@selector(timerFireMethod:)

                              userInfo:[self userInfo] repeats:YES];

    self.repeatingTimer = timer;

}

- (IBAction)stopRepeatingTimer:sender {

    [repeatingTimer invalidate];

    self.repeatingTimer = nil;

}

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1. 1. Unscheduled Timers & Using Invocation

// declare

@property (retain) NSTimer *unregisteredTimer;

// implements

- (IBAction)createUnregisteredTimer:sender {

    NSMethodSignature *methodSignature = [self methodSignatureForSelector:@selector(invocationMethod:)];

    NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:methodSignature];

    [invocation setTarget:self];

    [invocation setSelector:@selector(invocationMethod:)];

    NSDate *startDate = [NSDate date];

    [invocation setArgument:&startDate atIndex:2];

    NSTimer *timer = [NSTimer timerWithTimeInterval:0.5 invocation:invocation repeats:YES];

    self.unregisteredTimer = timer;

}

- (IBAction)startUnregisteredTimer:sender {

    if (unregisteredTimer != nil) {

        NSRunLoop *runLoop = [NSRunLoop currentRunLoop];

        [runLoop addTimer:unregisteredTimer forMode:NSDefaultRunLoopMode];

    }

}

- (IBAction)stopUnregisteredTimer:sender {

    [unregisteredTimer invalidate];

    self.unregisteredTimer = nil;

}