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，需要手動addTimer:forMode: 將timer添加到一個runloop中。

而scheduled的初始化方法將以默認mode直接添加到當前的runloop中.

舉例：

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

或

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

[[NSRunLoopcurrentRunLoop]addTimer:myTimerforMode:NSDefaultRunLoopMode];

2、觸發(啟動)

當定時器創建完(不用scheduled的，添加到runloop中后，該定時器將在初始化時指定的timeInterval秒后自動觸發。

可以使用-(void)fire;方法來立即觸發該定時器；

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.

在重復執行的定時器中調用此方法后立即觸發該定時器，但不會中斷其之前的執行計劃；

在不重復執行的定時器中調用此方法，立即觸發后，就會使這個定時器失效。

3、停止

- (void)invalidate;

這個是唯一一個可以將計時器從runloop中移出的方法。

注：

NSTimer可以精確到50-100毫秒.

NSTimer不是絕對準確的,而且中間耗時或阻塞錯過下一個點,那么下一個點就pass過去了.

延時函數和Timer的使用

//延時函數：[NSThread sleepForTimeInterval:5.0]； //暫停5s.//Timer的使用：NSTimer *connectionTimer; //timer對象//實例化timerself.connectionTimer=[NSTimer scheduledTimerWithTimeInterval:1.5 target:self selector:@selector(timerFired:) userInfo:nil repeats:NO];

[[NSRunLoop currentRunLoop]addTimer:self.connectionTimer forMode:NSDefaultRunLoopMode]; //用timer作為延時的一種方法do{

[[NSRunLoopcurrentRunLoop]runUntilDate:[NSDatedateWithTimeIntervalSinceNow:1.0]];

}while(!done); //timer調用函數-(void)timerFired:(NSTimer *)timer{

done =YES;

}

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

創建 NSTimer

Scheduled Timers & Using Selector

-

(

IBAction

)

startOneOffTimer:

sender

{

[

NSTimer

scheduledTimerWithTimeInterval:

2.0

target:

self

selector:

@selector

(

targetMethod:

)

userInfo:

[

self

userInfo

]

repeats:

NO

];

}

如上，如果沒有重復執行的timer相當于

[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

;

}

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;

}

總結

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