iOS中定時器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 = [NSTimer  timerWithTimeInterval:3.0 target:selfselector:@selector(timerFired:)userInfo:nilrepeats:NO];

[[NSRunLoop  currentRunLoop] 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划；

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不是絕對准確的,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

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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如上，如果沒有重復執行的timer相當於 

[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. 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;

 

}