iphone NStimer在2秒内开始

Question

我想在启动它后2秒运行一段代码。

我认为NSTimer可以做到这一点，但无法弄清楚。

Answer 1

下面将做你的需要：

NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval: 2 
            target:self 
            selector:@selector(handleTimer:) 
            userInfo:nil 
            repeats:NO]; 

然后委托函数：

-(void)handleTimer: (NSTimer *) timer 
{  
    //code 
} 

Answer 2

您应该能够将NSTimeInterval设置为2.0秒，并且应该在该时间段之后触发。你在看什么？你用来调用定时器的代码是什么？

Answer 3

的NSTimer可以使用，但另一种选择是使用performSelector:withObject:afterDelay:这基本上就像一个方法调用（消息发送）稍后发生。

这个例子将发出一个doStuff：延迟之后消息：

[self performSelector:@selector(doStuff:) withObject:self afterDelay:2]; 

导致得到2.0秒后调用此方法：

-(void)doStuff:(id)sender 
{ 
    /// do something 
} 

Answer 4

您还可以使用一些有用的代码：

NSObject + PerformBlock.h

@interface NSObject (PerformBlock) 

- (void)performBlock:(void(^)(void))block waitUntilDone:(BOOL)wait; 
- (void)performBlock:(void(^)(void))block afterDelay:(NSTimeInterval)delay; 
- (void)performBlock:(void(^)(void))block repeatCount:(NSUInteger)repeatCount timeInteval:(NSTimeInterval)timeInterval; 

@end 

NSObject的+ PerformBlock.m

@interface NSObject (PerformBlockHidden) 

- (void)performBlock:(void(^)(void))block; 

@end 

@implementation NSObject (PerformBlock) 

- (void)performBlock:(void(^)(void))block { 
    block(); 
} 

- (void)performBlock:(void(^)(void))block waitUntilDone:(BOOL)wait { 
    [self performSelector:@selector(performBlock:) onThread:nil withObject:[[block copy] autorelease] waitUntilDone:wait]; 
} 

- (void)performBlock:(void(^)(void))block afterDelay:(NSTimeInterval)delay { 
    [self performSelector:@selector(performBlock:) withObject:[[block copy] autorelease] afterDelay:delay]; 
} 

- (void)performBlock:(void(^)(void))block repeatCount:(NSUInteger)repeatCount timeInteval:(NSTimeInterval)timeInterval { 
    for (NSInteger repetition = 0; repetition < repeatCount; repetition++) 
     [self performBlock:block afterDelay:(repetition*timeInterval)]; 
} 

@end 

则只需导入NSObject的+ PerformBlock.h，并呼吁：

[myObject performBlock:^{ 
    // Code you want to perform after 2secs 
} afterDelay:2];