iOS开发-延迟执行

骑猪看日落 2022-08-24 15:30 236阅读 0赞

有时候,希望某段代码,某个时间在一定时间后执行,这时候就要用到延迟执行。

常见的方法有以下几种:

1.最直接的方法performSelector:withObject:afterDelay:

这种方法的缺点：每次要为延时写一个方法

[self performSelector:@selector(scale_2) withObject:nil afterDelay:0.5f];

-(void)scale_2
    {
        UIImageView *round_2 = [[UIImageView alloc]initWithFrame:CGRectMake(105, 210, 20, 20)];
        round_2.image = [UIImage imageNamed:@"round_"];
        [splashView addSubview:round_2];
        [self setAnimation:round_2];
    }

2.使用类别，用BOLCK执行

###     ###

@implementation NSObject (PerformBlockAfterDelay)
    - (void)performBlock:(void (^)(void))block
              afterDelay:(NSTimeInterval)delay
    {
        block = [[block copy] autorelease];
        [self performSelector:@selector(fireBlockAfterDelay:)
                   withObject:block
                   afterDelay:delay];
    }
    
    
    - (void)fireBlockAfterDelay:(void (^)(void))block {
        block();
    }
    
    @end

3.使用GCD

### \[代码\]c\#/cpp/oc代码： ###

void RunBlockAfterDelay(NSTimeInterval delay, void (^block)(void))
    {
    
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, NSEC_PER_SEC*delay),
          dispatch_get_current_queue(), block);
    
    }

poolo:注意 图中的dispatch\_getcurrent\_queue() 方法在ios6已经被kill了

现在用dispatch\_get\_global\_queue(DISPATCH\_QUEUE\_PRIORITY\_HIGH,0)

第一个参数是优先级有，第二个参数为0或nil

如果要要对界面操作则使用 dispatch\_get\_main\_queue ()；

参考：http://www.cnblogs.com/guwandong/archive/2012/08/08/2626211.html

4.可能是不太好的方法，用animation的completion参数

### \[代码\]c\#/cpp/oc代码： ###

[UIView animateWithDuration:0.0 delay:5.0 options:UIViewAnimationOptionAllowUserInteraction animations:^{
    
    } completion:^(BOOL finished) {
    
        //do stuff here
    
    }];

5.使用NSOperationQueue，在应用程序的下一个主循环执行：

### \[代码\]c\#/cpp/oc代码： ###

<table style="border-collapse:collapse!important; margin:0px!important; padding:0px!important; border:0px!important; float:none!important; vertical-align:baseline!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-size:10pt!important"> 
 <tbody> 
  <tr style="margin:0px!important; padding:0px!important; border:0px!important; float:none!important; vertical-align:baseline!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-size:10pt!important"> 
   <td style="font-size:10pt!important; margin:0px!important; padding:0px!important; border:0px!important; float:none!important; vertical-align:top!important; height:auto!important; width:3em!important; line-height:1.1em!important; color:rgb(56,86,111)!important"> <code style="font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:10pt!important; white-space:pre; margin:0px!important; padding:0px 0.3em 0px 0px!important; border:0px!important; text-align:right!important; float:none!important; vertical-align:baseline!important; height:auto!important; width:2.7em!important; line-height:1.1em!important; display:block!important">1</code></td> 
   <td style="font-size:10pt!important; margin:0px!important; padding:0px 0px 0px 0.5em!important; border-width:0px 0px 0px 3px!important; border-left-style:solid!important; border-left-color:rgb(67,90,95)!important; float:none!important; vertical-align:top!important; height:auto!important; width:auto!important; line-height:1.1em!important; color:rgb(185,189,182)!important"> <code style="font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:10pt!important; white-space:pre; margin:0px!important; padding:0px!important; border:0px!important; float:none!important; vertical-align:baseline!important; height:auto!important; width:auto!important; line-height:1.1em!important; color:rgb(209,237,255)!important">[[NSOperationQueue mainQueue] addOperationWithBlock:aBlock];</code></td> 
  </tr> 
 </tbody> 
</table>

这个和调用performSelector: with afterDelay of 0.0f等价

**学习的路上,与君共勉。**