iOS開發-順延強制

有時候,希望某段代碼,某個時間在一定時間後執行,這時候就要用到順延強制。

常見的方法有以下幾種:

1.最直接的方法performSelector:withObject:afterDelay:這種方法的缺點：每次要為延時寫一個方法

    [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.使用類別，用BOLCK執行

@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[代碼]c#/cpp/oc代碼：

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 圖中的dispatch_getcurrent_queue() 方法在ios6已經被kill了現在用dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH,0)第一個參數是優先順序有，第二個參數為0或nil如果要要對介面操作則使用dispatch_get_main_queue()；參考：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參數[代碼]c#/cpp/oc代碼：

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

5.使用NSOperationQueue，在應用程式的下一個主迴圈執行：[代碼]c#/cpp/oc代碼：

1	[[NSOperationQueue mainQueue] addOperationWithBlock:aBlock];

這個和調用performSelector: with afterDelay of 0.0f等價

學習的路上,與君共勉。