关于延迟调用
1.使用sleep（5）
会阻塞当前线程，不建议使用，若在主线程期调用，会使界面卡死，不能动
2、使用performSelector
- (void)performSelector:(SEL)aSelector withObject:(id)anArgument afterDelay:(NSTimeInterval)delay;
这个方法是单线程的，也就是说只有当前调用次方法的函数执行完毕后，selector方法才会被调用。
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
3、[UIView animateWithDuration 但不确定后台是否有不执行的问题
[UIView animateWithDuration:0.0delay:5.0options:UIViewAnimationOptionAllowUserInteraction animations:^{
} completion:^(BOOL finished) {
//do stuff here
}];
4.使用NSOperationQueue，在应用程序的下一个主循环执行：
[代码]c#/cpp/oc代码：
[[NSOperationQueue mainQueue] addOperationWithBlock:aBlock];
这个和调用performSelector: with afterDelay of 0.0f等价
5使用dispatch_after
// after 0.01 sec, since in certain cases the sliding view is reset.
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 10.0 * NSEC_PER_SEC), dispatch_get_main_queue(), ^(void){
NSLog(@"10s以后---");
});
double delayInSeconds = 0.5;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
dispatch_after(popTime, _cacheInfoQueue, ^(void){
NSLog(@"0.5s 以后-----");
});
补充：点击打开链接
比如：
- (void)changeText:(NSString *)string
{
label.text = string;
NSLog(@"changeText:(NSString *)string");
}
- (void)changePopoverSize
{
[self performSelector:@selector(changeText:) withObject:@"Happy aha" afterDelay:1];
NSLog(@"changePopoverSize#####end");
sleep(5);
NSLog(@"changePopoverSize-----end");
}
执行结果（注意时间）：
2012-08-17 17:14:06.697 awrbv[1973:f803] changePopoverSize#####end
2012-08-17 17:14:11.698 awrbv[1973:f803] changePopoverSize-----end
2012-08-17 17:14:11.701 awrbv[1973:f803] changeText:(NSString *)string
如果要想多线程的话，可以是使用
- (void)performSelectorInBackground:(SEL)aSelector withObject:(id)arg
或者
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(id)arg waitUntilDone:(BOOL)wait;
代码如下：
- (void)changeText:(NSString *)string
{
label.text = string;
NSLog(@"changeText:(NSString *)string");
}
- (void)changePopoverSize
{
[self performSelectorOnMainThread:@selector(changeText:) withObject:@"Happy aha111" waitUntilDone:YES];
NSLog(@"changePopoverSize#####end");
sleep(5);
NSLog(@"changePopoverSize-----end");
}
执行结果如下：
2012-08-17 17:19:29.618 awrbv[2024:f803] changeText:(NSString *)string
2012-08-17 17:19:29.619 awrbv[2024:f803] changePopoverSize#####end
2012-08-17 17:19:34.620 awrbv[2024:f803] changePopoverSize-----end
可以看出，如果waitUntilDone:YES那么等changeText执行完毕后再往下执行
如果waitUntilDone:NO的话，结果如下：
2012-08-17 17:21:12.135 awrbv[2049:f803] changePopoverSize#####end
2012-08-17 17:21:17.137 awrbv[2049:f803] changePopoverSize-----end
2012-08-17 17:21:17.139 awrbv[2049:f803] changeText:(NSString *)string