1. [self performSelector:@selector() withObject:nil afterDelay:];
2. dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1.5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
});
3. [NSTimer scheduledTimerWithTimeInterval:1.5 target:self selector:@selector() userInfo:nil repeats:NO];
4.或者NSThread
5. 开发者我用的方法 1 、2 比较多
