很简单的NSTimer例子

NSTimer就如.net的Timer一样，是一个时钟。

 -(void)viewDidLoad

{
    CGRect RectFrame;
    RectFrame.origin.x = 25;
    RectFrame.origin.y = 300;
    RectFrame.size.width = 20;
    RectFrame.size.height = 20;
    
    for(int i = 0; i < 10; i++)
    {
        UIView *myView = [[UIView alloc] initWithFrame:RectFrame];
        [myView setTag:i];
        [myView setBackgroundColor:[UIColor yellowColor]];
        
        RectFrame.origin.x = RectFrame.origin.x + RectFrame.size.width + 10;
        [self.view addSubview:myView];
    }
    
    Timer = [NSTimer scheduledTimerWithTimeInterval:.1 target:self selector:@selector(moveRect) userInfo:nil repeats:YES];
}

//--------------------------------------------------------
-(void)moveRect
{
    int r = rand() % 10;
    
    for(UIView *aView in [self.view subviews])
    {
        if([aView tag] == r)
        {
            int movement = rand() % 100;
            CGRect RectFrame = aView.frame;
            RectFrame.origin.y = RectFrame.origin.y - movement;
            
            [UIView beginAnimations:nil context:NULL];
            [UIView setAnimationDuration:.2];
            [aView setFrame:RectFrame];
            [UIView commitAnimations];
            
            if(RectFrame.origin.y < 0)
            {
                [Timer invalidate];
            }
        }
    }
}