iOS UIViewAinmation 坑

[UIView animateWithDuration:5 animations:^{                    [self.view setBackgroundColor:[UIColor colorWithRed:(arc4random()%255/255.00) green:(arc4random()%255/255.00) blue:(arc4random()%255/255.00) alpha:1]];                } completion:^(BOOL finished) {                    NSLog(@"%d",i);                }]

当 animation Block 内 如果没有动画内容那么 他会瞬间调用 finished；结束动画！！！！！