UI：改变UIView背景颜色

//每隔一秒改变一次颜色

[NSTimer
scheduledTimerWithTimeInterval:1
target:self
selector:@selector(changeColor)
userInfo:nil
repeats:YES];

#pragma mark 改变颜色

- (void)changeColor{

//动画开始

[UIView
beginAnimations:nil
context:nil];

[UIView
setAnimationDuration:0.5];

self.view.backgroundColor
= [[UIColor
alloc]initWithRed:(double)(arc4random()%256)/256
green:(double)(arc4random()%256)/256
blue:(double)(arc4random()%256)/256
alpha:0.5];

//动画结束

[UIView
commitAnimations];

}