UIView的层次调整，及子view布局模式自动布局模式（停靠模式）

UIView*view1=[[UIView alloc]initWithFrame:CGRectMake(10,30,300,30)];

view1.backgroundColor=[UIColor redColor];

[self.window addSubview:view1];

[view1 release];

UIView*view2=[[UIView alloc]init];

view2.frame=CGRectMake(30,20,50,100);

view2.backgroundColor=[UIColor blueColor];

[self.window addSubview:view2];

[view2 release];

UIView*view3=[[UIView alloc]initWithFrame:CGRectMake(20,50,200,200)];

view3.backgroundColor=[UIColor yellowColor];

[self.window addSubview:view3];

//把某一个view放到最下层

[self.window sendSubviewToBack:view2];

//把某一个view放到最上层

[self.window bringSubviewToFront:view2];

//把某一个view加入到指定层

[self.window insertSubview:view2 atIndex:1];

//把某一个view加入到某层的下面

[self.window insertSubview:view2 belowSubview:view1];

//把某一个view加入到某层的上面

[self.window insertSubview:view2 aboveSubview:view1];

//交换两个层的view

[self.window exchangeSubviewAtIndex:0 withSubviewAtIndex:1];

//自动布局模式（停靠模式）

//前面把_backgroundView设置成了成员变量，为了方便，没有写出来

_backgroundView=[[UIView alloc]initWithFrame:CGRectMake(110,300,100,100)];

_backgroundView.background=[UIColor blackColor];

//设置父view允许子view自动布局

_backgroundView.autoresizesSubviews=YES;

[self.window addSubview:_backgroundView];

UIView*topView=[[UIView alloc]initWithFrame:CGRectMake(25,25,50,50)];

topView.backgroundColor=[UIColor orangeColor];

//设置子view的自动布局模式

//下面设置会让topView跟着_backgroundView变化而变化，中心点不变

topView.autoresizingMask=UIViewAutoresizingFlexibleBottomMargin|UIViewAutoresizingFlexibleHeight|UIViewAutoresizingFlexibleLeftMargin|UIViewAutoresizingFlexibleRightMargin|UIViewAutoresizingFlexibleTopMargin|UIViewAutoresizingFlexibleWidth;

[_backgroundView addSubview:topView];

//创建一个按钮，点一下，_backgroundView会变大

UIButton*btn=[UIButton buttonWithType:UIButtonTypeRoundedRect];

btn.frame=CGRectMake(10,230,300,20);

[btn addTarget:self action:@selector(click) forControlEvents:UIControlEventTouchUpInside];

[self.window addSubview:btn];

-(void)click

{

_backgroundView.frame=CGRectMake(_backgroundView.frame.origin.x-2,_backgroundView.frame.orgin.y-2,_backgroundView.frame.size.width+4,_backgroundView.frame.height+4);

}