子视图的插入、删除

- (void)viewDidLoad{    [super viewDidLoad];    //创建一个UIView作为一个子视图,添加到父视图中    UIView * pView1 = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 150, 150)];    pView1.backgroundColor = [UIColor redColor];    [self.view addSubview:pView1];    //创建第二个子视图    UIView * pView2 = [[UIView alloc]initWithFrame:CGRectMake(50, 50, 200, 200)];    pView2.backgroundColor = [UIColor blueColor];    [self.view addSubview:pView2];    //创建第三个子视图    UIView * pView3 = [[UIView alloc]initWithFrame:CGRectMake(100, 100, 250, 250)];    pView3.backgroundColor = [UIColor yellowColor];    [self.view addSubview:pView3];    //添加子视图    [self.view insertSubview:pView1 aboveSubview:pView3];    [self.view insertSubview:pView3 atIndex:0];    [self.view insertSubview:pView3 belowSubview:pView2];    //重新排序子视图    [self.view exchangeSubviewAtIndex:0 withSubviewAtIndex:1];    [self.view sendSubviewToBack:pView3];    [self.view bringSubviewToFront:pView1];   //删除子视图   [self.view removeFromSuperview];}