几个单词

Hierarchy['ha r k ]n.层级

思考：每个视图有一个父视图，有0个或者多个子视图

Manipulation[m ,n pj 'le ( )n] n.操纵；操作

Descendant[d 'send( )nt] n. 后裔；子孙

UIWindow

Feature：

1、UIWindow set up by default in Xcodetemplate project,and contains the entire view hierarchy

2、UIWindow just a view,and adds someadditional to top level view

3、Views live inside of a window

思考：UIWIndow位于toplevel，启动APP的时候首先启动，其他所有在上面的View依次渲染出现

Principle

UIView的属性

@property(nonatomic,readonly) UIView *superview;
@property(nonatomic,readonly,copy) NSArray *subviews;
@property(nonatomic,readonly) UIWindow *window;

思考：每一个View都有一个superview，有一个对应的subviews（注意是NSArraay），有一个window.所有对子视图的操作，其实本质上来讲也就是对数组的操作。视图的增删改，对应的就是数组的增删改。当然也有视图的回调方法用于跟踪视图改变。

ViewManipulation

1、add or remove in IB or using UIVIew methods

(void)addSubview:(UIView *)view;

(void)removeFromSuperview;

示例：

    // UIWindow
    self.window.backgroundColor = [UIColor darkGrayColor];
    // view_blue
    UIView *view_a = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 100, 100)];
    view_a.backgroundColor = [UIColor blueColor];
    // view_yellow
    UIView *view_b = [[UIView alloc]initWithFrame:CGRectMake(50, 50, 100, 100)];
    view_b.backgroundColor = [UIColor yellowColor];
   
    // 依次添加view_blue、view_yellow到UIWindow
    [self.window addSubview:view_blue];
    [self.window addSubview:view_yellow];

思考：上图很清楚的看出来，视图的层次关系是：UIWindow -> View_blue -> View_yellow

此时如果更改添加顺序，代码和效果图如下：

    // 添加view_yellow、view_blue到UIWindow
    [self.window addSubview:view_yellow];
    [self.window addSubview:view_blue];
    [self.window addSubview:view_yellow];
    [self.window addSubview:view_blue];

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3、otherViewmanipulationmethods

- (void)insertSubview:(UIView *)view atIndex:(NSInteger)index;
- (void)insertSubview:(UIView *)view belowSubview:(UIView *)siblingSubview;
- (void)insertSubview:(UIView *)view aboveSubview:(UIView *)siblingSubview;
 
- (void)bringSubviewToFront:(UIView *)view;
- (void)sendSubviewToBack:(UIView *)view;
- (void)exchangeSubviewAtIndex:(NSInteger)index1 withSubviewAtIndex:(NSInteger)index2;

思考：每一个View的子视图其实就是一个数组，对View的子视图的操作也就是对当前view的子视图数组进行操作。常见的操作无非尾部增加、特定位置增加、删除、调整在数组中的位置、调换2个数组元素的位置而已。

示例：

//UIWindow
    self.window.backgroundColor = [UIColor darkGrayColor];
    //view_blue
    UIView *view_blue = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 100, 100)];
    view_blue.backgroundColor = [UIColor blueColor];
    //view_yellow
    UIView *view_yellow =[[UIView alloc]initWithFrame:CGRectMake(50, 50, 100, 100)];
    view_yellow.backgroundColor = [UIColor yellowColor];
   
    //view_red
    UIView *view_red = [[UIView alloc]initWithFrame:CGRectMake(25, 25, 100, 100)];
    view_red.backgroundColor = [UIColor redColor];
   
    // 添加view_yellow、view_blue到UIWindow
    [self.window addSubview:view_yellow];
    [self.window addSubview:view_blue];
    [self.window insertSubview:view_red atIndex:0];
   
    NSLog(@"views:%@",self.window.subviews);

思考：上面的[self.windowinsertSubview:view_redatIndex:0];这句话其实就是把红色的view添加到UIWindow子视图数组的第1个位置，所以位于blue、yellow的下层

如果在这句话[self.windowinsertSubview:view_redatIndex:0];后面加上这句话

[self.windowinsertSubview:view_redatIndex:0];那么产生的效果如下：

思考：其实本质都是对UIWIndow子视图数组的操作

4、Tracks theadditions and removals of subviews

- (void)didAddSubview:(UIView *)subview;
- (void)willRemoveSubview:(UIVie

0515.View Hierarchy [UIKit](一)

几个单词

// 添加view_yellow、view_blue到UIWindow [self.window addSubview:view_yellow]; [self.window addSubview:view_blue]; [self.window addSubview:view_yellow]; [self.window addSubview:view_blue];