iOS编程(双语版)-视图-Frame/Bounds/Center-白红宇

1. Frame

每个视图都有一个frame属性，它是CGRect结构，它描述了视图所在的矩形在其父视图中的位置。

（屏幕坐标系默认的原点在左上角，x轴向右伸展，y轴向下伸展）

设置frame通常通过视图的指定初始化器initWithFrame

下面来看个例子，该例子初始化了3个相互叠加的矩形区域

(Objective-C代码)

UIView* v1 = [[UIView alloc] initWithFrame:CGRectMake(113, 111, 132, 194)];v1.backgroundColor = [UIColor colorWithRed:1 green:.4 blue:1 alpha:1];UIView* v2 = [[UIView alloc] initWithFrame:CGRectMake(41, 56, 132, 194)];v2.backgroundColor = [UIColor colorWithRed:.5 green:1 blue:0 alpha:1];UIView* v3 = [[UIView alloc] initWithFrame:CGRectMake(43, 197, 160, 230)];v3.backgroundColor = [UIColor colorWithRed:1 green:0 blue:0 alpha:1];[mainview addSubview: v1];[v1 addSubview: v2];[mainview addSubview: v3];

(Swift代码 iOS9)

let v1 = UIView(frame:CGRectMake(113, 111, 132, 194))v1.backgroundColor = UIColor(red: 1, green: 0.4, blue: 1, alpha: 1)let v2 = UIView(frame:CGRectMake(41, 56, 132, 194))v2.backgroundColor = UIColor(red: 0.5, green: 1, blue: 0, alpha: 1)let v3 = UIView(frame:CGRectMake(43, 197, 160, 230))v3.backgroundColor = UIColor(red: 1, green: 0, blue: 0, alpha: 1)mainview.addSubview(v1)v1.addSubview(v2)mainview.addSubview(v3)

运行结果：

2. Bounds

Bounds也是CGRect结构，和Frame不同，它描述的是视图自身的矩形区域，是相对于自身的坐标系而言的。

下面的例子创建了2个叠加的矩形视图，子视图为绿色较小的那个

(Objective-C代码)

UIView* v1 = [[UIView alloc] initWithFrame:CGRectMake(113, 111, 132, 194)];v1.backgroundColor = [UIColor colorWithRed:1 green:.4 blue:1 alpha:1];// 在一个视图内部画图时，通常需要使用该视图的boundsUIView* v2 = [[UIView alloc] initWithFrame:CGRectInset(v1.bounds, 10, 10)];v2.backgroundColor = [UIColor colorWithRed:.5 green:1 blue:0 alpha:1];[mainview addSubview: v1];[v1 addSubview: v2];

(Swift代码 iOS9)

let v1 = UIView(frame:CGRectMake(113, 111, 132, 194))v1.backgroundColor = UIColor(red: 1, green: 0.4, blue: 1, alpha: 1)// 在一个视图内部画图时，通常需要使用该视图的boundslet v2 = UIView(frame:v1.bounds.insetBy(dx: 10, dy: 10))v2.backgroundColor = UIColor(red: 0.5, green: 1, blue: 0, alpha: 1)mainview.addSubview(v1)v1.addSubview(v2)

运行结果：

下面的例子通过改变绿色子视图的bounds将父视图完全覆盖

(Objective-C代码)

UIView* v1 = [[UIView alloc] initWithFrame:CGRectMake(113, 111, 132, 194)];v1.backgroundColor = [UIColor colorWithRed:1 green:.4 blue:1 alpha:1];UIView* v2 = [[UIView alloc] initWithFrame:CGRectInset(v1.bounds, 10, 10)];v2.backgroundColor = [UIColor colorWithRed:.5 green:1 blue:0 alpha:1];[mainview addSubview: v1];[v1 addSubview: v2];// 重定义子视图的boundsCGRect r = v2.bounds;r.size.height += 20;r.size.width += 20;v2.bounds = r;

(Swift代码 iOS9)

let v1 = UIView(frame:CGRectMake(113, 111, 132, 194))v1.backgroundColor = UIColor(red: 1, green: 0.4, blue: 1, alpha: 1)let v2 = UIView(frame:v1.bounds.insetBy(dx: 10, dy: 10))v2.backgroundColor = UIColor(red: 0.5, green: 1, blue: 0, alpha: 1)mainview.addSubview(v1)v1.addSubview(v2)v2.bounds.size.height += 20v2.bounds.size.width += 20

运行结果：

下面的例子，紫色父视图的原点进行少量偏移

(Objective-C代码)

UIView* v1 = [[UIView alloc] initWithFrame:CGRectMake(113, 111, 132, 194)];v1.backgroundColor = [UIColor colorWithRed:1 green:.4 blue:1 alpha:1];UIView* v2 = [[UIView alloc] initWithFrame:CGRectInset(v1.bounds, 10, 10)];v2.backgroundColor = [UIColor colorWithRed:.5 green:1 blue:0 alpha:1];[mainview addSubview: v1];[v1 addSubview: v2];// 改变父视图的原点坐标CGRect r = v1.bounds;r.origin.x += 10;r.origin.y += 10;v1.bounds = r;

(Swift代码 iOS9)

let v1 = UIView(frame:CGRectMake(113, 111, 132, 194))v1.backgroundColor = UIColor(red: 1, green: 0.4, blue: 1, alpha: 1)let v2 = UIView(frame:v1.bounds.insetBy(dx: 10, dy: 10))v2.backgroundColor = UIColor(red: 0.5, green: 1, blue: 0, alpha: 1)mainview.addSubview(v1)v1.addSubview(v2)// 改变父视图的原点坐标v1.bounds.origin.x += 10v1.bounds.origin.y += 10

运行结果:

3. Center

Center即视图的中心点位置坐标

4. 关于主窗口和设备屏幕

设备屏幕(UIScreen.mainScreen())没有frame, 但它有bounds。

主窗口没有父视图，但是它的frame可以设为屏幕的bounds。

let w = UIWindow(frame: UIScreen.mainScreen().bounds)

5. 关于frame和bounds的区别

一言以蔽之，就是前者相对于父视图，而后者相对于自身。

我们还是用图片来看一下吧，这样更直观

在视图未旋转的情况下，它们差不多，坐标稍有区别，如下图：

而在视图作了类似旋转的transform之后，它们的坐标则有很大的差别了，见下图：