iOS View的Frame和bounds之区别,setbounds使用（深入探究）

前言:

在ios开发中经常遇到两个词Frame和bounds，本文主要阐述Frame和bound的区别，尤其是bound很绕，较难理解。

一、首先，看一下公认的资料：

先看到下面的代码你肯定就明白了一些：

-(CGRect)frame{

    return CGRectMake(self.frame.origin.x,self.frame.origin.y,self.frame.size.width,self.frame.size.height);

}

-(CGRect)bounds{

    return CGRectMake(,,self.frame.size.width,self.frame.size.height);

}

很明显，bounds的原点是(0,0)点（就是view本身的坐标系统，默认永远都是0，0点，除非调用了setbounds函数），而frame的原点却是任意的（相对于父视图中的坐标位置）。

二、再看一下斯坦福iOS教程视频中的图片

翻译如下：

    frame: 该view在父view坐标系统中的位置和大小。（参照点是，父亲的坐标系统）

    bounds：该view在本地坐标系统中的位置和大小。（参照点是，本地坐标系统，就相当于ViewB自己的坐标系统，以0,0点为起点）

    center：该view的中心点在父view坐标系统中的位置和大小。（参照点是，父亲的坐标系统）

三、下面阐述一下frame和bound的区别

frame就容易理解一些：frame的(frame.origin.x,frame.origin.y)就是相对于父坐标系的偏移量。

bounds稍微有点费解，稍不留神，想的多了，就会绕进去。每个view都有一个本地坐标系统。这个坐标系统作用比较重要，比如触摸的回调函数中的UITouch里面的>坐标值都是参照这个本地坐标系统的坐标。当然bounds这个属性也是参照这个本地坐标系统来的。

其实本地坐标系统的关键就是要知道的它的原点（，）在什么位置（这个位置又是相对于上层的view的本地坐标系统而言的，最上层view就是 window它的本地坐标系统原点就是屏幕的左上角了）。

通过修改view的bounds属性可以修改本地坐标系统的原点位置。

所以，bounds的有这么一个特点：

它是参考自己坐标系，它可以修改自己坐标系的原点位置，进而影响到“子view”的显示位置。

四、用Demo论证一下

[objc] view plain copy
在CODE上查看代码片派生到我的代码片

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

[view1 setBounds:CGRectMake(-, -, , )];

view1.backgroundColor = [UIColor redColor];

[self.view addSubview:view1];//添加到self.view

NSLog(@"view1 frame:%@========view1 bounds:%@",NSStringFromCGRect(view1.frame),NSStringFromCGRect(view1.bounds));  

UIView *view2 = [[UIView alloc] initWithFrame:CGRectMake(, , , )];

view2.backgroundColor = [UIColor yellowColor];

[view1 addSubview:view2];//添加到view1上,[此时view1坐标系左上角起点为(-30,-30)]

NSLog(@"view2 frame:%@========view2 bounds:%@",NSStringFromCGRect(view2.frame),NSStringFromCGRect(view2.bounds));

这段代码没什么特别的地方。view1加入view中，view2加入view1中。代码第二行，对view1进行了setBounds设置。注释和打开这行代码的效果如图：

aaarticlea/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAIAAACQd1PeAAAAGXRFWHRTb2Z0d2FyZQBBZG9iZSBJbWFnZVJlYWR5ccllPAAAAyBpVFh0WE1MOmNvbS5hZG9iZS54bXAAAAAAADw/eHBhY2tldCBiZWdpbj0i77u/IiBpZD0iVzVNME1wQ2VoaUh6cmVTek5UY3prYzlkIj8+IDx4OnhtcG1ldGEgeG1sbnM6eD0iYWRvYmU6bnM6bWV0YS8iIHg6eG1wdGs9IkFkb2JlIFhNUCBDb3JlIDUuMC1jMDYwIDYxLjEzNDc3NywgMjAxMC8wMi8xMi0xNzozMjowMCAgICAgICAgIj4gPHJkZjpSREYgeG1sbnM6cmRmPSJodHRwOi8vd3d3LnczLm9yZy8xOTk5LzAyLzIyLXJkZi1zeW50YXgtbnMjIj4gPHJkZjpEZXNjcmlwdGlvbiByZGY6YWJvdXQ9IiIgeG1sbnM6eG1wPSJodHRwOi8vbnMuYWRvYmUuY29tL3hhcC8xLjAvIiB4bWxuczp4bXBNTT0iaHR0cDovL25zLmFkb2JlLmNvbS94YXAvMS4wL21tLyIgeG1sbnM6c3RSZWY9Imh0dHA6Ly9ucy5hZG9iZS5jb20veGFwLzEuMC9zVHlwZS9SZXNvdXJjZVJlZiMiIHhtcDpDcmVhdG9yVG9vbD0iQWRvYmUgUGhvdG9zaG9wIENTNSBXaW5kb3dzIiB4bXBNTTpJbnN0YW5jZUlEPSJ4bXAuaWlkOkJDQzA1MTVGNkE2MjExRTRBRjEzODVCM0Q0NEVFMjFBIiB4bXBNTTpEb2N1bWVudElEPSJ4bXAuZGlkOkJDQzA1MTYwNkE2MjExRTRBRjEzODVCM0Q0NEVFMjFBIj4gPHhtcE1NOkRlcml2ZWRGcm9tIHN0UmVmOmluc3RhbmNlSUQ9InhtcC5paWQ6QkNDMDUxNUQ2QTYyMTFFNEFGMTM4NUIzRDQ0RUUyMUEiIHN0UmVmOmRvY3VtZW50SUQ9InhtcC5kaWQ6QkNDMDUxNUU2QTYyMTFFNEFGMTM4NUIzRDQ0RUUyMUEiLz4gPC9yZGY6RGVzY3JpcHRpb24+IDwvcmRmOlJERj4gPC94OnhtcG1ldGE+IDw/eHBhY2tldCBlbmQ9InIiPz6p+a6fAAAAD0lEQVR42mJ89/Y1QIABAAWXAsgVS/hWAAAAAElFTkSuQmCC" alt="" data-type="gif" data-w="320" data-ratio="1" data-src="http://mmbiz.qpic.cn/mmbiz/8RTSPr4mlymTrCLI2MSHRAyG6dLsf8D3JD4GibtiaSS8icTz2jx1Bz2n6JDQFJ7qaibndgMKmyO0dHuHVrUoyaBawQ/0?wx_fmt=gif" />

[view1 setBounds:CGRectMake(-, -,,)];

这行代码起到了：让view2的位置改变的作用。为何（-30，-30）的偏移量，却可以让view2向右下角移动呢？

这是因为setBounds的作用是：强制将自己（view1）坐标系的左上角点，改为（-30，-30）。那么view1的原点，自然就向在右下方偏移（30，30）。

上面代码控制台输出如下：

aaarticlea/png;base64,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" alt="" data-type="jpeg" data-w="" data-ratio="0.08812949640287769" data-src="http://mmbiz.qpic.cn/mmbiz/8RTSPr4mlymTrCLI2MSHRAyG6dLsf8D3pjG1oLPqJmvzUzvNwVXZSU8ibtvA9xiafqjVxwT4nTTTyQkibFmnJtIXw/0?wx_fmt=jpeg" />

(log输出日志表明，每个新的view默认的bounds其实都是（0,0）,且bounds的width和height都是跟frame一致)

事情还没完

上面代码中view和bounds的大小都是一样的。如果view的frame和bounds不是一样大小，又会如何呢？

就上面的代码段，将view1的bounds改大！例如：[view1 setBounds:CGRectMake(-30, -30, 250, 250)];

aaarticlea/png;base64,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" alt="" data-w="" data-ratio="0.08812949640287769" data-s="300,640" data-type="jpeg" data-src="http://mmbiz.qpic.cn/mmbiz/8RTSPr4mlymTrCLI2MSHRAyG6dLsf8D3sZMOs4zmiaK1192pmAs2Myj3RyPW4DbsMKTwKPibUybjzZ98hzabfaYQ/0?wx_fmt=jpeg" />

log显示：view1的frame已经被修改了。这是因为setBounds的问题。如图所示：

aaarticlea/png;base64,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" alt="" data-type="gif" data-w="320" data-ratio="1" data-src="http://mmbiz.qpic.cn/mmbiz/8RTSPr4mlymTrCLI2MSHRAyG6dLsf8D3fx80g2EUMOyqFAqclBibTRMaHwfxZLN1re9Zsy6Tl9lBLWaziayXqqqQ/0?wx_fmt=gif" />

frame定义了一个相对父视图的一个框架（容器），bounds则是真实显示区域。如果，bounds比frame小了，可以放到框架（容器）里。如果bounds比frame大，感觉frame被“撑大”了。frame变成了{{25, 25}, {250, 250}}了。25是如何得出的？bounds比frame长，宽各大了50像素，那么四条边平衡一下，各溢出“25”像素。如图所示：

aaarticlea/png;base64,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" alt="" data-type="jpeg" data-w="472" data-ratio="0.6588983050847458" data-src="http://mmbiz.qpic.cn/mmbiz/8RTSPr4mlymTrCLI2MSHRAyG6dLsf8D3u3J6Xk0thlWYEBZEZIhibygNNBZehAiblPCZqSvX6xu938Io1dBibChcw/0?wx_fmt=jpeg" />

五、结论

bounds的有以下两个特点，可以从bounds自身的来剖析：bounds是一个Rectangle，前半部分是point后半部分是view的size。这两个属性也预示着两个特点：

bounds像是浮于frame之上的。frame是一个框架，bounds是显示子view的东西，下面总结bounds的两个特征：

第一、对于bound的point：它可以不会改变frame的原点，改变的是bounds自己的原点，进而影响到“子view”的显示位置。这个作用更像是移动bounds原点的意思。

第二、对于bound的size：它可以改变的frame。如果bounds的size比frame的size大。那么frame也会跟着变大，那么frame的原点也会变。这个作用更像边界的意思。

可以推测一下，setBound第一个特性可以用于view的滑动，手势动作，因为可以影响子view的显示位置。

工程中经常修改tablewview的contentInset值。该技巧常用于屏幕两边，上下头部的“留白”。修改contentInset的时候其实修改的也是bounds。

● 比如，self.tableView.contentInset = UIEdgeInsetsMake(3.5, 0, 0, 0);，那么tableview的bounds已经变了，y的值已经变为-3.5了。contentInset了解更多

● 比如我在一段时间内进行多次setBound函数：

[view1 setBounds:CGRectMake(-, , , )];

[view1 setBounds:CGRectMake(-, , , )];

[view1 setBounds:CGRectMake(-, , , )];

[view1 setBounds:CGRectMake(-, , , )];

[view1 setBounds:CGRectMake(-, , , )];

[view1 setBounds:CGRectMake(-, , , )];

[view1 setBounds:CGRectMake(-, , , )];

[view1 setBounds:CGRectMake(-, , , )];

[view1 setBounds:CGRectMake(-, , , )];

[view1 setBounds:CGRectMake(-, , , )];

[view1 setBounds:CGRectMake(-, , , )];

效果如下：

aaarticlea/png;base64,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" alt="" data-type="gif" data-w="321" data-ratio="1" data-src="http://mmbiz.qpic.cn/mmbiz/8RTSPr4mlymTrCLI2MSHRAyG6dLsf8D3ja4GSe67AHFBG9K3PSbsPS18dqImgdKsqeyg6AwfxUOCtYSpWABzBw/0?wx_fmt=gif" />

第二个特性如何使用呢？从网上找到一个案例：可以将下图中cell拉伸：

代码如下，重写cell的layoutSubviews方法即可：

// MyCustomUITableViewCell.h  

- (void)layoutSubviews

{

    self.bounds = CGRectMake(self.bounds.origin.x,

                             self.bounds.origin.y,

                             self.bounds.size.width - ,

                             self.bounds.size.height);  

    [super layoutSubviews];

}