我们修改frame中的某个值，需要进行繁琐的书写，例如：
(1). 直接设置位置大小
view.frame = CGRectMake(0, 0, 320, 150);
(2). 只修改某个值
view.frame = CGRectMake(view.frame.origin.x, 100, view.frame.size.width, view.frame.size.height);
这种写法在界面元素较多的排版中，会让程序员非常痛苦，而且可读性也会减弱
如果能够人性化一点，可以单独地修改某个值，或者再人性化一点，可以输出view中每一个点的坐标，将更有利于布局。我们可以通过建立view的类别 category 来实现这个人性化的布局操作
一、建立类别
建立一个名为Layout的UIView类别，类别的代码如下：
1. UIView+Layout.h
.h 文件定义了 x, y, width, height 等方便读写的属性，代码如下：
#import <UIKit/UIKit.h>
@interface UIView (Layout)
@property (assign, nonatomic) CGFloat top;
@property (assign, nonatomic) CGFloat bottom;
@property (assign, nonatomic) CGFloat left;
@property (assign, nonatomic) CGFloat right;
@property (assign, nonatomic) CGFloat x;
@property (assign, nonatomic) CGFloat y;
@property (assign, nonatomic) CGPoint origin;
@property (assign, nonatomic) CGFloat centerX;
@property (assign, nonatomic) CGFloat centerY;
@property (assign, nonatomic) CGFloat width;
@property (assign, nonatomic) CGFloat height;
@property (assign, nonatomic) CGSize size;
@end
2. UIView+Layout.m
.m 文件实现各个属性的setter和getter方法，代码如下：
#import "UIView+Layout.h"
@implementation UIView (Layout)
@dynamic top;
@dynamic bottom;
@dynamic left;
@dynamic right;
@dynamic width;
@dynamic height;
@dynamic size;
@dynamic x;
@dynamic y;
- (CGFloat)top
{
return self.frame.origin.y;
}
- (void)setTop:(CGFloat)top
{
CGRect frame = self.frame;
frame.origin.y = top;
self.frame = frame;
}
- (CGFloat)left
{
return self.frame.origin.x;
}
- (void)setLeft:(CGFloat)left
{
CGRect frame = self.frame;
frame.origin.x = left;
self.frame = frame;
}
- (CGFloat)bottom
{
return self.frame.size.height + self.frame.origin.y;
}
- (void)setBottom:(CGFloat)bottom
{
CGRect frame = self.frame;
frame.origin.y = bottom - frame.size.height;
self.frame = frame;
}
- (CGFloat)right
{
return self.frame.size.width + self.frame.origin.x;
}
- (void)setRight:(CGFloat)right
{
CGRect frame = self.frame;
frame.origin.x = right - frame.size.width;
self.frame = frame;
}
- (CGFloat)x
{
return self.frame.origin.x;
}
- (void)setX:(CGFloat)value
{
CGRect frame = self.frame;
frame.origin.x = value;
self.frame = frame;
}
- (CGFloat)y
{
return self.frame.origin.y;
}
- (void)setY:(CGFloat)value
{
CGRect frame = self.frame;
frame.origin.y = value;
self.frame = frame;
}
- (CGPoint)origin
{
return self.frame.origin;
}
- (void)setOrigin:(CGPoint)origin
{
CGRect frame = self.frame;
frame.origin = origin;
self.frame = frame;
}
- (CGFloat)centerX
{
return self.center.x;
}
- (void)setCenterX:(CGFloat)centerX
{
CGPoint center = self.center;
center.x = centerX;
self.center = center;
}
- (CGFloat)centerY
{
return self.center.y;
}
- (void)setCenterY:(CGFloat)centerY
{
CGPoint center = self.center;
center.y = centerY;
self.center = center;
}
- (CGFloat)width
{
return self.frame.size.width;
}
- (void)setWidth:(CGFloat)width
{
CGRect frame = self.frame;
frame.size.width = width;
self.frame = frame;
}
- (CGFloat)height
{
return self.frame.size.height;
}
- (void)setHeight:(CGFloat)height
{
CGRect frame = self.frame;
frame.size.height = height;
self.frame = frame;
}
- (CGSize)size
{
return self.frame.size;
}
- (void)setSize:(CGSize)size
{
CGRect frame = self.frame;
frame.size = size;
self.frame = frame;
}
@end
二、使用
类别创建完成以后，view的布局就显得轻松很多了
例如原来你要修改y坐标时要这样写：
view.frame = CGRectMake(view.frame.origin.x, 100, view.frame.size.width, view.frame.size.height);
而现在只需要这样写：
view.y = 100;
既简洁又方便
