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详解iOS中UIButton的三大UIEdgeInsets属性用法

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UIEdgeInsets是什么 UIEdgeInsets是什么?我们点进去看一下: typedef struct UIEdgeInsets { CGFloat top, left, bottom, right; // specify amount to inset (positive) for each of the edges. values can be negative to 'outset'} UIEdg

UIEdgeInsets是什么

UIEdgeInsets是什么?我们点进去看一下:

typedef struct UIEdgeInsets {
  CGFloat top, left, bottom, right; // specify amount to inset (positive) for each of the edges. values can be negative to 'outset'
} UIEdgeInsets;

UIEdgeInsets是个结构体类型。里面有四个参数,分别是:top, left, bottom, right。这四个参数表示距离上边界、左边界、下边界、右边界的距离。

哪三个UIEdgeInsets属性

不知道大家发现没有,UIButton里面有三个UIEdgeInsets属性,分别是:

@property(nonatomic)     UIEdgeInsets contentEdgeInsets UI_APPEARANCE_SELECTOR; // default is UIEdgeInsetsZero

@property(nonatomic)     UIEdgeInsets titleEdgeInsets;        // default is UIEdgeInsetsZero

@property(nonatomic)     UIEdgeInsets imageEdgeInsets;        // default is UIEdgeInsetsZero

contentEdgeInsets后面有个UI_APPEARANCE_SELECTOR是什么意思呢?

提示:UI_APPEARANCE_SELECTOR标记的属性都支持通过外观代理来定制。
举例,设置UIButton的contentEdgeInsets属性,可以直接调用:

[[UIButton appearance] setTitleEdgeInsets:UIEdgeInsetsMake(0, 0, 0, 0)];

创建UIButton:

UIButton *button = [[UIButton alloc] init];
button.frame = CGRectMake(50, 200, 200, 50);
[button setTitle:@"我是UIButton" forState:UIControlStateNormal];
[button setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];
[button setBackgroundColor:[UIColor orangeColor]];
button.titleLabel.textAlignment = NSTextAlignmentLeft;
button.contentHorizontalAlignment = UIControlContentHorizontalAlignmentLeft;
[self.view addSubview:button];

创建一个button,让button的title居左,以便观察:

2016425143210943.png (146×97)

UIButton的contentEdgeInsets属性

@property(nonatomic)     UIEdgeInsets contentEdgeInsets UI_APPEARANCE_SELECTOR; 

// default is UIEdgeInsetsZero

contentEdgeInsets里有一个content应该指的就是UIButton的title。

参数含义:

上面我们讲了UIEdgeInsets是个结构体类型。里面有四个参数,分别是:top, left, bottom, right。这四个参数表示距离上边界、左边界、下边界、右边界的距离。

这四个参数的值可以为正值,也可以为负值。拿left举例:

left = 10; //代表以当前位置为基准,向右移动10个像素
left = -10; //代表以当前位置为基准,向左移动10个像素

向右移动20个像素

button.contentEdgeInsets = UIEdgeInsetsMake(0, 20, 0, 0);

向右移动20个像素,left = 20,就可以了。

2016425143256442.png (154×80)

向左移动20个像素

button.contentEdgeInsets = UIEdgeInsetsMake(0, -20, 0, 0);

2016425143338999.png (146×80)

UIButton的titleEdgeInsets属性

titleEdgeInsets和contentEdgeInsets的作用差不多。我们及设置contentEdgeInsets,又设置titleEdgeInsets,会怎样呢?

button.titleEdgeInsets = UIEdgeInsetsMake(0, 20, 0, 0);
button.contentEdgeInsets = UIEdgeInsetsMake(0, 20 , 0, 0);

看一下效果:

2016425143400935.png (152×97)

UIButton的imageEdgeInsets属性

创建一个带照片的button:

UIButton *button = [[UIButton alloc] init];
button.frame = CGRectMake(50, 200, 200, 200);
[button setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];
[button setBackgroundColor:[UIColor orangeColor]];
[button setImage:[UIImage imageNamed:@"test"] forState:UIControlStateNormal];
[self.view addSubview:button];

运行一下:

2016425143505909.png (169×161)

向右移动50个像素

button.imageEdgeInsets = UIEdgeInsetsMake(0, 50, 0, 0);

看看效果:

2016425143526865.png (170×190)

向左移动50个像素

button.imageEdgeInsets = UIEdgeInsetsMake(0, -50, 0, 0);

看看效果:

2016425143547866.png (181×178)

大家可以自行设置其他三个参数看看效果是怎样的,自己动手便于理解。

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