易采站长站为您分析iOS中UIButton的三大UIEdgeInsets属性用法,分别讲解了contentEdgeInsets、imageEdgeInsets和titleEdgeInsets三个属性在创建UIButton时对样式的控制,需要的朋友可以参考下
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：
UIButton的contentEdgeInsets属性
@property(nonatomic) UIEdgeInsets contentEdgeInsets UI_APPEARANCE_SELECTOR;
// default is UIEdgeInsetsZero
