iOS-UIButton的titleEdgeInsets和ima

UIButton控件上自带了一个UILabel和一个UIImageView的子控件，默认情况下图片居左，文字居右，两个子控件作为一个整体可以通过UIButton的contentHorizontalAlignment属性设置其位置，默认为居中。

//水平居中 
UIControlContentHorizontalAlignmentCenter = 0,
//水平居左 
UIControlContentHorizontalAlignmentLeft   = 1,
//水平居右
UIControlContentHorizontalAlignmentRight  = 2,
//水平适应
UIControlContentHorizontalAlignmentFill   = 3,

本文主要探讨UIButton的imageEdgeInsets和titleEdgeInsets属性的使用，以满足日常开发中的需求。

首先要搞清楚默认状态下UIButton的UILabel和UIImageView的位置：图像和文字都居中显示，imageView在左，label在右，中间没有空隙。

<1>如果要imageView在左边，label在右边，两者都居中显示，imageView离button左边界至少距离为10，label离button右边界距离为至少为10，imageView和label之间的距离为5，具体代码如下：

//button的width：BUTTON_WIDTH
//button上控件imageView的的图片为image
NSString *title = @"label文字";
[button setTitle:title forState:UIControlStateNormal];
[button setImage:image forState:UIControlStateNormal];
CGSize strSize = [title sizeWithFont:button.titleLabel.font];
CGFloat totalLen = strSize.width + 5 + image.size.width;
CGFloat edgeLen = (BUTTON_WIDTH - totalLen) / 2;
if (edgeLen < 10) {
   edgeLen = 10;
}
[button setImageEdgeInsets:UIEdgeInsetsMake(0, edgeLen, 0, edgeLen + 5)];
[button setTitleEdgeInsets:UIEdgeInsetsMake(0, edgeLen + 5, 0, edgeLen)];

<2>如果label在左边，imageView在右边，imageView离button右边界为固定值10，label离button左边界也为固定值10，具体代码如下：

NSString *title = @"label文字";
[button setTitle:title forState:UIControlStateNormal];
[button setImage:image forState:UIControlStateNormal];
CGSize strSize = [title sizeWithFont:button.titleLabel.font];
[button setImageEdgeInsets:UIEdgeInsetsMake(0, BUTTON_WIDTH - 10 - image.size.width, 0, (10 - strSize.width))];    
CGFloat titleRightInset = BUTTON_WIDTH - 10 - strSize.width;
if (titleRightInset < 10 + image.size.width) {
   titleRightInset = 10 + image.size.width;
}
[button setTitleEdgeInsets:UIEdgeInsetsMake(0, (10 - image.size.width), 0, titleRightInset)];

<3>如果imageView在上边，label在下边，imageView与button上边界距离为10，label与button下边界距离为10，具体代码如下：

//button的height：BUTTON_HEIGHT
NSString *title = @"label文字";
[button setTitle:title forState:UIControlStateNormal];
[button setImage:image forState:UIControlStateNormal];
[button setImageEdgeInsets:UIEdgeInsetsMake(10, 0, BUTTON_HEIGHT - 10 - image.size.height , 0)];    
[button setTitleEdgeInsets:UIEdgeInsetsMake(BUTTON_HEIGHT - 10 - button.titleLabel.frame.size.height, 0, 10, 0)];

可以看到在竖直方向上，imageView与label独立变化，不用考虑彼此。