根据图片大小，自动设置按钮大小。用(CGREC){CGPointZero,leftImage.size}强转
不要直接拿按钮文字，拿出来的是空的。因为按钮文字是分状态的。要用NSString *btnTitle = [btn titleForState:UIControlStateNormal
锚点anchorPoint和position。btn.layer.anchorPoint;btn.layer.position
//点击触发方法，pointInside和hitTest
通过position定义可以知道position是layer中的anchorPoint点在superLayer中的位置坐标.position点是相对superLayer的.
anchorPoint是相对于自身layer，anchorPoint点(锚点)的值是用相对bounds的比例值来确定的
/* Defines the anchor point of the layer's bounds rect, as a point in
* normalized layer coordinates - '(0, 0)' is the bottom left corner of
* the bounds rect, '(1, 1)' is the top right corner. Defaults to
* '(0.5, 0.5)', i.e. the center of the bounds rect. Animatable. */
open var anchorPoint: CGPoint
https://www.jianshu.com/p/f9a83a72e274
图片拉伸
[image resizableImageWithCapInsets:UIEdgeInsetsMake(5, 5, 5, 5) resizingMode:UIImageResizingModeStretch];
// 代表按钮变为UIControlStateDisabled状态
share.enabled = NO;
// 设置分享按钮的选中状态是真
share.selected = YES;
// 按钮在高亮的时候不需要变灰色
share.adjustsImageWhenHighlighted = NO;