sizeToFit()和sizeThatFits(_:)
sizeToFit()会调用sizeThatFits(_:)方法，将现在的frame作为参数。然后根据函数返回的结果更新view。
sizeToFit will simply call through to sizeThatFits: passing the view's current size as the argument. It will then update the view's frame based on the value it gets back. So all the important logic goes in sizeThatFits:, and this is the method you should override for your own custom controls.
UIButton标题的shadow效果与反转
myButton?.titleLabel?.shadowOffset = CGSizeMake(2.0, 2.0)
myButton?.setTitleShadowColor(UIColor.redColor(), forState: .Normal)
// myButton?.showsTouchWhenHighlighted = true
myButton?.reversesTitleShadowWhenHighlighted = true
未选中
高亮态
加上选中态亮瞎眼的效果
myButton?.showsTouchWhenHighlighted = true
亮瞎眼
UIButton的布局与UIEdgeInsets
有三个UIEdgeInsets
- contentEdgeInsets
使用sizeThatFits(_:)计算时用到。 - titleEdgeInsets
使用sizeThatFits(_:)计算时不会用到。 - imageEdgeInsets
使用sizeThatFits(_:)计算时不会用到。
You can specify a different value for each of the four insets (top, left, bottom, right). A positive value shrinks, or insets, that edge—moving it closer to the center of the button. A negative value expands, or outsets, that edge.
举例说明
- contentEdgeInsets
contentEdgeInsets
left和right都是30，会使左边向中间移动30pt，右边向中间移动30pt。也就是左间距和右间距都是30pt。由于contentEdgeInsets参与
sizeThatFits(_:)的计算，所以最终表现为整个button被拉宽。
- titleEdgeInsets
titleEdgeInsets
保持contentEdgeInsets不变，设置titleEdgeInsets的left为15。由于titleEdgeInsets在
sizeThatFits(_:)中不参与，因此button没有被拉宽，只是titleLabel的左边向右（中心）移动了15pt，右边保持不变。导致字符串没有被显示全。
设置titleEdgeInsets的right为-15，结果是titleLabel的右边向右移动了15pt，从而整体的显示范围不变。
- imageEdgeInsets
图像在右，标题在左
button.transform = CGAffineTransformMakeScale(-1.0, 1.0);
button.titleLabel.transform = CGAffineTransformMakeScale(-1.0, 1.0);
button.imageView.transform = CGAffineTransformMakeScale(-1.0, 1.0);
