Custom UIView

Posted on Edited on

最近项目需要自定义一个 UIView，虽然不是第一次做，但是还是出现了很多问题，其中最严重是的获取的 self.bounds 是不对。

Debug 能力真的需要提高了，调试了很久，还是靠断点，逐个对比 bounds 才知道问题所在。

http://stackoverflow.com/questions/29763818/making-a-custom-uiview-subview-that-fills-its-superview

这一篇解释的很清楚，我自己混淆了几种方法的使用，还忘记了手动设置 frame 时，还忘了layoutSubviews()。以前可能是宽高确定或根据 UIScreen 来的计算的，一直没出现问题。

  1. Use Auto Layout
    • Interface Builder
    • Programmatically
  2. Manual Layout
    • Resizing Masks
    • Layout Subviews

关键代码

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override init(frame: CGRect) {
    super.init(frame: frame)
    setupViews()
}

required init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
    setupViews()
}

private func setupViews() {
   	        
    let view = UIView(frame: CGRectZero)
    view.setTranslatesAutoresizingMaskIntoConstraints(false)
    super.init(frame: frame)
    let viewsDict = ["view": view]
    addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|-0-[view]-0-|", options: .allZeros, metrics: nil, views: viewsDict))
    addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|-0-[view]-0-|", options: .allZeros, metrics: nil, views: viewsDict))
    addSubview(view)

}

原因

viewDidLoad 时获取的size 可能是错误的。

viewDidLoad

The view controller has obtained its view. See the discussion earlier in this chapter of how a view controller gets its view. Recall that this does not mean that the view is in the interface or even that it has been given its correct size.