为什么自动布局不更改视图框架

Question

我在其父视图的函数中创建了一个视图

let black = NSView(frame: NSRect(x: 0, y: 0, width: 10, height: 10))

black.translatesAutoresizingMaskIntoConstraints = false
black.wantsLayer = true
black.layer?.backgroundColor = NSColor.black.cgColor
self.addSubview(black)

black.bottomAnchor.constraint(equalTo: self.bottomAnchor, constant: -15).isActive = true
black.leadingAnchor.constraint(equalTo: self.leadingAnchor, constant: 15).isActive = true
black.heightAnchor.constraint(equalToConstant: 115).isActive = true
black.widthAnchor.constraint(equalToConstant: 115).isActive = true

print ("origin (\(black.frame.origin.x),\(black.frame.origin.y)) size (\(black.frame.size.width),\(black.frame.size.height)) ")

输出为 origin(0,0)、size(10,10)，这些是创建视图时使用的值。在屏幕上，黑色视图的位置符合预期 origin:(15,15) size:(115,115).

为什么框架没有更新？

Answer 1

设置约束后，您可以调用相同的 layoutIfNeeded 函数更新视图框架 Cocoa:

black.layoutSubtreeIfNeeded()

为什么自动布局不更改视图框架

Why doesn't Autolayout change a views frame

cocoa

frame

uikit

autolayout

swift