ViewController 在 Xcode Playground - 框架报告双倍大小 (viewDidLoad)

Question

我在 Xcode Swift 游乐场中使用 UIViewController 子类。控制器的视图显然报告为双倍大小。我是做错了什么还是遇到了错误？

当我将一半宽度的黄色子视图放入视图时，它覆盖了整个宽度。

Xcode 版本 8.2.1 (8C1002)

import UIKit
import PlaygroundSupport


class ViewController : UIViewController {
  override func viewDidLoad() {
    title = "Double Frame"
    super.viewDidLoad()
    view.frame // inspecting the frame size: 768 x 1024

    let halfV = UIView(frame: CGRect(x: 0, y: 200,
                                     width: Int(view.frame.width / 2),
                                     height: Int(view.frame.width / 2)))
    halfV.backgroundColor = UIColor.yellow
    view.addSubview(halfV)

  }
}
PlaygroundPage.current.liveView = UINavigationController(rootViewController: ViewController())

Answer 1

您的视图控制器的视图将使用自动布局调整大小。自动布局过程将在 viewDidLoad 之后发生。如果你想通过引用视图控制器视图的 frame 来编程调整子视图的大小，你应该将该代码移动到 viewDidLayoutSubviews。例如：

class ViewController : UIViewController {
    let halfV = UIView()

    override func viewDidLoad() {
        title = "Double Frame"
        super.viewDidLoad()
        view.frame // inspecting the frame size: 768 x 1024


        halfV.backgroundColor = UIColor.yellow
        view.addSubview(halfV)
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        halfV.frame = CGRect(x: 0, y: 200,
               width: CGFloat(view.frame.width / 2),
               height: CGFloat(view.frame.width / 2))
    }
}
PlaygroundPage.current.liveView = UINavigationController(rootViewController: ViewController())

ViewController 在 Xcode Playground - 框架报告双倍大小 (viewDidLoad)

ViewController in Xcode Playground - frame reporting double sized (viewDidLoad)

xcode

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viewdidload

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swift-playground