创建约束以重新定位以编程方式调整大小的视图上的按钮

Question

我正在开发一款调整形状大小的应用。我以视图为例。

我画了我的观点：

以编程方式创建了一个按钮，并添加了一个UIPanGestureRecognizer：

import UIKit

class ViewController: UIViewController {

    @IBOutlet var rect: UIView!

    override func viewDidLoad() {
        super.viewDidLoad()

        let rectFrame = rect.frame
        let selectorColor = UIColor(red: 0.000, green: 0.000, blue: 0.000, alpha: 0.700)

        let resizeTopLeft = UIButton(frame: CGRect(x: rectFrame.size.width - 20, y: rectFrame.size.height - 20, width: 20, height: 20))
        resizeTopLeft.backgroundColor = selectorColor

        let panTopLeft = UIPanGestureRecognizer(target: self, action: "panTopLeft:")
        resizeTopLeft.addGestureRecognizer(panTopLeft)

        rect.addSubview(resizeTopLeft)
    }

    func panTopLeft(gesture: UIPanGestureRecognizer){
        let location = gesture.locationInView(rect)
        rect.frame.size = CGSize(width: location.x + 20, height: location.y + 20)
    }
}

在运行时，它显示如下：

当移动屏幕按钮时，视图会按预期调整大小。但按钮仍然在同一个地方。

这就是问题：当按钮被定位为约束时，我需要你调整视图的大小。我尝试制作了几个约束，没有按预期工作。

我的问题：如何创建约束以重新定位以编程方式调整大小的视图？

Answer 1

在这里你应该使用自动布局。否则你也应该在t pan手势选择器中设置按钮的位置。

这是我的自动布局解决方案。

第1步：   为视图添加前导，顶部，宽度和高度约束。喜欢

第2步：   通过IBOutlet连接宽度和高度约束。像

 @IBOutlet weak var rectHeightConstraint: NSLayoutConstraint!
 @IBOutlet weak var rectWidthConstraint: NSLayoutConstraint!

第3步：   添加具有自动布局约束的按钮

    //Create UIButton
    let selectorColor = UIColor(red: 0.000, green: 0.000, blue: 0.000, alpha: 0.700)
    let resizeTopLeft = UIButton()
    resizeTopLeft.backgroundColor = selectorColor
    resizeTopLeft.translatesAutoresizingMaskIntoConstraints = false

    //Add gesture recognizer
    let panTopLeft = UIPanGestureRecognizer(target: self, action: "panTopLeft:")
    resizeTopLeft.addGestureRecognizer(panTopLeft)

    rect.addSubview(resizeTopLeft)

    //Add auto layout constraints for the button
    let views = ["resizeTopLeft" : resizeTopLeft]

    let horizontalConstraints = NSLayoutConstraint.constraintsWithVisualFormat("H:[resizeTopLeft(20)]|", options: NSLayoutFormatOptions(rawValue: 0), metrics: nil, views: views)
    self.rect.addConstraints(horizontalConstraints)

    let verticalConstraints = NSLayoutConstraint.constraintsWithVisualFormat("V:[resizeTopLeft(20)]|", options: NSLayoutFormatOptions(rawValue: 0), metrics: nil, views: views)
    self.rect.addConstraints(verticalConstraints)

第4步：   在平移手势方法中更新高度和宽度约束。

func panTopLeft(gesture: UIPanGestureRecognizer) {
    let location = gesture.locationInView(rect)
    //To avoid zero sized view.
    if (location.y < 0) || (location.x < 0) {
        return
    }
    rectHeightConstraint.constant = location.y + 20
    rectWidthConstraint.constant = location.x + 20
}