Ios 拖动时调整UIView框架

我正在尝试在拖动时更改UIView帧。我将UIView子类化，并编写了TouchesBegind和touchesMoved方法。这是：

override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
    let touch = touches.first
    startPosition = touch?.locationInView(self)
}

override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {
    let touch = touches.first
    let endPosition = touch?.locationInView(self)
    let difference = endPosition!.y - startPosition.y
    let newFrame = CGRectMake(self.frame.origin.x, self.frame.origin.y, self.frame.width, self.frame.height + difference)
    self.frame = newFrame
}

但结果我有了意想不到的行为。这有点难以形容。小dragabout 20px使帧在大约100px上变大

我的自定义视图也有一些限制。自定义视图底部的图像应始终保持不变：

因此，问题是：

如何在用户拖动的距离上使视图变大。 为什么在更改框架后不应用约束以及如何再次应用约束？

---

视图快速增长的原因是，您总是根据第一次触地后移动的距离更新当前视图高度。应始终添加移动到视图原始高度的距离，而不是修改当前高度

class ViewController: UIViewController {

    @IBOutlet weak var customViewHeight: NSLayoutConstraint!

    @IBOutlet weak var customView: CustomView!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Assign the layout constraint to the custom view so that it can update it itself
        customView.customViewHeight = customViewHeight
    }
}

class CustomView: UIView {

    var startPosition: CGPoint?
    var originalHeight: CGFloat = 0
    var customViewHeight: NSLayoutConstraint!

    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
        let touch = touches.first
        startPosition = touch?.locationInView(self)
        originalHeight = customViewHeight.constant
    }

    override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {
        let touch = touches.first
        let endPosition = touch?.locationInView(self)
        let difference = endPosition!.y - startPosition!.y
        customViewHeight.constant = originalHeight + difference
    }

}

向自定义视图添加另一个特性，以跟踪视图的原始高度。在touchsbegined中设置，然后在touchsmoved中计算帧时使用该原始高度：

---

在您的例子中，我认为您应该更改底部约束的常量，而不是更改视图的框架。另外，您最好使用手势，而不是覆盖触摸方法，因为手势是更高级的API，更易于维护

基本上，使用自动布局的项目应该避免使用框架更改视图

class ViewController: UIViewController {

    @IBOutlet weak var customViewHeight: NSLayoutConstraint!

    @IBOutlet weak var customView: CustomView!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Assign the layout constraint to the custom view so that it can update it itself
        customView.customViewHeight = customViewHeight
    }
}

class CustomView: UIView {

    var startPosition: CGPoint?
    var originalHeight: CGFloat = 0
    var customViewHeight: NSLayoutConstraint!

    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
        let touch = touches.first
        startPosition = touch?.locationInView(self)
        originalHeight = customViewHeight.constant
    }

    override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {
        let touch = touches.first
        let endPosition = touch?.locationInView(self)
        let difference = endPosition!.y - startPosition!.y
        customViewHeight.constant = originalHeight + difference
    }

}