想要限制一个imageView swift 5上的平移手势区域

Question

我有一个具有 2 个手势识别器的图像视图 1）捏 2)平移

我可以使用 scale 属性捏合图像并进行缩放 我无法实现的是，当我缩放该图像并拖动到所有 4 个边时，我可以拖动图像并且能够看到图像视图后面的背景视图 想要限制图像视图的拖动，直到显示该缩放图像

这是捏和平移手势的代码

  @objc func pinchRecognized(pinch: UIPinchGestureRecognizer) {

            if let view = pinch.view {
                view.transform = view.transform.scaledBy(x: pinch.scale, y: pinch.scale)
                pinch.scale = 1
            }
        }
    
    @objc func PangestureMethod(gestureRecognizer: UIPanGestureRecognizer){
       guard gestureRecognizer.view != nil else {return}
       let piece = gestureRecognizer.view!
  
    
       let translation = gestureRecognizer.translation(in: piece.superview)
        
       if gestureRecognizer.state == .began {
          self.initialCenter = piece.center
       }
       if gestureRecognizer.state != .cancelled {
          let newCenter = CGPoint(x: initialCenter.x + translation.x, y: initialCenter.y + translation.y)
          piece.center = newCenter
       }
       else {
          piece.center = initialCenter
       }
    }

Answer 1

首先，重置平移手势的平移（可能）更容易，因此我们正在计算相对移动：

if gestureRecognizer.state != .cancelled {
    
    // translation will be + or - a small number of points
    // do what's needed to move the view

    // reset recognizer
    gestureRecognizer.setTranslation(.zero, in: superV)

}

否则，假设您向右拖动（平移）300 点，但视图只能移动 20 点，那么直到您向左拖动 280 点，它才会开始向左移动。

所以，当水平拖动时，我们想在拖动视图位于其 superView 的左侧或右侧时停止...

• 计算 MAX centerX 位置
  • 这将是拖动视图宽度的 1/2
• 计算 MIN centerX 位置
  • 这将是 superView 的宽度减去拖动视图宽度的 1/2

例如，如果superView的宽度是100，而drag-view的宽度是200，那么MAX centerX就是100，MIN centerX就是Zero。

然后我们对 centerY 位置做同样的事情。

尝试使用它作为你的 Pan Gesture 处理程序：

@objc func PangestureMethod(gestureRecognizer: UIPanGestureRecognizer){
    
    // unwrap the view from the gesture
    // AND
    // unwrap that view's superView
    guard let piece = gestureRecognizer.view,
          let superV = piece.superview
    else {
        return
    }
    
    let translation = gestureRecognizer.translation(in: superV)
    
    if gestureRecognizer.state == .began {
        self.initialCenter = piece.center
    }
    if gestureRecognizer.state != .cancelled {

        // what the new centerX and centerY will be
        var newX: CGFloat = piece.center.x + translation.x
        var newY: CGFloat = piece.center.y + translation.y

        // MAX centerX is 1/2 the width of the piece's frame
        let mxX = piece.frame.width * 0.5
        
        // MIN centerX is Width of superView minus 1/2 the width of the piece's frame
        let mnX = superV.bounds.width - piece.frame.width * 0.5
        
        // make sure new centerX is neither greater than MAX nor less than MIN
        newX = max(min(newX, mxX), mnX)
        
        // MAX centerY is 1/2 the height of the piece's frame
        let mxY = piece.frame.height * 0.5
        
        // MIN centerY is Height of superView minus 1/2 the height of the piece's frame
        let mnY = superV.bounds.height - piece.frame.height * 0.5
        
        // make sure new centerY is neither greater than MAX nor less than MIN
        newY = max(min(newY, mxY), mnY)
        
        // set the new center
        piece.center = CGPoint(x: newX, y: newY)
        
        // reset recognizer
        gestureRecognizer.setTranslation(.zero, in: superV)

    }
    else {
        piece.center = initialCenter
    }
}

---

编辑

为了防止 Pinch Gesture 将视图缩小到小于其 superView 帧，我们可以将手势中的新缩放值应用到视图 frame 的 CGRect，然后再将其应用到视图。

然后，仅当生成的矩形不小于 superView 的框架时才对视图应用缩放。

试试这个：

@objc func pinchRecognized(pinch: UIPinchGestureRecognizer) {

    // unwrap the view from the gesture
    // AND
    // unwrap that view's superView
    guard let piece = pinch.view,
          let superV = piece.superview
    else {
        return
    }

    // this is a bit verbose for clarity
    
    // get the new scale
    let sc = pinch.scale
    
    // get current frame of "piece" view
    let currentPieceRect = piece.frame
    
    // apply scaling transform to the rect
    let futureRect = currentPieceRect.applying(CGAffineTransform(scaleX: sc, y: sc))
    
    // if the resulting rect's width will be
    //  greater-than-or-equal to superView's width
    if futureRect.width >= superV.bounds.width {
        // go ahead and scale the piece view
        piece.transform = piece.transform.scaledBy(x: sc, y: sc)
    }
    pinch.scale = 1
    
}