旋转手势会产生不需要的旋转

Question

我需要仅使用一根手指的动作来根据用户的动作旋转 UIImageview。为此，我使用旋转手势，然后使用以下代码覆盖 touchesMoved：

  override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {

    let touch = touches.first
    if touch!.view === rotateImageView {
        let position = touch!.locationInView(self.view)

        let target = rotateImageView.center
        let angle = atan2(target.y-position.y, target.x-position.x)
        rotateImageView.transform = CGAffineTransformMakeRotation(angle)
    }
  }

只要用户停止触摸屏幕并在屏幕的另一部分进行动作，此功能就会起作用。在这种情况下，当用户开始移动手指时，UIImageview 会在不需要的位置旋转。我需要保持 UIImageview 的原始旋转位置来避免这种情况，但我不知道该怎么做。

此 gif 显示了我拥有的项目原型的当前行为。如您所见，当我开始在右侧旋转时，火焰图标突然出现在触摸点附近，这就是我要防止的。

2016 年 8 月 23 日更新

我使用了 Matt 和 Dasem 关于使用 CGAffineTransformRotate 的建议，但我仍然看到跳跃。我采用了 Dasem 代码并像下面这样适应了我的项目（如果适应有误请告诉我）：

override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {

    origin = (touches.first?.locationInView(self.view))!

    //save the current transform
    tempTransform = rotateImageView.transform

}

override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {

    let touchPoint = touches.first?.locationInView(self.view)

    xOffSet = CGVector(dx:(origin.x)-rotateImageView.center.x, dy:(origin.x) - rotateImageView.center.y)
    yOffSet = CGVector(dx:touchPoint!.x - rotateImageView.center.x, dy:touchPoint!.y - rotateImageView.center.y)

    let angle = atan2(yOffSet.dy,yOffSet.dx) - atan2(xOffSet.dy,xOffSet.dx)
    rotateImageView.transform = CGAffineTransformRotate(tempTransform, angle)

}

当用户触摸触摸屏的不同区域时，此更改会产生类似的效果。在此 gif 中，我更改了图像并删除了图标以使效果更加明显。

更新解决方案

使用 Jasem 更新重新应用代码并且它有效，以下代码在不使用子类化的情况下解决了问题

override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {

    origin = (touches.first?.locationInView(self.view))!
    xOffSet = CGVector(dx:(origin.x)-rotateImageView.center.x, dy:(origin.y) - rotateImageView.center.y)
    startingAngle = atan2(xOffSet.dy,xOffSet.dx)

    //save the current transform
    tempTransform = rotateImageView.transform
}

override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {

    let touchPoint = touches.first?.locationInView(self.view)
    yOffSet = CGVector(dx:touchPoint!.x - rotateImageView.center.x, dy:touchPoint!.y - rotateImageView.center.y)
    let angle = atan2(yOffSet.dy,yOffSet.dx)

    let deltaAngle = angle - startingAngle!
    rotateImageView.transform = CGAffineTransformRotate(tempTransform, deltaAngle)
}

override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
    startingAngle = nil
}

//reset in case drag is cancelled
override func touchesCancelled(touches: Set<UITouch>?, withEvent event: UIEvent?) {
    rotateImageView.transform = tempTransform
    startingAngle = nil
}

Answer 1

问题是你说的是

rotateImageView.transform = CGAffineTransformMakeRotation(angle)

因此，图像视图已经（从之前的旋转）进行的任何变换都被丢弃并完全替换新的变换开始在 angle。这就是您看到的 "jump"。

您要做的是对图像视图的现有变换应用旋转变换。您可以通过调用 CGAffineTransformRotate 而不是 CGAffineTransformMakeRotation 来做到这一点。

Answer 2

您可能想将 self.superview 更改为 self.view（我的是子类）

var xOffSet:CGVector = CGVectorMake(0, 0)
var yOffSet:CGVector = CGVectorMake(0, 0)
var origin:CGPoint = CGPointZero
var tempTransform=CGAffineTransform()
var startingAngle:CGFloat?


   override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {

    origin = (touches.first?.locationInView(self.superview))!
    xOffSet = CGVector(dx:(origin.x)-self.center.x, dy:(origin.y) - self.center.y)
    startingAngle = atan2(xOffSet.dy,xOffSet.dx)

    //save the current transform
    tempTransform = self.transform
}

override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {

    let touchPoint = touches.first?.locationInView(self.superview)
    yOffSet = CGVector(dx:touchPoint!.x - self.center.x, dy:touchPoint!.y - self.center.y)
    let angle = atan2(yOffSet.dy,yOffSet.dx)

    let deltaAngle = angle - startingAngle!
    self.transform = CGAffineTransformRotate(tempTransform, deltaAngle) 
}


override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {  
  startingAngle = nil
}

//reset in case drag is cancelled
override func touchesCancelled(touches: Set<UITouch>?, withEvent event: UIEvent?) {
        self.transform = tempTransform
        startingAngle = nil
    }

旋转手势会产生不需要的旋转

Rotation gesture produces undesired rotation

rotation

uiimageview

uigesturerecognizer

swift