使用多个对象的手势识别器来移动对象

Question

I am trying to make an app where you can use Stickers like on Snapchat and Instagram. It fully worked to find a technique, that adds the images, but now I want that if you swipe the object around the object changes its position (I also want to make the scale / rotate function).

My code looks like this:

@objc func StickerLaden() {
   for i in 0 ..< alleSticker.count {
        let imageView = UIImageView(image: alleSticker[i])

        imageView.frame = CGRect(x: StickerXScale[i], y:StickerYScale[i], width: StickerScale[i], height: StickerScale[i])

        ImageViewsSticker.append(imageView)
        ImageView.addSubview(imageView)
        imageView.isUserInteractionEnabled = true

        let aSelector : Selector = "SlideFunc"
        let slideGesture = UISwipeGestureRecognizer(target: self, action: aSelector)

        imageView.addGestureRecognizer(slideGesture)
    }
}

func SlideFunc(fromPoint:CGPoint, toPoint: CGPoint) {
}

Answer 1

Here are the high-level steps you need to take:

• Add one UIPanGestureRecognizer to the parent view that has the images on it.
• Implement UIGestureRecognizerDelegate methods to keep track of the user touching and releasing the screen.
• On first touch, loop through all your images and call image.frame.contains(touchPoint) . Add all images that are under the touch point to an array.
• Loop through the list of touched images and calculate the distance of the touch point to the center of the image. Chose the image whose center is closest to the touched point.
• Move the chosen image to the top of the view stack. [You now have selected an image and made it visible.]
• Next, when you receive pan events, change the frame of the chosen image accordingly.
• Once the user releases the screen, reset any state variables you may have, so that you can start again when the next touch is done.

The above will give you a nicely working pan solution. It's a good amount of things you need to sort out, but it's not very difficult.

As I said in my comment, scale and rotate are very tricky. I advise you to forget that for a bit and first implement other parts of your app.