What happens when you tap an image with Swift?

Currently, I am creating an iOS app that retrieves multiple thumbnails from a single video I read and arranges them horizontally.I was able to get thumbnails from the video and arrange them side by side, but when I tap one thumbnail from there, I want to display it in another UIImageView, but I can't do it well.

The current method is to create a class that inherits UIImageView and send the value to the tap event, but random numbers such as 15 digits instead of 0, 1, 2 are displayed.

I don't know why such a value is returned, so I would appreciate it if you could let me know.Another way is fine.

The following are the source code, execution results and reference sites.

Source Code

import UIKit
import AVFoundation
import AssetsLibrary

classViewController:UIViewController, UIGestureRecognizerDelegate{

    @IBOutlet weak var topimage:UIImageView!
    @IBOutlet weak var scroll:UIScrollView!

    let time = 20

    class MyUIImageView:UIImageView {
        let x —Int
        letty —Int
        init(x:Int, y:Int, frame:CGRect){
            self.x = x
            self.y = y
            super.init (frame:frame)
        }
        required init (coder adecoder:NSCoder) {
            fatalError("***init(coder:)has not been implemented")
        }
    }

    override func viewDidLoad(){
        super.viewDidLoad()

        let filePath: URL = URL (fileURLWithPath: "Video Path")
        letasset=AVURLAsset(url:filePath, options:nil)
        let imgGenerator = AVAssetImageGenerator (asset:asset)
        imgGenerator.appliesPreferredTrackTransform=true

        scroll.contentSize=CGSize(width:time*100, height:200)
        scroll.bounce=false
        self.scroll.isScrollEnabled=true
        self.scroll.showsHorizontalScrollIndicator=false

        do{
            for x in 0 ... time-1 {
            // Create a view while changing the position
                letiv: UIImageView= MyUIImageView(
                    x —x,
                    y—1,
                    frame —CGRect (x:CGFloat(x)*100, y:100, width:100, height:150))

                // Creating Thumbnails
                let cgImage=try imgGenerator.copyCGImage(at:CMTimeMake(Int64(seconds/(time-x))), 3),actualTime:nil)
                let thumbnail=UIImage(cgImage:cgImage)

                // Add image to view
                iv.image=thumbnail
                // Tap gesture
                iv.isUserInteractionEnabled=true
                iv.addGestureRecognizer(UITapGestureRecognizer(
                    target —self,
                    action:#selector(imageViewTapped)))

                // Add to screen
                scroll.addSubview(iv)
            }
        }catchlet error {
            print("***Error generating thumbnail:\(error.localizedDescription)")
        }
    }

    @objc funcimageViewTapped(views:MyUIImageView, gestureRecognizer:UITapGestureRecognizer){
        // If I can get x here, I think I can display it if I write the same program as above.
        print(views.x)
    }

    override funcdidReceiveMemoryWarning(){
        super.didReceiveMemoryWarning()

    }
}

Run Results

 view at (140434724710272) is tapped // 1st thumbnail
view at(0)is tapped // Second thumbnail
view at (140434743678464) is taped // Third thumbnail
view at (140434724710848) is taped // 4th thumbnail

Reference Site
https://qiita.com/fetaro/items/199e36d71ee9c0015488

swift ios

2022-09-30 21:27

1 Answers

When calling the method specified in the selector from the iOS side, the parameters you want to pass are determined by which iOS features you use.

For UIGestureRecognizer, it must be one of the following signatures:

@IBAction func myActionMethod()
@ IBAction func myActionMethod(_sender:UIGestureRecognizer)

@IBAction is just a document description, so you can quickly ignore it, and the point is that you can take up to one argument, one of which represents UIGestureRecognizer.

Even if arguments are added in the method declaration, iOS ignores them at all and passes the first argument an instance of UIGestureRecognizer (UITapGestureRecognizer in your case).Your method forcibly interprets it as MyUIImageView and calls a property getter for MyUIImageView, so it's safe to crash immediately rather than get a proper value back.

Declare the exact arguments for the method called by the selector.

@objc funcimageViewTapped(_gestureRecognizer:UITapGestureRecognizer){
    // Use the `view` property to retrieve the view to which you want to set the UIGestureRecognizer
    // I intentionally use `!` or `as!` to inform you of the crash if the UITapGestureRecognizer is misconfigured.
    let myImageView=gestureRecognizer.view!as!MyUIImageView
    print(myImageView.x)
}

2022-09-30 21:27

If you have any answers or tips

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