Swift开发问题：解除两ImageView关联约束实现独立移动

Hey there! I see exactly what's going on here—your blue and green image views are tied together by that blueMove.leadingAnchor.constraint(equalTo: greenMove.trailingAnchor, constant: 0) constraint, so moving one forces the other to follow. Let's fix this by breaking that link only when a user selects either image view, while keeping the initial layout intact.

Key Issues to Address: #

• The persistent leading constraint between the two views is enforcing their relative position even when you try to move them.
• Your current existingTransition variable is shared between both views, which will cause their movement states to clash.
• You're adding a tap gesture recognizer every time the pan gesture runs, which leads to duplicate gesture handlers.

Step-by-Step Solution: #

1. Store the linking constraint separately: We'll keep a reference to that leading constraint so we can deactivate it later when a view is selected.
2. Add tap gestures upfront: Instead of adding tap gestures during panning, set them up once in viewDidLoad to handle view selection.
3. Track transforms per view: Use separate variables to store the translation state for each image view, so their movements don't interfere with each other.
4. Deactivate the linking constraint on selection: When a user taps either image view, disable that shared leading constraint to let the views move independently.

Modified Full Code: #

import UIKit

class ViewController: UIViewController {
    // Layout constraints
    var image1Width: NSLayoutConstraint!
    var image1Height: NSLayoutConstraint!
    var image1Width2: NSLayoutConstraint!
    var image1Height2: NSLayoutConstraint!
    // Store the linking constraint separately so we can deactivate it later
    var blueToGreenLeadingConstraint: NSLayoutConstraint!
    
    // UI Elements
    var greenMove = UIImageView()
    var slider = UISlider()
    var blueMove = UIImageView()
    
    // Track transform state PER view (no more shared state!)
    var greenTransform: CGAffineTransform?
    var blueTransform: CGAffineTransform?
    
    var clock = Int()
    var currentView: UIView?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        greenMove.isUserInteractionEnabled = true
        blueMove.isUserInteractionEnabled = true
        
        // Add pan gestures
        let greenPan = UIPanGestureRecognizer(target: self, action: #selector(handlePan(_:)))
        greenMove.addGestureRecognizer(greenPan)
        
        let bluePan = UIPanGestureRecognizer(target: self, action: #selector(handlePan(_:)))
        blueMove.addGestureRecognizer(bluePan)
        
        // Add tap gestures upfront (no more duplicate gestures!)
        let greenTap = UITapGestureRecognizer(target: self, action: #selector(handleTap(_:)))
        greenMove.addGestureRecognizer(greenTap)
        
        let blueTap = UITapGestureRecognizer(target: self, action: #selector(handleTap(_:)))
        blueMove.addGestureRecognizer(blueTap)
        
        // Set colors
        greenMove.backgroundColor = .systemGreen
        blueMove.backgroundColor = .blue
        
        // Add subviews
        [greenMove, slider, blueMove].forEach {
            view.addSubview($0)
            $0.translatesAutoresizingMaskIntoConstraints = false
        }
        
        // Setup size constraints
        image1Width = greenMove.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 0.2)
        image1Height = greenMove.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.20)
        
        image1Width2 = blueMove.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 0.2)
        image1Height2 = blueMove.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.20)
        
        // Store the linking constraint separately
        blueToGreenLeadingConstraint = blueMove.leadingAnchor.constraint(equalTo: greenMove.trailingAnchor, constant: 0)
        
        // Activate all initial constraints
        NSLayoutConstraint.activate([
            greenMove.topAnchor.constraint(equalTo: view.topAnchor, constant: 0),
            image1Width,
            image1Height,
            greenMove.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 0),
            blueMove.topAnchor.constraint(equalTo: view.topAnchor, constant: 0),
            image1Width2,
            image1Height2,
            blueToGreenLeadingConstraint
        ])
        
        // Setup slider target
        slider.addTarget(self, action: #selector(adjustSize), for: .valueChanged)
    }
    
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews() // Don't forget to call super!
        NSLayoutConstraint.activate([
            slider.topAnchor.constraint(equalTo: greenMove.bottomAnchor, constant: 0), // Better to pin to green view's bottom
            slider.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.20),
            slider.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 0.20),
            slider.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 0),
        ])
    }
    
    @objc func handleTap(_ gesture: UITapGestureRecognizer) {
        guard let tappedView = gesture.view else { return }
        currentView = tappedView
        
        // Deactivate the linking constraint if it's still active
        if blueToGreenLeadingConstraint.isActive {
            blueToGreenLeadingConstraint.isActive = false
            print("Linking constraint disabled—views can now move independently!")
        }
    }
    
    @objc func handlePan(_ sender: UIPanGestureRecognizer) {
        guard let child = sender.view else { return }
        
        // Set clock based on which view is being panned
        clock = child == greenMove ? 1 : 2
        
        let transitionPoint = sender.translation(in: self.view)
        let newTransition = CGAffineTransform(translationX: transitionPoint.x, y: transitionPoint.y)
        
        // Use view-specific transform storage
        switch child {
        case greenMove:
            switch sender.state {
            case .ended, .cancelled:
                greenTransform = newTransition.concatenating(greenTransform ?? .identity)
            default:
                child.transform = newTransition.concatenating(greenTransform ?? .identity)
            }
        case blueMove:
            switch sender.state {
            case .ended, .cancelled:
                blueTransform = newTransition.concatenating(blueTransform ?? .identity)
            default:
                child.transform = newTransition.concatenating(blueTransform ?? .identity)
            }
        default:
            break
        }
        
        self.view.layoutIfNeeded()
    }
    
    @objc func adjustSize() {
        switch clock {
        case 1:
            image1Width.constant = CGFloat(slider.value) * view.frame.size.width * 0.25
            image1Height.constant = CGFloat(slider.value) * view.frame.size.height * 0.25
        case 2:
            image1Width2.constant = CGFloat(slider.value) * view.frame.size.width * 0.25
            image1Height2.constant = CGFloat(slider.value) * view.frame.size.height * 0.25
        default:
            break
        }
    }
}

What Changed: #

• Separate transform tracking: greenTransform and blueTransform replace the shared existingTransition, so each view keeps its own movement state.
• Link constraint reference: blueToGreenLeadingConstraint is stored as a class property, making it easy to deactivate when a view is tapped.
• Tap gestures added once: No more adding tap gestures every time you pan—they're set up once in viewDidLoad.
• Improved slider layout: The slider is now pinned to the green view's bottom instead of using a fixed constant, which is more reliable.
• Consistent pan handling: The pan gesture handler now checks which view is being moved and uses the correct transform variable.

Now when you run the app, the initial layout stays intact. Tap either image view, and the linking constraint will be disabled—you can move each view independently without the other following along!

内容的提问来源于stack exchange，提问作者user13245026