IOS_Boss/IOS_study/Library/PinchZoomView.swift

//
//  PinchZoomView.swift
//  双指捏合放大扩展
//
//  Created by CC-star on 2025/7/22.
//

import SwiftUI

//图片查看器-用法：
//Image("Zoom").pinchToZoom()
class PinchZoomView: UIView {
   weak var delegate: PinchZoomViewDelgate?
   private(set) var scale: CGFloat = 0 {
      didSet { delegate?.pinchZoomView(self, didChangeScale: scale) }
   }
   
   private(set) var anchor: UnitPoint = .center {
      didSet { delegate?.pinchZoomView(self, didChangeAnchor: anchor) }
   }
   
   private(set) var offset: CGSize = .zero {
      didSet { delegate?.pinchZoomView(self, didChangeOffset: offset) }
   }
   
   private(set) var isPinching: Bool = false {
      didSet { delegate?.pinchZoomView(self, didChangePinching: isPinching) }
   }
   
   private var startLocation: CGPoint = .zero
   private var location: CGPoint = .zero
   private var numberOfTouches: Int = 0
   
   init() {
      super.init(frame: .zero)
      let pinchGesture = UIPinchGestureRecognizer(target: self, action: #selector(pinch(gesture:)))
      pinchGesture.cancelsTouchesInView = false
      addGestureRecognizer(pinchGesture)
   }
   
   required init?(coder: NSCoder) { fatalError() }
   
   @objc private func pinch(gesture: UIPinchGestureRecognizer) {
      switch gesture.state {
      case .began:
         isPinching = true
         startLocation = gesture.location(in: self)
         anchor = UnitPoint(x: startLocation.x / bounds.width, y: startLocation.y / bounds.height)
         numberOfTouches = gesture.numberOfTouches
      case .changed:
         if gesture.numberOfTouches != numberOfTouches {
            // If the number of fingers being used changes, the start location needs to be adjusted to avoid jumping.
            let newLocation = gesture.location(in: self)
            let jumpDifference = CGSize(width: newLocation.x - location.x, height: newLocation.y - location.y)
            startLocation = CGPoint(x: startLocation.x + jumpDifference.width, y: startLocation.y + jumpDifference.height)
            
            numberOfTouches = gesture.numberOfTouches
         }
         scale = gesture.scale
         location = gesture.location(in: self)
         offset = CGSize(width: location.x - startLocation.x, height: location.y - startLocation.y)
      case .ended, .cancelled, .failed:
         isPinching = false
         //加动画--在源代码上改动的地方
         //withAnimation(.interactiveSpring(response: 0.2, dampingFraction: 0.75, blendDuration: 0.1))
         withAnimation(.interactiveSpring(response: 0.2, dampingFraction: 0.65, blendDuration: 0.1)) {
            scale = 1.0
            anchor = .center
            offset = .zero
         }
      default: break
      }
   }
   
}

protocol PinchZoomViewDelgate: AnyObject {
   func pinchZoomView(_ pinchZoomView: PinchZoomView, didChangePinching isPinching: Bool)
   func pinchZoomView(_ pinchZoomView: PinchZoomView, didChangeScale scale: CGFloat)
   func pinchZoomView(_ pinchZoomView: PinchZoomView, didChangeAnchor anchor: UnitPoint)
   func pinchZoomView(_ pinchZoomView: PinchZoomView, didChangeOffset offset: CGSize)
}

struct PinchZoom: UIViewRepresentable {
   @Binding var scale: CGFloat
   @Binding var anchor: UnitPoint
   @Binding var offset: CGSize
   @Binding var isPinching: Bool
   
   func makeCoordinator() -> Coordinator { Coordinator(self) }
   func makeUIView(context: Context) -> PinchZoomView {
      let pinchZoomView = PinchZoomView()
      pinchZoomView.delegate = context.coordinator
      return pinchZoomView
   }
   func updateUIView(_ pageControl: PinchZoomView, context: Context) { }
   class Coordinator: NSObject, PinchZoomViewDelgate {
      var pinchZoom: PinchZoom
      init(_ pinchZoom: PinchZoom) { self.pinchZoom = pinchZoom }
      func pinchZoomView(_ pinchZoomView: PinchZoomView, didChangePinching isPinching: Bool) {
         pinchZoom.isPinching = isPinching
      }
      func pinchZoomView(_ pinchZoomView: PinchZoomView, didChangeScale scale: CGFloat) {
         pinchZoom.scale = scale
      }
      func pinchZoomView(_ pinchZoomView: PinchZoomView, didChangeAnchor anchor: UnitPoint) {
         pinchZoom.anchor = anchor
      }
      func pinchZoomView(_ pinchZoomView: PinchZoomView, didChangeOffset offset: CGSize) {
         pinchZoom.offset = offset
      }
   }
}
struct PinchToZoom: ViewModifier {
   @State var scale: CGFloat = 1.0
   @State var anchor: UnitPoint = .center
   @State var offset: CGSize = .zero
   @State var isPinching: Bool = false
   func body(content: Content) -> some View {
      content.scaleEffect(scale, anchor: anchor).offset(offset)
      //原代码中有这个，但效果不好，需要在上面pinch中加withanimation才行，故注释
      //         .animation(isPinching ? .none : .spring(), value: scale)
      //         .animation(.spring(duration: 1), value: scale)
         .overlay(PinchZoom(scale: $scale, anchor: $anchor, offset: $offset, isPinching: $isPinching))
      //         .onChange(of: isPinching) {
      //            if !isPinching {
      //               // 在松开手势时触发动画恢复
      //               withAnimation(.spring()) {
      //                  scale = 1.0
      //                  offset = .zero
      //                  anchor = .center
      //               }
      //            }
      //         }
   }
}
extension View {
   func pinchToZoom() -> some View { self.modifier(PinchToZoom()) }
}