SwiftUI中的PencilKit [英] PencilKit in SwiftUI

问题描述

我正在尝试在SwiftUI中使用PencilKit.

I'm trying to use PencilKit in SwiftUI.

1. 如何在updateUIView函数中检测到哪个Binding变量已更新?例如，更改颜色时我不想清除画布.
2. 还有比清除布尔值更好的清除画布的方法吗?切换布尔值会强制执行updateUIView函数.

1. How can I detect in the updateUIView-function, which Binding-variable was updated? For example I don't want to clear the canvas when changing the color.
2. And is there a better way to clear the canvas than toggling a boolean? Toggling a boolean forces the updateUIView-function to execute.

import SwiftUI
import UIKit
import PencilKit

struct ContentView: View {
    @State var color = UIColor.black
    @State var clear = false

    var body: some View {
        VStack{
            PKCanvas(color: $color, clear:$clear)
            VStack(){
                Button("Change to BLUE"){ self.color = UIColor.blue }
                Button("Change to GREEN"){ self.color = UIColor.green }
                Button("Clear Canvas"){ self.clear.toggle() }
            }
        }
    }
}

struct PKCanvas: UIViewRepresentable {
    class Coordinator: NSObject, PKCanvasViewDelegate {
        var pkCanvas: PKCanvas

        init(_ pkCanvas: PKCanvas) {
            self.pkCanvas = pkCanvas
        }
    }

    @Binding var color:UIColor
    @Binding var clear:Bool

    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }

    func makeUIView(context: Context) -> PKCanvasView {
        let canvas = PKCanvasView()
        canvas.tool = PKInkingTool(.pen, color: color, width: 10)

        canvas.delegate = context.coordinator
        return canvas
    }

    func updateUIView(_ canvasView: PKCanvasView, context: Context) {
        // clears the canvas
        canvasView.drawing = PKDrawing()

        // sets a new color
        canvasView.tool = PKInkingTool(.pen, color: color, width: 10)
    }
}

推荐答案

这可以解决问题:

    func updateUIView(_ canvasView: PKCanvasView, context: Context) {
        if clear != context.coordinator.pkCanvas.clear{
            canvasView.drawing = PKDrawing()
        }
        canvasView.tool = PKInkingTool(.pen, color: color, width: 10)
    }

这篇关于SwiftUI中的PencilKit的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！