问题描述
我正在尝试将 PKCanvasView
包装为一个名为 CanvasView
的 SwiftUI 视图。我希望能够在另一个视图之上切换整个画布。当 CanvasView
出现时,我希望 PKToolPicker
出现。当它消失时,我希望 PKToolPicker
消失。
我在这里找到了一些类似的方法,但它们只涉及显示选择器或使用按钮切换选择器;我希望选择器可见性与视图可见性相关联。
在下面的示例中,您可以看到可以切换画布,但是一旦工具选择器可见,它就会保持可见。
这是我的CanvasView
:
import SwiftUI
import Pencilkit
struct CanvasView: UIViewRepresentable {
class Coordinator: NSObject,PKCanvasViewDelegate {
var canvasView: Binding<PKCanvasView>
let onChange: () -> Void
init(canvasView: Binding<PKCanvasView>,onChange: @escaping () -> Void) {
self.canvasView = canvasView
self.onChange = onChange
}
func canvasViewDrawingDidChange(_ canvasView: PKCanvasView) {
if canvasView.drawing.bounds.isEmpty == false {
onChange()
}
}
}
@Binding var canvasView: PKCanvasView
@Binding var toolPickerIsActive: Bool
private let toolPicker = PKToolPicker()
let onChange: () -> Void
func makeUIView(context: Context) -> PKCanvasView {
canvasView.backgroundColor = .clear
canvasView.isOpaque = true
canvasView.delegate = context.coordinator
showToolPicker()
return canvasView
}
func updateUIView(_ uiView: PKCanvasView,context: Context) {
toolPicker.setVisible(toolPickerIsActive,forFirstResponder: uiView)
}
func showToolPicker() {
toolPicker.setVisible(true,forFirstResponder: canvasView)
toolPicker.addobserver(canvasView)
canvasView.becomeFirstResponder()
}
func makeCoordinator() -> Coordinator {
Coordinator(canvasView: $canvasView,onChange: onChange)
}
}
还有一个例子ContentView
:
struct ContentView: View {
@State private var canvasView = PKCanvasView()
@State private var toolPickerIsActive = false
@State private var canvasIsVisible = false
var body: some View {
ZStack {
if canvasIsVisible {
CanvasView(canvasView: $canvasView,toolPickerIsActive: $toolPickerIsActive,onChange: canvasDidChange)
.onAppear { toolPickerIsActive = true }
.ondisappear { toolPickerIsActive = false }
}
Button(action: {
canvasIsVisible.toggle()
},label: {
Text("Toggle canvas view")
})
}
}
private func canvasDidChange() {
// Do something with updated canvas.
}
}
任何指导将不胜感激!
解决方法
在您的场景中,CanvasView
在消失时被销毁,因此 SwiftUI 渲染引擎不会在任何状态更改时更新它(因为它认为不需要)。
此用例的可能解决方案是在协调器 deinit
上隐藏选择器(因为它已被所有者视图销毁)。
这是一个演示。使用 Xcode 12.4 / iOS 14.4 测试
struct CanvasView: UIViewRepresentable {
class Coordinator: NSObject,PKCanvasViewDelegate {
var canvasView: Binding<PKCanvasView>
let onChange: () -> Void
private let toolPicker: PKToolPicker
deinit { // << here !!
toolPicker.setVisible(false,forFirstResponder: canvasView.wrappedValue)
toolPicker.removeObserver(canvasView.wrappedValue)
}
init(canvasView: Binding<PKCanvasView>,toolPicker: PKToolPicker,onChange: @escaping () -> Void) {
self.canvasView = canvasView
self.onChange = onChange
self.toolPicker = toolPicker
}
func canvasViewDrawingDidChange(_ canvasView: PKCanvasView) {
if canvasView.drawing.bounds.isEmpty == false {
onChange()
}
}
}
@Binding var canvasView: PKCanvasView
@Binding var toolPickerIsActive: Bool
private let toolPicker = PKToolPicker()
let onChange: () -> Void
func makeUIView(context: Context) -> PKCanvasView {
canvasView.backgroundColor = .clear
canvasView.isOpaque = true
canvasView.delegate = context.coordinator
showToolPicker()
return canvasView
}
func updateUIView(_ uiView: PKCanvasView,context: Context) {
toolPicker.setVisible(toolPickerIsActive,forFirstResponder: uiView)
}
func showToolPicker() {
toolPicker.setVisible(true,forFirstResponder: canvasView)
toolPicker.addObserver(canvasView)
canvasView.becomeFirstResponder()
}
func makeCoordinator() -> Coordinator {
Coordinator(canvasView: $canvasView,toolPicker: toolPicker,onChange: onChange)
}
}
struct ContentView: View {
@State private var canvasView = PKCanvasView()
@State private var toolPickerIsActive = false
@State private var canvasIsVisible = false
var body: some View {
ZStack {
if canvasIsVisible {
CanvasView(canvasView: $canvasView,toolPickerIsActive: $toolPickerIsActive,onChange: canvasDidChange)
.onAppear { toolPickerIsActive = true }
// .onDisappear { toolPickerIsActive = false }
}
Button(action: {
canvasIsVisible.toggle()
},label: {
Text("Toggle canvas view")
})
}
}
private func canvasDidChange() {
// Do something with updated canvas.
}
}
注意:所有权可能会重新设计,因此 toolPicker
将仅存在于协调器中,但它不会改变想法,由您决定。