Using PKToolPicker without PKCanvasView - ios

Question

I am trying to use PKToolPicker from PencilKit (iOS/Swift) from a custom view (which is NOT PKCanvasView). The custom view conforms to PKToolPickerObserver. Everything works fine during compile time but I never get to see the PKToolPicker! If I replace my custom view with PKCanvasView, everything works fine!
I am doing this in SwiftUI with UIViewRepresentable (thus First Responder seems a mystery!).
Here is the SwiftUI view in question:
struct PencilKitView: UIViewRepresentable {
typealias UIViewType = myView
let coordinator = Coordinator()
class Coordinator: NSObject, PKToolPickerObserver {
func toolPickerSelectedToolDidChange(_ toolPicker: PKToolPicker) {
// some code
}
func toolPickerVisibilityDidChange(_ toolPicker: PKToolPicker) {
// some code
}
}
func makeCoordinator() -> PencilKitView.Coordinator {
return Coordinator()
}
func makeUIView(context: Context) -> myView {
let canvasView = myView()
canvasView.isOpaque = false
canvasView.backgroundColor = UIColor.clear
canvasView.becomeFirstResponder()
if let window = UIApplication.shared.windows.filter({$0.isKeyWindow}).first,
let toolPicker = PKToolPicker.shared(for: window) {
toolPicker.addObserver(canvasView)
toolPicker.addObserver(coordinator)
toolPicker.setVisible(true, forFirstResponder: canvasView)
}
return canvasView
}
func updateUIView(_ uiView: myView, context: Context) {
}
}
If I replace myView with PKCanvasView above, the PKToolPicker will be seen.
For the sake of completeness, here is the MyView stub:
class myView: UIScrollView, PKToolPickerObserver {
override init(frame: CGRect) {
super.init(frame: frame)
}
required init?(coder: NSCoder) {
super.init(coder: coder)
}
public func toolPickerVisibilityDidChange(_ toolPicker: PKToolPicker) {
/// some code
}
public func toolPickerSelectedToolDidChange(_ toolPicker: PKToolPicker) {
/// some code
}
public func toolPickerIsRulerActiveDidChange(_ toolPicker: PKToolPicker) {
/// some code
}
public func toolPickerFramesObscuredDidChange(_ toolPicker: PKToolPicker) {
/// some code
}
}
Anyone has succeeded in doing this? Is there some undocumented requirement for adopting PKToolPicker?

Answer 1

Here is simplest demo to show PKToolPicker for any custom UIView in SwiftUI.
Tested with Xcode 11.4 / iOS 13.4
struct ToolPickerDemo: View {
#State private var showPicker = false
var body: some View {
Button("Picker") { self.showPicker.toggle() }
.background(ToolPickerHelper(isActive: $showPicker))
}
}
class PickerHelperView: UIView {
override var canBecomeFirstResponder: Bool { true }
}
struct ToolPickerHelper: UIViewRepresentable {
#Binding var isActive: Bool
func makeUIView(context: Context) -> PickerHelperView {
PickerHelperView()
}
func updateUIView(_ uiView: PickerHelperView, context: Context) {
guard let window = uiView.window else { return }
let picker = PKToolPicker.shared(for: window)
picker?.setVisible(isActive, forFirstResponder: uiView)
DispatchQueue.main.async {
uiView.becomeFirstResponder()
}
}
}