ios - SwiftUI View 无法正确呈现为UIImage

Question

由于我定义的方法，这可能是一个非常小众的问题，但希望有人可以帮助发现此代码中的错误。

因此，一方面，我将Multiline TextField定义为：

struct MultilineTextField: View {

    @State var dynamicHeight: CGFloat = 60

    @Binding var text: String

    var body: some View {
        UITextViewWrapper(text: $text, calculatedHeight: $dynamicHeight)
            .frame(height: dynamicHeight)
    }

}


fileprivate struct UITextViewWrapper: UIViewRepresentable {

    @Binding var text: String
    @Binding var calculatedHeight: CGFloat

    func makeUIView(context: Context) -> UITextView {
        let textField = UITextView()

        textField.delegate = context.coordinator
        textField.isEditable = true
        textField.font = UIFont.preferredFont(forTextStyle: .headline)
        textField.isSelectable = true
        textField.isUserInteractionEnabled = true
        textField.isScrollEnabled = false
        textField.backgroundColor = UIColor.clear
        textField.returnKeyType = .done
        textField.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
        textField.textAlignment = .center
        textField.textContainerInset = UIEdgeInsets(top: 10, left: 10, bottom: 10, right: 10)

        return textField
    }

    func updateUIView(_ uiView: UITextView, context: Context) {

        uiView.text = self.text

        UITextViewWrapper.recalculateHeight(view: uiView, result: $calculatedHeight)
    }

    fileprivate static func recalculateHeight(view: UIView, result: Binding<CGFloat>) {

        let newSize = view.sizeThatFits(CGSize(width: view.frame.size.width, height: CGFloat.greatestFiniteMagnitude))

        if result.wrappedValue != newSize.height {
            DispatchQueue.main.async {
                result.wrappedValue = newSize.height // !! must be called asynchronously
            }
        }
    }

    func makeCoordinator() -> Coordinator {
        return Coordinator(text: $text, height: $calculatedHeight)
    }

    final class Coordinator: NSObject, UITextViewDelegate {
        var text: Binding<String>
        var calculatedHeight: Binding<CGFloat>

        init(text: Binding<String>, height: Binding<CGFloat>) {
            self.text = text
            self.calculatedHeight = height
        }

        func textViewDidChange(_ uiView: UITextView) {
            text.wrappedValue = uiView.text
            UITextViewWrapper.recalculateHeight(view: uiView, result: calculatedHeight)
        }

        func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText 
            return
        }

    }

}

然后，我有一种方法可以将SwiftUI视图转换为UIImage，定义为：

extension View {
    func asImage() -> UIImage {
        let controller = UIHostingController(rootView: self)

        controller.view.frame = CGRect(x: 0, y: CGFloat(Int.max), width: 1, height: 1)
        UIApplication.shared.windows.first!.rootViewController?.view.addSubview(controller.view)

        let size = controller.sizeThatFits(in: UIScreen.main.bounds.size)
        controller.view.bounds = CGRect(x: 0, y: 0, width: size.width, height: size.height)
        controller.view.sizeToFit()

        controller.view.backgroundColor  = UIColor.white.withAlphaComponent(0.0)

        let image = controller.view.asImage()
        controller.view.removeFromSuperview()
        return image
    }
}

extension UIView {
    func asImage() -> UIImage {
        let renderer = UIGraphicsImageRenderer(bounds: bounds)
        return renderer.image { rendererContext in
            layer.render(in: rendererContext.cgContext)
        }
    }
}

但是，当我尝试将MultilineTextField转换为UIImage时，MultilineTextField的高度始终不正确。无论里面有多少文本，它似乎始终默认为60。

为了进行比较，当我在其他SwiftUI视图中使用MultilineTextField时，高度可以正常工作和更新，并根据MultilineTextField内部的文本进行增加和减少。

我的假设是，当我尝试将MultilineTextField视图转换为UIView时，我没有正确创建一个虚拟的subView来添加它（出于将其捕获为UIImage的目的）。但是我真的不知道。

Answer 1

通常，我发现最好使用UIViewControllerRepresentable而不是UIViewRepresentable ...，在那里您将拥有更多的访问生命周期，可以调整大小。