@Binding 值更改时更新 UIView（在 UIViewRepresentable 内）

Question

我尝试在绑定值发生变化时更新 UIView（在 UIViewRepresentable 中），但我不知道如何捕捉绑定值的变化来更新 UIView？我使用了接收函数，但显示一条警告消息（接收未使用的调用结果）

示例代码：

struct CustomPickerView: UIViewRepresentable {
    
    let data: [String]
    @Binding var selectedValue: String
    
    //makeCoordinator()
    func makeCoordinator() -> CustomPickerView.Coordinator {
        return CustomPickerView.Coordinator(self)
    }

    //makeUIView(context:)
    func makeUIView(context: UIViewRepresentableContext<CustomPickerView>) -> UIPickerView {
        let picker = UIPickerView(frame: .zero)
        // allows rows to be compressed in swiftUI
        picker.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
        picker.setContentCompressionResistancePriority(.defaultLow, for: .vertical)
        // allows rows to be expanded
        picker.setContentHuggingPriority(.defaultLow, for: .horizontal)
        picker.dataSource = context.coordinator
        picker.delegate = context.coordinator
        
        picker.selectRow(data.firstIndex(of: selectedValue) ?? 0, inComponent: 0, animated: false)
        return picker
    }

    //updateUIView(_:context:)
    func updateUIView(_ view: UIPickerView, context: UIViewRepresentableContext<CustomPickerView>) {

        onReceive(selectedValue.publisher) { newValue in

       // I try to update the picker view selected row when binding value changes...

            view.selectRow(data.firstIndex(of: newValue.debugDescription) ?? 0, inComponent: 0, animated: true)
        }
    }

// The rest of code ...

}

Answer 1

不需要使用onReceive和watch publisher -- updateUIView会在selectedValue变化时被调用，直接使用即可：

struct ContentView: View {
    @State private var selected = "3"
    
    var body: some View {
        CustomPickerView(data: ["1","2","3"], selectedValue: $selected)
        Button("Choose 1") {
            selected = "1"
        }
    }
}

struct CustomPickerView: UIViewRepresentable {
    
    let data: [String]
    @Binding var selectedValue: String
    
    //makeCoordinator()
    func makeCoordinator() -> CustomPickerView.Coordinator {
        return CustomPickerView.Coordinator(self)
    }

    //makeUIView(context:)
    func makeUIView(context: UIViewRepresentableContext<CustomPickerView>) -> UIPickerView {
        let picker = UIPickerView(frame: .zero)
        // allows rows to be compressed in swiftUI
        picker.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
        picker.setContentCompressionResistancePriority(.defaultLow, for: .vertical)
        // allows rows to be expanded
        picker.setContentHuggingPriority(.defaultLow, for: .horizontal)
        picker.dataSource = context.coordinator
        picker.delegate = context.coordinator
        
        picker.selectRow(data.firstIndex(of: selectedValue) ?? 0, inComponent: 0, animated: false)
        return picker
    }

    func updateUIView(_ view: UIPickerView, context: UIViewRepresentableContext<CustomPickerView>) {
        view.selectRow(data.firstIndex(of: selectedValue) ?? 0, inComponent: 0, animated: true)
    }
    
    class Coordinator : NSObject, UIPickerViewDataSource, UIPickerViewDelegate {
        func numberOfComponents(in pickerView: UIPickerView) -> Int {
            1
        }
        
        func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
            parent.data.count
        }

        func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String?
        {
            parent.data[row]
        }
        
        var parent: CustomPickerView
        
        init(_ input : CustomPickerView) {
            self.parent = input
        }
    }
}

@Binding 值更改时更新 UIView（在 UIViewRepresentable 内）

Update UIView (inside UIViewRepresentable) when @Binding value changes

uikit

ios

swift

swiftui

uiviewrepresentable