SwiftUI boundingRect doesn't work fine by UIViewRepresentable updateUIView

问题

I want to highlight texts in UITextView. Here is the CustomTextView I made.


    struct CustomTextView: UIViewRepresentable {
    
    @ObservedObject var tmpTextVM: TmpTextViewModel
        
        func makeUIView(context: UIViewRepresentableContext<CustomTextView>) -> UITextView {
            let textView = UITextView()
            textView.backgroundColor = UIColor.clear
            textView.isScrollEnabled = false
            textView.text = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
            textView.font = UIFont(name: "ArialMT", size: 20)
            textView.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
            return textView
        }
    
        func updateUIView(_ uiView: UITextView, context: Context) {
            
            uiView.textColor = tmpTextVM.color

            
            let range = (uiView.text as NSString).range(of: uiView.text)
            var rect = uiView.layoutManager.boundingRect(forGlyphRange: range, in: uiView.textContainer)
            
            rect.size.width += 25
            rect.size.height += 10
            rect.origin.x += uiView.textContainerInset.left - 10
            rect.origin.y += uiView.textContainerInset.top - 5
            
            uiView.viewWithTag(300)?.removeFromSuperview()

            let view = UIView()
            
            view.backgroundColor = UIColor.blue
            
            view.layer.cornerRadius = 10
            view.frame = rect
            view.tag = 300
            
            uiView.addSubview(view)
            uiView.sendSubviewToBack(view)
            
        }
}

And using this like below.

struct TmpView7View: View {
    
    @ObservedObject var tmpTextVM: TmpTextViewModel
    
    var body: some View {
        VStack {
            
            Button(action: {
                  tmpTextVM.changeColor(UIColor.red)
              }){
                  Image(systemName:"eyedropper.full")
              }
            
            CustomTextView(tmpTextVM: tmpTextVM)
                .frame(width:300, height: 300, alignment: .topLeading)
                .border(Color.red, width: 1)
        }
    }
}

But it highlights only first line of UITextView. And if it was updated by tapping the button, it highlights all text. It seems like if updeteUIView is called again, texts are highlighted properly. I want it to be highlighted at the first time when the textView was rendered. Is it possible to do that??

来源：https://stackoverflow.com/questions/65168981/swiftui-boundingrect-doesnt-work-fine-by-uiviewrepresentable-updateuiview

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swift

swiftui