ios - 在 SwiftUI 的 UITextView 中禁用向上滚动

Question

我在项目中使用 UITextView，我需要它只能向下滚动(不能向上滚动)。有没有办法可以相对容易地做到这一点？如果不是，我可能会继承 UIScrollView 或一些奇怪的东西，但我真的不想这样做。
这是我的基本 UIViewRepresentable 结构

struct TextView: UIViewRepresentable {
    
    typealias UIViewType = UITextView
    var configuration = { (view: UIViewType) in }
    
    func makeUIView(context: UIViewRepresentableContext<Self>) -> UIViewType {
        let view = UIViewType()
        view.isEditable = false
        
        return view
    }
    
    func updateUIView(_ uiView: UIViewType, context: UIViewRepresentableContext<Self>) {
        configuration(uiView)
    }
}

谢谢!

Answer 1

可以通过 UITextView 的简单子(monad)类来完成处理平移手势激活。
使用 Xcode 12 测试

class BottomScrollTextView: UITextView {
    override func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
        guard let gr = gestureRecognizer as? UIPanGestureRecognizer else { return true }

        return gr.translation(in: self).y < 0    // << allow only to down
    }

    private var _contentOffset = CGPoint.zero
    override var contentOffset: CGPoint {
        get { super.contentOffset }
        set {
            if newValue.y > super.contentOffset.y || self.isDecelerating {
                super.contentOffset = newValue
            }
        }
    }
}

struct TextView: UIViewRepresentable {

    typealias UIViewType = UITextView
    var configuration = { (view: UIViewType) in }

    func makeUIView(context: UIViewRepresentableContext<Self>) -> UIViewType {
        let view = BottomScrollTextView()   // << here !!

        // ... other code