我正在尝试在斯坦福大学193p 2021上使用EmojiArt应用程序，如果该参考有帮助的话。否则，正如标题所述，我试图在每个表情符号上添加onDrag修饰符，但似乎当我拖动一个时，整个表情符号字符串都会被拖动。如何解决这个问题？

import SwiftUI

struct EmojiArtDocumentView: View {
    @ObservedObject var document: EmojiArtDocument
    let defaultmojiFontSize: CGFloat = 40
    var body: some View {
        VStack(spacing: 0) {
            documentBody
            palette
        }
        .padding()
    }
    
    var documentBody: some View {
        GeometryReader { geometry in
            ZStack {
                Color.yellow
                ForEach(document.emojis) { emoji in
                    Text(emoji.text)
                        .font(.system(size: fontSize(for: emoji)))
                        .position(position(for: emoji, in: geometry))
                }
            }
        }
//        .onDrop(of: [.plainText], isTargeted: nil) {
//            providers, location in
//            return false
//        }
    }
    
    private func drop(providers: [NSItemProvider], at location: CGPoint) -> Bool {
        false
    }
    
    private func fontSize(for emoji: EmojiArt.Emoji) -> CGFloat {
        CGFloat(emoji.size)
    }
    
    private func position(for emoji: EmojiArt.Emoji, in geometry: GeometryProxy) -> CGPoint {
        convertFromEmojiCoordinates((emoji.x, emoji.y), in: geometry)
    }
    
    private func convertFromEmojiCoordinates(_ location: (x: Int, y: Int), in geometry: GeometryProxy) -> CGPoint {
        let center = geometry.frame(in: .local).center
        return CGPoint(
            x: center.x + CGFloat(location.x),
            y: center.y + CGFloat(location.y)
        )
    }
    
    var palette: some View {
        ScrollingEmojisView(emojis: testemojis)
            .font(.system(size: defaultmojiFontSize))
    }
    
    let testemojis = "😀🥰😌😇🤓🤩🤪😤👻"
}

struct ScrollingEmojisView: View {
    let emojis: String
    
    var body: some View {
        ScrollView(.horizontal) {
            HStack {
                ForEach(emojis.map {String($0) }, id: \.self) { emoji in
                    Text(emoji)
                        .onDrag {
                            NSItemProvider(object: emoji as NSString)
                        }
                }
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        EmojiArtDocumentView(document: EmojiArtDocument())
    }
}

extension CGRect {
    var center: CGPoint {
        CGPoint(x: midX, y: midY)
    }
}