考虑遵循简化的代码，用于可以拖动的元素，
HStack {
Icon(icon: .iconDrag)
Text("Title")
Spacer()
}
.padding(16)
.onDrag {
return NSItemProvider(object: id.uuidString as NSString)
}
这导致了下面的行为，其中一旦开始拖动，预览元素就会显示出来，但它是原始元素的一小部分大小，并且具有透明度.
我试着用相同的原始元素复制添加preview : {}到onDrag，但它的大小仍然不准确，它有透明度.有没有一种方法来扩展预览(比如使用uikit)，使其与原始元素完全相同？我相信预览元素的最大宽度在哪一点开始收缩也许？
您可以try 通过采用UIViewRepresentable中的UIDragInteractionDelegate来实现自定义拖动预览，以包装SwiftUI视图:通过使用UIDragPreview并设置UIDragItem的预览提供程序，您可以为预览指定一个与原始视图大小相同且不具有任何透明度的自定义视图.
+---------------------------------+
| +----+ +-------------------+ |
| |Icon| |Title | |
| +----+ +-------------------+ |
| | UIViewRepresentable wrapper |
| +-------------------------------+
| | UIDragInteractionDelegate |
+---------------------------------+
|
| Custom drag behavior
| (UIDragInteractionDelegate)
v
+----------------------------------+
| UIDragPreview (Custom preview) |
| Same size, no transparency |
+----------------------------------+
灵感来自Client/Frontend/TabChrome/TopBar/LocationView/LocationViewTouchHandler.swift
import SwiftUI
import UIKit
// Wrap your SwiftUI view in a UIViewRepresentable
struct DraggableView: UIViewRepresentable {
var text: String
func makeUIView(context: Context) -> UIView {
let view = UIHostingController(rootView: DraggableTextView(text: text)).view!
view.backgroundColor = .clear
let dragInteraction = UIDragInteraction(delegate: context.coordinator)
view.addInteraction(dragInteraction)
return view
}
func updateUIView(_ uiView: UIView, context: Context) {}
func makeCoordinator() -> Coordinator {
Coordinator()
}
class Coordinator: NSObject, UIDragInteractionDelegate {
func dragInteraction(_ interaction: UIDragInteraction, itemsForBeginning session: UIDragSession) -> [UIDragItem] {
let provider = NSItemProvider(object: "Dragged content" as NSString)
let item = UIDragItem(itemProvider: provider)
item.previewProvider = { return UIDragPreview(view: interaction.view!) }
return [item]
}
}
}
// Your original SwiftUI view
struct DraggableTextView: View {
var text: String
var body: some View {
HStack {
Image(systemName: "hand.point.up.left.fill") // Example icon
Text(text)
Spacer()
}
.padding(16)
.background(Color.gray) // For demo purposes
}
}
struct ContentView: View {
var body: some View {
DraggableView(text: "Draggable Text")
}
}
代码中的关键部分应该允许"相同大小，无透明度"的拖动预览是previewProvider关闭UIDragItem.
item.previewProvider = { return UIDragPreview(view: interaction.view!) }
UIDragPreview初始化器被传递给interaction.view，这是由UIHostingController创建的UI视图，内部有SwiftUI视图.由于您使用的是原始视图本身进行预览，所以它的大小应该与原始视图相同.