为什么我的视图右上角有一个“加号”图标？

Question

我正在尝试为我的LazyHGridview. 当我尝试将视图放到另一个视图上时，视图的右上角会显示绿色圆圈内的“加号”图标。

struct TestView: View {
var d: GridData
  @Binding var list: [GridData]
  @State private var dragOver = false
   
  var body: some View {
    VStack {
      Text(String(d.id))
        .font(.headline)
        .foregroundColor(.white)
    }
    .frame(width: 160, height: 240)
    .background(colorPalette[d.id])
    .onDrag {
      let item = NSItemProvider(object: String(d.id) as NSString)
      item.suggestedName = String(d.id)
      return item
    }
    .onDrop(of: [UTType.text], isTargeted: $dragOver) { providers in
       
      return true
    }
    .border(Color(UIColor.label), width: dragOver ? 8 : 0)
  }
}
}

Answer 1

它由DropProposal放置操作管理，默认情况下（如果您不提供显式放置委托）.copy如文档所述，添加“+”符号。通过此您可以通知用户某些内容将被复制。

/// Tells the delegate that a validated drop moved inside the modified view.
///
/// Use this method to return a drop proposal containing the operation the
/// delegate intends to perform at the drop ``DropInfo/location``. The
/// default implementation of this method returns `nil`, which tells the
/// drop to use the last valid returned value or else
/// ``DropOperation/copy``.
public func dropUpdated(info: DropInfo) -> DropProposal?

如果您想显式管理它，请为 DropDelegate 提供已实现的放置更新，如下面的演示所示

func dropUpdated(info: DropInfo) -> DropProposal?
   // By this you inform user that something will be just relocated
   return DropProposal(operation: .move)
}