为什么我的视图的右上角有一个“加号”图标？

问题描述

我正在尝试将拖放功能实现到我的LazyHGridview。当我尝试将视图放到另一个视图上时，该视图的右上角会显示一个绿色圆圈内的“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)
  }
}
}

解决方法

它由DropProposal放置操作管理，默认情况下（如果未提供显式放置委托）为.copy，如记录所示，它会添加“ +”号。通过这种方式，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?

如果您想对其进行显式管理，则向DropDelegate提供已实现的drop update，如下面的演示中所示

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

,

这是正常的用户界面，指示在此时手指所处的位置，可以拖放要拖动的视图。