要构建一个支持拖拽上传文件的用户界面,可以使用UIDragInteraction
和UIDropInteraction
这两个类来实现。下面是一个简单的示例代码:
import UIKit
class DragDropViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let imageView = UIImageView(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
imageView.backgroundColor = .lightGray
imageView.isUserInteractionEnabled = true
view.addSubview(imageView)
let dragInteraction = UIDragInteraction(delegate: self)
imageView.addInteraction(dragInteraction)
let dropInteraction = UIDropInteraction(delegate: self)
view.addInteraction(dropInteraction)
}
}
extension DragDropViewController: UIDragInteractionDelegate {
func dragInteraction(_ interaction: UIDragInteraction, itemsForBeginning session: UIDragSession) -> [UIDragItem] {
guard let image = (interaction.view as? UIImageView)?.image else { return [] }
let itemProvider = NSItemProvider(object: image)
let dragItem = UIDragItem(itemProvider: itemProvider)
return [dragItem]
}
}
extension DragDropViewController: UIDropInteractionDelegate {
func dropInteraction(_ interaction: UIDropInteraction, performDrop session: UIDropSession) {
for item in session.items {
if item.canLoadObject(ofClass: UIImage.self) {
item.loadObject(ofClass: UIImage.self) { (image, error) in
if let image = image as? UIImage {
DispatchQueue.main.async {
(interaction.view as? UIImageView)?.image = image
}
}
}
}
}
}
}
在这个示例中,我们创建了一个UIImageView
并为其添加了UIDragInteraction
和UIDropInteraction
。在UIDragInteractionDelegate
的实现中,我们指定了拖动操作的UIDragItem
为UIImageView
的图像。而在UIDropInteractionDelegate
的实现中,我们在放置操作时将拖动的图像设置为UIImageView
的图像。这样就实现了一个支持拖拽上传文件的用户界面。
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