Question

我有一个包含在UIView对象A中的UIView对象。我希望能够触摸X并将其从对象A中移除并将其移动到对象B（另一个UIView）中。对象A和A都是B在同一个超级UIView里面。

  A        B
_____    _____
|   |    |   |
| X | -> |   |
|___|    |___|

这是我到目前为止所做的。

@implementation X_UIView

float deltaX;
float deltaY;

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    [self.superview.superview addSubview:self]; //pop dragged view outside of container view

    CGPoint beginCenter = self.center;

    UITouch * touch = [touches anyObject];
    CGPoint touchPoint = [touch locationInView:self.superview];

    deltaX = touchPoint.x - beginCenter.x;
    deltaY = touchPoint.y - beginCenter.y;
}

- (void) touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event {
    UITouch * touch = [touches anyObject];
    CGPoint touchPoint = [touch locationInView:self.superview];

    // Set the correct center when touched 
    touchPoint.x -= deltaX;
    touchPoint.y -= deltaY;

    self.center = touchPoint;
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    //discover view that event ended was over and add self as a subview.
}

@end

Answer 1

调用[[touches anyObject] locationInView: self.superview]以获取容器视图中手指下的点。然后发送self.superview -hitTest:withEvent:以找出X在里面的视图。请注意，它将始终返回X，因此您必须覆盖-pointIsInside:withEvent:或-hitTest:withEvent:以在拖动时返回nil。这种kludge是我在容器视图中实现这种跟踪的原因，而不是在拖动视图中。

Answer 2

使用iOS 11，您可以使用拖放API解决您的问题。以下Swift 4代码显示了如何操作。

ViewContainer.swift

import MobileCoreServices
import UIKit

enum ViewContainerError: Error {
    case invalidType, unarchiveFailure
}

class ViewContainer: NSObject {

    let view: UIView

    required init(view: UIView) {
        self.view = view
    }

}

extension ViewContainer: NSItemProviderReading {

    static var readableTypeIdentifiersForItemProvider = [kUTTypeData as String]

    static func object(withItemProviderData data: Data, typeIdentifier: String) throws -> Self {
        if typeIdentifier == kUTTypeData as String {
            guard let view = NSKeyedUnarchiver.unarchiveObject(with: data) as? UIView else { throw ViewContainerError.unarchiveFailure }
            return self.init(view: view)
        } else {
            throw ViewContainerError.invalidType
        }
    }

}

extension ViewContainer: NSItemProviderWriting {

    static var writableTypeIdentifiersForItemProvider = [kUTTypeData as String]

    func loadData(withTypeIdentifier typeIdentifier: String, forItemProviderCompletionHandler completionHandler: @escaping (Data?, Error?) -> Void) -> Progress? {
        if typeIdentifier == kUTTypeData as String {
            let data = NSKeyedArchiver.archivedData(withRootObject: view)
            completionHandler(data, nil)
        } else {
            completionHandler(nil, ViewContainerError.invalidType)
        }
        return nil
    }

}

ViewController.swift

import UIKit

class ViewController: UIViewController {

    let redView = UIView()
    let greenView = UIView()

    override func viewDidLoad() {
        super.viewDidLoad()

        let blueView = UIView()
        blueView.backgroundColor = .blue

        greenView.backgroundColor = .green
        greenView.isUserInteractionEnabled = true
        greenView.addSubview(blueView)
        setConstraintsInSuperView(forView: blueView)

        redView.backgroundColor = .red
        redView.isUserInteractionEnabled = true

        let greenViewDropInteraction = UIDropInteraction(delegate: self)
        let greenViewDragInteraction = UIDragInteraction(delegate: self)
        greenViewDragInteraction.isEnabled = true
        redView.addInteraction(greenViewDragInteraction)
        greenView.addInteraction(greenViewDropInteraction)

        let redViewDropInteraction = UIDropInteraction(delegate: self)
        let redViewDragInteraction = UIDragInteraction(delegate: self)
        redViewDragInteraction.isEnabled = true
        greenView.addInteraction(redViewDragInteraction)
        redView.addInteraction(redViewDropInteraction)

        let stackView = UIStackView(arrangedSubviews: [greenView, redView])
        view.addSubview(stackView)
        stackView.distribution = .fillEqually
        stackView.frame = view.bounds
        stackView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    }

}

extension ViewController {

    // MARK: - Helper methods

    func setConstraintsInSuperView(forView subView: UIView) {
        subView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate(NSLayoutConstraint.constraints(withVisualFormat: "H:|-[subView]-|", options: [], metrics: nil, views: ["subView": subView]))
        NSLayoutConstraint.activate(NSLayoutConstraint.constraints(withVisualFormat: "V:|-[subView]-|", options: [], metrics: nil, views: ["subView": subView]))
    }

}

extension ViewController: UIDragInteractionDelegate {

    func dragInteraction(_ interaction: UIDragInteraction, itemsForBeginning session: UIDragSession) -> [UIDragItem] {
        guard let containedView = interaction.view?.subviews.first else { return [] }
        let viewContainer = ViewContainer(view: containedView)
        let itemProvider = NSItemProvider(object: viewContainer)
        let item = UIDragItem(itemProvider: itemProvider)
        item.localObject = viewContainer.view
        return [item]
    }

    func dragInteraction(_ interaction: UIDragInteraction, sessionWillBegin session: UIDragSession) {
        guard let containedView = interaction.view?.subviews.first else { return }
        containedView.removeFromSuperview()
    }

    func dragInteraction(_ interaction: UIDragInteraction, previewForLifting item: UIDragItem, session: UIDragSession) -> UITargetedDragPreview? {
        guard let containedView = interaction.view?.subviews.first else { return nil }
        return UITargetedDragPreview(view: containedView)
    }

    func dragInteraction(_ interaction: UIDragInteraction, item: UIDragItem, willAnimateCancelWith animator: UIDragAnimating) {
        animator.addCompletion { _ in
            guard let containedView = item.localObject as? UIView else { return }
            interaction.view!.addSubview(containedView)
            self.setConstraintsInSuperView(forView: containedView)
        }
    }

    func dragInteraction(_ interaction: UIDragInteraction, prefersFullSizePreviewsFor session: UIDragSession) -> Bool {
        return true
    }

}

extension ViewController: UIDropInteractionDelegate {

    func dropInteraction(_ interaction: UIDropInteraction, canHandle session: UIDropSession) -> Bool {
        return session.canLoadObjects(ofClass: ViewContainer.self) && session.items.count == 1
    }

    func dropInteraction(_ interaction: UIDropInteraction, sessionDidUpdate session: UIDropSession) -> UIDropProposal {
        let dropLocation = session.location(in: view)
        let operation: UIDropOperation
        if interaction.view!.frame.contains(dropLocation) && session.localDragSession != nil {
            operation = .move
        } else {
            operation = .cancel
        }
        return UIDropProposal(operation: operation)
    }

    func dropInteraction(_ interaction: UIDropInteraction, performDrop session: UIDropSession) {
        session.loadObjects(ofClass: ViewContainer.self) { viewContainers in
            guard let viewContainers = viewContainers as? [ViewContainer], let viewContainer = viewContainers.first else { return }
            interaction.view!.addSubview(viewContainer.view)
            self.setConstraintsInSuperView(forView: viewContainer.view)
        }
    }

}

在UIViews之间拖动UIView

2 个答案: