iOS: 拖动一个按钮的副本

Question

我不确定是否有人问过这个问题，但我没有找到解决方案。我在按钮上实现平移手势，但想法是：按钮固定在一个位置，当用户拖动它时，会创建按钮的副本并随手势移动；原始按钮保留在其初始位置（因此视图中将有 2 个按钮）。当平移结束时，新按钮被用于一些处理，之后它应该消失（原来的按钮保持原样；所以整个过程可以重复）。目前我所拥有的如下：

private func addPanGesture() {
    for btn in self.selectors { //selectors is a list of buttons which needs this gesture
        let pan = UIPanGestureRecognizer(target: self, action:#selector(self.panDetected(_:)))
        pan.minimumNumberOfTouches = 1
        pan.maximumNumberOfTouches = 1
        btn.addGesturerecognizer(pan)
    }
}

@objc private func panDetected(_ panGesture: UIPanGestureRecognizer) {
    var translation = panGesture.translation(in: view)
    panGesture.setTranslation(CGPoint(x: 0, y: 0), in: view)

    var newButton = UIButton()
    if let initButton = panGesture.view as? UIButton {
        print ("Button recognized!") // this msg is printed out
        newButton.center = CGPoint(x: initButton.center.x + translation.x, y: initButton.center.y + translation.y)
        newButton.setImage(UIImage(named: "somename"), for: .normal)
    }

    if panGesture.state == UIGestureRecognizerState.began {
        self.view.addSubview(newButton)
    }
    if panGesture.state == UIGestureRecognizerState.ended {
        //some other processing
    }
    if panGesture.state == UIGestureRecognizerState.changed {
        self.view.addSubview(newButton)
    }
    // printed-out msgs show began, ended, changed states have all been reached
}

但是我的视图中没有显示新按钮。我可以知道如何解决这个问题吗？

Answer 1

不调试很难说，但我看到了一些事情：

你每次通过panDetected创建一个新按钮，每次都添加到视图中。您应该只在 .began 状态下创建一个添加按钮。

您应该使用 init(frame:) 创建您的按钮，并将其初始化为图像的大小。

您似乎正在将平移手势附加到按钮上。然后你在按钮的坐标系中得到了平移坐标，这是没有意义的。您应该将平移手势转换为按钮的超级视图的坐标系，并且不应调用 setTranslation 除非平移手势的状态为 .began.

每次收到 1st.changed` 消息时，您应该将按钮的坐标设置为平移手势的新位置。

Answer 2

您只需要在 .began 上创建新按钮并将其添加为子视图，并在 .ended 上将其删除。
因此您需要保留对新按钮的引用。
您正在设置新按钮的中心，而不是它的大小。您可以设置它的 .frame.
您不需要为平移手势设置翻译。当您获得 var translation = panGesture.translation(in: view) 时，您将获得所需的一切。

我只为一个按钮编写了以下代码，但是如果您要允许同时拖动按钮，则需要保留一个移动按钮列表而不是 var movingButton: UIButton?

    private func addPanGesture() {
        let pan = UIPanGestureRecognizer(target: self, action:#selector(self.panDetected(_:)))
        pan.minimumNumberOfTouches = 1
        pan.maximumNumberOfTouches = 1
        btn.addGestureRecognizer(pan)
    }

    @objc private func panDetected(_ panGesture: UIPanGestureRecognizer) {
        let translation = panGesture.translation(in: view)

        let initButton = panGesture.view as! UIButton


        if panGesture.state == UIGestureRecognizerState.began {
            // this is just copying initial button
            // this might be overkill
            // just make sure you set the frame, title and image of the new button correctly
            let initButtonData = NSKeyedArchiver.archivedData(withRootObject: initButton)
            let newButton = NSKeyedUnarchiver.unarchiveObject(with: initButtonData) as! UIButton

            // we store new button's reference since we will just move it while it is added to view
            movingButton = newButton
            self.view.addSubview(movingButton!)

        }
        if panGesture.state == UIGestureRecognizerState.ended {
            //some other processing

            // when we are done just we just remove it from superview
            movingButton!.removeFromSuperview()
        }
        if panGesture.state == UIGestureRecognizerState.changed {

            // at any change, all we need to do is update movingButton's frame
            var buttonFrame = initButton.frame;
            buttonFrame.origin = CGPoint(x: buttonFrame.origin.x + translation.x, y: buttonFrame.origin.y + translation.y)
            movingButton!.frame = buttonFrame
        }
    }

iOS: 拖动一个按钮的副本

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