Question

我不确定是否有人问过，但我找不到解决办法。我正在按钮上实现平移手势，但想法是：按钮固定到一个位置，当用户拖动它时，创建按钮的副本并随手势移动;原始的一个停留在它的初始位置（因此视图中将有2个按钮）。当平移结束时，新按钮用于某些处理，之后它应该消失（原始按钮保持不变;因此整个过程可以重复）。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

很难说没有调试它，但我看到的一些事情：

每次通过panDetected创建一个新按钮，并每次将其添加到视图中。您应该只创建一个添加.began状态的按钮。

您应该使用init(frame:)创建按钮，并将其初始化为图像的大小。

看起来您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坐标系，除非平移手势的状态为.began，否则不应调用setTranslation。

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

您只需在.began上创建新按钮并将其添加为子视图，然后在.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，但不是它的大小。您可以设置其.frame。
您无需为平移手势设置翻译。获得var translation = panGesture.translation(in: view)后，您将获得所需的一切。

我只为一个按钮编写了下面的代码，但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：拖动按钮的副本

2 个答案: