Swift 3 个可拖动的 UIButton

Question

抱歉，我仍在学习 Swift 的基础知识。

我试图在拖动按钮时移动它，这听起来很简单。我不知道如何将发件人信息传递给拖动功能，以便我可以将其与正在拖动的按钮相关联。

我创建了多个只有文本的单字按钮，并为每个按钮附加了一个平移手势识别器：

let pan = UIPanGestureRecognizer(target: self, action: #selector(panButton(_:)))
let word = UIButton(type: .system)
word.addGestureRecognizer(pan)

我创建了这个函数来在按钮移动时触发：

func panButton(sender: UIPanGestureRecognizer){
    if sender.state == .began {
        //wordButtonCenter = button.center // store old button center
    } else if sender.state == .ended || sender.state == .failed || sender.state == .cancelled {
        //button.center = wordButtonCenter // restore button center
    } else {
        let location = sender.location(in: view) // get pan location
        //button.center = location // set button to where finger is
    }
}

我收到以下错误：

Use of unresolved identifier 'panButton'

Answer 1

首先，您的操作需要成为 Swift 3 中的一个选择器。所以它看起来像这样：

let pan = UIPanGestureRecognizer(target: self, action: #selector(panButton(_:))

此外，您不能通过选择器传递按钮的值，因此您需要将 func 更改为：

func panButton(sender: UIPanGestureRecognizer){
    ...
}

如果您想知道如果不能将按钮作为参数传递应该如何找到该按钮，那么您可以考虑使用标签。

Answer 2

正如@benjamin 在Swift 3 中指出的那样，您需要成为一个选择器。我已将代码更新为以下内容以提取按钮标签：

let panGesture = UIPanGestureRecognizer(target: self, action: #selector(self.panGestureHandler(panGesture:)))
    panGesture.minimumNumberOfTouches = 1
    let word = UIButton(type: .system)

使用以下选择器：

@objc func panGestureHandler(panGesture recognizer: UIPanGestureRecognizer) {

    let buttonTag = (recognizer.view?.tag)!
    if let button = view.viewWithTag(buttonTag) as? UIButton {

        if recognizer.state == .began {
            wordButtonCenter = button.center // store old button center
        } else if recognizer.state == .ended || recognizer.state == .failed || recognizer.state == .cancelled {
            button.center = wordButtonCenter // restore button center
        } else {
            let location = recognizer.location(in: view) // get pan location
            button.center = location // set button to where finger is
        }
    }
}

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