ios - 尝试使用 UIPanGesture 在 UIView 上绘图

Question

class theView: UIView
{
 var kl = 1
    var px : CGFloat = 0.0
    var py : CGFloat = 0.0

override func drawRect(rect: CGRect)
    {
        color()
        setNeedsDisplay()
    }


        func move(gesture : UIPanGestureRecognizer)
            {
            let state = gesture.state
            switch state
            {
            case .Began: print("started")
            case .Ended: fallthrough
            case .Changed:
                let translation = gesture.translationInView(self)
                px = translation.x
                py = translation.y
                print("x:\(px), y:\(py)")
            default: break
            }
        }
        func color()
        {
            let path = UIBezierPath()
            path.moveToPoint(CGPointZero)
            path.addLineToPoint(CGPoint(x: px, y: py))
            UIColor.blueColor().set()
            path.stroke()
            self.setNeedsDisplay()
        }
}

这是我认为的代码。我错过了什么并且它没有显示在我的屏幕上？它确实识别了我的移动，因为 px 和 py 更改了值。这是更大项目的一部分，所以请告诉我如果有任何编译错误..

我的 View Controller 是:

class ViewController: UIViewController, Moveable
{
    var k = 1

    @IBOutlet weak var sdasd: theView!
        {
            didSet
            {
                    sdasd.k = self
                    sdasd.addGestureRecognizer(recognizer)
                    let panRecognizer = UIPanGestureRecognizer(target: sdasd, action: "move:")
                    sdasd.addGestureRecognizer(panRecognizer)
                    sdasd.setNeedsDisplay()
            }
        }

还有人可以告诉我到底需要把 setNeedsDisplay() 放在哪里吗？我需要将它放在我的 View Controller 中吗？我的超控抽屉？谢谢。如果你需要什么就告诉我。我希望它能在我看来划清界限。就像绘画一样

Answer 1

setNeedsDisplay() 通知您的 UIView 它需要在下一个绘制周期内重新绘制。在 drawRect 函数中，您指定应在 UIView 上绘制的内容。您希望每次在 GestureRecognizer 中处于 Changed 状态时更改 UIView 的外观，因此这也是您需要通知 View 重绘的地方，即调用 setNeedsDisplay()，而且仅在那里。

编辑

我相信这是您正在寻找的类(class)

class theView: UIView
{
    var kl = 1
    var px : CGFloat = 0.0
    var py : CGFloat = 0.0
    var pxStart : CGFloat = 0.0
    var pyStart : CGFloat = 0.0

    override init(frame: CGRect) {
        super.init(frame: frame)
        let panRecognizer = UIPanGestureRecognizer(target: self, action: "move:")
        self.addGestureRecognizer(panRecognizer)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func drawRect(rect: CGRect)
    {
        let path = UIBezierPath()
        path.moveToPoint(CGPoint(x: pxStart, y: pyStart))
        path.addLineToPoint(CGPoint(x: pxStart+px, y: pyStart+py))
        UIColor.blueColor().set()
        path.stroke()
    }

    func move(gesture : UIPanGestureRecognizer)
    {
        let state = gesture.state
        switch state
        {
        case .Began:
            pxStart = gesture.locationInView(self).x
            pyStart = gesture.locationInView(self).y
        case .Ended: fallthrough
        case .Changed:
            let translation = gesture.translationInView(self)
            px = translation.x
            py = translation.y
            self.setNeedsDisplay()
        default: break
        }
    }
}