如何在iOS上的谷歌地图上进行徒手画？

问题描述

在绘图应用程序中，我们可以识别用户何时开始绘制和移动手指以形成线条/形状。我想在地图上做同样的事情，我该怎么办？

In drawing application we can identify when the user is starting to draw and moving the finger to make a line/shape. I'm trying to do the same on a map, how can I do this?

推荐答案

基本步骤将涉及：

1）每当用户开始绘制时添加叠加视图。

lazy var canvasView:CanvasView = {

    var overlayView = CanvasView(frame: self.googleMapView.frame)
    overlayView.isUserInteractionEnabled = true
    overlayView.delegate = self
    return overlayView

}()
@IBAction func drawActn(_ sender: AnyObject?) {

    self.coordinates.removeAll()
    self.view.addSubview(canvasView)
    let origImage = UIImage(named: "pen")
    let tintedImage = origImage?.withRenderingMode(UIImageRenderingMode.alwaysTemplate)
    drawBtn.setImage(tintedImage, for: .normal)
    drawBtn.tintColor = UIColor.white
    drawBtn.backgroundColor = UIColor.red

}

2）自由手绘图叠加视图。

class CanvasView: UIImageView {

    weak var delegate:NotifyTouchEvents?
    var lastPoint = CGPoint.zero
    let brushWidth:CGFloat = 3.0
    let opacity :CGFloat = 1.0


    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {


        if let touch = touches.first {

            self.delegate?.touchBegan(touch: touch)
            lastPoint = touch.location(in: self)
        }
    }


    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {

        if let touch = touches.first  {

            self.delegate?.touchMoved(touch: touch)
            let currentPoint = touch.location(in: self)
            drawLineFrom(fromPoint: lastPoint, toPoint: currentPoint)
            lastPoint = currentPoint
        }
    }

    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {

        if let touch = touches.first  {

            self.delegate?.touchEnded(touch: touch)

        }
    }

    func drawLineFrom(fromPoint: CGPoint, toPoint: CGPoint) {

        UIGraphicsBeginImageContext(self.frame.size)
        let context = UIGraphicsGetCurrentContext()
        self.image?.draw(in: CGRect(x: 0, y: 0, width: self.frame.size.width, height: self.frame.size.height))

        context?.move(to: fromPoint)
        context?.addLine(to: toPoint)

        context?.setLineCap(.round)
        context?.setLineWidth(brushWidth)
        context?.setStrokeColor(UIColor.black.cgColor)
        context?.setBlendMode(.normal)
        context?.strokePath()

        self.image = UIGraphicsGetImageFromCurrentImageContext()
        self.alpha = opacity
        UIGraphicsEndImageContext()

    }

}

3）从OverlayView获取数组中的所有坐标到控制器使用委托模式

//MARK: GET DRAWABLE COORDINATES
extension ViewController:NotifyTouchEvents{

    func touchBegan(touch:UITouch){

        let location = touch.location(in: self.googleMapView)
        let coordinate = self.googleMapView.projection.coordinate(for: location)
        self.coordinates.append(coordinate)

    }

    func touchMoved(touch:UITouch){

        let location = touch.location(in: self.googleMapView)
        let coordinate = self.googleMapView.projection.coordinate(for: location)
        self.coordinates.append(coordinate)

    }

    func touchEnded(touch:UITouch){

        let location = touch.location(in: self.googleMapView)
        let coordinate = self.googleMapView.projection.coordinate(for: location)
        self.coordinates.append(coordinate)
        createPolygonFromTheDrawablePoints()
    }
}

4）将坐标更改为多边形。

   func createPolygonFromTheDrawablePoints(){

        let numberOfPoints = self.coordinates.count
        //do not draw in mapview a single point
        if numberOfPoints > 2 { addPolyGonInMapView(drawableLoc: coordinates) }//neglects a single touch
        coordinates = []
        self.canvasView.image = nil
        self.canvasView.removeFromSuperview()

        let origImage = UIImage(named: "pen")
        let tintedImage = origImage?.withRenderingMode(UIImageRenderingMode.alwaysTemplate)
        drawBtn.setImage(tintedImage, for: .normal)
        drawBtn.tintColor = UIColor.red
        drawBtn.backgroundColor = UIColor.white

    }

    func  addPolyGonInMapView( drawableLoc:[CLLocationCoordinate2D]){

        isDrawingModeEnabled = true
        let path = GMSMutablePath()
        for loc in drawableLoc{

            path.add(loc)

        }
        let newpolygon = GMSPolygon(path: path)
        newpolygon.strokeWidth = 3
        newpolygon.strokeColor = UIColor.black
        newpolygon.fillColor = UIColor.black.withAlphaComponent(0.5)
        newpolygon.map = googleMapView
        if cancelDrawingBtn.isHidden == true{ cancelDrawingBtn.isHidden = false }
        userDrawablePolygons.append(newpolygon)
        addPolygonDeleteAnnotation(endCoordinate: drawableLoc.last!,polygon: newpolygon)
    }

我已经为绘图创建了一个演示项目/在Swift 3中删除谷歌地图上的多个多边形。

I have created a demo project for drawing/deleting multiple polygons on Google Map in Swift 3 here.

请记住在AppDelegate中设置API密钥并更改捆绑包标识符以便运行项目。

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