如何在Mapbox 3.6中旋转汽车标记图像？

Question

我想根据路线方向旋转标记图像。我已经使用Map box SDK实现了地图。坐标&方向是通过webservice获取的。 我试过imageForMarker，但它没有奏效。 Implemetation是使用自定义的重用标识符遵循

func mapView(_ mapView: MGLMapView, imageFor annotation: MGLAnnotation) -> MGLAnnotationImage? { 

    let img = imageRotatedByDegrees(oldImage: UIImage(named: "car")!, deg: CGFloat(self.bearing)) 

    return MGLAnnotationImage(image: img, reuseIdentifier: "car") 
} 
func imageRotatedByDegrees(oldImage: UIImage, deg degrees: CGFloat) -> UIImage 
{ 
    let size = oldImage.size 

    UIGraphicsBeginImageContext(size) 

    let bitmap: CGContext = UIGraphicsGetCurrentContext()! 
    //Move the origin to the middle of the image so we will rotate and scale around the center. 
    bitmap.translateBy(x: size.width/2, y: size.height/2) 
    //Rotate the image context 
    bitmap.rotate(by: (degrees * CGFloat(Double.pi/180))) 
    //Now, draw the rotated/scaled image into the context 
    bitmap.scaleBy(x: 1.0, y: -1.0) 

    let origin = CGPoint(x: -size.width/2, y: -size.width/2) 

    bitmap.draw(oldImage.cgImage!, in: CGRect(origin: origin, size: size)) 

    let newImage: UIImage = UIGraphicsGetImageFromCurrentImageContext()! 
    UIGraphicsEndImageContext() 
    return newImage 
} 

Answer 1

尝试，就像这样：

func mapView(_ mapView: MGLMapView, imageFor annotation: MGLAnnotation) -> MGLAnnotationImage? { 
    let annotation = annotation as! CustomMapAnnotation 

    var annotationImage = mapView.dequeueReusableAnnotationImage(withIdentifier: annotation.id) 

    if annotationImage == nil { 
     var image = UIImage(named: "taxi")! 

     if let heading = annotation.heading { 
      image = image.imageRotatedByDegrees(degrees: heading) 
     } 
     image = image.withAlignmentRectInsets(UIEdgeInsets(top: 0, left: 0, bottom: image.size.height/2, right: 0)) 

     annotationImage = MGLAnnotationImage(image: image, reuseIdentifier: annotation.id) 
    } 

    return annotationImage 
} 

Answer 2

看来，这样做的正确方法是使用MGLSymbolStyleLayer与注释，而不是添加注释直接使用mapview委托方法：https://www.mapbox.com/ios-sdk/api/3.6.2/Classes/MGLSymbolStyleLayer.html#/c:objc(cs)MGLSymbolStyleLayer(py)iconRotation

有一个iconRotation属性可以使用，它需要度数。

这是不幸的，因为我的用例有几个相同的图像，但不同的标题，所以我必须为每个图层添加一个图层。