MapKit ios的渐变多段线

| 我正在尝试使用叠加层（MKOverlay）在MKMapView上跟踪路线。但是，根据当前速度，如果颜色正在更改（例如，如果用户以65mph的速度从30mph行驶到绿色，则从绿色变为橙色），我想在跟踪路线时使用类似Nike的应用程序进行渐变操作。这是我想要的屏幕截图：因此，每20米，我使用以下方法从旧坐标到新坐标添加一个叠加层：

// Create a c array of points. 
MKMapPoint *pointsArray = malloc(sizeof(CLLocationCoordinate2D) * 2);

// Create 2 points.
MKMapPoint startPoint = MKMapPointForCoordinate(CLLocationCoordinate2DMake(oldLatitude, oldLongitude));
MKMapPoint endPoint = MKMapPointForCoordinate(CLLocationCoordinate2DMake(newLatitude, newLongitude));

// Fill the array.
pointsArray[0] = startPoint;
pointsArray[1] = endPoint;

// Erase polyline and polyline view if not nil.
if (self.routeLine != nil)
    self.routeLine = nil;

if (self.routeLineView != nil)
    self.routeLineView = nil;

// Create the polyline based on the array of points.
self.routeLine = [MKPolyline polylineWithPoints:pointsArray count:2];

// Add overlay to map.
[self.mapView addOverlay:self.routeLine];

// clear the memory allocated earlier for the points.
free(pointsArray);

// Save old coordinates.
oldLatitude = newLatitude;
oldLongitude = newLongitude;

基本上，我会添加很多小的叠加层。然后，我想在此小线条图上创建渐变，因此我尝试在叠加委托中这样做：

- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay {
    MKOverlayView* overlayView = nil;

    if(overlay == self.routeLine) {
        // If we have not yet created an overlay view for this overlay, create it now. 
        if(self.routeLineView == nil) {
            self.routeLineView = [[[MKPolylineView alloc] initWithPolyline:self.routeLine] autorelease];

            if (speedMPH < 25.0) {
                self.routeLineView.fillColor = [UIColor redColor];
                self.routeLineView.strokeColor = [UIColor redColor];
            }
            else if (speedMPH >= 25.0 && speedMPH < 50.0) {
                self.routeLineView.fillColor = [UIColor orangeColor];
                self.routeLineView.strokeColor = [UIColor orangeColor];
            }
            else {
                self.routeLineView.fillColor = [UIColor greenColor];
                self.routeLineView.strokeColor = [UIColor greenColor];
            }

            // Size of the trace.
            self.routeLineView.lineWidth = routeLineWidth;

            // Add gradient if color changed.
            if (oldColor != self.routeLineView.fillColor) {
                CAGradientLayer *gradient = [CAGradientLayer layer];
                    gradient.frame = self.routeLineView.bounds;
                    gradient.colors = [NSArray arrayWithObjects:(id)[oldColor CGColor], (id)[self.routeLineView.fillColor CGColor], nil];
                    [self.routeLineView.layer insertSublayer:gradient atIndex:0];
            }

            // Record old color for gradient.
            if (speedMPH < 25.0)
                oldColor = [UIColor redColor];
            else if (speedMPH >= 25.0 && speedMPH < 50.0)
                oldColor = [UIColor orangeColor];
            else
                oldColor = [UIColor greenColor];
        }

        overlayView = self.routeLineView;
    }

    return overlayView;
}

我正在尝试以这种方式添加渐变，但是我猜这不是做到这一点的方法，因为我无法使其正常工作。每当用户位置（在位置对象的委托中）或每20米以上有一次更新时，我还可以跟踪路线。您能帮我解决这个问题，给我提示！谢谢！

已邀请:

3 个回复

薄响

我想到的一个想法是创建一个CGPath并在每次调用drawMapRect方法时使用渐变对其进行描边，因为在ios7中将MKPolylineView替换为MKPlolylineRenderer。我试图通过将ѭ5子类化来实现这一点，但是我没有挑选出单独的CGPath，然后发现了一个名为-(void) strokePath:(CGPathRef)path inContext:(CGContextRef)context的神秘方法，听起来像我需要的，但是如果您在不调用super方法时不会调用它覆盖您的drawMapRect。那就是我目前正在解决的问题。我会继续努力，因此，如果我解决了一些问题，我会回来并更新答案。 =========更新======================================== ======== 所以这就是我最近要解决的问题，我几乎实现了上面提到的基本思想，但是是的，我仍然无法根据特定的mapRect挑选单个PATH，因此，当所有路径的boundingBox与当前mapRect相交。技巧很差，但现在就可以工作。在render类的-(void) drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CGContextRef)context方法中，我这样做：

CGMutablePathRef fullPath = CGPathCreateMutable();
BOOL pathIsEmpty = YES;

//merging all the points as entire path
for (int i=0;i< polyline.pointCount;i++){
    CGPoint point = [self pointForMapPoint:polyline.points[i]];
    if (pathIsEmpty){
        CGPathMoveToPoint(fullPath, nil, point.x, point.y);
        pathIsEmpty = NO;
    } else {
        CGPathAddLineToPoint(fullPath, nil, point.x, point.y);
    }
}

//get bounding box out of entire path.
CGRect pointsRect = CGPathGetBoundingBox(fullPath);
CGRect mapRectCG = [self rectForMapRect:mapRect];
//stop any drawing logic, cuz there is no path in current rect.
if (!CGRectIntersectsRect(pointsRect, mapRectCG))return;

然后，我逐点拆分整个路径以分别绘制其渐变。请注意，包含色调值的“ 10”数组映射每个位置的速度。

for (int i=0;i< polyline.pointCount;i++){
    CGMutablePathRef path = CGPathCreateMutable();
    CGPoint point = [self pointForMapPoint:polyline.points[i]];
    ccolor = [UIColor colorWithHue:hues[i] saturation:1.0f brightness:1.0f alpha:1.0f];
    if (i==0){
        CGPathMoveToPoint(path, nil, point.x, point.y);
    } else {
        CGPoint prevPoint = [self pointForMapPoint:polyline.points[i-1]];
        CGPathMoveToPoint(path, nil, prevPoint.x, prevPoint.y);
        CGPathAddLineToPoint(path, nil, point.x, point.y);
        CGFloat pc_r,pc_g,pc_b,pc_a,
        cc_r,cc_g,cc_b,cc_a;
        [pcolor getRed:&pc_r green:&pc_g blue:&pc_b alpha:&pc_a];
        [ccolor getRed:&cc_r green:&cc_g blue:&cc_b alpha:&cc_a];
        CGFloat gradientColors[8] = {pc_r,pc_g,pc_b,pc_a,
                                    cc_r,cc_g,cc_b,cc_a};

        CGFloat gradientLocation[2] = {0,1};
        CGContextSaveGState(context);
        CGFloat lineWidth = CGContextConvertSizeToUserSpace(context, (CGSize){self.lineWidth,self.lineWidth}).width;
        CGPathRef pathToFill = CGPathCreateCopyByStrokingPath(path, NULL, lineWidth, self.lineCap, self.lineJoin, self.miterLimit);
        CGContextAddPath(context, pathToFill);
        CGContextClip(context);//<--clip your context after you SAVE it, important!
        CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
        CGGradientRef gradient = CGGradientCreateWithColorComponents(colorSpace, gradientColors, gradientLocation, 2);
        CGColorSpaceRelease(colorSpace);
        CGPoint gradientStart = prevPoint;
        CGPoint gradientEnd = point;
        CGContextDrawLinearGradient(context, gradient, gradientStart, gradientEnd, kCGGradientDrawsAfterEndLocation);
        CGGradientRelease(gradient);
        CGContextRestoreGState(context);//<--Don\'t forget to restore your context.
    }
    pcolor = [UIColor colorWithCGColor:ccolor.CGColor];
}

这就是所有核心绘制方法，当然，您的叠加层类中需要points和velocity并将它们输入CLLocationManager。最后一点是如何从速度中获得hue值，好吧，我发现如果色调范围从0.03到0.3准确地表示从红色到绿色，那么我对色调和速度做了一些比例映射。最后一个，这里是这个演示的完整资源：https：//github.com/wdanxna/GradientPolyline 如果看不到您画的线，不要惊慌，我只是将地图区域放在我的位置:)

蕉衫

我实现了受上述@wdanxna解决方案启发的Swift 4版本。某些事情已更改，该路径已在超类中创建。我没有将色相存储在渲染器中，而是制作了MKPolyline的子类来计算构造函数中的色相。然后，使用渲染器中的值来抓取折线。我将其映射到速度，但是我想您可以将渐变映射到任何您想要的。渐变折线

class GradientPolyline: MKPolyline {
    var hues: [CGFloat]?
    public func getHue(from index: Int) -> CGColor {
        return UIColor(hue: (hues?[index])!, saturation: 1, brightness: 1, alpha: 1).cgColor
    }
}

extension GradientPolyline {
    convenience init(locations: [CLLocation]) {
        let coordinates = locations.map( { $0.coordinate } )
        self.init(coordinates: coordinates, count: coordinates.count)

        let V_MAX: Double = 5.0, V_MIN = 2.0, H_MAX = 0.3, H_MIN = 0.03

        hues = locations.map({
            let velocity: Double = $0.speed

            if velocity > V_MAX {
                return CGFloat(H_MAX)
            }

            if V_MIN <= velocity || velocity <= V_MAX {
                return CGFloat((H_MAX + ((velocity - V_MIN) * (H_MAX - H_MIN)) / (V_MAX - V_MIN)))
            }

            if velocity < V_MIN {
                return CGFloat(H_MIN)
            }

            return CGFloat(velocity)
        })
    }
}

GradidentPolylineRenderer

class GradidentPolylineRenderer: MKPolylineRenderer {

    override func draw(_ mapRect: MKMapRect, zoomScale: MKZoomScale, in context: CGContext) {
        let boundingBox = self.path.boundingBox
        let mapRectCG = rect(for: mapRect)

        if(!mapRectCG.intersects(boundingBox)) { return }


        var prevColor: CGColor?
        var currentColor: CGColor?

        guard let polyLine = self.polyline as? GradientPolyline else { return }

        for index in 0...self.polyline.pointCount - 1{
            let point = self.point(for: self.polyline.points()[index])
            let path = CGMutablePath()


            currentColor = polyLine.getHue(from: index)

            if index == 0 {
               path.move(to: point)
            } else {
                let prevPoint = self.point(for: self.polyline.points()[index - 1])
                path.move(to: prevPoint)
                path.addLine(to: point)

                let colors = [prevColor!, currentColor!] as CFArray
                let baseWidth = self.lineWidth / zoomScale

                context.saveGState()
                context.addPath(path)

                let gradient = CGGradient(colorsSpace: nil, colors: colors, locations: [0, 1])

                context.setLineWidth(baseWidth)
                context.replacePathWithStrokedPath()
                context.clip()
                context.drawLinearGradient(gradient!, start: prevPoint, end: point, options: [])
                context.restoreGState()
            }
            prevColor = currentColor
        }
    }
}

如何使用从CLLocations数组创建一行

let runRoute = GradientPolyline(locations: locations)
self.mapView.addOverlay(runRoute)

在委托中传递GradientPolylineRenderer

func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
    if overlay is GradientPolyline {
        let polyLineRender = GradientMKPolylineRenderer(overlay: overlay)
        polyLineRender.lineWidth = 7
        return polyLineRender
    }
}

结果

膏焦凑

在我看来，您在线图视图中的drawRect缺少渐变的设置。图形可能会在叠加层的其他线程上发生。请发布代码。

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MapKit ios的渐变多段线

3 个回复

发起人

overlay

mapkit

gradient

ios

mkmapview

问题状态

MapKit ios的渐变多段线

与内容相关的链接

3 个回复

发起人

overlay

mapkit

gradient

ios

mkmapview

问题状态