iphone - 在自定义 MKOverlay 上绘图

Question

我正在使用自定义 MKOverlay 在 MKMapView 上绘制天气数据。绘图是在 CoreGraphics 中完成的。对于这种特殊情况，由于它处理平铺的方式，在 drawMapRect:zoomScale:inContext: 方法中进行绘图是不够的。我需要立即绘制整个图像，而不是像 drawMapRect 方法那样平铺。

之前，我将雷达图像保存在 .gif 中，因此我只需向其中添加一个 imageView 并在 drawMapRect 中调整 imageView 框架的大小。

我的计划是做类似的事情。添加一个自定义 UIView 并在 drawMapRect 中对其调用 setNeedsDisplay。

这是相关代码。

MKOverlay对象的boundingMapRect属性:

- (MKMapRect)boundingMapRect
{
    CLLocationCoordinate2D upperLeftCoord = 
    CLLocationCoordinate2DMake(weatherData.radarArray.connectedRadar.latitude + 2.5,
                           weatherData.radarArray.connectedRadar.longitude - 2.5);

    MKMapPoint upperLeft = MKMapPointForCoordinate(upperLeftCoord);

    CLLocationCoordinate2D lowerRightCoord = 
    CLLocationCoordinate2DMake(weatherData.radarArray.connectedRadar.latitude - 2.5,
                           weatherData.radarArray.connectedRadar.longitude + 2.5);

    MKMapPoint lowerRight = MKMapPointForCoordinate(lowerRightCoord);

    double width = lowerRight.x - upperLeft.x;
    double height = lowerRight.y - upperLeft.y;

    MKMapRect bounds = MKMapRectMake(upperLeft.x, upperLeft.y, width, height);

    return bounds;
}

工作的drawMapRect:zoomScale:inContext:代码(太慢了)。

- (void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CGContextRef)context {

    int numPaths = parser.dataPaths.size();

    // We have to pad the map rect a lot to allow for visibility testing that works well.
    MKMapRect testMapRect = MKMapRectMake(mapRect.origin.x - 40000, mapRect.origin.y - 40000, mapRect.size.width + 40000, mapRect.size.height + 40000);;

    // Only draw inside the area we are suppose to
    //CGRect rect = [self rectForMapRect:mapRect];
    //CGContextClipToRect(context, rect);

    // How see through is the radar data. 1 = opaque, 0 = completely transparent
    CGContextSetAlpha(context, 1);
    for (int i = 0; i < numPaths; i++) {
        // Make sure the bin is actually visible in this region before drawing it
        if (MKMapRectContainsPoint(testMapRect, parser.dataPaths[i]->points[0]) ||
            MKMapRectContainsPoint(testMapRect, parser.dataPaths[i]->points[1]) ||
            MKMapRectContainsPoint(testMapRect, parser.dataPaths[i]->points[2]) ||
            MKMapRectContainsPoint(testMapRect, parser.dataPaths[i]->points[3])) {
            CGMutablePathRef path = CGPathCreateMutable();
            CGPoint currentP = [self pointForMapPoint:parser.dataPaths[i]->points[0]];
            CGContextBeginPath(context);
            CGPathMoveToPoint(path, NULL, currentP.x, currentP.y);
            currentP = [self pointForMapPoint:parser.dataPaths[i]->points[1]];
            CGPathAddLineToPoint(path, NULL, currentP.x, currentP.y);
            currentP = [self pointForMapPoint:parser.dataPaths[i]->points[2]];
            CGPathAddLineToPoint(path, NULL, currentP.x, currentP.y);
            currentP = [self pointForMapPoint:parser.dataPaths[i]->points[3]];
            CGPathAddLineToPoint(path, NULL, currentP.x, currentP.y);
            currentP = [self pointForMapPoint:parser.dataPaths[i]->points[0]];
            CGPathAddLineToPoint(path, NULL, currentP.x, currentP.y);
            CGPathCloseSubpath(path);
            CGContextSetFillColorWithColor(context, colors[parser.dataPaths[i]->dataVal]);
            CGContextAddPath(context, path);
            CGContextFillPath(context);
            CGPathRelease(path);
        }
}

新的drawMapRect:zoomScale:inContext:代码

- (void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CGContextRef)context {

    // We have to pad the map rect a lot to allow for visibility testing that works well.
    radarImageView.testMapRect = MKMapRectMake(mapRect.origin.x - 40000, mapRect.origin.y - 40000, mapRect.size.width + 40000, mapRect.size.height + 40000);

    radarImageView.frame = [self rectForMapRect:self.overlay.boundingMapRect];
    [radarImageView setNeedsDisplay];

}

自定义UIView的drawRect方法。

- (void)drawRect:(CGRect)rect {


    CGContextRef context = UIGraphicsGetCurrentContext();

    int numPaths = parser.dataPaths.size();

    CGContextSetAlpha(context, 1);
    for (int i = 0; i < numPaths; i++) {

        // Make sure the bin is actually visible in this region before drawing it
        if (MKMapRectContainsPoint(testMapRect, parser.dataPaths[i]->points[0]) ||
            MKMapRectContainsPoint(testMapRect, parser.dataPaths[i]->points[1]) ||
            MKMapRectContainsPoint(testMapRect, parser.dataPaths[i]->points[2]) ||
            MKMapRectContainsPoint(testMapRect, parser.dataPaths[i]->points[3])) {

            CGMutablePathRef path = CGPathCreateMutable();
            CGPoint currentP = [(RadarImageOverlayView *)self.superview pointForMapPoint:parser.dataPaths[i]->points[0]];

            CGContextBeginPath(context);
            CGPathMoveToPoint(path, NULL, currentP.x, currentP.y);

            currentP = [(RadarImageOverlayView *)self.superview pointForMapPoint:parser.dataPaths[i]->points[1]];
            CGPathAddLineToPoint(path, NULL, currentP.x, currentP.y);

            currentP = [(RadarImageOverlayView *)self.superview pointForMapPoint:parser.dataPaths[i]->points[2]];
            CGPathAddLineToPoint(path, NULL, currentP.x, currentP.y);

            currentP = [(RadarImageOverlayView *)self.superview pointForMapPoint:parser.dataPaths[i]->points[3]];
            CGPathAddLineToPoint(path, NULL, currentP.x, currentP.y);

            currentP = [(RadarImageOverlayView *)self.superview pointForMapPoint:parser.dataPaths[i]->points[0]];
            CGPathAddLineToPoint(path, NULL, currentP.x, currentP.y);

            CGPathCloseSubpath(path);
            CGContextSetFillColorWithColor(context, colors[parser.dataPaths[i]->dataVal]);
            CGContextAddPath(context, path);
            CGContextFillPath(context);
            CGPathRelease(path);
        }
    }
}

谢谢!

编辑

我认为问题与 RadarImageView 的上下文有关。我在drawRect:方法中获取上下文的方式可能有问题吗？

Answer 1

我建议看看 HazardMap苹果公司的 sample 。它有一些很好的例子，可以完全按照您的要求进行操作。

KMLViewer也可能有帮助!