将倒圆叠加添加到地图视图

Question

(使用iOS 5和Xcode 4.2.)

我按照这里的说明操作:http://developer.apple.com/library/ios/#documentation/UserExperience/Conceptual/LocationAwarenessPG/AnnotatingMaps/AnnotatingMaps.html#//apple_ref/doc/uid/TP40009497-CH6-SW15并使用MKCircle和MKCircleView类在我的MKMapView上添加圆形覆盖.

然而我真正想要的是倒圆形叠加,就像下面草图中的左侧地图(目前我有一个像右边那样的圆形叠加):

对于倒圆,叠加应覆盖整个地图 - 除了可见圆.

有没有一种简单的方法可以使用MKCircle/MKCircleView类来实现这一目的？或者我是否需要更深入地定义自定义叠加对象/视图？

谢谢您的帮助 :)

Answer 1

我有同样的任务,这就是我如何解决它:

注意:此代码仅适用于iOS7

在视图控制器的某个位置向地图添加叠加层:

MyMapOverlay *overlay = [[MyMapOverlay alloc] initWithCoordinate:coordinate];
[self.mapView addOverlay:overlay level:MKOverlayLevelAboveLabels];

在MKMapViewDelegate方法中写下:

- (MKOverlayRenderer *)mapView:(MKMapView *)map rendererForOverlay:(id<MKOverlay>)overlay {
    /// we need to draw overlay on the map in a way when everything except the area in radius of 500 should be grayed
    /// to do that there is special renderer implemented - NearbyMapOverlay
    if ([overlay isKindOfClass:[NearbyMapOverlay class]]) {
        MyMapOverlayRenderer *renderer = [[MyMapOverlayRenderer alloc] initWithOverlay:overlay];
        renderer.fillColor = [UIColor whateverColor];/// specify color which you want to use for gray out everything out of radius
        renderer.diameterInMeters = 1000;/// choose whatever diameter you need

        return renderer;
    }
    return nil;
}

MyMapOverlay本身应该是这样的:

@interface MyMapOverlay : NSObject<MKOverlay>
- (instancetype)initWithCoordinate:(CLLocationCoordinate2D)coordinate;
@end

@implementation MyMapOverlay

@synthesize coordinate = _coordinate;

- (instancetype)initWithCoordinate:(CLLocationCoordinate2D)coordinate {
    self = [super init];
    if (self) {
        _coordinate = coordinate;
    }
    return self;
}

- (MKMapRect)boundingMapRect {
    return MKMapRectWorld;
}

@end

和MyMapOverlayRenderer:

@interface MyMapOverlayRenderer : MKOverlayRenderer
@property (nonatomic, assign) double diameterInMeters;
@property (nonatomic, copy) UIColor *fillColor;
@end

@implementation MyMapOverlayRenderer

/// this method is called as a part of rendering the map, and it draws the overlay polygon by polygon
/// which means that it renders overlay by square pieces
- (void)drawMapRect:(MKMapRect)mapRect
      zoomScale:(MKZoomScale)zoomScale
      inContext:(CGContextRef)context {

    /// main path - whole area
    UIBezierPath *path = [UIBezierPath bezierPathWithRect:CGRectMake(mapRect.origin.x, mapRect.origin.y, mapRect.size.width, mapRect.size.height)];

    /// converting to the 'world' coordinates
    double radiusInMapPoints = self.diameterInMeters * MKMapPointsPerMeterAtLatitude(self.overlay.coordinate.latitude);
    MKMapSize radiusSquared = {radiusInMapPoints, radiusInMapPoints};
    MKMapPoint regionOrigin = MKMapPointForCoordinate(self.overlay.coordinate);
    MKMapRect regionRect = (MKMapRect){regionOrigin, radiusSquared}; //origin is the top-left corner
    regionRect = MKMapRectOffset(regionRect, -radiusInMapPoints/2, -radiusInMapPoints/2);
    // clamp the rect to be within the world
    regionRect = MKMapRectIntersection(regionRect, MKMapRectWorld);

    /// next path is used for excluding the area within the specific radius from current user location, so it will not be filled by overlay fill color
    UIBezierPath *excludePath = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(regionRect.origin.x, regionRect.origin.y, regionRect.size.width, regionRect.size.height) cornerRadius:regionRect.size.width / 2];
    [path appendPath:excludePath];

    /// setting overlay fill color
    CGContextSetFillColorWithColor(context, self.fillColor.CGColor);
    /// adding main path. NOTE that exclusionPath was appended to main path, so we should only add 'path'
    CGContextAddPath(context, path.CGPath);
    /// tells the context to fill the path but with regards to even odd rule
    CGContextEOFillPath(context);
}

因此,您将获得与问题中发布的左侧图像完全相同的视图.

Answer 2

执行此操作的最佳方法是子类化MKMapView并覆盖drawRect方法调用super,然后使用所需的颜色在地图上绘制.然后每次用户移动时,drawRect都应该适当地进行绘图.