26.IOS百度地图增加遮罩

需求：在百度地图表面和图标的中间，添加一层带透明度的遮罩
1.遵守BMKMapViewDelegate协议

2.实现协议方法

- (BMKOverlayView *)mapView:(BMKMapView *)mapView viewForOverlay:(id )overlay{
    if ([overlay isKindOfClass:[BMKCircle class]]){
        BMKCircleView* circleView = [[BMKCircleView alloc] initWithOverlay:overlay] ;
        circleView.fillColor = [RGB(254, 254, 254) colorWithAlphaComponent:0.3];
        circleView.strokeColor = [[UIColor blueColor] colorWithAlphaComponent:1];
        circleView.lineWidth = 1;
        
        return circleView;
    }
    
    if ([overlay isKindOfClass:[BMKGroundOverlay class]]){
        BMKGroundOverlayView *groundView = [[BMKGroundOverlayView alloc] initWithOverlay:overlay];
        return groundView;
    }
 
    return nil;
}

注意点，方法的执行要看的经纬度在不在可视区域内

3.添加代码
第一种圆形的
CLLocationCoordinate2D coor;
coor.latitude = 23.117055306224895;
coor.longitude = 113.2759952545166;

BMKCircle* circle = [BMKCircle circleWithCenterCoordinate:coor radius:500000];
[self.mapView addOverlay:circle];

第二种：区域的
CLLocationCoordinate2D coords[2] = {0};
coords[0].latitude = 39.815;
coords[0].longitude = 116.404;
coords[1].latitude = 23.117055306224895;
coords[1].longitude = 113.2759952545166;
BMKCoordinateBounds bound;
bound.southWest = coords[0];
bound.northEast = coords[1];
BMKGroundOverlay *ground2 = [BMKGroundOverlay groundOverlayWithBounds: bound
icon:[UIImage imageNamed:@"filColor"]];//背景图片
[self.mapView addOverlay:ground2];