CODEWITHSUNDEEP
iosiphonemkmapviewsubclassmktileoverlay
dehlen
dehlen

Reputation: 7391

MKTileOverlay subclass for cached tiles

Hello i am using MKTileOverlay to present OpenStreetMap tiles in my iOS7 App. Now i'd like to implement the ability to cache these tiles. I saw a post on NSHipster (http://nshipster.com/mktileoverlay-mkmapsnapshotter-mkdirections/) and did it accordingly.

This is my MKTileOverlay subclass:

#import "DETileOverlay.h"

@implementation DETileOverlay

- (void)loadTileAtPath:(MKTileOverlayPath)path
                result:(void (^)(NSData *data, NSError *error))result
{
    if (!result)
    {
        return;
    }

    NSData *cachedData = [self.cache objectForKey:[self URLForTilePath:path]];
    if (cachedData)
    {
        result(cachedData, nil);
    }
    else
    {
        NSURLRequest *request = [NSURLRequest requestWithURL:[self URLForTilePath:path]];
        [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
             result(data, connectionError);
         }];
    }
}

@end

Then i use it like this:

#import "DETileOverlay.h"

@interface DEMapViewController : UIViewController <MKMapViewDelegate> {
}
@property (nonatomic, retain) DETileOverlay *overlay;

-(void)viewDidLoad {
[super viewDidLoad];
    self.overlay = [[DETileOverlay alloc] initWithURLTemplate:@"http://tile.stamen.com/watercolor/{z}/{x}/{y}.jpg"];
        self.overlay.canReplaceMapContent = YES;
        self.overlay.mapView = map;
        [map addOverlay:self.overlay level:MKOverlayLevelAboveLabels];
}

// iOS 7
- (MKOverlayRenderer *)mapView:(MKMapView *)mapView rendererForOverlay:(id <MKOverlay>)ovl
    {
   MKTileOverlayRenderer *renderer = [[MKTileOverlayRenderer alloc]initWithOverlay:ovl];

        return renderer;
    }


    - (void)          mapView:(MKMapView *)mapView
        didUpdateUserLocation:(MKUserLocation *)userLocation
    {
        MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance(userLocation.location.coordinate, 300, 300);

        [map setRegion:region animated:YES];
    }

When i start my app no tiles are loaded. If i don't override the loadTileAtPath in my subclass everything works fine. What am i doing wrong ?

Thanks so much.

Upvotes: 2

Views: 2807

Answers (2)

Kevin
Kevin

Reputation: 446

I don't see it in your code, but be sure to initialize your cache and operation queue. Using your code exactly does not work. When I initialize the MKTileOverlay, I set its cache and operation queue. Then it all works.

Upvotes: 0

Jeremy Wiebe
Jeremy Wiebe

Reputation: 3963

Based on the comments you say you've solved it, but based on your code you never add the tiles to your cache. Without that I don't think you'll get any caching and will always be requesting the tiles anyway. So in your completionHandler you should be adding the resulting tile to your cache like this:

....
} else { 
    NSURLRequest *request = [NSURLRequest requestWithURL:[self URLForTilePath:path]];
    [NSURLConnection sendAsynchronousRequest:request queue:self.operationQueue completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
        // Should inspect the response to see if the request completed successfully!!
        [self.cache setObject:data forKey:[self URLForTilePath:path]];
        result(data, connectionError);
    }];
}

Upvotes: 2

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