Issue with Annotation Views disappearing on double tap zoom

Question

I've ran into a problem with annotation views in the MapKit on the iPhone. I manage to draw custom annotation views on the map - no problem there. I even manage to redraw them after dragging or zooming. However, there are cases where the redrawing does not work: an example would be double-tap zoom.

I attach some code where I draw a few rectangles at specific locations on the map, and when I zoom using a two finger gesture, everything works fine (i.e. the rectangles are redrawn). However, when I double tap, the rectangles disappear. What's even stranger is that all methods get called in the order that they should, and in the end, even the drawRect gets called - but the rectangles are not drawn.

So here's the code, please try for yourself - two finger zooming works, but double-tap zooming doesn't:

PlaygroundViewController.h

#import <UIKit/UIKit.h>
#import <MapKit/MapKit.h>

@interface PlaygroundViewController : UIViewController <MKMapViewDelegate>{
 MKMapView *mapView_;
 NSMutableDictionary* myViews_;
}

@end

PlaygroundViewController.m

#import "PlaygroundViewController.h"
#import "Territory.h"
#import "TerritoryView.h"

@implementation PlaygroundViewController

- (void)viewDidLoad {
    [super viewDidLoad];
 mapView_=[[MKMapView alloc] initWithFrame:self.view.bounds];
 [self.view insertSubview:mapView_ atIndex:0];
 mapView_.delegate = self;
 [mapView_ setMapType:MKMapTypeStandard];
    [mapView_ setZoomEnabled:YES];
    [mapView_ setScrollEnabled:YES];
 myViews_ = [[NSMutableDictionary alloc] init];
 for (int i = 0; i < 10; i++ ) {
  Territory *territory;
  territory = [[[Territory alloc] init] autorelease];
     territory.latitude_ = 40 + i;
  territory.longitude_ = -122 + i;
  [mapView_ addAnnotation:territory];

 }
}

- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation {
 MKAnnotationView* territoryView = (MKAnnotationView*)[mapView dequeueReusableAnnotationViewWithIdentifier:@"Territory"];
 if (!territoryView){
  territoryView = [[[TerritoryView alloc] initWithAnnotation:annotation reuseIdentifier:@"Territory"] autorelease];
  Territory* currentTerritory = (Territory*) annotation;
  [myViews_ setObject:territoryView forKey:currentTerritory.territoryID_];
 }  
    else{
  territoryView.annotation = annotation;
 }  
 return territoryView; 
}

- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated {
 for (NSObject* key in [myViews_ allKeys]) {
  TerritoryView* territoryView = [myViews_ objectForKey:key];
  [territoryView initRedraw];
 }
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
}

- (void)dealloc {
    [super dealloc];
}

Territory.h

#import <Foundation/Foundation.h>
#import <MapKit/MapKit.h>


@interface Territory : NSObject <MKAnnotation> {
 float latitude_;
 float longitude_;
 NSString* territoryID_;
}

@property (nonatomic) float latitude_;
@property (nonatomic) float longitude_;
@property (nonatomic, retain) NSString* territoryID_;


@end

Territory.m

#import "Territory.h"

@implementation Territory

@synthesize latitude_;
@synthesize longitude_;
@synthesize territoryID_;


- (CLLocationCoordinate2D)coordinate {
 CLLocationCoordinate2D coord_ = {self.latitude_, self.longitude_};
 return coord_;
}

-(id) init {
 if (self = [super init]) {
  self.territoryID_ = [NSString stringWithFormat:@"%p", self];
 }
 return self;
}


@end

TerritoryView.h

#import <Foundation/Foundation.h>
#import <MapKit/MapKit.h>

@interface TerritoryView : MKAnnotationView {

}

- (id)initWithAnnotation:(id <MKAnnotation>)annotation reuseIdentifier:(NSString *)reuseIdentifier;
- (void)initRedraw;

@end

TerritoryView.m

#import "TerritoryView.h"

@implementation TerritoryView

- (id)initWithAnnotation:(id <MKAnnotation>)annotation reuseIdentifier:(NSString *)reuseIdentifier {
    if ([super initWithAnnotation:annotation reuseIdentifier:@"Territory"]) {
  self.initRedraw;
    }
    return self;
}

- (void)initRedraw {
 self.frame = CGRectMake(0,0,40,40);
 [self setNeedsDisplay];
}

- (void)drawRect:(CGRect)rect {
 NSLog(@"in draw rect");
}

@end

Any help is appreciated. Here's the zipped project: link

Answer 1

Keep in mind that the frame's origin is in the coordinate system of its parent, so setting it to zero is probably putting it off screen. I suspect that the reason it ever works at all is the it's getting reset behind your back in most situations, but not in those where it's failing.

replace: self.frame = CGRectMake(0,0,40,40);

with: self.frame = CGRectMake(self.frame.origin.x,self.frame.origin.y,40,40);