Issue with Annotation Views disappearing on double tap zoom - iphone

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);