无法使用plist文件获取其他图钉图像

Question

I use plist file to store annotation data that have Name, Address, Coordinates and Icon (pin image name) strings in dictionary. I need to show my annotations on map with pin image depending on Icon string in plist. I loop my annotation dictionaries but it show on map pin image from first dict on all my pins.

My code:

- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation
{


    if ([annotation isKindOfClass:[MKUserLocation class]])
        return nil;

    static NSString* AnnotationIdentifier = @"AnnotationIdentifier";
    MKPinAnnotationView* pinView = [[MKPinAnnotationView alloc]
                                    initWithAnnotation:annotation reuseIdentifier:AnnotationIdentifier];


    NSString *path = [[NSBundle mainBundle] pathForResource:@"data" ofType:@"plist"];
    NSDictionary *dict = [NSDictionary dictionaryWithContentsOfFile:path];

    for(path in dict){

        NSString *theCategory;

        theCategory = [NSString stringWithFormat:@"%@", path];
        NSLog(@"%@", path);

        NSArray *anns = [dict objectForKey:theCategory];

        pinView.image = [UIImage imageNamed:[[anns objectAtIndex:0] objectForKey:@"Icon"]];

    }

    pinView.canShowCallout=YES;


    return pinView;
}

My plist file construction:

What it show to me:

Answer 1

The viewForAnnotation delegate method will get called for each annotation added.

The for-loop you have inside that method will run the same way for each annotation. All the for-loop ends up doing (every time for each annotation) is setting pinView.image to the last item read by the for-loop. This happens to be the first item in the first dictionary in the plist.

You need to instead set pinView.image to the Icon of the item that is for the current annotation that viewForAnnotation is being called for (ie. the annotation parameter that is passed). So you could keep the for-loop and check if the item matches annotation and only then set pinView.image (and then break out of the for-loop).

But it's not a good idea to constantly be re-reading and looping through a plist in that delegate method. It's better to make Icon a property of your annotation class, set the property when creating the annotation (you are probably looping through the plist to create the annotations in the first place), and then just use that property directly from the annotation object itself in the viewForAnnotation delegate method.

Assuming you have some custom annotation class, add Icon as a property:

@interface MyAnnotationClass : NSObject<MKAnnotation>

@property (nonatomic, assign) CLLocationCoordinate2D coordinate;
@property (nonatomic, copy) NSString *title;
@property (nonatomic, copy) NSString *subtitle;
@property (nonatomic, copy) NSString *icon;  //<---and @synthesize it in .m

Then in the place where you loop through the plist to create the annotations, set the icon property just like you are setting the title property:

ann.title = [item objectForKey:@"Name"];
ann.icon = [item objectForKey:@"Icon"];

Finally, in viewForAnnotation , you can read the icon property directly from the annotation . But first, you should check that annotation is of your custom class type (so the user location blue dot is not affected and to be reasonably sure annotation will have the property you're about to access):

- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation
{
    if (![annotation isKindOfClass:[MyAnnotationClass class]])
    {
        // Note "!" sign in front of above condition.
        // Return nil (default view) if annotation is 
        // anything but your custom class.
        return nil;
    }

    static NSString* AnnotationIdentifier = @"AnnotationIdentifier";

    MKAnnotationView *pinView = [mapView dequeueReusableAnnotationViewWithIdentifier:AnnotationIdentifier];
    // Create an MKAnnotationView instead of MKPinAnnotationView
    // because we are setting a custom image.
    // Using MKPinAnnotationView sometimes overrides custom image
    // with the built-in pin view.
    if (pinView == nil)
    {
        pinView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:AnnotationIdentifier];
        pinView.canShowCallout = YES;
    }
    else
        pinView.annotation = annotation;

    MyAnnotationClass *myAnn = (MyAnnotationClass *)annotation;
    pinView.image = [UIImage imageNamed:myAnn.icon];
    // May want to check if myAnn.icon is blank (length == 0)
    // (OR if pinView.image is still nil after setting)
    // and show some default image in that case otherwise
    // annotation will be invisible.

    return pinView;
}

By the way, in your plist file, Test3 has no Icon setting.