基于选定的MKAnnotationView动态更改leftCalloutAccessoryView

在里面 viewForAnnotation ,而不是“获取管脚的索引”(这会有效,但效率比使用 UITableView ),我建议将所需的数据添加到注释类本身。

这样,数据就更加独立,委托方法或其他地方的代码不需要担心、知道或与注释对象的位置或类型保持同步 存储 只要您有对注释对象的引用,您将立即拥有该注释所需的所有数据(或者至少它将包含对自身中相关数据的引用)。

这个 注释视图 委托方法提供对它需要视图的注释对象的引用( annotation 参数)。它的类型一般为 id<MKAnnotation> 但它实际上是创建的确切类型的实例( SandwichAnnotation 由您或 MKUserLocation 通过地图视图)。

一种选择是使父级 Sandwich 类本身实现 MKAnnotation 并消除 三明治注释 班这样,根本不需要搜索或引用,因为 注释 参数将实际 是 一 三明治 .

但是,您可能希望为注释对象保留一个单独的类(这很好)。在这种情况下,可以在注释类中添加对父对象的引用。例子:

@interface SandwichAnnotation : NSObject<MKAnnotation>
@property (nonatomic,assign) CLLocationCoordinate2D coordinate;
@property (nonatomic,copy) NSString * title;
@property (nonatomic,copy) NSString * subtitle;
@property (nonatomic,retain) Sandwich * whichSandwich;  // <-- add reference
@end

创建 三明治注释 ,设置引用 三明治 注释用于:

for (Sandwich *currentSandwich in self.sandwiches) {
    SandwichAnnotation *sa = [[SandwichAnnotation alloc] init...];
    sa.coordinate = ...
    sa.title = ...
    sa.whichSandwich = currentSandwich; // <-- set reference

    [mapView addAnnotation:sa];
}

最后,在 注释视图 如果 注释 属于类型 三明治注释 ,设置 leftCalloutAccessoryView :

- (MKAnnotationView *)mapView:(MKMapView *)mv viewForAnnotation:(id <MKAnnotation>)annotation
{
    if (! [annotation isKindOfClass:[SandwichAnnotation class]]) {
        //If annotation is not a SandwichAnnotation, return default view...
        //This includes MKUserLocation.
        return nil;
    }

    //At this point, we know annotation is of type SandwichAnnotation.
    //Cast it to that type so we can get at the custom properties.
    SandwichAnnotation *sa = (SandwichAnnotation *)annotation;

    NSString *annotationIdentifier = @"PinViewAnnotation";

    MyAnnotationView *pinView = (MyAnnotationView *) [mv dequeueReusableAnnotationViewWithIdentifier:annotationIdentifier];


    if (!pinView)
    {
        pinView = [[MyAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:annotationIdentifier];

       pinView.canShowCallout = YES;

       //Here, just initialize a blank UIImageView ready to use.
       //Set image below AFTER we have a dequeued or new view ready.
       UIImageView *houseIconView = [[UIImageView alloc] init];
       [houseIconView setFrame:CGRectMake(0, 0, 30, 30)];
       pinView.leftCalloutAccessoryView = houseIconView;
    }
    else
    {
        pinView.annotation = annotation;
    }

    //At this point, we have a dequeued or new view ready to use
    //and pointing to the correct annotation.
    //Update image on the leftCalloutAccessoryView here
    //(not just when creating the view otherwise an annotation
    //that gets a dequeued view will show an image of another annotation).

    UIImageView *houseIconView = (UIImageView *)pinView.leftCalloutAccessoryView;
    NSString *saImageName = sa.whichSandwich.imageName;
    UIImage *houseIcon = [UIImage imageNamed: saImageName];

    if (houseIcon == nil) {
        //In case the image was not found,
        //set houseIcon to some default image.
        houseIcon = someDefaultImage;
    }

    houseIconView.image = houseIcon;

    return pinView;

}