ios - 根据所选的 MKAnnotationView 动态更改 leftCalloutAccessoryView

Question

我有一组图像，它们与 map 上的每个 Annotation 相关联。我可以向 leftCalloutAccessoryView 静态添加图像，但我不确定如何使其动态化。我希望它清楚我在问什么。每个注释都有自己想要显示的图像，但我不确定如何在以下方法中引用图像；

- (MKAnnotationView *)mapView:(MKMapView *)mv viewForAnnotation:(id <MKAnnotation>)annotation
{
    if([annotation isKindOfClass:[MKUserLocation class]])
    return nil;

    NSString *annotationIdentifier = @"PinViewAnnotation";

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


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

       pinView.canShowCallout = YES;

       UIImageView *houseIconView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"Icon"]];//static image
        [houseIconView setFrame:CGRectMake(0, 0, 30, 30)];
        pinView.leftCalloutAccessoryView = houseIconView;

    }
    else
    {
        pinView.annotation = annotation;
    }

    return pinView;

}

我的数组“self.sandwiches”包含具有名称 (NSString) 和图像名称 ('NSString') 的 Sandwich 对象。

我正在寻找一种解决方案，我可以在其中获取所选引脚的索引，类似于 UITableView，您可以在其中获取其索引，并使用 indexPath 从数组中访问它.行.

我的注释类；。H ＃进口 ＃进口 #导入

@interface SandwichAnnotation : NSObject<MKAnnotation>
@property (nonatomic,assign) CLLocationCoordinate2D coordinate;
@property (nonatomic,copy) NSString * title;
@property (nonatomic,copy) NSString * subtitle;

@end

.m

#import "SandwichAnnotation.h"

@implementation SandwichAnnotation
@synthesize coordinate,title,subtitle;

@end

Answer 1

在viewForAnnotation ，而不是“获取 pin 的索引”(这可以工作但效率低于 UITableView )，我建议将所需的数据添加到注释类本身。

这样，数据更加独立，委托(delegate)方法或其他地方的代码无需担心、了解或与注释对象的位置或类型保持同步存储 中。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(或者至少它本身将包含对相关数据的引用)。

viewForAnnotation delegate 方法提供对它需要查看的注释对象的引用(annotation 参数)。一般输入为 id<MKAnnotation>但它实际上是创建的确切类型的实例(由您创建 SandwichAnnotation 或由 map View 创建 MKUserLocation)。

一种选择是使父级 Sandwich类本身实现 MKAnnotation并消除 SandwichAnnotation类(class)。这样，自 annotation 以来根本不需要搜索或引用。参数实际上是一个Sandwich .

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，您可以在注释类中添加对父对象的引用。示例:

@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 SandwichAnnotation 时, 设置引用 Sandwich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 viewForAnnotation , 如果 annotation类型为 SandwichAnnotation , 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;

}