MKOverlayRenderer在地图视图上显示UIImage

问题描述

我正在尝试在iOS 7中的地图视图上显示图像。

I'm trying to display an image over a map view in iOS 7.

我将MKOverlayRenderer子类化如下：

I subclassed MKOverlayRenderer as follows:

MapOverlayRenderer.h

MapOverlayRenderer.h

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

@interface MapOverlayRenderer : MKOverlayRenderer

@end

MapOverlayRenderer.m

MapOverlayRenderer.m

#import "MapOverlayRenderer.h"

@implementation MapOverlayRenderer

- (void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CGContextRef)context {

    UIImage *image = [UIImage imageNamed:@"marker"];
    CGImageRef imageReference = image.CGImage;

    MKMapRect theMapRect = [self.overlay boundingMapRect];
    CGRect theRect = [self rectForMapRect:theMapRect];

    CGContextScaleCTM(context, 1.0, -1.0);
    CGContextTranslateCTM(context, 0.0, -theRect.size.height);

    CGContextDrawImage(context, theRect, imageReference);
}

@end

我有以下内容我的视图控制器包含地图视图：

And I have the following in my view controller which contains the map view:

ViewController.m

ViewController.m

#import "ViewController.h"
#import "MapOverlayRenderer.h"
@import MapKit;

@interface ViewController () <MKMapViewDelegate>

@property (weak,nonatomic) IBOutlet MKMapView *mapView;

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    [self.mapView setDelegate:self];
}

- (MKOverlayRenderer *)mapView:(MKMapView *)mapView rendererForOverlay:(id<MKOverlay>)overlay {

    MapOverlayRenderer *mapOverlay = [[MapOverlayRenderer alloc] init];
    return mapOverlay;
}

- (IBAction)showSeattle:(id)sender {

    CLLocationCoordinate2D location = {47.61167908,-122.33325958};
    int radius = 100000; //radius in meters
    MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance(location, radius, radius);
    [self.mapView setRegion:[self.mapView regionThatFits:region] animated:YES];
}

@end

当<$ c $调用c> IBAction 将地图缩放到某个位置，我在地图视图顶部看不到图像。

When the IBAction is called to zoom the map to a location, I do not see the image on top of the map view.

怎么能你在iOS 7中使用 MKOverlayRenderer 在地图视图上显示图像？

How can you use the MKOverlayRenderer in iOS 7 to display images on top of a map view?

推荐答案

有几个问题：

1. 通过调用 addOverlay ，代码实际上在地图中添加了一个叠加层？您需要创建一个 id< MKOverlay> 类型的对象，并在 addOverlay 调用中传递它。您可以创建一个实现 MKOverlay 的自定义类，但在这种情况下，您可以使用 MKCircle 表示图像的位置和大小。在 showSeattle：方法中：

1. Where is the code actually adding an overlay to the map by calling addOverlay? You'll need to create an object of type id<MKOverlay> and pass it in the addOverlay call. You could create a custom class that implements MKOverlay but in this case, you could just use MKCircle to represent the position and size of your image. In the showSeattle: method:

CLLocationCoordinate2D location = {47.61167908,-122.33325958};
int radius = 100000; //radius in meters

MKCircle *c = [MKCircle circleWithCenterCoordinate:location radius:radius];
[self.mapView addOverlay:c];

MKCoordinateRegion region = ...

rendererForOverlay ，代码正在创建 MapOverlayRenderer 的实例，但没有为它提供对底层 overlay 模型对象。改为调用 initWithOverlay ：

In rendererForOverlay, the code is creating an instance of MapOverlayRenderer but not giving it a reference to the underlying overlay model object. Call initWithOverlay instead:

MapOverlayRenderer *mapOverlay
    = [[MapOverlayRenderer alloc] initWithOverlay:overlay];

因此，您可以使用注释更轻松地将图像放在该位置（但是图像不会随着基于叠加层的图像的缩放级别缩放）。不确定你想要哪种功能。

By the way, you could put an image at the location much more easily using an annotation (but the image won't scale with the zoom level as an overlay-based image will). Not sure which functionality you want.

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