消除 MKMapView 中的引脚重叠

Question

我正在使用基于 MKMapView 的应用程序。我需要澄清是否可以消除 MKMapView 中的引脚 OverLap？因为有些地方有大量的图钉显示。我很难识别引脚。

Answer 1

如果您有 Apple 开发者帐户，我强烈建议您获取 2011 WWDC 大会的第 111 期视频会议，标题为“使用 MapKit 可视化地理信息”。其中一个部分专门介绍了如何对大型数据集中的内容进行聚类，以便您可以根据不同缩放级别的密度对图钉进行分组或取消分组。

他们的示例非常简单，但问题的核心是您想要用单个引脚替换一组重叠的引脚，并且当您放大时，单个引脚将分裂回各个引脚。

您决定如何以及何时对事物进行分组可能会有很大差异。苹果的解决方案只是将地图细分为一个网格，任何具有超过 1 个图钉的方框都会形成一个组。您还可以采用算法方法，例如使用 kMeansCluster 算法，该算法非常简单，您可以通过该算法提供所有注释，并从另一端获得逻辑组织的一组组。

从那里开始，需要跟踪所有单独的引脚以及在放大和缩小时它们如何分组。您将仅显示每个组或剩余的任何单个引脚的单个注释。还可以在地图放大和缩小时为过渡设置动画，以便您可以在视觉上强化正在发生的事情。

我自己的技术与 Apple 的方法密切相关，因此我无法在这里发布，因此我希望您可以访问上面的视频，其中涵盖了几乎所有这些要点。

Answer 2

为此，您必须在地图中实现聚类概念。通过使用 Apple 演示代码，可以轻松在我们的代码中实现聚类概念。 参考链接

我们可以简单地使用以下代码进行聚类

实现聚类的步骤

Step1： 重要的是对于聚类，我们使用两个mapview(allAnnotationsMapView, )，一个用于参考(allAnnotationsMapView)。

@property (nonatomic, strong) MKMapView *allAnnotationsMapView;
@property (nonatomic, strong) IBOutlet MKMapView *mapView;

在viewDidLoad中

    _allAnnotationsMapView = [[MKMapView alloc] initWithFrame:CGRectZero];

Step2：将所有注释添加到_allAnnotationsMapView中，下面的_photos是注释数组。

        [_allAnnotationsMapView addAnnotations:_photos];
        [self updateVisibleAnnotations];

Step3： 添加以下聚类方法，其中 PhotoAnnotation 是自定义注释。
MapViewDelegate方法

 - (void)mapView:(MKMapView *)aMapView regionDidChangeAnimated:(BOOL)animated {

    [self updateVisibleAnnotations];
}

- (void)mapView:(MKMapView *)aMapView didAddAnnotationViews:(NSArray *)views {

    for (MKAnnotationView *annotationView in views) {
        if (![annotationView.annotation isKindOfClass:[PhotoAnnotation class]]) {
            continue;
        }

        PhotoAnnotation *annotation = (PhotoAnnotation *)annotationView.annotation;

        if (annotation.clusterAnnotation != nil) {
            // animate the annotation from it's old container's coordinate, to its actual coordinate
            CLLocationCoordinate2D actualCoordinate = annotation.coordinate;
            CLLocationCoordinate2D containerCoordinate = annotation.clusterAnnotation.coordinate;

            // since it's displayed on the map, it is no longer contained by another annotation,
            // (We couldn't reset this in -updateVisibleAnnotations because we needed the reference to it here
            // to get the containerCoordinate)
            annotation.clusterAnnotation = nil;

            annotation.coordinate = containerCoordinate;

            [UIView animateWithDuration:0.3 animations:^{
                annotation.coordinate = actualCoordinate;
            }];
        }
    }
}

聚类处理方法

    - (id<MKAnnotation>)annotationInGrid:(MKMapRect)gridMapRect usingAnnotations:(NSSet *)annotations {

    // first, see if one of the annotations we were already showing is in this mapRect
    NSSet *visibleAnnotationsInBucket = [self.mapView annotationsInMapRect:gridMapRect];
    NSSet *annotationsForGridSet = [annotations objectsPassingTest:^BOOL(id obj, BOOL *stop) {
        BOOL returnValue = ([visibleAnnotationsInBucket containsObject:obj]);
        if (returnValue)
        {
            *stop = YES;
        }
        return returnValue;
    }];

    if (annotationsForGridSet.count != 0) { 
        return [annotationsForGridSet anyObject];
    }

    // otherwise, sort the annotations based on their distance from the center of the grid square,
    // then choose the one closest to the center to show
    MKMapPoint centerMapPoint = MKMapPointMake(MKMapRectGetMidX(gridMapRect), MKMapRectGetMidY(gridMapRect));
    NSArray *sortedAnnotations = [[annotations allObjects] sortedArrayUsingComparator:^(id obj1, id obj2) {
        MKMapPoint mapPoint1 = MKMapPointForCoordinate(((id<MKAnnotation>)obj1).coordinate);
        MKMapPoint mapPoint2 = MKMapPointForCoordinate(((id<MKAnnotation>)obj2).coordinate);

        CLLocationDistance distance1 = MKMetersBetweenMapPoints(mapPoint1, centerMapPoint);
        CLLocationDistance distance2 = MKMetersBetweenMapPoints(mapPoint2, centerMapPoint);

        if (distance1 < distance2) {
            return NSOrderedAscending;
        } else if (distance1 > distance2) {
            return NSOrderedDescending;
        }

        return NSOrderedSame;
    }];

    PhotoAnnotation *photoAnn = sortedAnnotations[0];
    NSLog(@"lat long %f %f", photoAnn.coordinate.latitude, photoAnn.coordinate.longitude);

    return sortedAnnotations[0];
}

- (void)updateVisibleAnnotations {

    // This value to controls the number of off screen annotations are displayed.
    // A bigger number means more annotations, less chance of seeing annotation views pop in but decreased performance.
    // A smaller number means fewer annotations, more chance of seeing annotation views pop in but better performance.
    static float marginFactor = 2.0;

    // Adjust this roughly based on the dimensions of your annotations views.
    // Bigger numbers more aggressively coalesce annotations (fewer annotations displayed but better performance).
    // Numbers too small result in overlapping annotations views and too many annotations on screen.
    static float bucketSize = 60.0;

    // find all the annotations in the visible area + a wide margin to avoid popping annotation views in and out while panning the map.
    MKMapRect visibleMapRect = [self.mapView visibleMapRect];
    MKMapRect adjustedVisibleMapRect = MKMapRectInset(visibleMapRect, -marginFactor * visibleMapRect.size.width, -marginFactor * visibleMapRect.size.height);

    // determine how wide each bucket will be, as a MKMapRect square
    CLLocationCoordinate2D leftCoordinate = [self.mapView convertPoint:CGPointZero toCoordinateFromView:self.view];
    CLLocationCoordinate2D rightCoordinate = [self.mapView convertPoint:CGPointMake(bucketSize, 0) toCoordinateFromView:self.view];
    double gridSize = MKMapPointForCoordinate(rightCoordinate).x - MKMapPointForCoordinate(leftCoordinate).x;
    MKMapRect gridMapRect = MKMapRectMake(0, 0, gridSize, gridSize);

    // condense annotations, with a padding of two squares, around the visibleMapRect
    double startX = floor(MKMapRectGetMinX(adjustedVisibleMapRect) / gridSize) * gridSize;
    double startY = floor(MKMapRectGetMinY(adjustedVisibleMapRect) / gridSize) * gridSize;
    double endX = floor(MKMapRectGetMaxX(adjustedVisibleMapRect) / gridSize) * gridSize;
    double endY = floor(MKMapRectGetMaxY(adjustedVisibleMapRect) / gridSize) * gridSize;

    // for each square in our grid, pick one annotation to show
    gridMapRect.origin.y = startY;
    while (MKMapRectGetMinY(gridMapRect) <= endY) {
        gridMapRect.origin.x = startX;

        while (MKMapRectGetMinX(gridMapRect) <= endX) {
            NSSet *allAnnotationsInBucket = [self.allAnnotationsMapView annotationsInMapRect:gridMapRect];
            NSSet *visibleAnnotationsInBucket = [self.mapView annotationsInMapRect:gridMapRect];

            // we only care about PhotoAnnotations
            NSMutableSet *filteredAnnotationsInBucket = [[allAnnotationsInBucket objectsPassingTest:^BOOL(id obj, BOOL *stop) {
                return ([obj isKindOfClass:[PhotoAnnotation class]]);
            }] mutableCopy];

            if (filteredAnnotationsInBucket.count > 0) {
                PhotoAnnotation *annotationForGrid = (PhotoAnnotation *)[self annotationInGrid:gridMapRect usingAnnotations:filteredAnnotationsInBucket];

                [filteredAnnotationsInBucket removeObject:annotationForGrid];

                // give the annotationForGrid a reference to all the annotations it will represent
                annotationForGrid.containedAnnotations = [filteredAnnotationsInBucket allObjects];

                [self.mapView addAnnotation:annotationForGrid];

                for (PhotoAnnotation *annotation in filteredAnnotationsInBucket) {
                    // give all the other annotations a reference to the one which is representing them
                    annotation.clusterAnnotation = annotationForGrid;
                    annotation.containedAnnotations = nil;

                    // remove annotations which we've decided to cluster
                    if ([visibleAnnotationsInBucket containsObject:annotation]) {
                        CLLocationCoordinate2D actualCoordinate = annotation.coordinate;
                        [UIView animateWithDuration:0.3 animations:^{
                            annotation.coordinate = annotation.clusterAnnotation.coordinate;
                        } completion:^(BOOL finished) {
                            annotation.coordinate = actualCoordinate;
                            [self.mapView removeAnnotation:annotation];
                        }];
                    }
                }
            }

            gridMapRect.origin.x += gridSize;
        }

        gridMapRect.origin.y += gridSize;
    }
}

通过以上步骤我们就可以在mapview上实现聚类，不需要使用任何第三方代码或框架。请在此处查看 Apple 示例代码。如果您对此有任何疑问，请告诉我。

Answer 3

实现您自己的注释集群框架非常容易。下面是一个基本示例，您可以在此处进行参考。

Answer 4

如果您的图钉重叠，那么该位置的缩放级别一定很高。
您可以考虑删除该缩放级别中的一些注释，直到没有注释重叠，并且在放大时可以添加注释，以便注释之间有足够的空间。