将 MKMapView 区域设置为以两个注释为中心

Question

我正在寻求一些帮助，以根据当前位置注释和我设置的注释完成一些关于在 MKMapView 上设置区域的代码。

我想计算两者之间的距离并设置两者之间的中心，然后缩小以使两者都在视图中。对我来说，它在模拟器中似乎工作正常，但不幸的是 userLocation.coordinate 固定在 Apple HQ 上。当我在设备上进行测试时，我看到了奇怪的行为。如果两个注释在同一纬度上有点水平，它通常会缩小并设置适当的区域，但如果垂直距离较大，则不能正确缩小。

我使用了找到 here 的代码，并进行了一些编辑以满足我的需要：

CLLocationCoordinate2D southWest = mapView.userLocation.coordinate;
CLLocationCoordinate2D northEast = southWest;

southWest.latitude = MIN(southWest.latitude, annotation.coordinate.latitude);
southWest.longitude = MIN(southWest.longitude, annotation.coordinate.longitude);

northEast.latitude = MAX(northEast.latitude, annotation.coordinate.latitude);
northEast.longitude = MAX(northEast.longitude, annotation.coordinate.longitude);

CLLocation *locSouthWest = [[CLLocation alloc] initWithLatitude:southWest.latitude longitude:southWest.longitude];
CLLocation *locNorthEast = [[CLLocation alloc] initWithLatitude:northEast.latitude longitude:northEast.longitude];

// This is a diag distance (if you wanted tighter you could do NE-NW or NE-SE)
CLLocationDistance meters = [locSouthWest distanceFromLocation:locNorthEast];

MKCoordinateRegion region;
region.center.latitude = (southWest.latitude + northEast.latitude) / 2.0;
region.center.longitude = (southWest.longitude + northEast.longitude) / 2.0;
region.span.latitudeDelta = meters / 111319.5;
region.span.longitudeDelta = 0.0;

MKCoordinateRegion savedRegion = [mapView regionThatFits:region];
[mapView setRegion:savedRegion animated:YES];

[locSouthWest release];
[locNorthEast release];

让我困惑的一件事是他说northEast = southWest...

提前感谢任何获得帮助和意见的人:)

Answer 1

对于 iOS7 转发，最好的方法是：

//from API docs: 
//- (void)showAnnotations:(NSArray *)annotations animated:(BOOL)animated NS_AVAILABLE(10_9, 7_0);
[self.mapView showAnnotations:self.mapView.annotations animated:YES];

对于我的个人项目（iOS7 之前），我只是在 MKMapView 类上添加了一个类别来封装“可见区域”功能，用于一个非常常见的操作：将其设置为能够查看当前加载的所有注释MKMapView 实例（这包括您可能放置的尽可能多的图钉，以及用户的位置）。结果是这样的：

.h 文件

#import <MapKit/MapKit.h>

@interface MKMapView (Extensions)

-(void)ij_setVisibleRectToFitAllLoadedAnnotationsAnimated:(BOOL)animated;
-(void)ij_setVisibleRectToFitAnnotations:(NSArray *)annotations animated:(BOOL)animated;


@end

.m 文件

#import "MKMapView+Extensions.h"

@implementation MKMapView (Extensions)

/**
 *  Changes the currently visible portion of the map to a region that best fits all the currently loadded annotations on the map, and it optionally animates the change.
 *
 *  @param animated is the change should be perfomed with an animation.
 */
-(void)ij_setVisibleRectToFitAllLoadedAnnotationsAnimated:(BOOL)animated
{
    MKMapView * mapView = self;

    NSArray * annotations = mapView.annotations;

    [self ij_setVisibleRectToFitAnnotations:annotations animated:animated];

}


/**
 *  Changes the currently visible portion of the map to a region that best fits the provided annotations array, and it optionally animates the change.
    All elements from the array must conform to the <MKAnnotation> protocol in order to fetch the coordinates to compute the visible region of the map.
 *
 *  @param annotations an array of elements conforming to the <MKAnnotation> protocol, holding the locations for which the visible portion of the map will be set.
 *  @param animated    wether or not the change should be perfomed with an animation.
 */
-(void)ij_setVisibleRectToFitAnnotations:(NSArray *)annotations animated:(BOOL)animated
{
    MKMapView * mapView = self;

    MKMapRect r = MKMapRectNull;
    for (id<MKAnnotation> a in annotations) {
        ZAssert([a conformsToProtocol:@protocol(MKAnnotation)], @"ERROR: All elements of the array MUST conform to the MKAnnotation protocol. Element (%@) did not fulfill this requirement", a);
        MKMapPoint p = MKMapPointForCoordinate(a.coordinate);
        //MKMapRectUnion performs the union between 2 rects, returning a bigger rect containing both (or just one if the other is null). here we do it for rects without a size (points)
        r = MKMapRectUnion(r, MKMapRectMake(p.x, p.y, 0, 0));
    }

    [mapView setVisibleMapRect:r animated:animated];

}

@end

如您所见，到目前为止，我添加了 2 种方法：一种用于将地图的可见区域设置为适合 MKMapView 实例上所有当前加载的注释的区域，另一种用于将其设置为任何数组的方法的对象。 因此，要设置 mapView 的可见区域，代码将非常简单：

   //the mapView instance  
    [self.mapView ij_setVisibleRectToFitAllLoadedAnnotationsAnimated:animated]; 

希望对你有帮助=)

Answer 2

不要被前两行吓到，你可以忽略 = 符号的右边，因为它会在下面被覆盖...

我认为问题就在这里：

region.span.longitudeDelta = 0.0;

Answer 3

Swift 4 版本Robertibiris 答案：

mapView.showAnnotations(mapView.annotations, animated: true)

Answer 4

这篇博文可能会为您提供所需的洞察力

http://codisllc.com/blog/zoom-mkmapview-to-fit-annotations/

-(void)zoomToFitMapAnnotations:(MKMapView*)mapView
{
    if([mapView.annotations count] == 0)
        return;

    CLLocationCoordinate2D topLeftCoord;
    topLeftCoord.latitude = -90;
    topLeftCoord.longitude = 180;

    CLLocationCoordinate2D bottomRightCoord;
    bottomRightCoord.latitude = 90;
    bottomRightCoord.longitude = -180;

    for(MapAnnotation* annotation in mapView.annotations)
    {
        topLeftCoord.longitude = fmin(topLeftCoord.longitude, annotation.coordinate.longitude);
        topLeftCoord.latitude = fmax(topLeftCoord.latitude, annotation.coordinate.latitude);

        bottomRightCoord.longitude = fmax(bottomRightCoord.longitude, annotation.coordinate.longitude);
        bottomRightCoord.latitude = fmin(bottomRightCoord.latitude, annotation.coordinate.latitude);
    }

    MKCoordinateRegion region;
    region.center.latitude = topLeftCoord.latitude - (topLeftCoord.latitude - bottomRightCoord.latitude) * 0.5;
    region.center.longitude = topLeftCoord.longitude + (bottomRightCoord.longitude - topLeftCoord.longitude) * 0.5;
    region.span.latitudeDelta = fabs(topLeftCoord.latitude - bottomRightCoord.latitude) * 1.1; // Add a little extra space on the sides
    region.span.longitudeDelta = fabs(bottomRightCoord.longitude - topLeftCoord.longitude) * 1.1; // Add a little extra space on the sides

    region = [mapView regionThatFits:region];
    [mapView setRegion:region animated:YES];
}