有没有办法限制 MKMapView 最大缩放级别？

Question

问题是 - 有没有办法限制 MKMapView 的最大缩放级别？或者有没有办法在用户缩放到没有可用地图图像的级别时进行跟踪？

Answer 1

如果您仅使用 iOS 7+，则可以获取/设置一个新的 camera.altitude 属性以强制缩放级别。它相当于azdev的解决方案，但不需要外部代码。

在测试中，我还发现如果你反复尝试放大细节可能会进入无限循环，所以我在下面的代码中设置了一个 var 来防止这种情况。

- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated {
    // enforce maximum zoom level
    if (_mapView.camera.altitude < 120.00 && !_modifyingMap) {
        _modifyingMap = YES; // prevents strange infinite loop case

        _mapView.camera.altitude = 120.00;

        _modifyingMap = NO;
    }
}

Answer 2

您可以使用mapView:regionWillChangeAnimated: 委托方法来侦听区域更改事件，如果该区域比您的最大区域宽，则使用setRegion:animated: 将其设置回最大区域，以向您的用户表明他们可以' t 缩小那么远。方法如下：

- (void)mapView:(MKMapView *)mapView regionWillChangeAnimated:(BOOL)animated
- (void)setRegion:(MKCoordinateRegion)region animated:(BOOL)animated

Answer 3

我刚刚花了一些时间为我正在构建的应用程序工作。这是我想出的：

1. 我从 Troy Brant 的 this page 脚本开始，我认为这是设置地图视图的更好方法。

2. 我添加了一个返回当前缩放级别的方法。

   在MKMapView+ZoomLevel.h中：

   - (double)getZoomLevel;
   

   在MKMapView+ZoomLevel.m中：

   // Return the current map zoomLevel equivalent, just like above but in reverse
   - (double)getZoomLevel{
       MKCoordinateRegion reg=self.region; // the current visible region
       MKCoordinateSpan span=reg.span; // the deltas
       CLLocationCoordinate2D centerCoordinate=reg.center; // the center in degrees
       // Get the left and right most lonitudes
       CLLocationDegrees leftLongitude=(centerCoordinate.longitude-(span.longitudeDelta/2));
       CLLocationDegrees rightLongitude=(centerCoordinate.longitude+(span.longitudeDelta/2));
       CGSize mapSizeInPixels = self.bounds.size; // the size of the display window
   
       // Get the left and right side of the screen in fully zoomed-in pixels
       double leftPixel=[self longitudeToPixelSpaceX:leftLongitude]; 
       double rightPixel=[self longitudeToPixelSpaceX:rightLongitude];
       // The span of the screen width in fully zoomed-in pixels
       double pixelDelta=abs(rightPixel-leftPixel);
   
       // The ratio of the pixels to what we're actually showing
       double zoomScale= mapSizeInPixels.width /pixelDelta;
       // Inverse exponent
       double zoomExponent=log2(zoomScale);
       // Adjust our scale
       double zoomLevel=zoomExponent+20; 
       return zoomLevel;
   }
   

   此方法依赖于上面链接代码中的一些私有方法。

3. 我将此添加到我的 MKMapView 委托中（正如上面@vladimir 推荐的那样）

   - (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated {
       NSLog(@"%f",[mapView getZoomLevel]);
       if([mapView getZoomLevel]<10) {
           [mapView setCenterCoordinate:[mapView centerCoordinate] zoomLevel:10 animated:TRUE];
       }
   }
   

   如果用户离得太远，这会产生重新缩放的效果。您可以使用 regionWillChangeAnimated 来防止地图“弹回”。

   关于上面的循环cmets，看起来这个方法只迭代一次。

Answer 4

是的，这是可行的。首先，使用MKMapView+ZoomLevel扩展MKMapView。

然后，在您的 MKMapViewDelegate 中实现它：

- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated
{
    // Constrain zoom level to 8.
    if( [mapView zoomLevel] < 8 )
    {
        [mapView setCenterCoordinate:mapView.centerCoordinate 
            zoomLevel:8 
            animated:NO];
    }
}

Answer 5

这是使用MKMapView+ZoomLevel 和@T.Markle 用 Swift 3 重写的代码答案：

import Foundation
import MapKit

fileprivate let MERCATOR_OFFSET: Double = 268435456
fileprivate let MERCATOR_RADIUS: Double = 85445659.44705395

extension MKMapView {

    func getZoomLevel() -> Double {

        let reg = self.region
        let span = reg.span
        let centerCoordinate = reg.center

        // Get the left and right most lonitudes
        let leftLongitude = centerCoordinate.longitude - (span.longitudeDelta / 2)
        let rightLongitude = centerCoordinate.longitude + (span.longitudeDelta / 2)
        let mapSizeInPixels = self.bounds.size

        // Get the left and right side of the screen in fully zoomed-in pixels
        let leftPixel = self.longitudeToPixelSpaceX(longitude: leftLongitude)
        let rightPixel = self.longitudeToPixelSpaceX(longitude: rightLongitude)
        let pixelDelta = abs(rightPixel - leftPixel)

        let zoomScale = Double(mapSizeInPixels.width) / pixelDelta
        let zoomExponent = log2(zoomScale)
        let zoomLevel = zoomExponent + 20

        return zoomLevel
    }

    func setCenter(coordinate: CLLocationCoordinate2D, zoomLevel: Int, animated: Bool) {

        let zoom = min(zoomLevel, 28)

        let span = self.coordinateSpan(centerCoordinate: coordinate, zoomLevel: zoom)
        let region = MKCoordinateRegion(center: coordinate, span: span)

        self.setRegion(region, animated: true)
    }

    // MARK: - Private func

    private func coordinateSpan(centerCoordinate: CLLocationCoordinate2D, zoomLevel: Int) -> MKCoordinateSpan {

        // Convert center coordiate to pixel space
        let centerPixelX = self.longitudeToPixelSpaceX(longitude: centerCoordinate.longitude)
        let centerPixelY = self.latitudeToPixelSpaceY(latitude: centerCoordinate.latitude)

        // Determine the scale value from the zoom level
        let zoomExponent = 20 - zoomLevel
        let zoomScale = NSDecimalNumber(decimal: pow(2, zoomExponent)).doubleValue

        // Scale the map’s size in pixel space
        let mapSizeInPixels = self.bounds.size
        let scaledMapWidth = Double(mapSizeInPixels.width) * zoomScale
        let scaledMapHeight = Double(mapSizeInPixels.height) * zoomScale

        // Figure out the position of the top-left pixel
        let topLeftPixelX = centerPixelX - (scaledMapWidth / 2)
        let topLeftPixelY = centerPixelY - (scaledMapHeight / 2)

        // Find delta between left and right longitudes
        let minLng: CLLocationDegrees = self.pixelSpaceXToLongitude(pixelX: topLeftPixelX)
        let maxLng: CLLocationDegrees = self.pixelSpaceXToLongitude(pixelX: topLeftPixelX + scaledMapWidth)
        let longitudeDelta: CLLocationDegrees = maxLng - minLng

        // Find delta between top and bottom latitudes
        let minLat: CLLocationDegrees = self.pixelSpaceYToLatitude(pixelY: topLeftPixelY)
        let maxLat: CLLocationDegrees = self.pixelSpaceYToLatitude(pixelY: topLeftPixelY + scaledMapHeight)
        let latitudeDelta: CLLocationDegrees = -1 * (maxLat - minLat)

        return MKCoordinateSpan(latitudeDelta: latitudeDelta, longitudeDelta: longitudeDelta)
    }

    private func longitudeToPixelSpaceX(longitude: Double) -> Double {
        return round(MERCATOR_OFFSET + MERCATOR_RADIUS * longitude * M_PI / 180.0)
    }

    private func latitudeToPixelSpaceY(latitude: Double) -> Double {
        if latitude == 90.0 {
            return 0
        } else if latitude == -90.0 {
            return MERCATOR_OFFSET * 2
        } else {
            return round(MERCATOR_OFFSET - MERCATOR_RADIUS * Double(logf((1 + sinf(Float(latitude * M_PI) / 180.0)) / (1 - sinf(Float(latitude * M_PI) / 180.0))) / 2.0))
        }
    }

    private func pixelSpaceXToLongitude(pixelX: Double) -> Double {
        return ((round(pixelX) - MERCATOR_OFFSET) / MERCATOR_RADIUS) * 180.0 / M_PI
    }


    private func pixelSpaceYToLatitude(pixelY: Double) -> Double {
        return (M_PI / 2.0 - 2.0 * atan(exp((round(pixelY) - MERCATOR_OFFSET) / MERCATOR_RADIUS))) * 180.0 / M_PI
    }
}

在视图控制器中的使用示例：

func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool) {
        print("Zoom: \(mapView.getZoomLevel())")
        if mapView.getZoomLevel() > 6 {
            mapView.setCenter(coordinate: mapView.centerCoordinate, zoomLevel: 6, animated: true)
        }
    }

Answer 6

如果您的目标是 iOS 13+，请使用 MKMapView setCameraZoomRange 方法。只需提供最小和最大中心坐标距离（以米为单位）。

在此处查看 Apple 的文档：https://developer.apple.com/documentation/mapkit/mkmapview/3114302-setcamerazoomrange

Answer 7

不要使用regionWillChangeAnimated。使用regionDidChangeAnimated

• 我们也可以使用setRegion(region, animated: true)。通常，如果我们使用regionWillChangeAnimated，它会冻结MKMapView，但使用regionDidChangeAnimated 它可以完美运行

  func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool) {
    mapView.checkSpan()
  }
  
  extension MKMapView {
    func zoom() {
      let region = MKCoordinateRegionMakeWithDistance(userLocation.coordinate, 2000, 2000)
      setRegion(region, animated: true)
    }
  
    func checkSpan() {
      let rect = visibleMapRect
      let westMapPoint = MKMapPointMake(MKMapRectGetMinX(rect), MKMapRectGetMidY(rect))
      let eastMapPoint = MKMapPointMake(MKMapRectGetMaxX(rect), MKMapRectGetMidY(rect))
  
      let distanceInMeter = MKMetersBetweenMapPoints(westMapPoint, eastMapPoint)
  
      if distanceInMeter > 2100 {
        zoom()
      }
    }
  }
  

Answer 8

使用此示例锁定最大缩放范围，同样您可以限制最小范围

map.cameraZoomRange = MKMapView.CameraZoomRange(maxCenterCoordinateDistance: 1200000)

Answer 9

MKMapView 内部有一个MKScrollView（私有API），它是UIScrollView 的子类。这个MKScrollView 的代表是它自己的mapView。

所以，为了控制最大缩放，请执行以下操作：

创建MKMapView的子类：

MapView.h

#import <UIKit/UIKit.h>
#import <MapKit/MapKit.h>

@interface MapView : MKMapView <UIScrollViewDelegate>

@end

地图视图.m

#import "MapView.h"

@implementation MapView

-(void)scrollViewDidZoom:(UIScrollView *)scrollView {

    UIScrollView * scroll = [[[[self subviews] objectAtIndex:0] subviews] objectAtIndex:0];

    if (scroll.zoomScale > 0.09) {
        [scroll setZoomScale:0.09 animated:NO];
    }

}

@end

然后，访问滚动子视图并查看zoomScale 属性。当缩放大于数字时，设置最大缩放。

Answer 10

Raphael Petegrosso 发布的带有扩展 MKMapView 的帖子在进行一些小的修改后效果很好。 下面的版本也更加“用户友好”，因为一旦用户松开屏幕，它就会优雅地“捕捉”回定义的缩放级别，感觉类似于 Apple 自己的弹性滚动。

编辑：这个解决方案不是最优的，会破坏/损坏地图视图，我在这里找到了一个更好的解决方案：How to detect any tap inside an MKMapView。这使您可以拦截捏合和其他动作。

---

MyMapView.h

#import <MapKit/MapKit.h>


@interface MyMapView : MKMapView <UIScrollViewDelegate>
@end

MyMapView.m

#import "MyMapView.h"

@implementation MyMapView

- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale
{
    if (scale > 0.001)
    {
        [scrollView setZoomScale:0.001 animated:YES];
    }
}
@end

对于硬限制，请使用：

#import "MyMapView.h"

@implementation MyMapView

-(void)scrollViewDidZoom:(UIScrollView *)scrollView
{
    if (scrollView.zoomScale > 0.001)
    {
        [scrollView setZoomScale:0.001 animated:NO];
    }

}

@end

Answer 11

以下代码对我有用，并且在概念上易于使用，因为它根据以米为单位的距离设置区域。 代码来源于@nevan-king 发布的答案和@Awais-Fayyaz 发布的使用 regionDidChangeAnimated 的评论

将以下扩展添加到您的 MapViewDelegate

var currentLocation: CLLocationCoordinate2D?

extension MyMapViewController: MKMapViewDelegate {
    func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool) {
        if self.currentLocation != nil, mapView.region.longitudinalMeters > 1000 {
            let initialLocation = CLLocation(latitude: (self.currentLocation?.latitude)!,
                                         longitude: (self.currentLocation?.longitude)!)
            let coordinateRegion = MKCoordinateRegionMakeWithDistance(initialLocation.coordinate,
                                                                  regionRadius, regionRadius)
            mapView.setRegion(coordinateRegion, animated: true)
        }
    }
}

然后为 MKCoordinateRegion 定义一个扩展，如下所示。

extension MKCoordinateRegion {
    /// middle of the south edge
    var south: CLLocation {
        return CLLocation(latitude: center.latitude - span.latitudeDelta / 2, longitude: center.longitude)
    }
    /// middle of the north edge
    var north: CLLocation {
        return CLLocation(latitude: center.latitude + span.latitudeDelta / 2, longitude: center.longitude)
    }
    /// middle of the east edge
    var east: CLLocation {
        return CLLocation(latitude: center.latitude, longitude: center.longitude + span.longitudeDelta / 2)
    }
    /// middle of the west edge
    var west: CLLocation {
        return CLLocation(latitude: center.latitude, longitude: center.longitude - span.longitudeDelta / 2)
    }
    /// distance between south and north in meters. Reverse function for MKCoordinateRegionMakeWithDistance
    var latitudinalMeters: CLLocationDistance {
        return south.distance(from: north)
    }
    /// distance between east and west in meters. Reverse function for MKCoordinateRegionMakeWithDistance
    var longitudinalMeters: CLLocationDistance {
        return east.distance(from: west)
    }
}

上面的 MKCoordinateRegion 的 sn-p 是由@Gerd-Castan 在这个问题上发布的：

Reverse function of MKCoordinateRegionMakeWithDistance?

Answer 12

我在工作中遇到了这个问题，并且在没有设置全局限制的情况下创建了一些运行良好的东西。

我利用的 MapView 代表是： - mapViewDidFinishRendering - mapViewRegionDidChange

我的解决方案背后的前提是，由于卫星视图呈现一个没有数据的区域，所以它始终是同一件事。这个可怕的图像 (http://imgur.com/cm4ou5g) 如果我们可以放心地依赖该失败案例，我们可以将其用作确定用户所看到内容的关键。地图渲染后，我截取渲染的地图边界并确定平均 RGB 值。根据该 RGB 值，我假设相关区域没有数据。如果是这种情况，我会将地图弹出回正确渲染的最后一个跨度。

我唯一的全局检查是当它开始检查地图时，您可以根据需要增加或减少该设置。下面是完成此操作的原始代码，并将组合一个示例项目以供贡献。您可以提供的任何优化将不胜感激，希望对您有所帮助。

@property (assign, nonatomic) BOOL isMaxed;
@property (assign, nonatomic) MKCoordinateSpan lastDelta;

self.lastDelta = MKCoordinateSpanMake(0.006, 0.006);

- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated {
    if (mapView.mapType != MKMapTypeStandard && self.isMaxed) {
            [self checkRegionWithDelta:self.lastDelta.longitudeDelta];
    }
}


- (void)checkRegionWithDelta:(float)delta {
    if (self.mapView.region.span.longitudeDelta < delta) {
        MKCoordinateRegion region = self.mapView.region;
        region.span = self.lastDelta;
        [self.mapView setRegion:region animated:NO];
    } else if (self.mapView.region.span.longitudeDelta > delta) {
        self.isMaxed = NO;
    }
}


- (void)mapViewDidFinishRenderingMap:(MKMapView *)mapView fullyRendered:(BOOL)fullyRendered {
    if (mapView.mapType != MKMapTypeStandard && !self.isMaxed) {
        [self checkToProcess:self.lastDelta.longitudeDelta];
    }
}


- (void)checkToProcess:(float)delta {
    if (self.mapView.region.span.longitudeDelta < delta) {
        UIGraphicsBeginImageContext(self.mapView.bounds.size);
        [self.mapView.layer renderInContext:UIGraphicsGetCurrentContext()];
        UIImage *mapImage = UIGraphicsGetImageFromCurrentImageContext();
        [self processImage:mapImage];
    }
}


- (void)processImage:(UIImage *)image {
    self.mapColor = [self averageColor:image];
    const CGFloat* colors = CGColorGetComponents( self.mapColor.CGColor );
    [self handleColorCorrection:colors[0]];
}


- (void)handleColorCorrection:(float)redColor {
    if (redColor < 0.29) {
        self.isMaxed = YES;
        [self.mapView setRegion:MKCoordinateRegionMake(self.mapView.centerCoordinate, self.lastDelta) animated:YES];
    } else {
        self.lastDelta = self.mapView.region.span;
    }
}


- (UIColor *)averageColor:(UIImage *)image {
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    unsigned char rgba[4];
    CGContextRef context = CGBitmapContextCreate(rgba, 1, 1, 8, 4, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);

    CGContextDrawImage(context, CGRectMake(0, 0, 1, 1), image.CGImage);
    CGColorSpaceRelease(colorSpace);
    CGContextRelease(context);

    if(rgba[3] > 0) {
        CGFloat alpha = ((CGFloat)rgba[3])/255.0;
        CGFloat multiplier = alpha/255.0;
        return [UIColor colorWithRed:((CGFloat)rgba[0])*multiplier
                               green:((CGFloat)rgba[1])*multiplier
                                blue:((CGFloat)rgba[2])*multiplier
                               alpha:alpha];
    }
    else {
        return [UIColor colorWithRed:((CGFloat)rgba[0])/255.0
                               green:((CGFloat)rgba[1])/255.0
                                blue:((CGFloat)rgba[2])/255.0
                               alpha:((CGFloat)rgba[3])/255.0];
    }
}