iphone - 如何使用注释降低 MKMapview 的缩放级别？

Question

我在 map View 中只有一个注释。

我正在使用以下代码缩放到该注释图钉

- (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(id<MKAnnotation> 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) * 0.1;

    region.span.longitudeDelta = fabs(bottomRightCoord.longitude - topLeftCoord.longitude) * 0.1;

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

但它缩放到极致，我需要降低缩放级别，以便用户可以看到注释周围的一些区域。

我尝试更改 region.span 的值，但无法得到解决方案。

如有任何建议，我们将不胜感激。

Answer 1

你确定这段代码:

region.span.latitudeDelta = fabs(topLeftCoord.latitude - bottomRightCoord.latitude) * 0.1;

region.span.longitudeDelta = fabs(bottomRightCoord.longitude - topLeftCoord.longitude) * 0.1;

不返回纬度/经度 = 0 吗？尝试将跨度硬编码为 0.05 或接近的值。

下面的代码将使您的 map 以您当前的位置为中心，您可以将 locationManager.coordinates 更改为您的 annotation.coordinates。

CLLocationManager *locationManager = [[CLLocationManager alloc] init];
locationManager.distanceFilter = kCLDistanceFilterNone; 
locationManager.desiredAccuracy = kCLLocationAccuracyBest;
[locationManager startUpdatingLocation];

MKCoordinateSpan span;
MKCoordinateRegion region;
span.latitudeDelta = 0.05;
span.longitudeDelta = 0.05;    
location.latitude = locationManager.location.coordinate.latitude;
location.longitude = locationManager.location.coordinate.longitude;
NSLog(@"%f",location.latitude);
region.span = span;
region.center = location;

[_mapVIew setRegion:region animated:YES];