如何找到可见MKMapView可见屏幕区域的半径? [英] How to find the radius of visible MKMapView visible screen area?

问题描述

我想知道iPhone屏幕上可见区域的半径，因为我会缩小并放大可见区域，所以我想知道那个特定区域的半径，我该怎么办?

I want to know the radius of visible area in iphone screen, as I will zoomout and zoom in the visible area will change, so I want to know the radius of that particular area, how can I do it?

推荐答案

不是半径.

您需要使用mapView中的region参数.

You need to use the region parameter from mapView.

查看Apple文档，从中可以很清楚地了解到.

Check out apple docs, it is pretty much clear from those.

通读本教程.它将为您带来很大帮助

Go thru this tutorial. It will help you a lot

icode博客mapkit演示

具体来说，您需要设置类似以下内容.

specifically you need to set something like this..

MKCoordinateSpan span = [self coordinateSpanWithMapView:self centerCoordinate:centerCoordinate andZoomLevel:zoomLevel];
MKCoordinateRegion region = MKCoordinateRegionMake(centerCoordinate, span);
[self setRegion:region animated:animated];

可以将跨度计算为

- (MKCoordinateSpan)coordinateSpanWithMapView:(MKMapView *)mapView
                         centerCoordinate:(CLLocationCoordinate2D)centerCoordinate
                             andZoomLevel:(NSUInteger)zoomLevel
{
// convert center coordiate to pixel space
double centerPixelX = [self longitudeToPixelSpaceX:centerCoordinate.longitude];
double centerPixelY = [self latitudeToPixelSpaceY:centerCoordinate.latitude];

// determine the scale value from the zoom level
NSInteger zoomExponent = 20 - zoomLevel;
double zoomScale = pow(2, zoomExponent);

// scale the map’s size in pixel space
CGSize mapSizeInPixels = mapView.bounds.size;
double scaledMapWidth = mapSizeInPixels.width * zoomScale;
double scaledMapHeight = mapSizeInPixels.height * zoomScale;

// figure out the position of the top-left pixel
double topLeftPixelX = centerPixelX - (scaledMapWidth / 2);
double topLeftPixelY = centerPixelY - (scaledMapHeight / 2);

// find delta between left and right longitudes
CLLocationDegrees minLng = [self pixelSpaceXToLongitude:topLeftPixelX];
CLLocationDegrees maxLng = [self pixelSpaceXToLongitude:topLeftPixelX + scaledMapWidth];
CLLocationDegrees longitudeDelta = maxLng - minLng;

// find delta between top and bottom latitudes
CLLocationDegrees minLat = [self pixelSpaceYToLatitude:topLeftPixelY];
CLLocationDegrees maxLat = [self pixelSpaceYToLatitude:topLeftPixelY + scaledMapHeight];
CLLocationDegrees latitudeDelta = -1 * (maxLat - minLat);

// create and return the lat/lng span
MKCoordinateSpan span = MKCoordinateSpanMake(latitudeDelta, longitudeDelta);
return span;
}

干杯:)

这篇关于如何找到可见MKMapView可见屏幕区域的半径?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！