确定地图视图的当前缩放比例

Question

如何计算 MKMapView 的当前缩放比例？

Answer 1

使用以下代码：

#define MERCATOR_RADIUS 85445659.44705395
#define MAX_GOOGLE_LEVELS 20

- (double)getZoomLevel {
    CLLocationDegrees longitudeDelta = self.mapView.region.span.longitudeDelta;
    CGFloat mapWidthInPixels = self.mapView.bounds.size.width;
    double zoomScale = longitudeDelta * MERCATOR_RADIUS * M_PI / (180.0 * mapWidthInPixels);
    double zoomer = MAX_GOOGLE_LEVELS - log2( zoomScale );
    if ( zoomer < 0 ) zoomer = 0;
    //  zoomer = round(zoomer);
    return zoomer;
}

getZoomLevel 方法的返回值将是 mapView 属性的当前缩放级别。