決定mapview的當前縮放比例

Question

如何計算MKMapView的當前縮放比例？

Answer 1

使用下面的代碼：

#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; 
} 

的getZoomLevel方法的返回值將是mapView屬性的當前縮放級別。