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Implement getVisibleRegion() with MKMapView.region #24

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Implement getVisibleRegion() with MKMapView.region #24

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28 changes: 7 additions & 21 deletions ios/Classes/MapView/MapViewExtension.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -228,32 +228,18 @@ public extension MKMapView {

func getVisibleRegion() -> Dictionary<String, Array<Double>> {
if self.bounds.size != CGSize.zero {
// convert center coordiate to pixel space
let centerPixelX = self.longitudeToPixelSpaceX(longitude: self.centerCoordinate.longitude)
let centerPixelY = self.latitudeToPixelSpaceY(latitude: self.centerCoordinate.latitude)

// determine the scale value from the zoom level
let zoomExponent = Double(21 - Holder._zoomLevel)
let zoomScale = pow(2.0, zoomExponent)

// 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);
let center = self.region.center
let span = self.region.span

// find the southwest coordinate
let minLng = self.pixelSpaceXToLongitude(pixelX: topLeftPixelX)
let minLat = self.pixelSpaceYToLatitude(pixelY: topLeftPixelY)
let minLng = center.longitude - span.longitudeDelta/2
let minLat = center.latitude - span.latitudeDelta/2

// find the northeast coordinate
let maxLng = self.pixelSpaceXToLongitude(pixelX: topLeftPixelX + scaledMapWidth)
let maxLat = self.pixelSpaceYToLatitude(pixelY: topLeftPixelY + scaledMapHeight)
let maxLng = center.longitude + span.longitudeDelta/2
let maxLat = center.latitude + span.latitudeDelta/2

return ["northeast": [minLat, maxLng], "southwest": [maxLat, minLng]]
return ["northeast": [maxLat, maxLng], "southwest": [minLat, minLng]]
}
return ["northeast": [0.0, 0.0], "southwest": [0.0, 0.0]]
}
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