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Create A Region

Creating regions is designed to be easy for the user and you (the developer).

The Example Application contains a great way you might want to allow your users to choose a region to download, and it shows how to use Provider to share a created region and the number of approximate tiles it has to a download screen.

Types Of Region

All regions (before conversion to DownloadableRegion) implement BaseRegion.

The most basic type of region, defined by two North West and South East coordinates that create a LatLngBounds.

final region = RectangleRegion(
    LatLngBounds(
        LatLng(), // North West
        LatLng(), // South East
    ),
);

Skewed parallelograms (rectangles with a 3rd control point) or rotated rectangles are not currently supported

A more advanced type of region, defined by a center coordinate and radius (in kilometers).

final region = CircleRegion(
    LatLng(), // Center
    0, // KM Radius
);

If you have two coordinates, one center, and one on the edge of the circle you want, you can use 'latlong2's Distance.distance() method, as below:

final region = CircleRegion(
    LatLng(), // Center
    const Distance(roundResult: false).distance(
        LatLng(), // Center
        LatLng(), // Edge Coord
    ) / 1000; // Convert to KM
);

The most advanced type of region, defined by a list of coordinates and radius (in meters).

final region = LineRegion(
    [LatLng(), LatLng(), ...], // Series of coordinates
    0, // M Radius
);

After you've created your region, you can convert it to a drawable polygon (below), or convert it to a DownloadableRegion ready for downloading.

Converting To Drawable Polygons

All BaseRegions can be drawn on a map with minimal effort from you or the user, using toDrawable().

Internally, this uses the toOutline(s) method to generate the points forming the Polygon, then it places this/these polygons into a PolygonLayer.