harmony(鸿蒙)Geocoding and Reverse Geocoding Capabilities

2022-08-09
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Geocoding and Reverse Geocoding Capabilities

When to Use

Describing a location using coordinates is accurate, but neither intuitive nor user-friendly. With the geocoding and reverse geocoding capabilities, you will be able to convert geographic description into specific coordinates and vice versa.

The geographic description helps users understand a location easily by providing several key attributes, for example, country, administrative region, street, house number, and address.

Available APIs

The following table describes APIs available for mutual conversion between coordinates and location information.

Table1 APIs for geocoding and reverse geocoding

API	Description
isGeoServiceAvailable(callback: AsyncCallback<boolean>) : void	Checks whether the (reverse) geocoding service is available. This function uses an asynchronous callback to return the result.
isGeoServiceAvailable() : Promise<boolean>	Checks whether the (reverse) geocoding service is available. This function uses a promise to return the result.
getAddressesFromLocation(request: ReverseGeoCodeRequest, callback: AsyncCallback<Array<GeoAddress>>) : void	Converts coordinates into geographic description through reverse geocoding. This function uses an asynchronous callback to return the result.
getAddressesFromLocation(request: ReverseGeoCodeRequest) : Promise<Array<GeoAddress>>;	Converts coordinates into geographic description through reverse geocoding. This function uses a promise to return the result.
getAddressesFromLocationName(request: GeoCodeRequest, callback: AsyncCallback<Array<GeoAddress>>) : void	Converts geographic description into coordinates through geocoding. This function uses an asynchronous callback to return the result.
getAddressesFromLocationName(request: GeoCodeRequest) : Promise<Array<GeoAddress>>	Converts geographic description into coordinates through geocoding. This function uses a promise to return the result.

How to Develop

NOTE

The GeoConvert instance needs to access backend services to obtain information. Therefore, before performing the following steps, ensure that your device is connected to the network.

Import the geolocation module by which you can implement all APIs related to the geocoding and reverse geocoding conversion capabilities.

   import geolocation from '@ohos.geolocation';

Query whether geocoder service is available.
- Call isGeoServiceAvailable to query whether the geocoder service is available. If the service is available, continue with step 3. geolocation.isGeoServiceAvailable((err, data) => { if (err) { console.log('isGeoServiceAvailable err: ' + JSON.stringify(err)); } else { console.log('isGeoServiceAvailable data: ' + JSON.stringify(data)); } });

Obtain the conversion result.

Call getAddressesFromLocation to convert coordinates into geographical location information.

  var reverseGeocodeRequest = {"latitude": 31.12, "longitude": 121.11, "maxItems": 1};
  geolocation.getAddressesFromLocation(reverseGeocodeRequest, (err, data) => {
      if (err) {
          console.log('getAddressesFromLocation err: ' + JSON.stringify(err));
      } else {
          console.log('getAddressesFromLocation data: ' + JSON.stringify(data));
      }
  });

Your application can obtain the GeoAddress list that matches the specified coordinates and then read location information from it. For details, see Geolocation. - Call getAddressesFromLocationName to convert geographic description into coordinates.

  var geocodeRequest = {"description": "No. xx, xx Road, Pudong District, Shanghai", "maxItems": 1};
  geolocation.getAddressesFromLocationName(geocodeRequest, (err, data) => {
      if (err) {
          console.log('getAddressesFromLocationName err: ' + JSON.stringify(err));
      } else {
          console.log('getAddressesFromLocationName data: ' + JSON.stringify(data));
      }
  });

Your application can obtain the GeoAddress list that matches the specified location information and read coordinates from it. For details, see Geolocation.

To improve the accuracy of location results, you can set the longitude and latitude ranges in GeoCodeRequest.