GPSFollowMovement (Function)

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Help / WLanguage / WLanguage functions / Standard functions / Geolocation functions

Retrieved properties
Notes
Operating mode in iPhone/iPad
Required permissions
Android 12 specific case

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GPSFollowMovement (Function)

In french: GPSSuitDéplacement

Requests to be notified periodically of the device's current location.

Example

// Branche une procédure pour recevoir régulièrement la position du périphérique
GPSFollowMovement(ProcDeplacement)

// Procédure
PROCEDURE ProcDeplacement(pos is geoPosition)

Info(" Latitude : " + pos.Latitude)  
Info(" Longitude : " + pos.Longitude)

Syntax

Enabling the notification mechanism (in a mobile) Hide the details

GPSFollowMovement(<WLanguage procedure> [, <Timeout> [, <Distance>]])

<WLanguage procedure>: Procedure name

Name of WLanguage procedure called at each notification.
This procedure has the following format:
PROCEDURE <Procedure name>(<Location>)
<Location> is a variable of type geoPosition that contains information about the device's location at the time of the notification.

<Timeout>: Optional integer or optional Duration

Minimum timeout (in hundredths of a second) between two notifications. If this parameter is not specified, the minimum timeout will be set to 60 seconds.
Note: This parameter can correspond to:
an integer corresponding to the number of hundredths of a second,
a Duration variable,
the duration in a readable format (e.g., 1 s or 10 ms).

<Distance>: Optional real

Minimum distance (in meters) between two notifications.
If this parameter is not specified, the minimum distance will be set to 5 meters.

Disabling the notification mechanism

GPSFollowMovement()

Remarks

Retrieved properties

To determine if a value was assigned to the Speed, Accuracy, Direction or Altitude properties of a geoPosition variable when the location was retrieved, use the SpeedValid, AccuracyValid, DirectionValid and AltitudeValid properties.
To reinitialize a geoPosition variable, use VariableReset.
It is recommended to reset the parameters of the location provider with GPSInitParameter before retrieving a location.
The positioning information retrieved corresponds to the device's last known position: it may therefore not correspond to the device's current position if, for example, the device has been moved while the GPS signal was invalid. You can use the MeasurementDate property of the geoPosition variable to determine the date and time at which the position was calculated.
Speed, Accuracy, Direction and Altitude will be specified only if the location provider allows it (otherwise, these properties will take their default value).
The location provider can be configured with GPSInitParameter.

Notes

Geolocation functions can consume a lot of resources on the device (battery, bandwidth, etc.). Therefore, we advise you not de define very small values for the minimum timeout and for the minimum distance between two notifications.
You can enable location tracking in the background without consuming resources via geoTrackingEnable, geoTrackingDisable, geoTrackingStatus and geoTrackingProcedure. For more details, see Location tracking.
When generating the application, you can allow GPSFollowMovement to be called when the application is in the background (option "Allow calling GPSFollowMovement and BeaconDetectPrecise when the application is in the background" in the "Configuration" step of the wizard).. In this case, the geolocation will continue when the application runs in the background or when the device is in standby mode. For more details, see Generating an iOS application.
To stop receiving notifications, call GPSFollowMovement without parameter or call GPSEnd.

Operating mode in iPhone/iPad

When a GPS function is first run, the system requests geolocation permission from the user. If the user refuses, all the GPS functions used in the rest of the application will fail (fatal error).

To re-allow the use of GPS for this application, the system configuration of the application must be modified.

Required permissions

This function changes the permissions required by the application.
Permission required: ACCESS_FINE_LOCATION.

Android 11 specific case: This function requires the ACCESS_BACKGROUND_LOCATION permission to access the device's location.
This permission allows using the function when the application is in the background.

If the application needs to use background location:

Manually add the "ACCESS_BACKGROUND_LOCATION" permission in the Android application generation wizard.

Explicitly request background location permission with PermissionRequest. For example:

PermissionRequest(permBackgroundLocation, Callback)
INTERNAL PROCEDURE Callback(p is Permission)
	IF p.Accordé THEN
		// Utilisation possible des fonctions nécessitant la localisation en arrière-plan
	END
END

A window allows users to:

allow access to the device location while the application is in the background,
allow access to the location only while the application is in use,
deny access to the location. The user can also change these permissions at any time in the Android settings.

Remarks:

Follow Google's guidelines for applications that require background location access. For more details, see https://support.google.com/googleplay/android-developer/answer/9799150. If these conditions are not met (especially user information requirements), applications may not be accepted for publication on Google Play.
The background location permission should only be requested if the location permission has been granted. Otherwise, PermissionRequest will fail.
If the option chosen by the user for the background location access request is more restrictive than the option chosen for the location access request, the application will be automatically restarted.
On devices running Android 10 or earlier, if location permission has been granted to the application, the background location permission will be granted without displaying a window.

Android 12 specific case

To execute the procedure called by GPSFollowMovement when the application is in the background, it is necessary to run a persistent thread (ThreadPersistent).

Related Examples:

Android (WINDEV Mobile): Android GPS

[ + ] This example presents the use of the GPS functions of WLanguage in an Android application.
It is used to retrieve at regular interval:
- The latitude
- The longitude
- The altitude
- The speed
- The direction

Cross-platform examples (WINDEV Mobile): WM Sports

[ + ] This example is a sport application used to save your performances.
The application calculates the distance, the time, the average speed and the number of calories spent according to the sport.
The run is displayed on a map control via markers and an itinerary.

The example also includes a server part used to synchronize the user data.
This webservice is available in the WEBDEV "WW_Sports" example.

Component: wd300java.dll