GPSGetPosition (Function)

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Managing locks
Retrieved properties
Operating mode in iPhone/iPad
Required permissions
Required application feature
Browsers allowing the geolocation

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GPSGetPosition (Function)

In french: GPSRécupèrePosition

Retrieves information about the current device position.

GPSGetPosition must be executed in a thread.

Example

MyLocation is géoPosition
MyLocation = GPSGetPosition()
// Checks the position validity with ErrorOccurred
IF ErrorOccurred THEN RETURN
Info(" Latitude : " + MyLocation.Latitude)
Info(" Longitude : " + MyLocation.Longitude)

// Geolocation from WEBDEV, a browser procedure is called.
// Process performed from a button whose action is "none"
GPSGetPosition(BrowserProc, 200)

// "BrowserProc" browser procedure
PROCÉDURE BrowserProc(MyLocation is géoPosition, nMyError is int)

SWITCH nMyError

CASE gpsErrorOK
// No error was detected
PAGE_Page1.EDT_NoName1 = MyLocation.Altitude + " " + ...
MyLocation.Longitude
CASE gpsErrorRights
PAGE_Page1.EDT_NoName1 = ...
"The browser has no sufficient rights " + ...
"to use the geolocation (or non-HTTPS site)."
CASE gpsErrorPosition
PAGE_Page1.EDT_NoName1 = "Unable to define the position " + ...
"(internal error of provider for example)."
CASE gpsErrorTimeout
PAGE_Page1.EDT_NoName1 = ...
"The position was not retrieved " + ...
" within the alloted time."
OTHER CASE
PAGE_Page1.EDT_NoName1 = "Undefined error"
END

Syntax

Retrieving information about a device (mobile, ...) Hide the details

<Result> = GPSGetPosition([<Timeout> [, <Message>]])

<Result>: geoPosition variable

geoPosition variable containing information about the device position. If the position is invalid, the ErrorOccurred variable is set to True and the error details are returned by ErrorInfo.
The PositionValid property of the geoPosition type determines if the position is valid.

<Timeout>: Optional integer or optional Duration

Maximum timeout (in hundredths of a second) for updating the device position.
An error occurs if the timeout ends before the position of the device is updated. This error can be detected by the ErrorOccurred variable and the error details can be returned by ErrorInfo.
If this parameter is not specified, the timeout is set to 1 minute.
Remark: 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).

<Message>: Optional character string

Message of hourglass displayed when updating the position.
Remark: This parameter is taken into account only if the call is performed in the main application thread.
This parameter is ignored.

Retrieving the information in browser code Hide the details

GPSGetPosition([<WLanguage procedure> [, <Timeout>]])

<WLanguage procedure>: Procedure name

Name of the WLanguage procedure in browser code ("callback") called when the location is retrieved.
This procedure has the following format:
PROCEDURE <Procedure name>(<Position>,<Error>)
where:
<Position> is a geoPosition variable containing the information about the position. 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.
<Error> is an Integer constant corresponding to the error code and that can take the following values:
gpsErrorOK No error was detected.
gpsErrorPosition Unable to determine the location (e.g., access provider internal error).
gpsErrorRights
The browser has no sufficient rights to use geolocation.
The browser is recent and the site is not using the HTTPS secure protocol.
gpsErrorTimeout The location could not be retrieved within the timeout.

<Timeout>: Optional integer or optional Duration

Maximum timeout (in hundredths of a second) for updating the device position.
If this timeout ends before the device position is updated, gpsErrorTimeOut is returned in the <Error> parameter of the WLanguage procedure.
If this parameter is not specified, the timeout is set to 1 minute.
Remark: 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).

Remarks

Managing locks

GPSGetPosition blocks execution until the current device location is retrieved or until the timeout defined by the <Timeout> parameter expires.

If the function is called in the main thread of the application, an hourglass will be displayed during the function execution. The message displayed by the hourglass can be specified via the <Message> parameter.
Otherwise, the execution of secondary thread will be locked during the function execution and no hourglass will be displayed.

This function is not locking.

Remark: To find out the last known device position without timeout, use GPSLastPosition. Caution, the positioning information that was retrieved may not correspond to the current device position if the device was moved while the GPS signal was not valid for example. You can use the MeasurementDate property of the geoPosition variable to determine the date and time at which the position was calculated.

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 that was retrieved corresponds to the last known device location: therefore, they may not correspond to the current device location if the device was moved while the GPS signal was not valid for example. 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.

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

The call to this function modifies the permissions required by the application.
Required permission: 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.Granted THEN
// Functions that require background location access can be used
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.

Required application feature

When this function is used, an application feature is declared in the application generation wizard.

Required feature: Geolocation

This feature allows the applications to access the geolocation features found on the device or on the computer.

Browsers allowing the geolocation

Caution: Geolocation is only available on certain modern browsers:

FireFox from version 3.5,
Chrome from version 5.0.342.1,
Opera from version 10.6,
Safari from version 5.0.

During the call to a geolocation function, the browser requests a location authorization.Remark: From Chrome 50 (including on Android), GPSGetPosition can only be used on the sites secured via an SSL certificate for example. If the site is not secured, the function returns a result that cannot be used. During the test in local (localhost), the function operates properly.

Business / UI classification: Business Logic

Component: wd300java.dll