Android Tutorial GPS / GNSS tutorial

The GNSS library replaces the old GPS library. The GNSS library is available here: https://www.b4x.com/android/forum/threads/gnss-library-an-updated-gps-library.109110/#content

Using it is quite simple:
1. Checking whether location services are available. If not take the user to the settings.
2. Request permission.

If the purpose is to get the user location then the FusedLocationProvider might be a better option: https://www.b4x.com/android/forum/threads/fusedlocationprovider-resolution-dialog.111652/#content

 

[gregmatthews]

ok, thanks

 

[rleiman]

Hi Everyone,

This is a nice library but I'm having some trouble figuring out how to work it. In my main activity I used this coding in Activity_Create.

    If Starter.GPS1.GPSEnabled = False Then
        ToastMessageShow("Please enable the GPS device.", True)
        StartActivity(Starter.GPS1.LocationSettingsIntent) 'Will open the relevant settings screen.
    Else
        Starter.rp.CheckAndRequest(Starter.rp.PERMISSION_ACCESS_FINE_LOCATION)
    End If

This code starts up the GPS.

In the starter I use this coding in GPS_LocationChanged.

Sub GPS_LocationChanged (Location1 As Location)
    CallSub2(Main, "LocationChanged", Location1)
End Sub

When I start my app for the first time the GPS turns on and GPS_LocationChanged inside the starter executes as expected calling "LocationChanged" in the Main activity. That in turn calls another subroutine in the Main activity which eventually calls StopGps.

After the GPS is turned off there is a call to StartGps in another part of the app and the GPS starts up. I was expecting GPS_LocationChanged to be called just like it did when I started up the app for the first time but that event never executes. I'm assuming I'm missing a step here.

Can you tell me the additional coding I need so GPS_LocationChanged can execute after the GPS is started?

Thanks.

 

[DonManfred]

You should always start a new thread for your questions.

 

[rleiman]

Hi Don,

Ok. Doing it now.

 

[Erel]

Example was updated:
1. The Activity_PermissionResult is handled with Wait For which is simpler.

2. The call to StartGPS and StopGPS is done with CallSubDelayed instead of CallSub. This is useful as there could be cases where the starter service is destroyed while the app is in the background. With CallSubDelayed the starter service will be restarted if needed.

 

[Johan Hormaza]

        If servicio.GPS.GPSEnabled = False Then
            ToastMessageShow("Por favor hailita el dispositivo GPS" & CRLF & "Y presiona el botón regresar", True)
            StartActivity(servicio.GPS.LocationSettingsIntent)
        Else
            servicio.Permisos.CheckAndRequest(servicio.Permisos.PERMISSION_ACCESS_FINE_LOCATION)
            Wait For Activity_PermissionResult (Permission As String, Result As Boolean)
            If Result Then CallSubDelayed(servicio,"StartGPS")
        End If

I do not understand why I get this error, the only thing I did was to place the previous code on a button in which a Service is started

 

[Erel]

Unless you can reproduce this error with the example attached to the first post then it is better to start a new thread for this.

 

[Colin Evans]

Hi Erel could you explain when I run this example i a list which state they are all False and no Lat or Long returned, I don't get any errors regarding GPS being on or not and my apps that use GPS seem to all be working okay

 

[Erel]

This means that the device is unable to find enough satellites or the reception is too weak. Are you testing it outside?

 

[Colin Evans]

Yes, initially I was inside but have tried outside with the same results, all False

 

[Erel]

It might be a hardware problem. Try to restart the device. The other apps probably don't use the GPS but rather a solution based on FusedLocationProvider.

I assume that you allowed the app to access location information.

For further discussion please start a new thread.

 

[Erel]

Example updated. Based on B4XPages and GNSS library.