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

 

[Erel]

Can you post your code? Is your time zone set correctly?

 

[GaNdAlF89]

How I can set my time zone?

In my code, I've modified only with

DateTime.DateFormat = "dd/MM/yyyy"
today=DateTime.Date(GPS_Timestamp)
...

 

[Erel]

DateTime.Date adds the system time zone. If the device time zone is wrong then the date string might also be wrong. You can set it to 0 by calling DateTime.SetTimeZone.

 

[GaNdAlF89]

ok..thanks for all!

 

[mjtaryan]

I think this is quite useful. However, for my current purposes I'm wondering if there is a way to read the current device location from the system? If so, how? Thanks.

 

[Erel]

You can use ABWifi library to get the last known location.

 

[GaNdAlF89]

Sub Service_Create
    DateTime.SetTimeZone(1)
End Sub


Sub MyGPS_LocationChanged (MyLocation As Location)

   TimestampGPS = MyLocation.Time
   
   DateGPS= DateTime.Date(TimestampGPS)
   TimeGPS= DateTime.Time(TimestampGPS)
End Sub

Timezone of device is set to +1. I receive the date of tomorrow, and the time of an hour ago. Please help me!

 

[Erel]

It seems like a problem in your device.

I tested the following code on multiple devices and it works as expected:

Sub Process_Globals
   Dim g As GPS
End Sub

Sub Globals

End Sub
Sub Activity_Create(FirstTime As Boolean)
   If FirstTime Then
      g.Initialize("g")
      g.Start(0, 0)
   End If
End Sub
Sub G_LocationChanged (Location1 As Location)
   ToastMessageShow(DateTime.Date(Location1.Time), True)
End Sub

 

[GaNdAlF89]

What can I do to resolve this problem?

 

[Erel]

Which device are you using (type and OS version)?

 

[GaNdAlF89]

my device is:

Samsung Galaxy Tab 7.0 Plus - Android 3.2 Honeycomb

 

[Erel]

Not sure if and how it can be resolved.

 

[phast]

I am very new to this, so sorry if this is completely wrong. I am trying to find the distance between a set lat and lon against where I am currently located. My current code is:

Sub GPS_LocationChanged (Location1 As Location)
   lblLat.Text = "Lat = " & Location1.ConvertToMinutes(Location1.Latitude)
   lblLon.Text = "Lon = " & Location1.ConvertToMinutes(Location1.Longitude)
   Location2.Latitude="40.4406"
   Location2.Longitude="79.9961"
   lblDist.Text = Location1.DistanceTo(Location2)
   'lblSpeed.Text = "Speed = " & Location1.Speed
End Sub

I have dim Location2 as Location

When I start the app it says "invalid double"




EDIT::

Sorry, I solved my own issue by removing the "" which I now assume makes the value a string?

 

[michelg]

You can't enable or disable the GPS device. However if it is enabled it will turn on when it needed and off when it is not needed (to save battery).

Hi,

I was trying to run the GPS app in the emulator. when I run the app,
on the emulator's screen this is what I see:
Lat:
Lon:
Speed:
and a quick message saying
GPS device enable=True

However I do not see any location information.

what should I do to see the location information?

 

[Erel]

You should test it on a real device.

 

[GaNdAlF89]

@Erel

I have reset my device, I set the timezone in settings to +1 (I'm italian).

In Main Activity:

Sub Activity_Create
    DateTime.SetTimeZone(1)
    DateTime.DateFormat = "dd/MM/yyyy" 'I prefer this format
End Sub

In GPS_Service

Sub MyGPS_LocationChanged (MyLocation As Location)
   GlobalModule.Latitudine = MyLocation.Latitude
   GlobalModule.Longitudine = MyLocation.Longitude   
   GlobalModule.Velocita = MyLocation.Speed*3.6 'I convert to km/h
   GlobalModule.TimestampGPS = MyLocation.Time

   'now I convert timestampGPS in date and time
   GlobalModule.DateGPS = DateTime.Date(GlobalModule.TimestampGPS)
   GlobalModule.TimeGPS = DateTime.Time(GlobalModule.TimestampGPS)
End Sub

I receive the date of tomorrow, and the time of an hour ago...I don't understand what's the problem!
Please help me

 

[Erel]

I'm sorry but it seems to be a problem in your device. Maybe updating the OS will fix it.

 

[GaNdAlF89]

I tried to convert the gps timestamp with an online converter, and I obtain the same result of my app...why??

 

[Erel]

Because your device returns the wrong result.

 

[michelg]

The GPS is an important feature of many Android devices.
Fortunately it is pretty easy to work with it.

Hi,

when I run the GPS program in the emulator this is what I see:


Lat:
Lon:
Speed:
Satellites:

I do not see any information:

I used b4a bridge to run it in my phone and the result is the same.

Can you please give me an idea of what could be wrong.

Thank you,