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]

It is not strange. Google Maps uses several sources to find the location. It can take the GPS several minutes to find the location.

It is not related to wifi.

 

[achtrade]

It is not strange. Google Maps uses several sources to find the location. It can take the GPS several minutes to find the location.

It is not related to wifi.

I just found out that the GPS_LocationChanged sub isn't fired when the app start. Is there any way to force it to fire when the app start ?

 

[Erel]

Are you testing it outdoors? It should fire very quickly if the GPS has a fix.

 

[achtrade]

Are you testing it outdoors? It should fire very quickly if the GPS has a fix.

Not yet, I'm testing my app inside an office. When I complete the app, I'll post an update.

 

[incendio]

Got these error when running the example

B4A version 4.30
Parsing code. 0.00
Compiling code. 0.02

ObfuscatorMap.txt file created in Objects folder.
Compiling layouts code. Error
Value cannot be null.
Parameter name: input
Error File: 1.bal

Go to the designer script page to debug this error.

EDITED :
It seem that the layout made in the old version.

Saved again with ver 4.3 fix the error.

 

[Glitchs]

Hello.

I cant see the source code either the libraries, then I put muy question: It's posible to get also the quality of measure GPS like the accuracy in meters o the DOP?
I want to crate an app using gps but is very important if the measured lat and long are good fixed.
Best regards.

 

[Erel]

Location.Accuracy returns the known accuracy measured in meters.

 

[Glitchs]

Thanks. A very good news. The Begginers Manual dont explain if this feature es available, and I did not find where to read about it.
Best Regards

 

[nicodh]

Hello Erel,
I'm trying to use the GPS library. I needd to retrieve the altitude, my code works, but the altitude is wrong.
The notification icon from android tells me 238 meters with an error of around 13 meters (wich is the correct altitude) but the gps tutorial or my app said i'm at 278 meters with an accuracy of 38 meters.
Am i missing something?
Why there is a difference between the notification from android and the b4a library?
Thanks.

BTW: I'm using android 4.4.2.

 

[Erel]

Hello Erel,

Please do not limit your questions to a single member.

The B4A library returns the results exactly as they come from the native API.

See this thread: https://www.b4x.com/android/forum/threads/gps-fails-in-height.13486/#post-76179

 

[nicodh]

Sorry for that erel, it wasn't intended.

Thanks for the link i'm reading it right now.

 

[klaus]

You should use the GPS_NMEA event like in this post.

 

[Glitchs]

Hello Erel,
I'm trying to use the GPS library. I needd to retrieve the altitude, my code works, but the altitude is wrong.
The notification icon from android tells me 238 meters with an error of around 13 meters (wich is the correct altitude) but the gps tutorial or my app said i'm at 278 meters with an accuracy of 38 meters.
Am i missing something?
Why there is a difference between the notification from android and the b4a library?
Thanks.

BTW: I'm using android 4.4.2.

Hello,

Your error could be the Geoid Ondulation, that is the diference of altitude between the Orthometric altitude and the elipsoidal altitude. All the GPS send the elipsoidal altitude. Then you have to know the Geoid Ondulation in order to correct the real altitude. For example here in spain the G.O. is about 45 meters.

Best regards.

 

[吳界明]

Could you give me an example, about when GPS position has been changed, that can Real-time display on the map updated location and marked
I want use the Webview component and not use google map API key

 

[Erel]

Please start a new thread for this. Note that there are several examples in the forum that use WebView with Google Maps.

 

[chrjak]

Hey,

I'm having a problem with GPS. It's in a service (started in foreground) and everything works. The Service normally doesn't get killed.

But some days ago i noticed a big problem.
My Phone had about 15% battery and when i locked my phone the service got paused. Not killed and it resumed immediately after unlocking my screen but that mustn't happen. It's for recording the location and when my screen was locked there were no points saved. How to solve that? Or better. Why does this happen?

Thanks for your reply

 

[Erel]

Please start a new thread for this question.

 

[SCIS]

Hi, I made a whole new project and used the exact same code as you. I also made the same layout with the same name but there's no txt showing up in the labels. The GPS icon is blinking tho so that should be working.
What should I do?

Thanks in advance!

 

[SCIS]

Satellites are working now but everything shows up as "false" instead of true. Latitude and longitude still aren't working.

 

[Danbicky]

Erel,

This is great, lets say I want a 1 mile radius from my home position, and to raise some form of alert if my phone goes outside of this, how is this achieved? Like a Geo Zone!

Big thanks

Dans