Android Question [SOLVED] Get GPS coordinate of a point shown on an OpenStreetMap panel

[adrianstanescu85]

Hello

I added an OpenStreetMap map inside a panel, which is working fine, and what I would need is to know the GPS coordinates (lat, long) of a certain point I'm specifying inside that panel.

Let's say the panel is 400 x 200 px, and I'd need to find out the GPS coordinates of the point shown inside that panel at 100 x 40 px at the current zoom level.

Does anyone know how to do that?

Thank you!
Adrian

 

[warwound]

Are you using OSMDroid?
If so look at the OSMDroid_Projection object.

 

[adrianstanescu85]

Yes, I'm using OSMDroid 3.0.8. Can you point a short example please? So far I wasn't able to find one, maybe I looked in the wrong places so far.
Thank you!

 

[warwound]

Version 3.0.8 never had the map projection wrapped/exposed to b4a.
Only version 4.1 wraps the map projection into a b4a object:
http://b4a.martinpearman.co.uk/osmdroid/

Maybe you could use some inline java to access the map projection using version 3.0.8.
I'll have a look at the documentation for you 3.0.8 tomorrrow.

 

[adrianstanescu85]

Inline java would do well too... for now converting to 4.1 might be pretty troublesome in the time left on the telemedicine project I'm working on. If you could pass a few inline java lines just for this map projection it would help a lot! Thank you!

 

[warwound]

Ok it actually looks quite simple...

This is the inline java you need to add to any Activity that you need to use it in:

#If JAVA
import org.osmdroid.util.GeoPoint;
import uk.co.martinpearman.b4a.osmdroid.util.wrappers.GeoPointWrapper;

public GeoPointWrapper FromPixels(org.osmdroid.views.MapView mapView, int x, int y){
	GeoPointWrapper wrapper=new GeoPointWrapper();
	wrapper.setObject((GeoPoint) mapView.getProjection().fromPixels(x, y));
	return wrapper;
}
#End If

And your b4a calling code should look something like:

Dim NativeMe As JavaObject
NativeMe.InitializeContext

Dim GeoPoint1 As GeoPoint=NativeMe.RunMethod("FromPixels", Array As Object(MyMapView, XCoord, YCoord))

' now test if GeoPoint1 is correct

Martin.

 

[adrianstanescu85]

I'll test it right now and let you know how it works! Thank you!

 

[adrianstanescu85]

I put the inline java at the end of the activity
Also put the NativeMe declaration in Process_Globals.
Set the InitializeContext in Activity_Create when ran the first time.
In the mean time the map was well working as already set.

I set a label with a LongClick event get the geopoint and then list the coordinates.

This is the error I'm receiving: "An error has occured in sub:amedicsef_labelpressscena_longclick (java line: 946) java.lang.ClassCastException: uk.co.martinpearman.b4a.osmdroid.util.weappers.GeoPointWrapper cannot be cast to org.osmdroid.util.GeoPoint Continue?"

Why could this happen?

 

[adrianstanescu85]

The exact code is:

Sub LabelPressScena_LongClick
    Dim GeoPoint1 As GeoPoint  =NativeMe.RunMethod("FromPixels", Array As Object(MV1, 50, 50))
   
    ToastMessageShow("Lat: " & GeoPoint1.Latitude & " ,Long: " & GeoPoint1.Longitude, False)
End Sub

where MV1 is a MapView object. Thought this might help.

 

[warwound]

Try this:

#If JAVA
import org.osmdroid.util.GeoPoint;

public GeoPoint FromPixels(org.osmdroid.views.MapView mapView, int x, int y){
	return (GeoPoint) mapView.getProjection().fromPixels(x, y);
}
#End If

 

[adrianstanescu85]

Yes, this works!

Wonderfull!

Thank you so much!!