Android Question B4XMap - draw a line

[AlpVir]

I'm trying to draw a GPS track on a map created using the B4XMap library.
Documentation is poor and the only useful instruction I've found is the following (draw a line between 2 dots)

shapes.Add(coMapUtilities.instanceShapeLine(fcvMap,coMapUtilities.initShapeLine(coMapUtilities.initLatLng(48.856614,2.3522219),coMapUtilities.initLatLng(31.630000,-8.008889),fxui.Color_ARGB(128,255,0,255),1dip,"Paris to Marrakech")))

However I can not indicate latitude and longitude with variables :
Point 1: (Lt, Lg)
Point 2: (PrecLt, PrecLg)

Something like that :

shapes.Add(coMapUtilities.instanceShapeLine(fcvMap,coMapUtilities.initShapeLine(coMapUtilities.initLatLng(" & PrecLt & "," & PrecLg & "),coMapUtilities.initLatLng(" & Lg & "," & Lt & "),fxui.Color_ARGB(128,255,0,255),1dip,"test")))

 

[RB Smissaert]

I'm trying to draw a GPS track on a map created using the B4XMap library.
Documentation is poor and the only useful instruction I've found is the following (draw a line between 2 dots)

shapes.Add(coMapUtilities.instanceShapeLine(fcvMap,coMapUtilities.initShapeLine(coMapUtilities.initLatLng(48.856614,2.3522219),coMapUtilities.initLatLng(31.630000,-8.008889),fxui.Color_ARGB(128,255,0,255),1dip,"Paris to Marrakech")))

However I can not indicate latitude and longitude with variables :
Point 1: (Lt, Lg)
Point 2: (PrecLt, PrecLg)

Something like that :

shapes.Add(coMapUtilities.instanceShapeLine(fcvMap,coMapUtilities.initShapeLine(coMapUtilities.initLatLng(" & PrecLt & "," & PrecLg & "),coMapUtilities.initLatLng(" & Lg & "," & Lt & "),fxui.Color_ARGB(128,255,0,255),1dip,"test")))

Here some code I use that will hopefully get you on the right track:

Sub btnMakeArea_Click
    
    If lstPolygonPoints.Size < 2 Then Return
    
    If Enums.bDrawnArea Then
        RemovePolygon
        Enums.bDrawnArea = False
        Return
    End If
    
    If lstPolygonPoints.Size = 2 Then
        Dim BB As TMapBoxLatLng = BoundingBoxFromtLL_List(lstPolygonPoints)
        RemovePolygon
        'closing the path is taken care of here!
        lstPolygonPoints = BB2lstPath(BB)
        BB2MinMax_LatLon(BB)
        Enums.bSquareFromTwotLLs = True
        Enums.bDrawnArea = True
    Else
        'to close the polygon in the list path!!
        lstPolygonPoints.Add(lstPolygonPoints.Get(0))
    End If

    Dim tMSP As TMapShapePolygon = MapUtilities.initShapePolygon(lstPolygonPoints, xui.Color_ARGB(128,255,0,255), False, 2dip, "MapArea")
    Dim cMSP As clsMapShapePolygon = MapUtilities.instanceShapePolygon(cvMap1, tMSP)
    mapPolygonLines.put("MapArea", "MapArea")
    mapShapes.Put("MapArea", cMSP)
    cvMap1.Draw
    Enums.bDrawnArea = True
    
End Sub

Sub BoundingBoxFromtLL_List(lsttLL As List) As TMapBoxLatLng
        
    Dim BB As TMapBoxLatLng
    
    Dim dMinLat As Double = 100
    Dim dMaxLat As Double = -100
    Dim dMinLng As Double = 200
    Dim dMaxLng As Double = -200
    
    For Each tLL As TMapLatLng In lsttLL
        If tLL.flat > dMaxLat Then
            dMaxLat = tLL.flat
        End If
        If tLL.flat < dMinLat Then
            dMinLat = tLL.flat
        End If
        If tLL.flng > dMaxLng Then
            dMaxLng = tLL.flng
        End If
        If tLL.flng < dMinLng Then
            dMinLng = tLL.flng
        End If
    Next
    
    Dim BB As TMapBoxLatLng = MapUtilities.initBoxLatLng(dMaxLat, dMinLng, dMinLat, dMaxLng)
    
    Return BB
    
End Sub

Sub RemovePolygon
    
    lstPolygonPoints.Clear
    
    For Each oKey As Object In mapPolygonLines.Keys
        'changed the list in type TMap (holding the shapes) to a map
        mapShapes.Remove(oKey)
    Next
    
    'this map keeps track of the polygon lines and the final polygon shape
    mapPolygonLines.Clear
    
    cvMap1.Draw
    
End Sub

Sub BB2lstPath(BB As TMapBoxLatLng) As List
        
    Dim lstPath As List

    lstPath.Initialize

    Dim tLLNW As TMapLatLng = MapUtilities.initLatLng(BB.fLeftTop.fLat, BB.fLeftTop.fLng)
    lstPath.Add(tLLNW) 'NW
    
    Dim tLLNE As TMapLatLng = MapUtilities.initLatLng(BB.fLeftTop.fLat, BB.fRightBottom.fLng)
    lstPath.Add(tLLNE) 'NE
    
    Dim tLLSE As TMapLatLng = MapUtilities.initLatLng(BB.fRightBottom.fLat, BB.fRightBottom.fLng)
    lstPath.Add(tLLSE) 'SE
    
    Dim tLLSW As TMapLatLng = MapUtilities.initLatLng(BB.fRightBottom.fLat, BB.fLeftTop.fLng)
    lstPath.Add(tLLSW) 'SW
    
    lstPath.Add(tLLNW) 'NW, again, to close the path
    
    Enums.bDrawnArea = True
    
    Return lstPath
    
End Sub

Sub BB2MinMax_LatLon(BB As TMapBoxLatLng)
    
    Dim strSQL As String
    
    'Need to make sure this table always has one row!
    '------------------------------------------------
    strSQL = "UPDATE MINMAX_LATLON SET MIN_LAT = ?, MAX_LAT = ?, MIN_LON = ?, MAX_LON = ?"
    SQL_ExecNonQuery2(strSQL, Array As String(BB.fRightBottom.fLat, _
                                                                 BB.fLeftTop.fLat, _
                                                                 BB.fLeftTop.fLng, _
                                                                 BB.fRightBottom.fLng))
End Sub

RBS

 

[AlpVir]

Thanks but that's not what I'm asking for: a GPS track (a line) and no polygons.

 

[TILogistic]

shapes.Add(coMapUtilities.instanceShapeLine(fcvMap,coMapUtilities.initShapeLine(coMapUtilities.initLatLng(" & PrecLt & "," & PrecLg & "),coMapUtilities.initLatLng(" & Lg & "," & Lt & "),fxui.Color_ARGB(128,255,0,255),1dip,"test")))

see variable

    Dim PrecL,PrecLg, Lg, Lt As Double
    shapes.Add(coMapUtilities.instanceShapeLine(fcvMap,coMapUtilities.initShapeLine(coMapUtilities.initLatLng( PrecL,PrecLg),coMapUtilities.initLatLng(Lt, Lg),fxui.Color_ARGB(128,255,0,255),1dip,"test")))

 

[RB Smissaert]

Thanks but that's not what I'm asking for: a GPS track (a line) and no polygons.

OK, this is the code I have to add an area point (and that means drawing a line):

Sub AddAreaPoint(tLL As TMapLatLng) As Double
    
    Dim oKey As Object
    Dim Location1 As Location
    Dim Location2 As Location
    Dim dMiles As Double
    
    If Enums.bDrawnArea Then
        Return 0
    End If
    
    Enums.bSquareFromTwotLLs = False
    
    Dim tLL1 As TMapLatLng
    Dim tLL2 As TMapLatLng
        
    tLL2.fLat = tLL.fLat
    tLL2.fLng = tLL.fLng

    If lstPolygonPoints.Size > 0 Then
        tLL1 = lstPolygonPoints.get(lstPolygonPoints.Size - 1)
        If tLL1.flat = tLL2.fLat Then
            If  tLL1.fLng = tLL2.fLng Then
                Return 0
            End If
        End If
    End If
        
    lstPolygonPoints.Add(tLL2)
    
    Location1.Initialize
    Location2.Initialize
    Location1.Latitude = tLL1.fLat
    Location1.Longitude = tLL1.fLng
    Location2.Latitude = tLL.fLat
    Location2.Longitude = tLL.fLng

    If lstPolygonPoints.Size > 1 Then
        oKey = "Polygon_Line" & lstPolygonPoints.Size
        Dim tMSL As TMapShapeLine = MapUtilities.initShapeLine(tLL1, tLL2, xui.Color_ARGB(128,255,0,255), 2dip, oKey)
        Dim cMSL As clsMapShapeLine = MapUtilities.instanceShapeLine(cvMap1, tMSL)
        mapPolygonLines.Put(oKey, oKey)
        mapShapes.Put(oKey, cMSL)
        cvMap1.Draw
    End If
    
    If lstPolygonPoints.Size > 1 Then
        dMiles = Location1.DistanceTo(Location2) / 1000 * dKM2Miles
    End If
    
    Return dMiles
    
End Sub

RBS

 

[AlpVir]

By entering 3 or 4 GPS coordinates, the track that connects them is actually displayed.
However, when it comes to downloading a GPS track consisting of 2 or 3 thousand points from the internet, an error appears which in my opinion is not attributable to the library but to the (wrong) succession of subs and events (Create and/or Resume).
Here is the error :

** Activity (main) Pause, UserClosed = false **
** Activity (mappaweb) Create, isFirst = true **
download https://www.******************/Tracks/20230208.txt
** Activity (mappaweb) Resume **
Sub fcvmap_ready
Error occurred on line: 323 (cvMap)
java.lang.NullPointerException: Attempt to read from field 'double alpvir.sq.comaputilities$_tmaplatlng.fLat' on a null object reference in method 'java.lang.String alpvir.sq.cvmap._setcenterlatlng(alpvir.sq.cvmap, alpvir.sq.comaputilities$_tmaplatlng)'
at alpvir.sonoqui.cvmap._setcenterlatlng(cvmap.java:2206)
at alpvir.sonoqui.cvmap._setmap(cvmap.java:119)
at java.lang.reflect.Method.invoke(Native Method)
at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:732)
at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:351)
at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:255)

Below is an essential summary of my code :

Sub Process_Globals
   Private fMap As TMap
   Private fxui As XUI
End Sub

Sub Globals
   Private fcvMap As cvMap
   Private shapes As List
   Dim PrecLT,PrecLg, Lg, Lt As Double
End Sub

Sub Activity_Create(FirstTime As Boolean)
   Activity.LoadLayout("Mappa_OSM")
   shapes.Initialize
   DownloadTraceGPS   ' sub
End sub

Sub DownloadTraceGPS
   Private JobDownload As HttpJob
   JobDownload.Initialize("JobDownload", Me)
   JobDownload.Download(URL)
   Wait For (JobDownload) JobDone(JobDownload As HttpJob)
   If JobDownload.Success = True Then
      Dim out As OutputStream = File.OpenOutput(Main.GlobalThisApp,  Main.TraceWeb, False)
      File.Copy2(JobDownload.GetInputStream, out)
      out.Close
      ReadShapes   ' sub
      ShowMap      ' sub
   end if
End sub

Sub ReadShapes
   dim N as int
   TextReader1.Initialize(File.OpenInput(Main.GlobalThisApp,  Main.TraceWeb))
   Do While Riga <> Null
      Riga = TextReader1.ReadLine
      ele = Regex.Split(",",Riga)
      Lt=ele(0).trim
      Lg= ele(1).trim
      if N>0 then
         shapes.Add(coMapUtilities.instanceShapeLine(fcvMap,coMapUtilities.initShapeLine(coMapUtilities.initLatLng( PrecLT,PrecLg),coMapUtilities.initLatLng(Lt, Lg),Colors.ARGB(128,255,0,255),2dip,"test")))
      end if
      N=N+1
      PrecLT=Lt:PrecLg=Lg
   Loop
   TextReader1.Close
End sub

Sub ShowMap
Log(shapes.size)  ' OK
' For Each ZZ As TMapShapeLine In shapes
'    Log(ZZ.fLatLng1.fLat & "  " & ZZ.fLatLng1.fLng & " TO " & ZZ.fLatLng2.fLat & "  " & ZZ.fLatLng2.fLng)
'  Next
   fMap=coMapUtilities.initMap(coMapUtilities.initLatLng(lt, lg), ZoomLevel, CompassDirection,   OfflineMode , ShowMenu, ShowGrid, ShowCenter, ShowLandmark, ShowCenterLatLon, ShowZoom, ShowScale, ShowCompass, ShowShapes, _
   shapes, _
   ShowGPS, FollowGPS,coMapUtilities.initGPS(coMapUtilities.initLatLng(0,0),0))
end sub

Sub Activity_Pause (UserClosed As Boolean)
   fMap=fcvMap.map
End Sub

private Sub fcvmap_ready
   fcvMap.TileServer="https://a.tile.openstreetmap.org/"   ' default
   fcvMap.UserAgent="User-AgentMozilla/5.0 (Windows NT 10.0; Win64; x64; rv:108.0) Gecko/20100101 Firefox/108.0"
   fcvMap.Map=fMap
   '--- draw the map
   fcvMap.draw
   fcvMap.Map=fMap
   fcvMap.draw
End Sub

Is it possible to have a suggestion to remedy the malfunction?
Thanks in advance.

 

[RB Smissaert]

By entering 3 or 4 GPS coordinates, the track that connects them is actually displayed.
However, when it comes to downloading a GPS track consisting of 2 or 3 thousand points from the internet, an error appears which in my opinion is not attributable to the library but to the (wrong) succession of subs and events (Create and/or Resume).
Here is the error :

Below is an essential summary of my code :

Sub Process_Globals
   Private fMap As TMap
   Private fxui As XUI
End Sub

Sub Globals
   Private fcvMap As cvMap
   Private shapes As List
   Dim PrecLT,PrecLg, Lg, Lt As Double
End Sub

Sub Activity_Create(FirstTime As Boolean)
   Activity.LoadLayout("Mappa_OSM")
   shapes.Initialize
   DownloadTraceGPS   ' sub
End sub

Sub DownloadTraceGPS
   Private JobDownload As HttpJob
   JobDownload.Initialize("JobDownload", Me)
   JobDownload.Download(URL)
   Wait For (JobDownload) JobDone(JobDownload As HttpJob)
   If JobDownload.Success = True Then
      Dim out As OutputStream = File.OpenOutput(Main.GlobalThisApp,  Main.TraceWeb, False)
      File.Copy2(JobDownload.GetInputStream, out)
      out.Close
      ReadShapes   ' sub
      ShowMap      ' sub
   end if
End sub

Sub ReadShapes
   dim N as int
   TextReader1.Initialize(File.OpenInput(Main.GlobalThisApp,  Main.TraceWeb))
   Do While Riga <> Null
      Riga = TextReader1.ReadLine
      ele = Regex.Split(",",Riga)
      Lt=ele(0).trim
      Lg= ele(1).trim
      if N>0 then
         shapes.Add(coMapUtilities.instanceShapeLine(fcvMap,coMapUtilities.initShapeLine(coMapUtilities.initLatLng( PrecLT,PrecLg),coMapUtilities.initLatLng(Lt, Lg),Colors.ARGB(128,255,0,255),2dip,"test")))
      end if
      N=N+1
      PrecLT=Lt:PrecLg=Lg
   Loop
   TextReader1.Close
End sub

Sub ShowMap
Log(shapes.size)  ' OK
' For Each ZZ As TMapShapeLine In shapes
'    Log(ZZ.fLatLng1.fLat & "  " & ZZ.fLatLng1.fLng & " TO " & ZZ.fLatLng2.fLat & "  " & ZZ.fLatLng2.fLng)
'  Next
   fMap=coMapUtilities.initMap(coMapUtilities.initLatLng(lt, lg), ZoomLevel, CompassDirection,   OfflineMode , ShowMenu, ShowGrid, ShowCenter, ShowLandmark, ShowCenterLatLon, ShowZoom, ShowScale, ShowCompass, ShowShapes, _
   shapes, _
   ShowGPS, FollowGPS,coMapUtilities.initGPS(coMapUtilities.initLatLng(0,0),0))
end sub

Sub Activity_Pause (UserClosed As Boolean)
   fMap=fcvMap.map
End Sub

private Sub fcvmap_ready
   fcvMap.TileServer="https://a.tile.openstreetmap.org/"   ' default
   fcvMap.UserAgent="User-AgentMozilla/5.0 (Windows NT 10.0; Win64; x64; rv:108.0) Gecko/20100101 Firefox/108.0"
   fcvMap.Map=fMap
   '--- draw the map
   fcvMap.draw
   fcvMap.Map=fMap
   fcvMap.draw
End Sub

Is it possible to have a suggestion to remedy the malfunction?
Thanks in advance.

Just guessing, but I think in places you will need Sleep (eg Sleep(10)) to make sure that cvMap is ready when it is called upon.
I found this in my code and adding the Sleep in a few places did solve it.

RBS

 

[AlpVir]

I also thought about inserting sleeps at various points but it didn't work. I have done numerous tests and attempts.
The cause is another.
Not even by inserting (for testing) MSGBOX.

 

[RB Smissaert]

I also thought about inserting sleeps at various points but it didn't work. I have done numerous tests and attempts.
The cause is another.
Not even by inserting (for testing) MSGBOX.

Could you post a small (as small as possible) demo project that demonstrates the problem?

RBS

 

[AlpVir]

I made a small project that does NOT display the map.
Could you take a look at it ?
I get an error like :

Error occurred on line: 323 (cvMap)
java.lang.NullPointerException: Attempt to read from field 'double alpvir.sq.comaputilities$_tmaplatlng.fLat' on a null object reference in method 'java.lang.String alpvir.sq.cvmap._setcenterlatlng(alpvir.sonoqui.cvmap, alpvir.sq.comaputilities$_tmaplatlng)'

EDIT: The line is missing in the project : Public gpsStarted As Boolean (but it is not significant)

 

[RB Smissaert]

I made a small project that does NOT display the map.
Could you take a look at it ?
I get an error like :



EDIT: The line is missing in the project : Public gpsStarted As Boolean (but it is not significant)

Could you send the full project, so including all the B4XMap classes?
After a tip from Klaus I have this at the top of B4XMainPage:
'Ctrl + click to export as zip: ide://run?File=%B4X%\Zipper.jar&Args=\%PROJECT_NAME%.zip
and that works nicely.

RBS

 

[AlpVir]

I don't understand what you are referring to when you write about "B4XMap classes".
I must specify that the example attached to the previous post was created by me excluding many other modules from a very large project that includes 26 libraries, 11 modules (for now) and no B4XPage.
Compressed occupies about 800 KB and would be difficult for anyone to understand since it is written, where possible, in my native language (Italian) and interacts heavily with the Web.
Just to understand the complexity of the project, I report a part of the file Project Name.b4a
By starting the project attached to the previous post, the error (ie the NOT visualization) of the map is already evident.
Thank you if you want to help me with this project of mine which is the reworking of another one which included the use of the OSMDroid library, now no longer current.
I am again attaching the project in *.zip format

 

[RB Smissaert]

I don't understand what you are referring to when you write about "B4XMap classes".
I must specify that the example attached to the previous post was created by me excluding many other modules from a very large project that includes 26 libraries, 11 modules (for now) and no B4XPage.
Compressed occupies about 800 KB and would be difficult for anyone to understand since it is written, where possible, in my native language (Italian) and interacts heavily with the Web.
Just to understand the complexity of the project, I report a part of the file Project Name.b4a
By starting the project attached to the previous post, the error (ie the NOT visualization) of the map is already evident.
Thank you if you want to help me with this project of mine which is the reworking of another one which included the use of the OSMDroid library, now no longer current.
I am again attaching the project in *.zip format

OK, I understand now you are using B4XMap as a library and you have the classes of that library not in your project.
I think it is better in this case to add the classes of B4XMap to your project and not use the library. This will make it a lot simpler to unravel this problem and also you can make changes if needed. I have made quite few alterations and additions
to those classes in my project and if you want I can send those.

RBS

 

[AlpVir]

Now I understand that your B4XMap code can be used as a "library" (as I have done so far) or as a "class".
I don't think these classes are available on this site.
Can you send them to me?
Thank you !

 

[RB Smissaert]

Now I understand that your B4XMap code can be used as a "library" (as I have done so far) or as a "class".
I don't think these classes are available on this site.
Can you send them to me?
Thank you !

Attached all the files.

RBS

 

[AlpVir]

I'm sorry but I couldn't get anything done.
I inserted all 7 BAS modules that you attached to the previous post into the small test project.
I then unplugged the additional B4XMap library.
After some errors, remedied by inserting some additional modules (B4XProgressBar and other) I stopped in front of a "General" variable of which I know nothing and it is mentioned in none of the numerous modules.
These errors are difficult to interpret.

clsMapTileManager - 378: Membro sconosciuto: reset
clsMapTileManager - 347: Membro sconosciuto: reset
clsMapTileManager - 338: Membro sconosciuto: reset
clsMapTileManager - 314: Membro sconosciuto: show
Main - 183: Membro sconosciuto: useragent
Main - 182: Membro sconosciuto: tileserver
MapUtilities - 301: Variabile 'general' non dichiarata, utilizzata prima che gli sia stato assegnato un valore.
MapUtilities - 300: Variabile 'general' non dichiarata, utilizzata prima che gli sia stato assegnato un valore.
clsMapTileManager - 382: Variabile 'general' non dichiarata, utilizzata prima che gli sia stato assegnato un valore.
clsMapTileManager - 293: Variabile 'general' non dichiarata, utilizzata prima che gli sia stato assegnato un valore.

Conversely, I believe that the library can be usefully employed, without using the classes, as long as one understands the order in which the instructions relating to the map follow one another over time.
When is the fcvmap_read event called?
Where should fcvMap.draw be inserted? Immediately or after the track has been downloaded ?
I am convinced that a simple move of the instructions to the right place can finally make the test project work.
Would you please take another look?

 

[RB Smissaert]

I'm sorry but I couldn't get anything done.
I inserted all 7 BAS modules that you attached to the previous post into the small test project.
I then unplugged the additional B4XMap library.
After some errors, remedied by inserting some additional modules (B4XProgressBar and other) I stopped in front of a "General" variable of which I know nothing and it is mentioned in none of the numerous modules.
These errors are difficult to interpret.

Conversely, I believe that the library can be usefully employed, without using the classes, as long as one understands the order in which the instructions relating to the map follow one another over time.
When is the fcvmap_read event called?
Where should fcvMap.draw be inserted? Immediately or after the track has been downloaded ?
I am convinced that a simple move of the instructions to the right place can finally make the test project work.
Would you please take another look?

Sorry, forgot about these General variables and Subs. General is a code module, but you can bypass all that.
There are the StopSW and StartSW Subs (for timing) >> just comment those out

Then there are these:
dLatDiff = General.dFindZoomFactorLat * iMultiply '0.00046
dLngDiff = General.dFindZoomFactorLng * iMultiply '0.00046
In MapUtilities.
Replace both General variables with the commented values 0.00046

I understand you have sorted out the progressbar, which is for downloading tiles from the internet.
If it is still a problem then just comment that out.

RBS

 

[AlpVir]

I scrupulously followed all your instructions, but no, nothing happened.
Chasing the flow of execution of complex code like the classes in question is very daunting.
I think it is useless to report the errors that have gradually followed one another.
They returned to trying to use the library, hoping by dint of attempts to get something positive.

 

[RB Smissaert]

I scrupulously followed all your instructions, but no, nothing happened.
Chasing the flow of execution of complex code like the classes in question is very daunting.
I think it is useless to report the errors that have gradually followed one another.
They returned to trying to use the library, hoping by dint of attempts to get something positive.

Could you zip the full project again (with the classes added) and post it?
This should be solvable.

RBS

 

[AlpVir]

Here is the project, expanded with all classes.
I marked with 4 apostrophes
''''
the points where I intervened.