Android Question How to access the whole of external SD card?

Sub Activity_Click
   Dim i As Intent
   i.Initialize("android.intent.action.OPEN_DOCUMENT_TREE", "")
   StartActivityForResult(i)
End Sub

Sub ion_Event (MethodName As String, Args() As Object) As Object
   If Args(0) = -1 Then 'resultCode = RESULT_OK
       Dim i As Intent = Args(1)
       Dim jo As JavaObject = i
       Dim treeUri As Uri = jo.RunMethod("getData", Null)
       Dim ctxt As JavaObject
       ctxt.InitializeContext
       Dim takeFlags As Int = Bit.And(i.Flags, 3)
       ctxt.RunMethodJO("getContentResolver", Null).RunMethod("takePersistableUriPermission", Array(treeUri, takeFlags))
       Dim uri As String = treeUri 'ignore
       'uri should be a process global variable and you can save it
   End If
   Return Null
End Sub

Sub GetPickedDir (uri As String) As JavaObject
   Dim ctxt As JavaObject
   ctxt.InitializeContext
   Dim DocumentFileStatic As JavaObject
   Dim treeUri As Uri
   treeUri.Parse(uri)
   Dim pickedDir As JavaObject = DocumentFileStatic.InitializeStatic("android.support.v4.provider.DocumentFile").RunMethod("fromTreeUri", Array(ctxt, treeUri))
   Return pickedDir
   'usage example of pickedDir
'   Dim files() As Object = pickedDir.RunMethod("listFiles", Null)
'   For Each f As JavaObject In files
'       Log(f.RunMethod("getName", Null))
'   Next
'   Dim newFile As JavaObject = pickedDir.RunMethod("createFile", Array("text/plain", "My Novel"))
'   Dim out As OutputStream = ctxt.RunMethodJO("getContentResolver", Null).RunMethod("openOutputStream", Array(newFile.RunMethod("getUri", Null)))
'   Dim tw As TextWriter
'   tw.Initialize(out)
'   tw.Write("this is a test")
'   tw.Close
End Sub

Sub StartActivityForResult(i As Intent)
   Dim jo As JavaObject = GetBA
   ion = jo.CreateEvent("anywheresoftware.b4a.IOnActivityResult", "ion", Null)
   jo.RunMethod("startActivityForResult", Array As Object(ion, i))
End Sub

Sub GetBA As Object
   Dim jo As JavaObject
   Dim cls As String = Me
   cls = cls.SubString("class ".Length)
   jo.InitializeStatic(cls)
   Return jo.GetField("processBA")
End Sub

jo=treeUri
Log(jo.RunMethod("getPath",Null))

private String getRealPathFromURI(Uri contentUri) 
{
    String[] proj = { MediaStore.Images.Media.DATA };
    CursorLoader loader = new CursorLoader(mContext, contentUri, proj, null, null, null);
    Cursor cursor = loader.loadInBackground();
    int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
    cursor.moveToFirst();
    String result = cursor.getString(column_index);
    cursor.close();
    return result;
}

java.lang.UnsupportedOperationException: Unsupported Uri content://com.android.externalstorage.documents/tree/17FC-3214%3Atff

Dim newFile As JavaObject = pickedDir.RunMethod("createFile", Array("text/plain", "My Novel"))

Sub StreamFileCopier(dirsource As String,filesource As String,dirdest As String,filedest As String)

    Dim inp As InputStream,out As OutputStream
    Dim suri,duri As String
    
    Dim sctxt,dctxt,spickedDir,dpickedDir As JavaObject
        
    suri=dirsource
    spickedDir=GetPickedDir(suri)
    sctxt.InitializeContext
    
    duri=dirdest
    dpickedDir=GetPickedDir(duri)
    dctxt.InitializeContext
    
    Dim oldFile As JavaObject = spickedDir.RunMethod("findFile", Array(filesource))
    inp = sctxt.RunMethodJO("getContentResolver", Null).RunMethod("openInputStream", Array(oldFile.RunMethod("getUri", Null)))
    
    Dim newFile As JavaObject = dpickedDir.RunMethod("createFile", Array("text/plain", filedest))
    out = dctxt.RunMethodJO("getContentResolver", Null).RunMethod("openOutputStream", Array(newFile.RunMethod("getUri", Null)))
    
    File.Copy2(inp,out)
    out.Close
    
End Sub