Sub CheckIfFileExists(dirname As String,filename As String) As Boolean
Dim dpickedDir As JavaObject
Dim ret As Boolean
dpickedDir=GetPickedFile(dirname,filename)
ret=dpickedDir.RunMethod("exists",Null)
Log(dpickedDir.RunMethod("getName",Null))
Return ret
End Sub
Sub GetPickedFile(uri As String,filename As String) As JavaObject
Dim ctxt As JavaObject
ctxt.InitializeContext
Dim DocumentFileStatic As JavaObject
Dim treeUri,baseuri As Uri
'treeUri.Parse(uri)
baseuri.Parse(uri)
treeUri.WithAppendedPath(baseuri,filename)
Dim pickedDir As JavaObject = DocumentFileStatic.InitializeStatic("android.support.v4.provider.DocumentFile").RunMethod("fromTreeUri", Array(ctxt, treeUri))
Return pickedDir
End Sub