Develop Reference

Problems with removable storage Hololens 2, unity and xamarin uwp

I'm relatively new to software development for the Hololens 2 and have a pretty big problem I've been messing around with for a long time and I'm slowly running out of ideas.
My project looks like this. I've written a Unity application to capture data and store it in a database (sqlite). A Xamarin.Forms UWP application is supposed to take the data from the database and use it to paint charts for better visualisation. The big problem is, both apps need to be able to access the same database on the Hololens 2. I thought that I could be the database on a usb stick and both apps could access the usb stick. In the Xamarin app and in the Unity app "removable storage" is enabled. In the Xamarin App I have made the file extension known under Appmanifest declaration. I am trying to get the connection with the following commands:
namespace ARScoliosis.XamarinApp.UWP.Services
{
public class DatabasePath : IDatabasePath
{
public async Task<string> GetLocalFilePath()
{
var messageDialog = new MessageDialog("No Usb connection has been found.");
StorageFolder externalDevices = KnownFolders.RemovableDevices;
if(externalDevices == null)
{
messageDialog.Commands.Add(new UICommand("No Devices", null));
}
StorageFolder usbStick = (await externalDevices.GetFoldersAsync()).FirstOrDefault(); <---According to debugging it stops here and jumps to optionsBuilder.UseSqlite($"Filename={databasePath}");
if (usbStick == null)
{
messageDialog.Commands.Add(new UICommand("No UsbStick", null));
}
var usbStickFolder = await usbStick.CreateFolderAsync("DB", CreationCollisionOption.OpenIfExists);
if (usbStickFolder == null)
{
messageDialog.Commands.Add(new UICommand("No Folder", null));
}
var file = await usbStickFolder.CreateFileAsync("Database.db", CreationCollisionOption.OpenIfExists);
if(file == null)
{
messageDialog.Commands.Add(new UICommand("No File", null));
}
//var success = await Launcher.LaunchFileAsync(file);
return file.ToString();
}
My dbcontext file looks something like this:
namespace XamarinApp.Authentication
{
public partial class DBContext : DbContext
{
public DBContext()
{
this.Database.EnsureCreated(); <--- Microsoft.Data.Sqlite.SqliteException: "SQLite Error 14: 'unable to open database file'."
this.Database.Migrate();
}
public virtual DbSet<ItemData> ItemDatas { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
if (!optionsBuilder.IsConfigured)
{
var databasePath = DependencyService.Get<IDatabasePath>().GetLocalFilePath();
optionsBuilder.UseSqlite($"Filename={databasePath}");
}
}
namespace XamarinApp.Helpers
{
public interface IDatabasePath
{
Task<string> GetLocalFilePath();
}
}
Unfortunately this code does not find the Usb stick on the Hololens, i think. When I look in file explorer, I see the stick with all its data. In the Unity App, the stick is also not found, although I use the same code here, only slightly modified.
Does anyone know where my error lies, why I can't access the USB stick with either of the two apps? Has anyone tried something similar and knows how to do it?
i would like to thank you in advance for your help.
Thank you very much.

****Hi Hernando - MSFT,
Please excuse my late reply. i had somehow forgotten. I have found a way where I can find my database on the usb stick.
public static async Task<string> GetUsbStick()
{
StorageFolder UsbDrive = (await Windows.Storage.KnownFolders.RemovableDevices.GetFoldersAsync()).FirstOrDefault();
if (UsbDrive == null)
{
throw new InvalidOperationException("Usb Drive Not Found");
}
else
{
IReadOnlyList<StorageFile> FileList = await UsbDrive.GetFilesAsync();
var Path = UsbDrive.Path.Replace('\\','/');
foreach (StorageFile File in FileList)
{
var DBFound = File.Name.Contains("test.db");
if (DBFound == true)
{
return Path + File.Name;
}
}
throw new InvalidOperationException("DataBaseNotFound");
}
}
There I get the exact path for the database output. Only that somehow brings nothing. I cannot open it in the next step. "Sqlite cant open database" it says.
public static async Task<int> Init()
{
try
{
DatabasePath = await GetUsbStick();
StrConnDatabase = "Data Source" + "=" + DatabasePath + ";Mode=ReadWrite;";
}
catch (Exception io)
{
IsInit = false;
throw new InvalidOperationException(io.Message);
}
finally
{
//Try to Open Database to Read
using (var db = new Microsoft.Data.Sqlite.SqliteConnection(StrConnDatabase))
{
try
{
db.Open(); //<- here it breaks off
db.Close();
IsInit = true;
}
catch (Exception io)
{
throw new InvalidOperationException(io.Message);
}
}
}
return 1; // Succes
}
What could be the reason that this does not work?
is there a way to create a working copy within the app, which is then written back to the usb stick?

KnownFolders.RemovableDevices doesn't be supported on the HoloLens, for more information please see:Known folders. It is recommended to take a try at File pickers to pick one file manually.

how to display custom permission message

I want to display a custom message to the user for app permission. I am using Plugin.Permissions for App permission. When i run the current code and run application this popup message display Allow {App Name} to access this device location?. Below is the function currently i am using.
public static async Task<bool> GetPermissions()
{
bool permissionsGranted = true;
var permissionsStartList = new List<Permission>()
{
Permission.Location,
Permission.Camera
};
var permissionsNeededList = new List<Permission>();
try
{
foreach (var permission in permissionsStartList)
{
var status = await CrossPermissions.Current.CheckPermissionStatusAsync(permission);
if (status != PermissionStatus.Granted)
{
permissionsNeededList.Add(permission);
}
}
}
catch (Exception ex)
{
}
var results = await CrossPermissions.Current.RequestPermissionsAsync(permissionsNeededList.ToArray());
try
{
foreach (var permission in permissionsNeededList)
{
var status = PermissionStatus.Unknown;
//Best practice to always check that the key exists
if (results.ContainsKey(permission))
status = results[permission];
if (status == PermissionStatus.Granted || status == PermissionStatus.Unknown)
{
permissionsGranted = true;
}
else
{
permissionsGranted = false;
break;
}
}
}
catch (Exception ex)
{
}
return permissionsGranted;
}
Thanks for your help and comments

Sadly there is no way to customize the text in the permission dialogs.
These are system dialogs and the app has no control over their content.
Quote from https://developer.android.com/training/permissions/requesting#perm-request
When your app receives PERMISSION_DENIED from checkSelfPermission(), you need to prompt the user for that permission. Android provides several methods you can use to request a permission, such as requestPermissions(), as shown in the code snippet below. Calling these methods brings up a standard Android dialog, which you cannot customize.
How this is displayed to the user depends on the device Android version as well as the target version of your application, as described in the Permissions Overview.

Puma.NET DLL Recognition of car numbers

I want to make an application - license plate recognition from image. I use OpenCvSharp and Puma.NET.
But when I start my application,writes that the number is not found.
When I use breakpoints - Exception - "Recognition engine halted with code:0"
I loaded three dll - dibapi.dll, puma.net.dll, puma.interop.dll.
Why numbers are not recognized?
public void RecognizePlate() //
{
plateList.Clear();
int i = 1;
foreach(var plateImage in plate)
{
plateList.Add(i.ToString()+ " ) " + RunPuma(plateImage));
i++;
}
}
string RunPuma(IplImage img) //
{
PumaPage Image = new PumaPage(img.ToBitmap());
using (Image)
{
Image.FileFormat = PumaFileFormat.RtfAnsi;
Image.AutoRotateImage = true;
Image.FontSettings.DetectBold = true;
Image.FontSettings.DetectItalic = true;
Image.EnableSpeller = false;
Image.Language = PumaLanguage.English;
try
{
string s = Image.RecognizeToString();
return s;
}
catch(Exception e)
{
return "This is NOT NUMBER";
}
}
return "Error";
}`

You will need to restart Visual Studio as Administrator and you should be able to work then.

The problem is an unsuccessful registration.
According the documentation, apuma.dll component should be registered during the installation. But *.bat file seems to be wrong, at least for my computer.
I solved problem with:
moving all files from Puma.NET\COM Server\Register to Puma.NET\COM Server
open console in Puma.NET\COM Server directory.
Typing this command: regsvr32 APuma.dll
If you get a successful registration message, George is your uncle!!

can not create activex object using C#

I am deploying a C# application on client machine. The Application need to access code from another program, so it can scrap text from the screen of another application. It is running fine on the development machine but on the client machine it is throwing an error "ActiveX Component cannot create Object" this is where i am getting the error from!
private ExtraSession objExtraSession;
private ExtraSessions objExtraSessions;
private ExtraScreen objExtraScreen;
private ExtraArea objExtraArea;
private ExtraSystem objExtraSystem;
protected void sessionInitializer()
{
try
{
objExtraSystem = (ExtraSystem) Microsoft.VisualBasic.Interaction.CreateObject("Extra.system");
if (objExtraSystem == null)
{
MessageBox.Show("Could not create system");
return;
}
objExtraSessions = objExtraSystem.Sessions;
if (objExtraSessions == null)
{
MessageBox.Show("Could not create sessions");
return;
}
if (!System.IO.File.Exists("C:\\Users\\" + userid + "\\Documents\\Attachmate\\EXTRA!\\Sessions\\SAS.edp"))
{
MessageBox.Show("File does not exist");
return;
}
objExtraSession = (ExtraSession) Microsoft.VisualBasic.Interaction.GetObject("C:\\Users\\"+ userid + "\\Documents\\Attachmate\\EXTRA!\\Sessions\\SAS.edp");
if (objExtraSession == null)
{
MessageBox.Show("Could not create session");
return;
}
if (objExtraSession.Visible == 0)
{
objExtraSession.Visible = 1;
}
objExtraScreen = objExtraSession.Screen;
}
catch (Exception ex)
{
MessageBox.Show(ex.StackTrace, "Failed to initialize Attachmate sessions");
}
}
The error is generated from objExtraSession = (ExtraSession) Microsoft.VisualBasic.Interaction.GetObject("C:\Users\"+ userid + "\Documents\Attachmate\EXTRA!\Sessions\SAS.edp");
Am I missing some step. Please help me out. Thanks in advance.

The most likely explanation is that your development machine has the ActiveX control installed, but the client machine does not. Read the deployment documentation for the control and do what is says is required to deploy to the client machine.

Thanks for all your responses... The method GetObject was creating an object whose activex component was not registered... I resolved by finding the corresponding *.ocx file and calling Regsvr32 on the file this resolved the problem...

How to close a file in Autocad using C# keeping acad.exe running?

I am using visual studio 2010 and I am having a .DWG file which I want to open in autocad. Till now I have used this.
Process p = new Process();
ProcessStartInfo s = new ProcessStartInfo("D:/Test File/" + fileName);
p.StartInfo = s;
p.Start();
But what I want is to close the file inside the Autocad but not the autocad itself. (Means atocad.exe should be kept running).
Till now I hve used this but its closing the acad.exe not the file.
foreach (Process Proc in Process.GetProcesses())
{
if (Proc.ProcessName.Equals("acad"))
{
Proc.CloseMainWindow();
Proc.Kill();
}
}

Take the Autocad .NET libraries from Autodesk Sites (http://usa.autodesk.com/adsk/servlet/index?id=773204&siteID=123112)
Then you will be able to use Application and Document classes.
They will give you full control over opening and closing documents within the application.
You can find many articles on that, and can ask further questions.

AutoCAD does have an api. there are 4 assemblys. Two for in-process and two for COM.
inprocess :
acdbmgd.dll
acmgd.dll
COMInterop :
Autodesk.Autocad.Interop.dll
Autodesk.Autocad.Interop.Common.dll
this is a method that will open a new instance of AutoCAD or it will connect to an existing running instance of AutoCAD.
you will need to load these .dlls into your project references.
using Autodesk.AutoCAD.Interop;
using Autodesk.AutoCAD.Interop.Common;
namespace YourNameSpace {
public class YourClass {
AcadApplication AcApp;
private const string progID = "AutoCAD.Application.18.2";// this is AutoCAD 2012 program id
private string profileName = "<<Unnamed Profile>>";
private const string acadPath = #"C:\Program Files\Autodesk\AutoCAD 2012 - English\acad.exe";
public void GetAcApp()
{
try
{
AcApp = (AcadApplication)Marshal.GetActiveObject(progID);
} catch {
try {
var acadProcess = new Process();
acadProcess.StartInfo.Arguments = string.Format("/nologo /p \"{0}\"", profileName);
acadProcess.StartInfo.FileName = (#acadPath);
acadProcess.Start();
while(AcApp == null)
{
try { AcApp = (AcadApplication)Marshal.GetActiveObject(progID); }
catch { }
}
} catch(COMException) {
MessageBox.Show(String.Format("Cannot create object of type \"{0}\"",progID));
}
}
try {
int i = 0;
var appState = AcApp.GetAcadState();
while (!appState.IsQuiescent)
{
if(i == 120)
{
Application.Exit();
}
// Wait .25s
Thread.Sleep(250);
i++;
}
if(AcApp != null){
// set visibility
AcApp.Visible = true;
}
} catch (COMException err) {
if(err.ErrorCode.ToString() == "-2147417846"){
Thread.Sleep(5000);
}
}
}
}
}
closeing it is as simple as
Application.Exit();
and forgive the code. its atrocious, this was one of my first methods when i just started developing...

I doubt you will be able to do this unless AutoCAD has an API that you can hook into and ask it to close the file for you.
Your c# app can only do things to the process (acad.exe) , it doesn't have access to the internal operations of that process.

Also, you shouldn't use Kill unless the process has become unresponsive and certainly not immediately after CloseMainWindow.
CloseMainWindow is the polite way to ask an application to close itself. Kill is like pulling the power lead from the socket. You aren't giving it the chance to clean up after itself and exit cleanly.

There is one other possibility - this will only work if your C# code is running on the same machine as the AutoCAD process and it is not really recommended, but, if you are really stuck and are prepared to put up with the hassle of window switching you can send key strokes to an application using the SendKeys command.
MSDN articles here:
http://msdn.microsoft.com/EN-US/library/ms171548(v=VS.110,d=hv.2).aspx
http://msdn.microsoft.com/en-us/library/system.windows.forms.sendkeys.send.aspx
Using this you could send the key strokes to simulate the user using the menu commands to close the file.

To perform the closing of file, best way out is to follow the steps at this ObjectARX SDK for c# and change the following code with the below code.
[CommandMethod("CD", CommandFlags.Session)]
static public void CloseDocuments()
{
DocumentCollection docs = Application.DocumentManager;
foreach (Document doc in docs)
{
// First cancel any running command
if (doc.CommandInProgress != "" &&
doc.CommandInProgress != "CD")
{
AcadDocument oDoc =
(AcadDocument)doc.AcadDocument;
oDoc.SendCommand("\x03\x03");
}
if (doc.IsReadOnly)
{
doc.CloseAndDiscard();
}
else
{
// Activate the document, so we can check DBMOD
if (docs.MdiActiveDocument != doc)
{
docs.MdiActiveDocument = doc;
}
int isModified =
System.Convert.ToInt32(
Application.GetSystemVariable("DBMOD")
);
// No need to save if not modified
if (isModified == 0)
{
doc.CloseAndDiscard();
}
else
{
// This may create documents in strange places
doc.CloseAndSave(doc.Name);
}
}
}