KeyDownEventHandler Delegate

Represents the method that will handle an event that has received KeyDownEventArgs data.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
Public Delegate Sub KeyDownEventHandler( _
   ByVal sender As Object, _
   ByVal e As KeyDownEventArgs _
)

'Usage
 
Dim instance As New KeyDownEventHandler(AddressOf HandlerMethod)

public delegate void KeyDownEventHandler( 
   object sender,
   KeyDownEventArgs e
)

public delegate void KeyDownEventHandler( 
   Object^ sender,
   KeyDownEventArgs^ e
)

Parameters

sender: The source of the event.
e: A KeyDownEventArgs object that contains the event data.

Remarks

Represents the method that will handle an event that has received KeyDownEventArgs data. When the KeyDownEvent event is raised in a toolkit object, any subscribed event handlers in your code will be called. See the Microsoft documentation on .NET Events and Delegates for more information about .NET delegates and events.

Example

Visual Basic
C#
WinRT C#
WinRT JavaScript
Silverlight C#
Silverlight VB

Copy Code

Imports Leadtools
Imports Leadtools.MediaFoundation
Imports LeadtoolsMediaFoundationExamples.Fixtures

Public _result As Boolean = False
Public _exit As Boolean = False
Public _form As New CaptureCtrlForm()
Public Sub KeyPressesExample()
    Dim capturectrl As CaptureCtrl = _form.CaptureCtrl
    Dim outFile As String = Path.Combine(LEAD_VARS.MediaDir, "CaptureCtrl_KeyPressesExample.avi")

    Try
        ' set a video device, use the name of your device here
        If capturectrl.VideoDevices("Analog") Is Nothing Then
            Throw New Exception("No Analog capture device available")
        End If

        capturectrl.VideoDevices("Analog").Selected = True

        ' set an audio device, use the name of your device here
        capturectrl.AudioDevices("USB").Selected = True

        ' enable preview
        capturectrl.Preview = True

        ' set the target output file
        capturectrl.TargetFile = outFile

        ' subscribe to the key events
        AddHandler capturectrl.KeyDown, AddressOf KeyDown_Helper
        AddHandler capturectrl.KeyUp, AddressOf KeyUp_Helper
        AddHandler capturectrl.KeyPress, AddressOf KeyPress_Helper

        ' capture it now!
        capturectrl.StartCapture(CaptureMode.AutoFramesAndAudio)
    Catch generatedExceptionName As Exception
        _result = False
    End Try

    ' we'll loop on the state and pump messages for this example.
    ' but you should not need to if running from a Windows Forms application.
    While _exit = False
        Application.DoEvents()
    End While

    ' clean up event handlers
    RemoveHandler capturectrl.KeyDown, AddressOf KeyDown_Helper
    RemoveHandler capturectrl.KeyUp, AddressOf KeyUp_Helper
    RemoveHandler capturectrl.KeyPress, AddressOf KeyPress_Helper
End Sub

Private Sub KeyPress_Helper(ByVal sender As Object, ByVal e As Leadtools.MediaFoundation.KeyPressEventArgs)
    Select Case e.keyAscii
        Case CShort("p")
            ' toggle preview mode
            _form.CaptureCtrl.TogglePreview()
        Case CShort("f")
            ' toggle full screen mode
            _form.CaptureCtrl.ToggleFullScreenMode()
        Case CShort("s")
            ' stop the capture and exit
            _form.CaptureCtrl.StopCapture()
            _exit = True
    End Select

    ' set result
    _result = True
End Sub

Private Sub KeyUp_Helper(ByVal sender As Object, ByVal e As KeyUpEventArgs)
    ' set result
    _result = True
End Sub

Public Sub KeyDown_Helper(ByVal sender As Object, ByVal e As KeyDownEventArgs)
    ' set result
    _result = True
End Sub

Public NotInheritable Class LEAD_VARS
Public Const MediaDir As String = "C:\Program Files (x86)\LEAD Technologies\LEADTOOLS 18\Media"
End Class

using Leadtools;
using Leadtools.MediaFoundation;
using LeadtoolsMediaFoundationExamples.Fixtures;

public bool _result = false;
public bool _exit = false;
public CaptureCtrlForm _form = new CaptureCtrlForm();
public void KeyPressesExample()
{
   CaptureCtrl capturectrl = _form.CaptureCtrl;
   string outFile = Path.Combine(LEAD_VARS.MediaDir,"CaptureCtrl_KeyPressesExample.avi");

   try
   {
      // set a video device, use the name of your device here
      if (capturectrl.VideoDevices["Analog"] == null)
         throw new Exception("No Analog capture device available");

      capturectrl.VideoDevices["Analog"].Selected = true;

      // set an audio device, use the name of your device here
      capturectrl.AudioDevices["USB"].Selected = true;

      // enable preview
      capturectrl.Preview = true;

      // set the target output file
      capturectrl.TargetFile = outFile;

      // subscribe to the key events
      capturectrl.KeyDown += KeyDown_Helper;
      capturectrl.KeyUp += KeyUp_Helper;
      capturectrl.KeyPress += KeyPress_Helper;

      // capture it now!
      capturectrl.StartCapture(CaptureMode.AutoFramesAndAudio);
   }
   catch (Exception)
   {
      _result = false;
   }

   // we'll loop on the state and pump messages for this example.
   // but you should not need to if running from a Windows Forms application.
   while (_exit == false)
      Application.DoEvents();

   // clean up event handlers
   capturectrl.KeyDown -= KeyDown_Helper;
   capturectrl.KeyUp -= KeyUp_Helper;
   capturectrl.KeyPress -= KeyPress_Helper;
}

void KeyPress_Helper(object sender, Leadtools.MediaFoundation.KeyPressEventArgs e)
{
   switch ((char)e.keyAscii)
   {
      case 'p':
         // toggle preview mode
         _form.CaptureCtrl.TogglePreview();
         break;
      case 'f':
         // toggle full screen mode
         _form.CaptureCtrl.ToggleFullScreenMode();
         break;
      case 's':
         // stop the capture and exit
         _form.CaptureCtrl.StopCapture();
         _exit = true;
         break;
   }

   // set result
   _result = true;
}

void KeyUp_Helper(object sender, KeyUpEventArgs e)
{
   // set result
   _result = true;
}

public void KeyDown_Helper(object sender, KeyDownEventArgs e)
{
   // set result
   _result = true;
}

static class LEAD_VARS
{
public const string MediaDir = @"C:\Program Files (x86)\LEAD Technologies\LEADTOOLS 18\Media";
}

Requirements

Target Platforms

Reference

KeyDownEventHandler Members
Leadtools.MediaFoundation Namespace