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KeyDownEventHandler Delegate

Summary

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

Syntax

C++

public delegate void KeyDownEventHandler( 
   object sender, 
   KeyDownEventArgs e 
)

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

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

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 20\Media"; 
}

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 20\Media" 
End Class

Requirements

Target Platforms

Reference

KeyDownEventHandler Members

Leadtools.MediaFoundation Namespace

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Help Version 20.0.2020.4.2

Leadtools.MediaFoundation Assembly

Introduction

Getting Started

Namespaces

Leadtools.MediaFoundation Namespace

Leadtools.MediaFoundation.Common Namespace

Assemblies