KeyEventHandler Delegato

Riferimento

Definizione

Spazio dei nomi:: System.Windows.Forms

Assembly:: System.Windows.Forms.dll

Importante

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Rappresenta il metodo che gestirà l'evento KeyUp o KeyDown di un oggetto Control.

public delegate void KeyEventHandler(System::Object ^ sender, KeyEventArgs ^ e);

public delegate void KeyEventHandler(object sender, KeyEventArgs e);

public delegate void KeyEventHandler(object? sender, KeyEventArgs e);

type KeyEventHandler = delegate of obj * KeyEventArgs -> unit

Public Delegate Sub KeyEventHandler(sender As Object, e As KeyEventArgs)

Parametri

sender: Object

Origine dell'evento.

e: KeyEventArgs

Oggetto KeyEventArgs che contiene i dati dell'evento.

Esempio

private:
   void treeView1_KeyDown( Object^ /*sender*/, KeyEventArgs^ e )
   {
      /* If the 'Alt' and 'E' keys are pressed,
         * allow the user to edit the TreeNode label. */
      if ( e->Alt && e->KeyCode == Keys::E )
      {
         treeView1->LabelEdit = true;
         
         // If there is a TreeNode under the mouse cursor, begin editing.
         TreeNode^ editNode = treeView1->GetNodeAt( treeView1->PointToClient( Control::MousePosition ) );
         if ( editNode != nullptr )
         {
            editNode->BeginEdit();
         }
      }
   }

   void treeView1_AfterLabelEdit( Object^ /*sender*/, NodeLabelEditEventArgs^ /*e*/ )
   {
      // Disable the ability to edit the TreeNode labels.
      treeView1->LabelEdit = false;
   }

private void treeView1_KeyDown(object sender, KeyEventArgs e)
{
   /* If the 'Alt' and 'E' keys are pressed,
      * allow the user to edit the TreeNode label. */
   if(e.Alt && e.KeyCode == Keys.E)
         
   {
      treeView1.LabelEdit = true;
      // If there is a TreeNode under the mouse cursor, begin editing. 
      TreeNode editNode = treeView1.GetNodeAt(
         treeView1.PointToClient(System.Windows.Forms.Control.MousePosition));
      if(editNode != null)
      { 
         editNode.BeginEdit();
      }
   }
}

private void treeView1_AfterLabelEdit(object sender, NodeLabelEditEventArgs e)
{
   // Disable the ability to edit the TreeNode labels.
   treeView1.LabelEdit = false;
}

Private Sub treeView1_KeyDown(sender As Object, _
  e As KeyEventArgs) Handles treeView1.KeyDown
   ' If the 'Alt' and 'E' keys are pressed,
   ' allow the user to edit the TreeNode label. 
   If e.Alt And e.KeyCode = Keys.E Then
      treeView1.LabelEdit = True
      ' If there is a TreeNode under the mouse cursor, begin editing. 
      Dim editNode As TreeNode = treeView1.GetNodeAt( _
        treeView1.PointToClient(System.Windows.Forms.Control.MousePosition))
      If (editNode IsNot Nothing) Then
         editNode.BeginEdit()
      End If
   End If
End Sub

Private Sub treeView1_AfterLabelEdit(sender As Object, _
  e As NodeLabelEditEventArgs) Handles treeView1.AfterLabelEdit
   ' Disable the ability to edit the TreeNode labels.
   treeView1.LabelEdit = False
End Sub

   // Boolean flag used to determine when a character other than a number is entered.
private:
   bool nonNumberEntered;

   // Handle the KeyDown event to determine the type of character entered into the control.
   void textBox1_KeyDown( Object^ /*sender*/, System::Windows::Forms::KeyEventArgs^ e )
   {
      // Initialize the flag to false.
      nonNumberEntered = false;

      // Determine whether the keystroke is a number from the top of the keyboard.
      if ( e->KeyCode < Keys::D0 || e->KeyCode > Keys::D9 )
      {
         // Determine whether the keystroke is a number from the keypad.
         if ( e->KeyCode < Keys::NumPad0 || e->KeyCode > Keys::NumPad9 )
         {
            // Determine whether the keystroke is a backspace.
            if ( e->KeyCode != Keys::Back )
            {
               // A non-numerical keystroke was pressed.
               // Set the flag to true and evaluate in KeyPress event.
               nonNumberEntered = true;
            }
         }
      }
      //If shift key was pressed, it's not a number.
      if (Control::ModifierKeys == Keys::Shift) {
         nonNumberEntered = true;
      }
   }

   // This event occurs after the KeyDown event and can be used to prevent
   // characters from entering the control.
   void textBox1_KeyPress( Object^ /*sender*/, System::Windows::Forms::KeyPressEventArgs^ e )
   {
      // Check for the flag being set in the KeyDown event.
      if ( nonNumberEntered == true )
      {         // Stop the character from being entered into the control since it is non-numerical.
         e->Handled = true;
      }
   }

// Boolean flag used to determine when a character other than a number is entered.
private bool nonNumberEntered = false;

// Handle the KeyDown event to determine the type of character entered into the control.
private void textBox1_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)
{
    // Initialize the flag to false.
    nonNumberEntered = false;

    // Determine whether the keystroke is a number from the top of the keyboard.
    if (e.KeyCode < Keys.D0 || e.KeyCode > Keys.D9)
    {
        // Determine whether the keystroke is a number from the keypad.
        if (e.KeyCode < Keys.NumPad0 || e.KeyCode > Keys.NumPad9)
        {
            // Determine whether the keystroke is a backspace.
            if(e.KeyCode != Keys.Back)
            {
                // A non-numerical keystroke was pressed.
                // Set the flag to true and evaluate in KeyPress event.
                nonNumberEntered = true;
            }
        }
    }
    //If shift key was pressed, it's not a number.
    if (Control.ModifierKeys == Keys.Shift) {
        nonNumberEntered = true;
    }
}

// This event occurs after the KeyDown event and can be used to prevent
// characters from entering the control.
private void textBox1_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
{
    // Check for the flag being set in the KeyDown event.
    if (nonNumberEntered == true)
    {
        // Stop the character from being entered into the control since it is non-numerical.
        e.Handled = true;
    }
}

 ' Boolean flag used to determine when a character other than a number is entered.
 Private nonNumberEntered As Boolean = False


 ' Handle the KeyDown event to determine the type of character entered into the control.
 Private Sub textBox1_KeyDown(sender As Object, e As System.Windows.Forms.KeyEventArgs) _
      Handles textBox1.KeyDown
     ' Initialize the flag to false.
     nonNumberEntered = False
   
     ' Determine whether the keystroke is a number from the top of the keyboard.
     If e.KeyCode < Keys.D0 OrElse e.KeyCode > Keys.D9 Then
         ' Determine whether the keystroke is a number from the keypad.
         If e.KeyCode < Keys.NumPad0 OrElse e.KeyCode > Keys.NumPad9 Then
             ' Determine whether the keystroke is a backspace.
             If e.KeyCode <> Keys.Back Then
                 ' A non-numerical keystroke was pressed. 
                 ' Set the flag to true and evaluate in KeyPress event.
                 nonNumberEntered = True
             End If
         End If
     End If
     'If shift key was pressed, it's not a number.
     If Control.ModifierKeys = Keys.Shift Then
         nonNumberEntered = true
     End If
 End Sub


 ' This event occurs after the KeyDown event and can be used 
 ' to prevent characters from entering the control.
 Private Sub textBox1_KeyPress(sender As Object, e As System.Windows.Forms.KeyPressEventArgs) _
     Handles textBox1.KeyPress
     ' Check for the flag being set in the KeyDown event.
     If nonNumberEntered = True Then
         ' Stop the character from being entered into the control since it is non-numerical.
         e.Handled = True
     End If
 End Sub

Commenti

Quando si crea un delegato KeyEventHandler, si identifica il metodo che gestirà l'evento. Per associare l'evento al gestore eventi in uso, aggiungere all'evento un'istanza del delegato. Il gestore eventi viene chiamato ogni volta che si verifica l'evento, a meno che non venga rimosso il delegato. Per altre informazioni sulla gestione degli eventi con delegati, vedere Gestione e generazione di eventi.

Metodi di estensione

GetMethodInfo(Delegate)

Ottiene un oggetto che rappresenta il metodo rappresentato dal delegato specificato.

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