Guide pratique pour gérer l'entrée au clavier au niveau du formulaire

Article
06/02/2023

Windows Forms offre la possibilité de gérer les messages de clavier au niveau du formulaire, avant que les messages n'atteignent un contrôle. Cette rubrique montre comment procéder.

Pour gérer un message de clavier au niveau du formulaire

Gérez l'événement KeyPress ou KeyDown du formulaire de démarrage et affectez la valeur true à la propriété KeyPreview du formulaire pour que les messages de clavier soient reçus par le formulaire avant qu'ils atteignent les contrôles sur le formulaire. L'exemple de code suivant gère l'événement KeyPress en détectant toutes les touches numériques et en consommant « 1 », « 4 » et « 7 ».

    // Detect all numeric characters at the form level and consume 1,
    // 4, and 7. Note that Form.KeyPreview must be set to true for this
    // event handler to be called.
private:
    void Form1_KeyPress(Object^ sender, KeyPressEventArgs^ e)
    {
        if ((e->KeyChar >= '0') && (e->KeyChar <= '9'))
        {
            MessageBox::Show("Form.KeyPress: '" +
                e->KeyChar.ToString() + "' pressed.");

            switch (e->KeyChar)
            {
            case '1':
            case '4':
            case '7':
                MessageBox::Show("Form.KeyPress: '" +
                    e->KeyChar.ToString() + "' consumed.");
                e->Handled = true;
                break;
            }
        }
    }

// Detect all numeric characters at the form level and consume 1,
// 4, and 7. Note that Form.KeyPreview must be set to true for this
// event handler to be called.
void Form1_KeyPress(object sender, KeyPressEventArgs e)
{
    if (e.KeyChar >= 48 && e.KeyChar <= 57)
    {
        MessageBox.Show("Form.KeyPress: '" +
            e.KeyChar.ToString() + "' pressed.");

        switch (e.KeyChar)
        {
            case (char)49:
            case (char)52:
            case (char)55:
                MessageBox.Show("Form.KeyPress: '" +
                    e.KeyChar.ToString() + "' consumed.");
                e.Handled = true;
                break;
        }
    }
}

' Detect all numeric characters at the form level and consume 1, 
' 4, and 7. Note that Form.KeyPreview must be set to true for this
' event handler to be called.
Sub Form1_KeyPress(ByVal sender As Object, _
    ByVal e As KeyPressEventArgs) Handles Me.KeyPress

    If e.KeyChar >= ChrW(48) And e.KeyChar <= ChrW(57) Then
        MessageBox.Show(("Form.KeyPress: '" + _
            e.KeyChar.ToString() + "' pressed."))

        Select Case e.KeyChar
            Case ChrW(49), ChrW(52), ChrW(55)
                MessageBox.Show(("Form.KeyPress: '" + _
                    e.KeyChar.ToString() + "' consumed."))
                e.Handled = True
        End Select
    End If
End Sub

Exemple

L'exemple de code suivant est l'application complète pour l'exemple ci-dessus. L'application comprend un TextBox avec plusieurs autres contrôles qui vous permettent de déplacer le focus hors du TextBox. L'événement KeyPress du Form principal consomme « 1 », « 4 » et « 7 » et l'événement KeyPress du TextBox consomme « 2 », « 5 » et « 8 » tout en affichant les touches restantes. Comparez la sortie de MessageBox quand vous appuyez sur une touche numérique pendant que le TextBox a le focus avec la sortie de MessageBox quand vous appuyez sur une touche numérique pendant que le focus est sur l'un des autres contrôles.

#using <System.Drawing.dll>
#using <System.Windows.Forms.dll>
#using <System.dll>

using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;
using namespace System::Security::Permissions;

namespace KeyboardInputForm
{
    public ref class Form1 sealed: public Form, public IMessageFilter
    {
        // The following Windows message value is defined in Winuser.h.
    private:
        static const int WM_KEYDOWN = 0x100;
    private:
        TextBox^ inputTextBox;
    public:
        Form1()
        {
            inputTextBox = gcnew TextBox();
            this->AutoSize = true;
            Application::AddMessageFilter(this);
            FlowLayoutPanel^ panel = gcnew FlowLayoutPanel();
            panel->AutoSize = true;
            panel->FlowDirection = FlowDirection::TopDown;
            panel->Controls->Add(gcnew Button());
            panel->Controls->Add(gcnew RadioButton());
            panel->Controls->Add(inputTextBox);
            this->Controls->Add(panel);
            this->KeyPreview = true;
            this->KeyPress +=
                gcnew KeyPressEventHandler(this, &Form1::Form1_KeyPress);
            inputTextBox->KeyPress +=
                gcnew KeyPressEventHandler(this,
                &Form1::inputTextBox_KeyPress);
        }

        // Detect all numeric characters at the
        // application level and consume 0.
        virtual bool PreFilterMessage(Message% m)
        {
            // Detect key down messages.
            if (m.Msg == WM_KEYDOWN)
            {
                Keys keyCode =  (Keys)((int)m.WParam) & Keys::KeyCode;
                // Determine whether the keystroke is a number from the top of
                // the keyboard, or a number from the keypad.
                if (((keyCode >= Keys::D0) && (keyCode <= Keys::D9))
                    ||((keyCode >= Keys::NumPad0)
                    && (keyCode <= Keys::NumPad9)))
                {
                    MessageBox::Show(
                        "IMessageFilter.PreFilterMessage: '" +
                        keyCode.ToString() + "' pressed.");

                    if ((keyCode == Keys::D0) || (keyCode == Keys::NumPad0))
                    {
                        MessageBox::Show(
                            "IMessageFilter.PreFilterMessage: '" +
                            keyCode.ToString() + "' consumed.");
                        return true;
                    }
                }
            }

            // Forward all other messages.
            return false;
        }

        // Detect all numeric characters at the form level and consume 1,
        // 4, and 7. Note that Form.KeyPreview must be set to true for this
        // event handler to be called.
    private:
        void Form1_KeyPress(Object^ sender, KeyPressEventArgs^ e)
        {
            if ((e->KeyChar >= '0') && (e->KeyChar <= '9'))
            {
                MessageBox::Show("Form.KeyPress: '" +
                    e->KeyChar.ToString() + "' pressed.");

                switch (e->KeyChar)
                {
                case '1':
                case '4':
                case '7':
                    MessageBox::Show("Form.KeyPress: '" +
                        e->KeyChar.ToString() + "' consumed.");
                    e->Handled = true;
                    break;
                }
            }
        }

        // Detect all numeric characters at the TextBox level and consume
        // 2, 5, and 8.
    private:
        void inputTextBox_KeyPress(Object^ sender, KeyPressEventArgs^ e)
        {
            if ((e->KeyChar >= '0') && (e->KeyChar <= '9'))
            {
                MessageBox::Show("Control.KeyPress: '" +
                    e->KeyChar.ToString() + "' pressed.");

                switch (e->KeyChar)
                {
                case '2':
                case '5':
                case '8':
                    MessageBox::Show("Control.KeyPress: '" +
                        e->KeyChar.ToString() + "' consumed.");
                    e->Handled = true;
                    break;
                }
            }
        }
    };
}

[STAThread]
int main()
{
    Application::EnableVisualStyles();
    Application::Run(gcnew KeyboardInputForm::Form1());
}

using System;
using System.Drawing;
using System.Windows.Forms;

namespace KeyboardInputForm
{
    class Form1 : Form
    {
        TextBox TextBox1 = new TextBox();

        [STAThread]
        public static void Main()
        {
            Application.EnableVisualStyles();
            Application.Run(new Form1());
        }

        public Form1()
        {
            this.AutoSize = true;

            FlowLayoutPanel panel = new FlowLayoutPanel();
            panel.AutoSize = true;
            panel.FlowDirection = FlowDirection.TopDown;
            panel.Controls.Add(TextBox1);
            this.Controls.Add(panel);

            this.KeyPreview = true;
            this.KeyPress +=
                new KeyPressEventHandler(Form1_KeyPress);
            TextBox1.KeyPress +=
                new KeyPressEventHandler(TextBox1_KeyPress);
        }

        // Detect all numeric characters at the form level and consume 1,
        // 4, and 7. Note that Form.KeyPreview must be set to true for this
        // event handler to be called.
        void Form1_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar >= 48 && e.KeyChar <= 57)
            {
                MessageBox.Show("Form.KeyPress: '" +
                    e.KeyChar.ToString() + "' pressed.");

                switch (e.KeyChar)
                {
                    case (char)49:
                    case (char)52:
                    case (char)55:
                        MessageBox.Show("Form.KeyPress: '" +
                            e.KeyChar.ToString() + "' consumed.");
                        e.Handled = true;
                        break;
                }
            }
        }

        // Detect all numeric characters at the TextBox level and consume
        // 2, 5, and 8.
        void TextBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar >= 48 && e.KeyChar <= 57)
            {
                MessageBox.Show("Control.KeyPress: '" +
                    e.KeyChar.ToString() + "' pressed.");

                switch (e.KeyChar)
                {
                    case (char)50:
                    case (char)53:
                    case (char)56:
                        MessageBox.Show("Control.KeyPress: '" +
                            e.KeyChar.ToString() + "' consumed.");
                        e.Handled = true;
                        break;
                }
            }
        }
    }
}

Imports System.Drawing
Imports System.Windows.Forms

Namespace KeyboardInputForm

     Class Form1
      Inherits Form

        Private WithEvents TextBox1 As New TextBox()

      <STAThread()> _
      Public Shared Sub Main()
         Application.EnableVisualStyles()
         Application.Run(New Form1())
      End Sub

      Public Sub New()
         Me.AutoSize = True

         Dim panel As New FlowLayoutPanel()
         panel.AutoSize = True
         panel.FlowDirection = FlowDirection.TopDown
         panel.Controls.Add(TextBox1)
         Me.Controls.Add(panel)

         Me.KeyPreview = True
        End Sub

        ' Detect all numeric characters at the form level and consume 1, 
        ' 4, and 7. Note that Form.KeyPreview must be set to true for this
        ' event handler to be called.
        Sub Form1_KeyPress(ByVal sender As Object, _
            ByVal e As KeyPressEventArgs) Handles Me.KeyPress

            If e.KeyChar >= ChrW(48) And e.KeyChar <= ChrW(57) Then
                MessageBox.Show(("Form.KeyPress: '" + _
                    e.KeyChar.ToString() + "' pressed."))

                Select Case e.KeyChar
                    Case ChrW(49), ChrW(52), ChrW(55)
                        MessageBox.Show(("Form.KeyPress: '" + _
                            e.KeyChar.ToString() + "' consumed."))
                        e.Handled = True
                End Select
            End If
        End Sub

      ' Detect all numeric characters at the TextBox level and consume  
      ' 2, 5, and 8.
      Sub TextBox1_KeyPress(ByVal sender As Object, _
          ByVal e As KeyPressEventArgs) Handles TextBox1.KeyPress

         If e.KeyChar >= ChrW(48) And e.KeyChar <= ChrW(57) Then
            MessageBox.Show(("Control.KeyPress: '" + _
                e.KeyChar.ToString() + "' pressed."))

            Select Case e.KeyChar
               Case ChrW(50), ChrW(53), ChrW(56)
                  MessageBox.Show(("Control.KeyPress: '" + _
                      e.KeyChar.ToString() + "' consumed."))
                  e.Handled = True
            End Select
         End If
      End Sub

   End Class
End Namespace

Compilation du code

Cet exemple nécessite :

des références aux assemblys System, System.Drawing et System.Windows.Forms.

Voir aussi

Entrée au clavier dans une application Windows Forms

Guide pratique pour gérer l'entrée au clavier au niveau du formulaire

Pour gérer un message de clavier au niveau du formulaire

Exemple

Compilation du code

Voir aussi

Commentaires

Ressources supplémentaires