HOW TO：將鍵盤輸入修改為標準控制項

發行項
08/12/2011

Windows Form 提供使用和修改鍵盤輸入的能力。使用按鍵表示在方法或事件處理常式中處理按鍵，因此訊息佇列中後面的其他方法和事件並不會收到按鍵值。修改按鍵表示修改按鍵的值，因此訊息佇列中後面的方法和事件處理常式會收到不同的按鍵值。本主題將示範如何完成這些工作。

若要使用按鍵

在 KeyPress 事件處理常式中，將 KeyPressEventArgs 類別的 Handled 屬性設定為 true。

-或-

在 KeyDown 事件處理常式中，將 KeyEventArgs 類別的 Handled 屬性設定為 true。

注意事項
在 KeyDown 事件處理常式中設定 Handled 屬性，並不會防止引發目前按鍵的 KeyPress 和 KeyUp 事件。為了這個目的，請使用 SuppressKeyPress 屬性。

下列範例摘錄自 switch 陳述式，它會檢查 KeyPress 事件處理常式所收到的 KeyPressEventArgs 的 KeyChar 屬性。此程式碼會使用 'A' 和 'a' 字元按鍵。

' Consume 'A' and 'a'.
Case ChrW(65), ChrW(97)
    MessageBox.Show(("Control.KeyPress: '" + _
        e.KeyChar.ToString() + "' consumed."))
    e.Handled = True

// Consume 'A' and 'a'.
case (char)65:
case (char)97:
    MessageBox.Show("Control.KeyPress: '" +
        e.KeyChar.ToString() + "' consumed.");
    e.Handled = true;
    break;

若要修改標準的字元按鍵

在 KeyPress 事件處理常式中，將 KeyPressEventArgs 類別的 KeyChar 屬性設定為新字元按鍵的值。

下列範例摘錄自 switch 陳述式，它會將 'B' 修改為 'A' 及將 'b' 修改為 'a'。請注意，KeyPressEventArgs 參數的 Handled 屬性會設定為 false，因此新按鍵值會傳送至訊息佇列中的其他方法和事件。

    ' Modify 'B' to 'A' and forward the key.
Case ChrW(66)
    MessageBox.Show(("Control.KeyPress: '" + _
        e.KeyChar.ToString() + "' replaced by 'A'."))
    e.KeyChar = ChrW(65)
    e.Handled = False

    ' Modify 'b' to 'a' and forward the key.
Case ChrW(98)
    MessageBox.Show(("Control.KeyPress: '" + _
        e.KeyChar.ToString() + "' replaced by 'a'."))
    e.KeyChar = ChrW(97)
    e.Handled = False

// Detect 'B', modify it to 'A', and forward the key.
case (char)66:
    MessageBox.Show("Control.KeyPress: '" +
        e.KeyChar.ToString() + "' replaced by 'A'.");
    e.KeyChar = (char)65;
    e.Handled = false;
    break;

// Detect 'b', modify it to 'a', and forward the key.
case (char)98:
    MessageBox.Show("Control.KeyPress: '" +
        e.KeyChar.ToString() + "' replaced by 'a'.");
    e.KeyChar = (char)97;
    e.Handled = false;
    break;

若要修改非字元按鍵

覆寫處理 Windows 訊息的 Control 方法、偵測 WM_KEYDOWN 或 WM_SYSKEYDOWN 訊息，並將 Message 參數的 WParam 屬性設定為表示新非字元按鍵的 Keys 值。

下列程式碼範例示範如何覆寫控制項的 PreProcessMessage 方法，以偵測按鍵 F1 至 F9，並將任何按下的 F3 按鍵修改為 F1。如需您可以覆寫以攔截鍵盤訊息的 Control 方法的詳細資訊，請參閱Windows Form 應用程式中的使用者輸入和鍵盤輸入的運作方式。

' Detect F1 through F9 during preprocessing and modify F3.
Public Overrides Function PreProcessMessage(ByRef m As Message) _
    As Boolean

    If m.Msg = WM_KEYDOWN Then
        Dim keyCode As Keys = CType(m.WParam, Keys) And Keys.KeyCode

        ' Detect F1 through F9.
        Select Case keyCode
            Case Keys.F1, Keys.F2, Keys.F3, Keys.F4, Keys.F5, _
                 Keys.F6, Keys.F7, Keys.F8, Keys.F9

                MessageBox.Show(("Control.PreProcessMessage: '" + _
                    keyCode.ToString() + "' pressed."))

                ' Replace F3 with F1, so that ProcessKeyMessage will  
                ' receive F1 instead of F3.
                If keyCode = Keys.F3 Then
                    m.WParam = CType(Keys.F1, IntPtr)
                    MessageBox.Show(("Control.PreProcessMessage: '" + _
                        keyCode.ToString() + "' replaced by F1."))
                End If
        End Select
    End If

    ' Send all other messages to the base method.
    Return MyBase.PreProcessMessage(m)
End Function

// Detect F1 through F9 during preprocessing and modify F3.
public override bool PreProcessMessage(ref Message m)
{
    if (m.Msg == WM_KEYDOWN)
    {
        Keys keyCode = (Keys)m.WParam & Keys.KeyCode;

        // Detect F1 through F9.
        switch (keyCode)
        {
            case Keys.F1:
            case Keys.F2:
            case Keys.F3:
            case Keys.F4:
            case Keys.F5:
            case Keys.F6:
            case Keys.F7:
            case Keys.F8:
            case Keys.F9:

                MessageBox.Show("Control.PreProcessMessage: '" +
                  keyCode.ToString() + "' pressed.");

                // Replace F3 with F1, so that ProcessKeyMessage will  
                // receive F1 instead of F3.
                if (keyCode == Keys.F3)
                {
                    m.WParam = (IntPtr)Keys.F1;
                    MessageBox.Show("Control.PreProcessMessage: '" +
                        keyCode.ToString() + "' replaced by F1.");
                }
                break;
        }
    }

    // Send all other messages to the base method.
    return base.PreProcessMessage(ref m);
}

範例

下列程式碼範例是前面幾節中程式碼範例的完整應用程式。此應用程式使用衍生自 TextBox 類別的自訂控制項來使用和修改鍵盤輸入。

Imports System
Imports System.Drawing
Imports System.Security
Imports System.Security.Permissions
Imports System.Windows.Forms


Namespace KeyboardInput
<System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _ 
    Class Form1
        Inherits Form

        ' The following Windows message value is defined in Winuser.h.
        Private WM_KEYDOWN As Integer = &H100
        Private WithEvents CustomTextBox1 As New CustomTextBox()

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

        Public Sub New()
            Me.AutoSize = True
            Me.Controls.Add(CustomTextBox1)
        End Sub

        ' Consume and modify several character keys.
        Sub CustomTextBox1_KeyPress(ByVal sender As Object, _
            ByVal e As KeyPressEventArgs) Handles CustomTextBox1.KeyPress

            Select Case e.KeyChar

                ' Consume 'A' and 'a'.
                Case ChrW(65), ChrW(97)
                    MessageBox.Show(("Control.KeyPress: '" + _
                        e.KeyChar.ToString() + "' consumed."))
                    e.Handled = True

                    ' Modify 'B' to 'A' and forward the key.
                Case ChrW(66)
                    MessageBox.Show(("Control.KeyPress: '" + _
                        e.KeyChar.ToString() + "' replaced by 'A'."))
                    e.KeyChar = ChrW(65)
                    e.Handled = False

                    ' Modify 'b' to 'a' and forward the key.
                Case ChrW(98)
                    MessageBox.Show(("Control.KeyPress: '" + _
                        e.KeyChar.ToString() + "' replaced by 'a'."))
                    e.KeyChar = ChrW(97)
                    e.Handled = False
            End Select
        End Sub
    End Class

<System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _ 
    Public Class CustomTextBox
        Inherits TextBox

        ' The following Windows message value is defined in Winuser.h.
        Private WM_KEYDOWN As Integer = &H100

        Public Sub New()
            Me.Size = New Size(100, 100)
            Me.AutoSize = False
        End Sub

        ' Detect F1 through F9 during preprocessing and modify F3.
        Public Overrides Function PreProcessMessage(ByRef m As Message) _
            As Boolean

            If m.Msg = WM_KEYDOWN Then
                Dim keyCode As Keys = CType(m.WParam, Keys) And Keys.KeyCode

                ' Detect F1 through F9.
                Select Case keyCode
                    Case Keys.F1, Keys.F2, Keys.F3, Keys.F4, Keys.F5, _
                         Keys.F6, Keys.F7, Keys.F8, Keys.F9

                        MessageBox.Show(("Control.PreProcessMessage: '" + _
                            keyCode.ToString() + "' pressed."))

                        ' Replace F3 with F1, so that ProcessKeyMessage will  
                        ' receive F1 instead of F3.
                        If keyCode = Keys.F3 Then
                            m.WParam = CType(Keys.F1, IntPtr)
                            MessageBox.Show(("Control.PreProcessMessage: '" + _
                                keyCode.ToString() + "' replaced by F1."))
                        End If
                End Select
            End If

            ' Send all other messages to the base method.
            Return MyBase.PreProcessMessage(m)
        End Function

        ' Detect F1 through F9 during processing.
        Protected Overrides Function ProcessKeyMessage(ByRef m As Message) _
            As Boolean

            If m.Msg = WM_KEYDOWN Then
                Dim keyCode As Keys = CType(m.WParam, Keys) And Keys.KeyCode

                ' Detect F1 through F9.
                Select Case keyCode
                    Case Keys.F1, Keys.F2, Keys.F3, Keys.F4, Keys.F5, _
                         Keys.F6, Keys.F7, Keys.F8, Keys.F9

                        MessageBox.Show(("Control.ProcessKeyMessage: '" + _
                            keyCode.ToString() + "' pressed."))
                End Select
            End If

            ' Send all messages to the base method.
            Return MyBase.ProcessKeyMessage(m)
        End Function

    End Class
End Namespace

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

namespace KeyboardInput
{
[System.Security.Permissions.PermissionSet(System.Security.Permissions.SecurityAction.Demand, Name="FullTrust")]
    class Form1 : Form
    {
        // The following Windows message value is defined in Winuser.h.
        private int WM_KEYDOWN = 0x100;
        CustomTextBox CustomTextBox1 = new CustomTextBox();

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

        public Form1()
        {
            this.AutoSize = true;
            this.Controls.Add(CustomTextBox1);
            CustomTextBox1.KeyPress +=
                new KeyPressEventHandler(CustomTextBox1_KeyPress);
        }

        // Consume and modify several character keys.
        void CustomTextBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            switch (e.KeyChar)
            {
                // Consume 'A' and 'a'.
                case (char)65:
                case (char)97:
                    MessageBox.Show("Control.KeyPress: '" +
                        e.KeyChar.ToString() + "' consumed.");
                    e.Handled = true;
                    break;

                // Detect 'B', modify it to 'A', and forward the key.
                case (char)66:
                    MessageBox.Show("Control.KeyPress: '" +
                        e.KeyChar.ToString() + "' replaced by 'A'.");
                    e.KeyChar = (char)65;
                    e.Handled = false;
                    break;

                // Detect 'b', modify it to 'a', and forward the key.
                case (char)98:
                    MessageBox.Show("Control.KeyPress: '" +
                        e.KeyChar.ToString() + "' replaced by 'a'.");
                    e.KeyChar = (char)97;
                    e.Handled = false;
                    break;
            }
        }
    }
[System.Security.Permissions.PermissionSet(System.Security.Permissions.SecurityAction.Demand, Name="FullTrust")]
    public class CustomTextBox : TextBox
    {
        // The following Windows message value is defined in Winuser.h.
        private int WM_KEYDOWN = 0x100;

        public CustomTextBox()
        {
            this.Size = new Size(100, 100);
            this.AutoSize = false;
        }

        // Detect F1 through F9 during preprocessing and modify F3.
        public override bool PreProcessMessage(ref Message m)
        {
            if (m.Msg == WM_KEYDOWN)
            {
                Keys keyCode = (Keys)m.WParam & Keys.KeyCode;

                // Detect F1 through F9.
                switch (keyCode)
                {
                    case Keys.F1:
                    case Keys.F2:
                    case Keys.F3:
                    case Keys.F4:
                    case Keys.F5:
                    case Keys.F6:
                    case Keys.F7:
                    case Keys.F8:
                    case Keys.F9:

                        MessageBox.Show("Control.PreProcessMessage: '" +
                          keyCode.ToString() + "' pressed.");

                        // Replace F3 with F1, so that ProcessKeyMessage will  
                        // receive F1 instead of F3.
                        if (keyCode == Keys.F3)
                        {
                            m.WParam = (IntPtr)Keys.F1;
                            MessageBox.Show("Control.PreProcessMessage: '" +
                                keyCode.ToString() + "' replaced by F1.");
                        }
                        break;
                }
            }

            // Send all other messages to the base method.
            return base.PreProcessMessage(ref m);
        }

        // Detect F1 through F9 during processing.
        protected override bool ProcessKeyMessage(ref Message m)
        {
            if (m.Msg == WM_KEYDOWN)
            {
                Keys keyCode = (Keys)m.WParam & Keys.KeyCode;

                // Detect F1 through F9.
                switch (keyCode)
                {
                    case Keys.F1:
                    case Keys.F2:
                    case Keys.F3:
                    case Keys.F4:
                    case Keys.F5:
                    case Keys.F6:
                    case Keys.F7:
                    case Keys.F8:
                    case Keys.F9:

                        MessageBox.Show("Control.ProcessKeyMessage: '" +
                          keyCode.ToString() + "' pressed.");
                        break;
                }
            }

            // Send all messages to the base method.
            return base.ProcessKeyMessage(ref m);
        }
    }
}

編譯程式碼

這個範例需要：

System、System.Drawing 和 System.Windows.Forms 組件的參考。

如需從 Visual Basic 或 Visual C# 的命令列建置這個範例的詳細資訊，請參閱從命令列建置 (Visual Basic) 或使用 csc.exe 建置命令列。您也可以透過將程式碼貼入新的專案，在 Visual Studio 中建置此範例。如需詳細資訊，請參閱HOW TO：使用 Visual Studio 編譯及執行完整的 Windows Form 程式碼範例和 HOW TO：使用 Visual Studio 編譯及執行完整的 Windows Form 程式碼範例和 HOW TO：使用 Visual Studio 編譯及執行完整的 Windows Form 程式碼範例和 HOW TO：使用 Visual Studio 編譯及執行完整的 Windows Form 程式碼範例和如何：使用 Visual Studio 編譯及執行完整的 Windows Form 程式碼範例.

請參閱

概念

Windows Form 應用程式中的使用者輸入

鍵盤輸入的運作方式

其他資源

Windows Form 應用程式中的鍵盤輸入