KeyPressEventHandler デリゲートとは何？わかりやすく解説 Weblio辞書

.NET Framework クラスライブラリリファレンス

索引トップ用語の索引ランキング

KeyPressEventHandler デリゲート

Control の KeyPress イベントを処理するメソッドを表します。

名前空間: System.Windows.Forms
アセンブリ: System.Windows.Forms (system.windows.forms.dll 内)
構文

Visual Basic (宣言)

Public Delegate Sub KeyPressEventHandler
 ( _
    sender As Object, _
    e As KeyPressEventArgs _
)

Visual Basic (使用法)

Dim instance As New KeyPressEventHandler(AddressOf
 HandlerMethod)

public delegate void KeyPressEventHandler (
    Object sender,
    KeyPressEventArgs e
)

C++

public delegate void KeyPressEventHandler (
    Object^ sender, 
    KeyPressEventArgs^ e
)

/** @delegate */
public delegate void KeyPressEventHandler (
    Object sender, 
    KeyPressEventArgs e
)

JScript

JScript では、デリゲートは使用できますが、新規に宣言することはできません。

パラメータ

sender: イベントのソース。

e: イベントデータを格納している KeyPressEventArgs。

解説

KeyPressEventArgs.Handled を true に設定して KeyPress イベントをキャンセルします。この結果、コントロールはキーを押す処理を行いません。

KeyPressEventHandler デリゲートを作成する場合は、イベントを処理するメソッドを識別してください。イベントをイベントハンドラに関連付けるには、デリゲートのインスタンスをイベントに追加します。デリゲートを削除しない限り、そのイベントが発生すると常にイベントハンドラが呼び出されます。デリゲートを使用したイベント処理の詳細については、「イベントとデリゲート」を参照してください。

使用例

Visual Basic

Imports System
Imports System.Windows.Forms

Public Class Form1
    Inherits Form

    Public Sub New()
        ' Create a TextBox control.
        Dim tb As New TextBox()
        Me.Controls.Add(tb)
        AddHandler tb.KeyPress, AddressOf keypressed
    End Sub 'New

    Private Sub keypressed(ByVal
 o As [Object], ByVal e As
 KeyPressEventArgs)
        ' The keypressed method uses the KeyChar property to check 
        ' whether the ENTER key is pressed. 

        ' If the ENTER key is pressed, the Handled property is set to
 true, 
        ' to indicate the event is handled.

        If e.KeyChar = Microsoft.VisualBasic.ChrW(Keys.Return)
 Then
            e.Handled = True
        End If
    End Sub 'keypressed

    Public Shared Sub Main()
        Application.Run(New Form1())
    End Sub 'Main
End Class 'Form1

using System;
using System.Windows.Forms;

public class Form1: Form
{
    public Form1()
    {
        // Create a TextBox control.
        TextBox tb = new TextBox();
        this.Controls.Add(tb);
        tb.KeyPress += new KeyPressEventHandler(keypressed);
    }

    private void keypressed(Object o, KeyPressEventArgs
 e)
    {
        // The keypressed method uses the KeyChar property to check
 
        // whether the ENTER key is pressed. 

        // If the ENTER key is pressed, the Handled property is set
 to true, 
        // to indicate the event is handled.
        if (e.KeyChar == (char)Keys.Return)
        {
            e.Handled = true;
        }
    }

    public static void Main()
    {
        Application.Run(new Form1());
    }
}

C++

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

using namespace System;
using namespace System::Windows::Forms;

public ref class Form1: public
 Form
{
public:
   Form1()
   {
      // Create a TextBox control.
      TextBox^ tb = gcnew TextBox;
      this->Controls->Add( tb );
      tb->KeyPress += gcnew KeyPressEventHandler( this, &Form1::keypressed
 );
   }

private:
   void keypressed( Object^ /*o*/, KeyPressEventArgs^ e )
   {
      // The keypressed method uses the KeyChar property to check 
      // whether the ENTER key is pressed. 
      // If the ENTER key is pressed, the Handled property is set to
 true, 
      // to indicate the event is handled.
      if ( e->KeyChar == (char)13 )
            e->Handled = true;
   }
};

int main()
{
   Application::Run( gcnew Form1 );
}

import System.*;
import System.Windows.Forms.*;

public class Form1 extends Form
{
    public Form1()
    {
        // Create a TextBox control.
        TextBox tb = new TextBox();
        this.get_Controls().Add(tb);
        tb.add_KeyPress(new KeyPressEventHandler(KeyPressed));
    } //Form1

    void KeyPressed(Object o, KeyPressEventArgs e)
    {
        // The keypressed method uses the KeyChar property to check
 
        // whether the ENTER key is pressed. 
        // If the ENTER key is pressed, the Handled property is set
 to true, 
        // to indicate the event is handled.
        if (e.get_KeyChar() == (char)(13))
 {
            e.set_Handled(true);
        }
    } // KeyPressed

    public static void main(String[]
 args)
    {
        Application.Run(new Form1());
    } //main
} //Form1

Visual Basic

    ' 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
    End Sub 'textBox1_KeyDown
   
   
    ' 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 'textBox1_KeyPress
End Class 'Form1

// 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;
            }
        }
    }
}

// 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;
    }
}

C++

   // 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;
            }
         }
      }
   }

   // 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 boolean 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.get_KeyCode().CompareTo(Keys.D0)) < 0 
        || (e.get_KeyCode().CompareTo(Keys.D9) > 0)) {

        // Determine whether the keystroke is a number from the keypad.
        if ((e.get_KeyCode().CompareTo(Keys.NumPad0) < 0 
            || (e.get_KeyCode().CompareTo(Keys.NumPad9)) > 0)) {

            // Determine whether the keystroke is a backspace.
            if (!(e.get_KeyCode().Equals(Keys.Back))) {
                    // A non-numerical keystroke was pressed.
                    // Set the flag to true and evaluate in KeyPress
 event.
                    nonNumberEntered = true;
            }
        }
    }
} //textBox1_KeyDown

// 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.set_Handled(true);
    }
} //textBox1_KeyPress