KeyPressEventArgs Class

Definition

KeyPress 事件提供数据。Provides data for the KeyPress event.

public ref class KeyPressEventArgs : EventArgs
[System.Runtime.InteropServices.ComVisible(true)]
public class KeyPressEventArgs : EventArgs
type KeyPressEventArgs = class
    inherit EventArgs
Public Class KeyPressEventArgs
Inherits EventArgs
Inheritance
KeyPressEventArgs
Attributes

Examples

下面的示例演示如何使用 KeyPressEventArgs 按顺序对键进行计数,并在每次按键后显示结果。The following example illustrates using the KeyPressEventArgs to count keys as they are pressed and to display the results after each key press. 然后,将 Handled 设置为 true,以防止操作系统进一步处理该密钥。Handled is then set to true to keep the operating system from further processing the key. 该示例假设窗体上放置了一个 TextBoxThe example assumes a form with a TextBox placed on it.

public ref class myKeyPressClass
{
private:
   static long keyPressCount = 0;
   static long backspacePressed = 0;
   static long returnPressed = 0;
   static long escPressed = 0;
   TextBox^ textBox1;
   void myKeyCounter( Object^ sender, KeyPressEventArgs^ ex )
   {
      switch ( ex->KeyChar )
      {
            // Counts the backspaces.
         case '\b':
         backspacePressed = backspacePressed + 1;
         break;

            // Counts the ENTER keys.
         case '\r':
         returnPressed = returnPressed + 1;
         break;

            // Counts the ESC keys.  
         case (char)27:
         escPressed = escPressed + 1;
         break;
            
            // Counts all other keys.
         default:
         keyPressCount = keyPressCount + 1;
         break;
      }
      textBox1->Text = String::Concat( 
         backspacePressed, " backspaces pressed\r\n",
         escPressed, " escapes pressed\r\n",
         returnPressed, " returns pressed\r\n",
         keyPressCount, " other keys pressed\r\n" );
      ex->Handled = true;
   }
};
public class myKeyPressClass 
 {
     static long keyPressCount = 0 ;
     static long backspacePressed =  0;
     static long returnPressed = 0 ;
     static long escPressed = 0 ;
     private TextBox textBox1 = new TextBox();
     private void myKeyCounter(object sender, KeyPressEventArgs ex)
     {
     switch(ex.KeyChar)
     {
             // Counts the backspaces.
         case '\b':
         backspacePressed = backspacePressed + 1;
         break ;
             // Counts the ENTER keys.
         case '\r':
         returnPressed = returnPressed + 1 ;
         break ;
             // Counts the ESC keys.  
         case (char)27:
         escPressed = escPressed + 1 ;
         break ;
             // Counts all other keys.
         default:
         keyPressCount = keyPressCount + 1 ;
         break;
     }
     
     textBox1.Text = 
         backspacePressed + " backspaces pressed\r\n" + 
         escPressed + " escapes pressed\r\n" +
         returnPressed + " returns pressed\r\n" +
         keyPressCount + " other keys pressed\r\n" ;
     ex.Handled = true ;
     }
 }
Public Class myKeyPressClass
    Private Shared keyPressCount As Long = 0
    Private Shared backspacePressed As Long = 0
    Private Shared returnPressed As Long = 0
    Private Shared escPressed As Long = 0
    Private textBox1 As TextBox
    
    Private Sub myKeyCounter(sender As Object, ex As KeyPressEventArgs)
        Select Case ex.KeyChar
            ' Counts the backspaces.
            Case ControlChars.Back
                backspacePressed = backspacePressed + 1
            ' Counts the ENTER keys.
            Case ControlChars.Lf
                returnPressed = returnPressed + 1
            ' Counts the ESC keys.  
            Case Convert.ToChar(27)
                escPressed = escPressed + 1
            ' Counts all other keys.
            Case Else
                keyPressCount = keyPressCount + 1
        End Select
        
        textBox1.Text = backspacePressed & " backspaces pressed" & _
            ControlChars.Lf & ControlChars.Cr & escPressed & _
            " escapes pressed" & ControlChars.CrLf & returnPressed & _
            " returns pressed" & ControlChars.CrLf & keyPressCount & _
            " other keys pressed" & ControlChars.CrLf
        ex.Handled = True
    End Sub
End Class

必须创建此类的新实例。You must create a new instance of this class. 还必须设置事件处理程序。You must also set the event handler. 可以在类的构造函数中执行此操作。You can do this in the constructor for your class.

public:
   myKeyPressClass^ myKeyPressHandler;

   Form1()
   {
      myKeyPressHandler = gcnew myKeyPressClass;

      InitializeComponent();

      textBox1->KeyPress += gcnew KeyPressEventHandler(
         myKeyPressHandler, &myKeyPressClass::myKeyCounter );
   }
myKeyPressClass myKeyPressHandler = new myKeyPressClass();
public Form1()
{
     InitializeComponent();
 
     textBox1.KeyPress += new KeyPressEventHandler(myKeyPressHandler.myKeyCounter);
}
Private myKeyPressHandler As New myKeyPressClass()

Public Sub New()
    InitializeComponent()
    
    AddHandler textBox1.KeyPress, AddressOf myKeyPressHandler.myKeyCounter
End Sub

当在控件中引发指定的事件时,将调用附加的方法,并且应用程序可以执行代码以响应事件。When the specified event is raised in the control, the attached method is called and the application can execute code in response to the event.

Remarks

一个 KeyPressEventArgs 指定用户按下某个键时构成的字符。A KeyPressEventArgs specifies the character that is composed when the user presses a key. 例如,当用户按下 SHIFT + K 时,KeyChar 属性返回一个大写的 K。For example, when the user presses SHIFT + K, the KeyChar property returns an uppercase K.

当用户按下某个键时,将发生 KeyPress 事件。A KeyPress event occurs when the user presses a key. KeyPress 事件密切相关的两个事件都 KeyUpKeyDownTwo events that are closely related to the KeyPress event are KeyUp and KeyDown. 当用户按下某个键时,KeyDown 事件位于每个 KeyPress 事件的前面,当用户释放某个键时,将发生 KeyUp 事件。The KeyDown event precedes each KeyPress event when the user presses a key, and a KeyUp event occurs when the user releases a key. 当用户按下某个键时,每次重复时,将发生重复 KeyDownKeyPress 事件。When the user holds down a key, duplicate KeyDown and KeyPress events occur each time the character repeats. 发布时,将生成一个 KeyUp 事件。One KeyUp event is generated upon release.

对于每个 KeyPress 事件,都将传递 KeyPressEventArgsWith each KeyPress event, a KeyPressEventArgs is passed. KeyEventArgs 随每个 KeyDownKeyUp 事件传递。A KeyEventArgs is passed with each KeyDown and KeyUp event. 一个 KeyEventArgs 指定是否将任何修改键(CTRL、SHIFT 或 ALT)与另一个键一起使用。A KeyEventArgs specifies whether any modifier keys (CTRL, SHIFT, or ALT) were pressed along with another key. (也可以通过 Control 类的 ModifierKeys 属性获取此修饰符信息。)(This modifier information can also be obtained through the ModifierKeys property of the Control class.)

Handled 设置为 true 以取消 KeyPress 事件。Set Handled to true to cancel the KeyPress event. 这会使控件不会按下键进行处理。This keeps the control from processing the key press.

Note

某些控件将处理 KeyDown上的某些关键笔画。Some controls will process certain key strokes on KeyDown. 例如,RichTextBox 在调用 KeyPress 之前处理 Enter 键。For example, RichTextBox processes the Enter key before KeyPress is called. 在这种情况下,不能取消 KeyPress 事件,而必须取消 KeyDown 中的键笔划。In such cases, you cannot cancel the KeyPress event, and must cancel the key stroke from KeyDown instead.

有关事件模型的信息,请参阅处理和引发事件For information about the event model, see Handling and Raising Events.

Constructors

KeyPressEventArgs(Char)

初始化 KeyPressEventArgs 类的新实例。Initializes a new instance of the KeyPressEventArgs class.

Properties

Handled

获取或设置一个值,该值指示是否处理过 KeyPress 事件。Gets or sets a value indicating whether the KeyPress event was handled.

KeyChar

获取或设置与按下的键对应的字符。Gets or sets the character corresponding to the key pressed.

Methods

Equals(Object)

确定指定的对象是否等于当前对象。Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetHashCode()

作为默认哈希函数。Serves as the default hash function.

(Inherited from Object)
GetType()

获取当前实例的 TypeGets the Type of the current instance.

(Inherited from Object)
MemberwiseClone()

创建当前 Object 的浅表副本。Creates a shallow copy of the current Object.

(Inherited from Object)
ToString()

返回表示当前对象的字符串。Returns a string that represents the current object.

(Inherited from Object)

Applies to

See also