Control.LostFocus Control.LostFocus Control.LostFocus Control.LostFocus Event

定义

在控件失去焦点时发生。Occurs when the control loses focus.

public:
 event EventHandler ^ LostFocus;
[System.ComponentModel.Browsable(false)]
public event EventHandler LostFocus;
member this.LostFocus : EventHandler 
Public Custom Event LostFocus As EventHandler 
属性

示例

下面的代码示例演示为 TextBox1 验证的文本。The following code example demonstrates validating the text for TextBox1. 它还演示了如何处理LostFocus通过设置事件FileDialog.InitialDirectoryTextBox1 中的文本的属性。It also demonstrates handling the LostFocus event by setting the FileDialog.InitialDirectory property to the text in TextBox1. 使用的代码示例ErrorProvider.GetError方法来打开文件对话框之前检查错误。The code example used the ErrorProvider.GetError method to check for an error before opening the file dialog box. 若要运行此示例中,请将以下代码粘贴到窗体包含TextBox名为TextBox1,则OpenFileDialog名为OpenFileDialog1Button名为Button1,和一个ErrorProvider名为ErrorProvider1To run this example, paste the following code into a form containing a TextBox named TextBox1, an OpenFileDialog named OpenFileDialog1, a Button named Button1, and an ErrorProvider named ErrorProvider1. 请确保所有事件都都具有其事件处理程序相关联。Ensure all events are associated with their event handlers.

private:
   void TextBox1_Validating( Object^ sender,
      System::ComponentModel::CancelEventArgs^ e )
   {
      // If nothing is entered,
      // an ArgumentException is caught; if an invalid directory is entered, 
      // a DirectoryNotFoundException is caught. An appropriate error message 
      // is displayed in either case.
      try
      {
         System::IO::DirectoryInfo^ directory = gcnew System::IO::DirectoryInfo( TextBox1->Text );
         directory->GetFiles();
         ErrorProvider1->SetError( TextBox1, "" );
      }
      catch ( System::ArgumentException^ ) 
      {
         ErrorProvider1->SetError( TextBox1, "Please enter a directory" );
      }
      catch ( System::IO::DirectoryNotFoundException^ ) 
      {
         ErrorProvider1->SetError( TextBox1, "The directory does not exist."
         "Try again with a different directory." );
      }
   }

   // This method handles the LostFocus event for TextBox1 by setting the 
   // dialog's InitialDirectory property to the text in TextBox1.
   void TextBox1_LostFocus( Object^ sender, System::EventArgs^ e )
   {
      OpenFileDialog1->InitialDirectory = TextBox1->Text;
   }

   // This method demonstrates using the ErrorProvider.GetError method 
   // to check for an error before opening the dialog box.
   void Button1_Click( System::Object^ sender, System::EventArgs^ e )
   {
      //If there is no error, then open the dialog box.
      if ( ErrorProvider1->GetError( TextBox1 )->Equals( "" ) )
      {
         ::DialogResult dialogResult = OpenFileDialog1->ShowDialog();
      }
   }
private void textBox1_Validating(object sender, 
	System.ComponentModel.CancelEventArgs e)
{
	// If nothing is entered,
	// an ArgumentException is caught; if an invalid directory is entered, 
	// a DirectoryNotFoundException is caught. An appropriate error message 
	// is displayed in either case.
	try
	{
		System.IO.DirectoryInfo directory = 
			new System.IO.DirectoryInfo(textBox1.Text);
		directory.GetFiles();
		errorProvider1.SetError(textBox1, "");

	}
	catch(System.ArgumentException ex1)
	{
		errorProvider1.SetError(textBox1, "Please enter a directory");

	}
	catch(System.IO.DirectoryNotFoundException ex2)
	{
		errorProvider1.SetError(textBox1, "The directory does not exist." +
			"Try again with a different directory.");
	}

}

// This method handles the LostFocus event for textBox1 by setting the 
// dialog's InitialDirectory property to the text in textBox1.
private void textBox1_LostFocus(object sender, System.EventArgs e)
{
	openFileDialog1.InitialDirectory = textBox1.Text;
}

// This method demonstrates using the ErrorProvider.GetError method 
// to check for an error before opening the dialog box.
private void button1_Click(System.Object sender, System.EventArgs e)
{
	//If there is no error, then open the dialog box.
	if (errorProvider1.GetError(textBox1)=="")
	{
		DialogResult dialogResult = openFileDialog1.ShowDialog();
	}
}
Private Sub TextBox1_Validating(ByVal sender As Object, _
ByVal e As System.ComponentModel.CancelEventArgs) _
Handles TextBox1.Validating

    ' If nothing is entered,
    ' an ArgumentException is caught; if an invalid directory is entered, 
    ' a DirectoryNotFoundException is caught. An appropriate error message 
    ' is displayed in either case.
    Try
        Dim directory As New System.IO.DirectoryInfo(TextBox1.Text)
        directory.GetFiles()
        ErrorProvider1.SetError(TextBox1, "")

    Catch ex1 As System.ArgumentException
        ErrorProvider1.SetError(TextBox1, "Please enter a directory")

    Catch ex2 As System.IO.DirectoryNotFoundException
        ErrorProvider1.SetError(TextBox1, _
        "The directory does not exist." & _
        "Try again with a different directory.")
    End Try

End Sub

' This method handles the LostFocus event for TextBox1 by setting the 
' dialog's InitialDirectory property to the text in TextBox1.
Private Sub TextBox1_LostFocus(ByVal sender As Object, _
    ByVal e As System.EventArgs) Handles TextBox1.LostFocus
    OpenFileDialog1.InitialDirectory = TextBox1.Text
End Sub


' This method demonstrates using the ErrorProvider.GetError method 
' to check for an error before opening the dialog box.
Private Sub Button1_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles Button1.Click

    'If there is no error, then open the dialog box.
    If ErrorProvider1.GetError(TextBox1) = "" Then
        Dim dialogResult As DialogResult = OpenFileDialog1.ShowDialog()
    End If

End Sub

注解

将焦点更改通过使用键盘 (TAB、 SHIFT + TAB,等),通过调用SelectSelectNextControl方法,或通过设置ContainerControl.ActiveControl到当前窗体的属性,将按以下顺序发生焦点事件:When you change the focus by using the keyboard (TAB, SHIFT+TAB, and so on), by calling the Select or SelectNextControl methods, or by setting the ContainerControl.ActiveControl property to the current form, focus events occur in the following order:

  1. Enter

  2. GotFocus

  3. Leave

  4. Validating

  5. Validated

  6. LostFocus

当更改焦点,使用鼠标或通过调用Focus方法时,按以下顺序执行的焦点事件:When you change the focus by using the mouse or by calling the Focus method, focus events occur in the following order:

  1. Enter

  2. GotFocus

  3. LostFocus

  4. Leave

  5. Validating

  6. Validated

如果CausesValidation属性设置为false,则ValidatingValidated所抑制的事件。If the CausesValidation property is set to false, the Validating and Validated events are suppressed.

如果Cancel的属性CancelEventArgs设置为trueValidating事件委托,通常会发生后的所有事件Validating所抑制的事件。If the Cancel property of the CancelEventArgs is set to true in the Validating event delegate, all events that would usually occur after the Validating event are suppressed.

备注

GotFocusLostFocus事件是绑定到的 WM_KILLFOCUS 和 WM_SETFOCUS Windows 消息的低级别的焦点事件。The GotFocus and LostFocus events are low-level focus events that are tied to the WM_KILLFOCUS and WM_SETFOCUS Windows messages. 通常情况下,GotFocusLostFocus更新时仅使用事件UICues或编写自定义控件时。Typically, the GotFocus and LostFocus events are only used when updating UICues or when writing custom controls. 相反EnterLeave事件应使用的所有控件除了Form类,使用ActivatedDeactivate事件。Instead the Enter and Leave events should be used for all controls except the Form class, which uses the Activated and Deactivate events. 有关详细信息GotFocusLostFocus事件,请参阅WM_KILLFOCUSWM_KILLFOCUS主题。For more information about the GotFocus and LostFocus events, see the WM_KILLFOCUS and WM_KILLFOCUS topics.

注意

不尝试将焦点设置在EnterGotFocusLeaveLostFocusValidating,或Validated事件处理程序。Do not attempt to set focus from within the Enter, GotFocus, Leave, LostFocus, Validating, or Validated event handlers. 执行此操作可能会导致你的应用程序或操作系统停止响应。Doing so can cause your application or the operating system to stop responding. 有关详细信息,请参阅WM_KILLFOCUS主题。For more information, see the WM_KILLFOCUS topic.

有关处理事件的详细信息,请参阅处理和引发事件For more information about handling events, see Handling and Raising Events.

适用于

另请参阅