Control.LostFocus 事件

定義

發生於控制項遺失焦點時。

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

事件類型

屬性

範例

下列程式碼範例示範驗證 TextBox1 的文字。 它也會示範如何藉由將 FileDialog.InitialDirectory 屬性設定為 TextBox1 中的文字來處理 LostFocus 事件。 程式碼範例使用 ErrorProvider.GetError 方法在開啟檔案對話方塊之前檢查錯誤。 若要執行此範例,請將下列程式碼貼到表單中,其中包含 TextBox 名為 的 、 OpenFileDialog 名為 的 、 Button 名為 Button1OpenFileDialog1 的 ,以及 ErrorProvider 名為 ErrorProvider1TextBox1 的 。 確定所有事件都與其事件處理常式相關聯。

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

備註

當您使用鍵盤 (TAB、SHIFT+TAB 等) 、呼叫 SelectSelectNextControl 方法,或將 屬性設定 ContainerControl.ActiveControl 為目前表單來變更焦點時,焦點事件會依下列順序發生:

  1. Enter

  2. GotFocus

  3. Leave

  4. Validating

  5. Validated

  6. LostFocus

當您使用滑鼠或呼叫 Focus 方法來變更焦點時,焦點事件會依下列順序發生:

  1. Enter

  2. GotFocus

  3. LostFocus

  4. Leave

  5. Validating

  6. Validated

CausesValidation如果 屬性設定為 false ,則會 Validating 隱藏 和 Validated 事件。

如果在事件委派中將 CancelCancelEventArgs 屬性設定為 true ,則通常會在隱藏事件之後 Validating 發生的所有事件。 Validating

注意

GotFocusLostFocus 事件是系結至WM_KILLFOCUS和WM_SETFOCUS Windows 訊息的低階焦點事件。 一般而言, GotFocus 只有在更新 UICues 或撰寫自訂控制項時,才會使用 和 LostFocus 事件。 相反地, EnterLeave 事件應該用於 類別以外的 Form 所有控制項,而這個類別會使用 ActivatedDeactivate 事件。 如需 和 LostFocus 事件的詳細資訊 GotFocus ,請參閱WM_KILLFOCUSWM_KILLFOCUS主題。

警告

請勿嘗試從 、 GotFocusLeaveLostFocusValidatingValidated 事件處理常式內 Enter 設定焦點。 這樣做可能會導致您的應用程式或作業系統停止回應。 如需詳細資訊,請參閱 WM_KILLFOCUS 主題。

如需處理事件的詳細資訊,請參閱 處理和引發事件

適用於

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