[说明] 以下代码实现了当用户推出界面时，判断TextEdit中的文字是否发生改变，弹出对话框判断，让用户选择选择是否保存文件或取消退出界面操作。阅读下面代码，补充完整。 [代码7-1] Begin VB.Form Forml //...窗体描述(略) Begin VB.TextBox TextEdit Height = 1830 Left = 180 TabIndex = 0 Text = "TextEdit" Top = 360 Width = 3885 End //...窗体描述(略) End [代码 7-2] Dim txtchange As Boolean Dim myval As String Private Sub Form Load ( ) TextEdit.Text = "CIU, 中国软考联盟! txtchange = False End Sub [代码 7-3] Private Sub TextEdit_Change ( ) Static notchange As Boolean (1) (2) End Sub Private Sub Form_Unload ( Cancel As Integer ) Dim myval As String If (3) Then myval = MsgBox ( "保存文件的更改吗", vbYesNoCancel, "提示信息" ) If (4) Then MsgBox "保存成功" End End If If (5) Then End If (6) Then Cancel = 1 End If End Sub