正在阅读：vb 高手搜集-常见问题总结(1)vb 高手搜集-常见问题总结(1)

2005-06-10 10:20 出处：作者：阳光宝宝责任编辑：moningfeng

如何用鼠标移动没有标题的 Form，或移动 Form 中的控制项 　　在声明区中放入以下声明：　　16 位版本： ( Sub 无返回值 )

Private Declare Sub ReleaseCapture Lib "User" () Private Declare Sub SendMessage Lib "User" (ByVal hwnd As Integer, ByVal wMsg As Integer, ByVal wParam As Integer, lParam As Long)

　　32 位版本： ( Function 有返回值，Integer 改成 Long )

Private Declare Function ReleaseCapture Lib "user32" () As Long Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long

　　共用常数：

Const WM_SYSCOMMAND = &H112 Const SC_MOVE = &HF012

　　若要移动 Form，程序码如下：

Private Sub Form_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single) Dim i As Long i = ReleaseCapture i = SendMessage(Form1.hwnd, WM_SYSCOMMAND, SC_MOVE, 0) End Sub

　　以上功能也适用于用鼠标在 Form 中移动控制项，程序码如下：

Private Sub Command1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single) Dim i As Long i = ReleaseCapture i = SendMessage(Command1.hwnd, WM_SYSCOMMAND, SC_MOVE, 0) End Sub

　　检查文件是否存在

Function FileExists(filename As String) As Integer Dim i As Integer On Error Resume Next i = Len(Dir$(filename)) If Err Or i = 0 Then FileExists = False Else FileExists = True End Function

　　如何设置对VB数据库连接的动态路径 　　我个人因为经常作一些数据库方面的程序，对于程序间如何与数据库进行接口的问题之烦是深有体会，因为VB在数据库链接的时候，一般是静态，即数据库存放的路径是固定的，如用VB的DATA，adodc,DataEnvironment 等到作数据库链接时，如果存放数据库的路径被改变的话，就会找不到路经，真是一个特别烦的事。　　　　笔者的解决方法是利用app.path 来解决这个问题。　　一、用data控件进行数据库链接，可以这样：　　在form_load()过程中放入：

private form_load() Dim str As String '定义 str = App.Path If Right(str, 1) <> "\" Then str = str + "\" End If data1.databasename=str & "\数据库名" data1.recordsource="数据表名" data1.refresh sub end

　　这几句话的意为，打开当前程序运行的目录下的数据库。　　　　你只要保证你的数据库在你程序所在的目录之下就行了。　　二、利用adodc（ADO Data Control)进行数据库链接：

private form_load () Dim str As String '定义 str = App.Path If Right(str, 1) <> "\" Then str = str + "\" End If str = "Provider=Microsoft.Jet.OLEDB.3.51;Persist Security Info=False;Data Source=" & str & "\tsl.mdb" Adodc1.ConnectionString = str Adodc1.CommandType = adCmdText Adodc1.RecordSource = "select * from table3" Adodc1.Refresh end sub

　　三、利用DataEnvironment进行数据库链接　　　　可在过程中放入：

On Error Resume Next If DataEnvironment1.rsCommand1.State <> adStateClosed Then DataEnvironment1.rsCommand1.Close '如果打开，则关闭 End If 'i = InputBox("请输入友人编号:", "输入") 'If i = "" Then Exit Sub DataEnvironment1.Connection1.Open App.Path & "\userdatabase\tsl.mdb" DataEnvironment1.rsCommand1.Open "select * from table3 where 编号='" & i & "'" 'Set DataReport2.DataSource = DataEnvironment1 'DataReport2.DataMember = "command1" 'DataReport2.show end sub

　　四、利用ADO(ActiveX Data Objects)进行编程：　　建立连接：

dim conn as new adodb.connection dim rs as new adodb.recordset dim str str = App.Path If Right(str, 1) <> "\" Then str = str + "\" End If str = "Provider=Microsoft.Jet.OLEDB.3.51;Persist Security Info=False;Data Source=" & str & "\tsl.mdb" conn.open str rs.cursorlocation=aduseclient rs.open "数据表名",conn,adopenkeyset.adlockpessimistic

　　用完之后关闭数据库：

conn.close set conn=nothing