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用VB6读写数据库中的图片

 2000-10-20 10:12:35 来源:WEB开发网   
核心提示:很多兄弟在这里问关于VB6读写数据库中的图片的问题,在此有一例,用VB6读写数据库中的图片,希有所启发, 1,将picture改为lob即可, 2,以人名和相关图片为例说明,数据库为access
很多兄弟在这里问关于VB6读写数据库中的图片的问题,在此有一例,希有所启发。
  1,以人名和相关图片为例说明,数据库为access,有如下字段:Name char,picture OLE object,FileLength
Number。当为ms sql时,将picture改为lob即可。
  2,示例包含control:commom dialog,picture,listbox。
源码如下:
Option Explicit

PRivate Declare Function GetTempFileName Lib "kernel32" Alias "GetTempFileNameA" (ByVal lpszPath As
String, ByVal lpPrefixString As String, ByVal wUnique As Long, ByVal lpTempFileName As String) As Long
Private Declare Function GetTempPath Lib "kernel32" Alias "GetTempPathA" (ByVal nBufferLength As Long,
ByVal lpBuffer As String) As Long
Private Const MAX_PATH = 260

Private m_DBConn As ADODB.Connection

Private Const BLOCK_SIZE = 10000
' Return a temporary file name.
Private Function TemporaryFileName() As String
Dim temp_path As String
Dim temp_file As String
Dim length As Long

  ' Get the temporary file path.
  temp_path = Space$(MAX_PATH)
  length = GetTempPath(MAX_PATH, temp_path)
  temp_path = Left$(temp_path, length)

  ' Get the file name.
  temp_file = Space$(MAX_PATH)
  GetTempFileName temp_path, "per", 0, temp_file
  TemporaryFileName = Left$(temp_file, InStr(temp_file, Chr$(0)) - 1)
End Function
Private Sub Form_Load()
Dim db_file As String
Dim rs As ADODB.Recordset

  ' Get the database file name.
  db_file = App.Path
  If Right$(db_file, 1) <> "\" Then db_file = db_file & "\"
  db_file = db_file & "dbpict.mdb"

  ' Open the database connection.
  Set m_DBConn = New ADODB.Connection
  m_DBConn.Open _
    "Provider=Microsoft.Jet.OLEDB.4.0;" & _
    "Data Source=" & db_file & ";" & _
    "Persist Security Info=False"

  ' Get the list of people.
  Set rs = m_DBConn.Execute("SELECT Name FROM People ORDER BY Name", , adCmdText)
  Do While Not rs.EOF
    lstPeople.AddItem rs!Name
    rs.MoveNext
  Loop

  rs.Close
  Set rs = Nothing
End Sub
Private Sub Form_Resize()
  lstPeople.Height = ScaleHeight
End Sub


' Display the clicked person.
Private Sub lstPeople_Click()
Dim rs As ADODB.Recordset
Dim bytes() As Byte
Dim file_name As String
Dim file_num As Integer
Dim file_length As Long
Dim num_blocks As Long
Dim left_over As Long
Dim block_num As Long
Dim hgt As Single

  picPerson.Visible = False
  Screen.MousePointer = vbHourglass
  DoEvents

  ' Get the record.
  Set rs = m_DBConn.Execute("SELECT * FROM People WHERE Name='" & _
    lstPeople.Text & "'", , adCmdText)
  If rs.EOF Then Exit Sub

  ' Get a temporary file name.
  file_name = TemporaryFileName()

  ' Open the file.
  file_num = FreeFile
  Open file_name For Binary As #file_num

  ' Copy the data into the file.
  file_length = rs!FileLength
  num_blocks = file_length / BLOCK_SIZE
  left_over = file_length Mod BLOCK_SIZE

  For block_num = 1 To num_blocks
    bytes() = rs!Picture.GetChunk(BLOCK_SIZE)
    Put #file_num, , bytes()
  Next block_num

  If left_over > 0 Then
    bytes() = rs!Picture.GetChunk(left_over)
    Put #file_num, , bytes()
  End If

  Close #file_num

  ' Display the picture file.
  picPerson.Picture = LoadPicture(file_name)
  picPerson.Visible = True

  Width = picPerson.Left + picPerson.Width + Width - ScaleWidth
  hgt = picPerson.Top + picPerson.Height + Height - ScaleHeight
  If hgt < 1440 Then hgt = 1440
  Height = hgt

  Kill file_name
  Screen.MousePointer = vbDefault
End Sub

Private Sub mnuRecordAdd_Click()
Dim rs As ADODB.Recordset
Dim person_name As String
Dim file_num As String
Dim file_length As String
Dim bytes() As Byte
Dim num_blocks As Long
Dim left_over As Long
Dim block_num As Long

  person_name = InputBox("Name")
  If Len(person_name) = 0 Then Exit Sub

  dlgPicture.Flags = _
    cdlOFNFileMustExist Or _
    cdlOFNHideReadOnly Or _
    cdlOFNExplorer
  dlgPicture.CancelError = True
  dlgPicture.Filter = "Graphics Files|*.bmp;*.ico;*.jpg;*.gif"

  On Error Resume Next
  dlgPicture.ShowOpen
  If Err.Number = cdlCancel Then
    Exit Sub
  ElseIf Err.Number <> 0 Then
    MsgBox "Error " & Format$(Err.Number) & _
      " selecting file." & vbCrLf & Err.Description
    Exit Sub
  End If

  ' Open the picture file.
  file_num = FreeFile
  Open dlgPicture.FileName For Binary Access Read As #file_num

  file_length = LOF(file_num)
  If file_length > 0 Then
    num_blocks = file_length / BLOCK_SIZE
    left_over = file_length Mod BLOCK_SIZE

    Set rs = New ADODB.Recordset
    rs.CursorType = adOpenKeyset
    rs.LockType = adLockOptimistic
    rs.Open "Select Name, Picture, FileLength FROM People", m_DBConn

    rs.AddNew
    rs!Name = person_name
    rs!FileLength = file_length

    ReDim bytes(BLOCK_SIZE)
    For block_num = 1 To num_blocks
      Get #file_num, , bytes()
      rs!Picture.AppendChunk bytes()
    Next block_num

    If left_over > 0 Then
      ReDim bytes(left_over)
      Get #file_num, , bytes()
      rs!Picture.AppendChunk bytes()
    End If

    rs.Update
    Close #file_num

    lstPeople.AddItem person_name
    lstPeople.Text = person_name
  End If
End Sub

Tags:VB 读写 数据库

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