改變預設印表機的方法

mhfo

http://sunh.hosp.ncku.edu.tw/~cww/html/q00238.html

在 VB 裡面， 原本改變預設印表機的方法是：(假設安裝有兩種印表機(驅動程式))

             Set Printer = Printers(0) ' 將預設印表機設定成第一種印表機
             Set Printer = Printers(1) ' 將預設印表機設定成第二種印表機

但實際上以上敘述有時候不會成功(原因不詳)， 為了能夠成功地改變預設印表機，以下是呼叫Windows API 的方法：( 此一解決方案適用於 Windows 95)

1. API 的宣告：

Const HWND_BROADCAST = &HFFFF&
Const WM_WININICHANGE = &H1A

Private Declare Function GetProfileString Lib "kernel32" Alias  _
         "GetProfileStringA" (ByVal lpAppName As String, ByVal lpKeyName As _
        String, ByVal lpDefault As String, ByVal lpReturnedString As String, _
         ByVal nSize As Long) As Long

Private Declare Function WriteProfileString Lib "kernel32" Alias _
         "WriteProfileStringA" (ByVal lpszSection As String, ByVal lpszKeyName _
        As String, ByVal lpszString As String) 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

2. 程式範例：

PrinterName = "您想設定的印表機名稱"
Dim S As String, length As Long, hKey As Long

S = String(80, Chr(0))
length = GetProfileString("devices", PrinterName, "", S, Len(S))
S = Left(S, length)
Call WriteProfileString("windows", "device", PrinterName & "," & S)
Call SendMessage(HWND_BROADCAST, WM_WININICHANGE, &H7FFF&, ByVal "windows")


至於改變 NT 預設印表機的方法， 則是改變登錄資料庫(Registry)印表機的設定，
在登錄資料庫中紀錄預設印表機的 Value 是:

   HKEY_CURRENT_USER
  \Software\Microsoft\WindowsNT\CurrentVersion\Windows subkey 的
  Device value