Question

我想从VB6应用程序下载多个文件（主要是图像）。目前我正在使用URLDownloadToFile，但它一次只允许一个文件，并且没有进度条。我想下载多个文件和进度条。请帮忙。提前谢谢。

我现在的代码：

Dim lngRetVal As Long
lngRetVal = URLDownloadToFile(0, URL, LocalFilename, 0, 0)
If lngRetVal = 0 Then DownloadFile = True

Answer 1

您希望异步下载文件，以便在下载发生时继续执行VB代码。使用UserControl和UserDocument对象的AsyncRead方法，是一种鲜为人知的方法，可以使用本机VB6执行此操作 - 无需API调用。

这是来自着名的VB6大师explanation and VB6 code for multiple simultaneous downloads的优秀Karl Peterson。 AsyncReadProgress事件为您提供BytesRead和BytesMax，它们允许您显示进度条。

Answer 2

你希望得到一个VB答案，但这不是一件轻而易举的事。

以下大多数内容来自http://www.experts-exchange.com/Programming/Languages/Visual_Basic/Q_20571958.html

IBindStatusCallback接口不是   可以直接从VB访问。它必须   被引入兼容类型   库。

您可以找到类型库   olelib.tlb：   http://www.domaindlx.com/e_morcillo/scripts/type/default.asp   要下载的zip文件名是：   tl_ole.zip

您还可以找到有关如何使用的示例   使用它包括在内。不确定你是否   你会找到一个具体的例子   IBindStatusCallback没有，但它   值得一试。

您可以编写自己的函数将数据转换为字符串，这样您就可以完全控制所有内容：

Option Explicit

Public Const INTERNET_OPEN_TYPE_PRECONFIG = 0
Public Const INTERNET_DEFAULT_HTTP_PORT = 80
Public Const INTERNET_SERVICE_HTTP = 3
Public Const INTERNET_FLAG_RELOAD = &H80000000
Public Const HTTP_QUERY_STATUS_CODE = 19
Public Const HTTP_ADDREQ_FLAG_ADD = &H20000000

Public Declare Function InternetOpen Lib "wininet.dll" Alias "InternetOpenA" (ByVal sAgent As String, ByVal lAccessType As Long, ByVal sProxyName As String, ByVal sProxyBypass As String, ByVal lFlags As Long) As Long
Public Declare Function InternetConnect Lib "wininet.dll" Alias "InternetConnectA" (ByVal hInternetSession As Long, ByVal sServerName As String, ByVal nServerPort As Integer, ByVal sUsername As String, ByVal sPassword As String, ByVal lService As Long, ByVal lFlags As Long, ByVal lContext As Long) As Long
Public Declare Function HttpOpenRequest Lib "wininet.dll" Alias "HttpOpenRequestA" (ByVal hHttpSession As Long, ByVal sVerb As String, ByVal sObjectName As String, ByVal sVersion As String, ByVal sReferer As String, ByVal something As Long, ByVal lFlags As Long, ByVal lContext As Long) As Long
Public Declare Function HttpSendRequest Lib "wininet.dll" Alias "HttpSendRequestA" (ByVal hHttpRequest As Long, ByVal sHeaders As String, ByVal lHeadersLength As Long, ByVal sOptional As String, ByVal lOptionalLength As Long) As Long
Public Declare Function HttpQueryInfo Lib "wininet.dll" Alias "HttpQueryInfoA" (ByVal hHttpRequest As Long, ByVal lInfoLevel As Long, ByRef sBuffer As Any, ByRef lBufferLength As Long, ByRef lIndex As Long) As Long
Public Declare Function InternetCloseHandle Lib "wininet.dll" (ByVal hInet As Long) As Integer
Public Declare Function HttpAddRequestHeaders Lib "wininet.dll" Alias "HttpAddRequestHeadersA" (ByVal hHttpRequest As Long, ByVal sHeaders As String, ByVal lHeadersLength As Long, ByVal lModifiers As Long) As Integer
Public Declare Function InternetReadFile Lib "wininet.dll" (ByVal hFile As Long, ByVal sBuffer As String, ByVal lNumberOfBytesToRead As Long, lNumberOfBytesRead As Long) As Integer
Public Declare Function InternetOpenUrl Lib "wininet.dll" Alias "InternetOpenUrlA" (ByVal hInternet&, ByVal lpszUrl As String, ByVal lpszHeaders As String, ByVal dwHeadersLength&, ByVal dwFlags&, ByVal dwContext&) As Long
Public Declare Function InternetQueryDataAvailable Lib "wininet.dll" (ByVal hFile As Long, lpdwNumberOfBytesAvailable As Long, ByVal dwFlags As Long, ByVal dwContext As Long) As Long

Public Function GetHTML(strURL As String) As String
Const BufferSize = 16384
Dim hSession&, hURL&, lRet&, lBytesAvail&
Dim Buffer As String * BufferSize
Dim BufferLen&, sResult$
    hSession = InternetOpen(vbNullString, INTERNET_OPEN_TYPE_PRECONFIG, vbNullString, vbNullString, 0)
    hURL = InternetOpenUrl(hSession, strURL, vbNullString, ByVal 0&, INTERNET_FLAG_RELOAD, ByVal 0&)
    sResult = ""
    Do
        InternetReadFile hURL, Buffer, Len(Buffer), BufferLen
        If BufferLen > 0 Then sResult = sResult & Left(Buffer, BufferLen)
    Loop Until BufferLen = 0
    GetHTML = sResult
    InternetCloseHandle hURL
    InternetCloseHandle hSession
End Function

您可以在此处找到用于执行回调方法的其他资源（向下滚动到底部）：

http://www.experts-exchange.com/Programming/Languages/.NET/Visual_Basic.NET/Q_21763861.html

http://www.experts-exchange.com/Programming/Languages/.NET/Visual_Basic.NET/Q_21746456.html

但老实说，如果你想要对它进行更多控制，你最好自己制作下载功能。 VB中的TCP / IP内容实际上非常简单。

- 亚当

如何使用进度条在VB6中下载多个文件？

2 个答案: