判斷一個文件是否在IE的緩存中

當你建立一個聯到網上文件的快捷方式時，你可能需要知道它是否已經被訪問過，于是你就可以適當地改變鏈接的顏色等等。這則小技巧

就是告訴你如何判斷一個文件是否在inte.net explorer的緩存中，以滿足你的須要。

　　新建一個項目、添加一個模塊。將以下代碼寫到模塊里：


private const error_insufficient_buffer = 122

private const eeerrorbase = 26720


private type filetime

　 dwlowdatetime as long

　 dwhighdatetime as long

end type


private type internet_cache_entry_info

　 dwstructsize as long

　 lpszsourceurlname as string

　 lpszlocalfilename as string

　 cacheentrytype as string

　 dwusecount as long

　 dwhitrate as long

　 dwsizelow as long

　 dwsizehigh as long

　 lastmodifiedtime as filetime

　 expiretime as filetime

　 lastaccesstime as filetime

　 lastsynctime as filetime

　 lpheaderinfo as long

　 dwheaderinfosize as long

　 lpszfileextension as string

　 dwreserved as long

end type


private declare function geturlcacheentryinfo lib "wininet.dll" _

alias "geturlcacheentryinfoa" (byval surlname as string, _

　 lpcacheentryinfo as any, lpdwcacheentryinfobuffersize _

　 as long) as long


’用來報告api產生的錯誤：

private const format_message_allocate_buffer = &h100

private const format_message_argument_array = &h2000

private const format_message_from_hmodule = &h800

private const format_message_from_string = &h400

private const format_message_from_system = &h1000

private const format_message_ignore_inserts = &h200

private const format_message_max_width_mask = &hff

private declare function formatmessage lib "kernel32" alias _

　 "formatmessagea" (byval dwflags as long, lpsource as any, _

　 byval dwmessageid as long, byval dwlanguageid as long, _

　 byval lpbuffer as string, byval nsize as long, arguments _

　 as long) as long


public function winapierror(byval llastdllerror as long) as string

dim sbuff as string

dim lcount as long


　 ’返回與lastdllerror相關的出錯信息：

　 sbuff = string$(256, 0)

　 lcount = formatmessage( _

　　　format_message_from_system or format_message_ignore_inserts, _

　　　0, llastdllerror, 0&, sbuff, len(sbuff), byval 0)

　 if lcount then

　　　winapierror = left$(sbuff, lcount)

　 end if


end function


public function getcacheentryinfo(byval hwnd as long, _

　 byval lpszurl as string) as boolean


dim dwentrysize as long

dim lpcacheentry as internet_cache_entry_info

dim dwtemp as long

dim lerr as long


　 if (geturlcacheentryinfo(lpszurl, byval 0&, dwentrysize)) = 0 then

　　　lerr = err.lastdllerror

　　　if (lerr <> error_insufficient_buffer) then

　　　　 ’預料外的錯誤。須要顯示出錯原因：

　　　　 err.raise eeerrorbase + 1, _

　　　　　　app.exename & ".mcacheentry", winapierror(lerr)


　　　　 getcacheentryinfo = false

　　　　 exit function

　　　else

　　　　 ’這是預料中的錯誤

　　　　 getcacheentryinfo = true

　　　end if

　 end if


end function



在窗體上添加一個command和一個text。然后加入這些代碼：


option explicit


private sub command1_click()

on error goto errorhandler

　 ’檢查text中的url地址是否出現在緩存中：

　 if (getcacheentryinfo(me.hwnd, text1.text)) then

　　　msgbox "url in cache.", vbinformation

　 else

　　　msgbox "url not in cache.", vbinformation

　 end if


exit sub


errorhandler:

　msgbox "url not in cache [" & err.description & "]",vbinformation


end sub


　　運行，在text中鍵入一個url地址（比如，http://www.vbaccelerator.com/index.html）當你按下command按鈕時，就會得到一則消息報告url在不在緩存中。如果windows給出了url沒找到的原因，它將被顯示在隨后的的方括號內。

原文轉自：http://www.anti-gravitydesign.com