VB的一段代码~~不知道在干什么，，求指点啊！~！

Question

Private Declare Function GetWindowsDirectory Lib "kernel32" Alias _
"GetWindowsDirectoryA" (ByVal lpBuffer As String, ByVal nSize As Long) As Long '在form窗体中声明改函数

Private Declare Function SystemParametersInfo Lib "user32" Alias _
"SystemParametersInfoA" (ByVal uAction&, ByVal uParam&, ByVal lpvParam As Any, ByVal fuWinIni&) As Long

Const SPI_SetDeskWallpaper = 20
Const SPIF_SENDWININICHANGE = &H2
Const SPIF_UPDATEINIFILE = &H1
Const REG_SZ As Long = 1
Const HKEY_CURRENT_USER = &H80000001

Private Declare Function RegCloseKey Lib "advapi32.dll" (ByVal hKey As Long) As Long

Private Declare Function RegOpenKeyEx Lib "advapi32.dll" Alias _
"RegOpenKeyExA" (ByVal hKey&, ByVal lpSubKey$, ByVal ulOptions&, ByVal samDesired&, phkResult&) As Long

Private Declare Function RegSetValueExString Lib "advapi32.dll" Alias _
"RegSetValueExA" (ByVal hKey&, ByVal lpValueName$, ByVal Reserved&, ByVal dwType&, ByVal lpValue$, ByVal cbData&) As Long

Private Declare Function RegSetValueExLong Lib "advapi32.dll" Alias _
"RegSetValueExA" (ByVal hKey&, ByVal lpValueName$, ByVal Reserved&, ByVal dwType&, lpValue&, ByVal cbData&) As Long

Answer 1

GetWindowsDirectory函数获取Windows目录的完整路径名
SystemParametersInfo函数查询或设置系统级参数
RegCloseKey保存注册表键值
RegOpenKeyEx打开注册表键值
RegSetValueExString修改注册表键值
这段代码主要是应用于自动切换桌面相关函数说明，他具体代码为
新建工程，在窗体加入一个timer控件，一个image控件
Private Declare Function GetWindowsDirectory Lib "kernel32" Alias "GetWindowsDirectoryA" (ByVal lpBuffer As String, ByVal nSize As Long) As Long

Private Declare Function SystemParametersInfo Lib "user32" Alias "SystemParametersInfoA" (ByVal uAction As Long, ByVal uParam As Long, ByVal lpvParam As Any, ByVal fuWinIni As Long) As Long

Const SPI_SETDESKWALLPAPER = 20
Const SPIF_SENDWININICHANGE = &H2
Const SPIF_UPDATEINIFILE = &H1
Const REG_SZ As Long = 1
Const HKEY_CURRENT_USER = &H80000001

Private Declare Function RegCloseKey Lib "advapi32.dll" (ByVal hKey As Long) As Long

Private Declare Function RegOpenKeyEx Lib "advapi32.dll" Alias "RegOpenKeyExA" (ByVal hKey As Long, ByVal lpSubKey As String, ByVal ulOptions As Long, ByVal samDesired As Long, phkResult As Long) As Long

Private Declare Function RegSetValueExString Lib "advapi32.dll" Alias "RegSetValueExA" (ByVal hKey As Long, ByVal lpValueName As String, ByVal Reserved As Long, ByVal dwType As Long, ByVal lpValue As String, ByVal cbData As Long) As Long

Private Declare Function RegSetValueExLong Lib "advapi32.dll" Alias "RegSetValueExA" (ByVal hKey As Long, ByVal lpValueName As String, ByVal Reserved As Long, ByVal dwType As Long, lpValue As Long, ByVal cbData As Long) As Long
Private Sub Form_Load()
Timer1.Interval = 5000
Timer1.Enabled = True
End Sub
Private Sub Timer1_Timer()
Static i As Integer
i = i Mod 2 + 1
Dim Path As String, strSave As String
strSave = String(50, Chr$(0))
Path = Left$(strSave, GetWindowsDirectory(strSave, Len(strSave)))
Image1.Picture = LoadPicture(App.Path & "\" & i & ".JPG")
SavePicture Image1, Path & "\" & i & ".bmp"
Dim aa As String
aa = Path & "\" & i & ".bmp"
ChangeWP = SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, aa, 0)
End Sub

然后把文件夹里的图片名称修改为1.JPG，2.JPG。。。。。会自动更换桌面
经测试通过

Answer 2

这些都是Windows系统提供的API函数和常量，具体含义可以分别百度，比如GetWindowsDirectory，百度百科的解释：http://baike.baidu.com/view/1292121.htm
每个API函数都有自己的用法，你可以看一些网上的例子，这些api函数也不光是VB可以用，VC、Delph等也可以用，是Windows系统本身提供的接口，语句里面的Lib "advapi32.dll"，表名了提供该函数的动态连接库文件是"advapi32.dll"，一般来说，无论xp、2000、win7，都支持这些API函数，但有个别是有限制的。

Answer 3

SystemParametersInfo
该函数查询或设置系统级参数。该函数也可以在设置参数中更新用户配置文件。
SystemParametersInfo
这个函数能获取Windows目录的完整路径名。在这个目录里，保存了大多数windows应用程序文件及初始化文件

后面的就是写组册表用的啦。你把函数在百度上搜一下都能找到

Answer 4

e ....什么啊这是。