SHBrowseForFolder可以用來得到一個用戶選擇的目錄。
可是有時候會有需要去指定一個初始目錄,比如希望上次用戶選擇的目錄可以保存下來。這該如何去做？
在BROWSEINFO結構體中提供了一個成員，這是一個指向函數的指針，通過這個回調函數，可以處理初始化的時候需要做的一些事情。
其中函數名是固定的:BrowseCallbackProc()
BrowseCallbackProc Function
Specifies an application-defined callback function used to send messages to,
and process messages from, a Browse dialog box displayed in response to a
call to SHBrowseForFolder.
Syntax
int CALLBACK BrowseCallbackProc(
HWND hwnd,
UINT uMsg,
LPARAM lParam,
LPARAM lpData
);
Parameters
- hwnd
- The window handle of the browse dialog box.
- uMsg
- The dialog box event that generated the message. One of the following
values.
- BFFM_INITIALIZED
- The dialog box has finished initializing.
- BFFM_IUNKNOWN
- An IUnknown interface
is available to the dialog box.
- BFFM_SELCHANGED
- The selection has changed in the dialog box.
- BFFM_VALIDATEFAILED
- Version 4.71. The
user typed an invalid name into the dialog's edit box. A nonexistent folder is
considered an invalid name.
- lParam
- A value whose meaning depends on the event specified in uMsg as
follows:
| uMsg |
lParam |
| BFFM_INITIALIZED |
Not used, value is NULL. |
| BFFM_IUNKNOWN |
A pointer to an IUnknown interface. |
| BFFM_SELCHANGED |
A pointer to an item identifier list (PIDL) identifying the newly selected
item. |
| BFFM_VALIDATEFAILED |
A pointer to a string containing the invalid name. An application can use
this data in an error dialog informing the user that the name was not
valid. |
- lpData
- An application-defined value that was specified in the lParam member
of the BROWSEINFO
structure used in the call to SHBrowseForFolder.
Return Value
Returns zero except in the case of BFFM_VALIDATEFAILED. For that
flag, returns zero to dismiss the dialog or nonzero to keep the dialog
displayed.
Remarks
To attach your BrowseCallbackProc to a dialog, specify its address in
the lpfn member of the BROWSEINFO structure used in a
SHBrowseForFolder call.
BrowseCallbackProc can also send messages to the dialog box through
SendMessage,
controlling these aspects of that dialog box.
- OK button enabled/disabled
- OK button text
- Selected folder
- Expanded folder
- Status text
Set the SendMessage function's Msg
parameter to one of the following values, providing additional information in
the wParam and lParam parameters as indicated for each message
type.
BFFM_ENABLEOK
Enables or disables the dialog box's OK button.
- wParam. Not used.
- lParam. To enable, set to a nonzero value. To disable, set to
zero.
BFFM_SETOKTEXT
Version 6.0. Sets
the text that is displayed on the dialog box's OK button.
- wParam. Not used.
- lParam. A pointer to a null-terminated Unicode string containing the desired
text.
BFFM_SETSELECTION
Specifies the path of a folder to select.
The path can be specified as a string or a PIDL.
To use a string:
- wParam. Set to TRUE.
- lParam. A pointer to the null-terminated Unicode string that specifies the
path.
To use a PIDL:
- wParam. Set to FALSE.
- lParam. The PIDL that specifies the path.
BFFM_SETEXPANDED
Version 6.0.
Specifies the path of a folder to expand in the Browse dialog box. The
path can be specified as a Unicode string or a PIDL.
To use a Unicode string:
- wParam. Set to TRUE
- lParam. A pointer to the null-terminated Unicode string that specifies the
path.
To use a PIDL:
- wParam. Set to FALSE
- lParam. The PIDL that specifies the path.
BFFM_SETSTATUSTEXT
Sets the status text. Set lpData to point to a null-terminated string
with the desired text.
- wParam. Not used.
- lParam. A pointer to a null-terminated string containing the desired text.
具體寫法如下：
int CALLBACK BrowseCallbackProc(HWND hwnd, UINT uMsg, LPARAM lParam, LPARAM lpData)
{
if (uMsg == BFFM_INITIALIZED )
{
::SendMessage(hwnd,BFFM_SETSELECTION,TRUE,lpData);
}
return 0;
}
//使用:
CString strLastPath = GetLastOpenDirectory();
LPITEMIDLIST pidlRoot = NULL;
BROWSEINFO bi;
ZeroMemory(&bi,sizeof(BROWSEINFO));
bi.hwndOwner = GetSafeHwnd();
bi.lpszTitle = _T("請選擇目錄");
bi.ulFlags = BIF_RETURNONLYFSDIRS | BIF_USENEWUI | BIF_NONEWFOLDERBUTTON;
bi.lpfn = NULL;
bi.pidlRoot = pidlRoot;
bi.lParam = (LPARAM)strLastPath.GetBuffer();
bi.lpfn = BrowseCallbackProc;
if(pidl == NULL)
return;
SHGetPathFromIDList(pidl, csPath.GetBuffer(MAX_PATH));
csPath.ReleaseBuffer();