CLongOperation is a class designed to give visual feedback for long-lasting operations. It has support for:

• Displaying a wait cursor
• Showing a text in the status bar
• Displaying a progress bar in a dynamically created status bar pane

We can use in the following 3 ways:

1、In the simplest case, this class can be used as a replacement for MFC's CWaitCursor:

	CLongOperation wait;
// some hard work going here...

2、To display some textual progress information in the status bar:

	CLongOperation wait;
wait.SetText("Pass 1");
// ...
wait.SetText("Pass 2");
// ...

3、To display a progress bar in the status bar:

	CLongOperation wait;
for (int i = 1; i < 100; i++)
{
wait.Step(i);
// ...do something.
}
wait.Stop();

When using this,我們必須把項目的字符集改為使用多字節符集，IDS_PLEASE_WAIT是一個字符串資源
/////////////////////////////////////////////////////////////////
// LongOperation.h
// (c) 1997, Klaus Gütter
class CLongOperation : public CObject
{
public:
// IDS_PLEASE_WAIT is a string resource ID for the default text,
// e.g. "Please wait..."
CLongOperation(UINT nIDText = IDS_PLEASE_WAIT, bool bStart = true);
CLongOperation(LPCTSTR lpszText, bool bStart = true);
~CLongOperation();
void Start();
void Stop();
void Step(int nPercentage = -1);
void SetText(LPCTSTR lpszText);
protected:
CString m_strText;
bool m_bStarted;
HWND m_hwndProgress;
void CreateProgressControl();
};
/////////////////////////////////////////////////////////////////
// LongOperation.cpp
// (c) 1997, Klaus Gütter
#include "stdafx.h"
#include <afxpriv.h> // defines WM_SETMESSAGESTRING
#include "LongOperation.h"
#ifdef _DEBUG
#undef THIS_FILE
#define new DEBUG_NEW
static char BASED_CODE THIS_FILE[] = __FILE__;
#endif
CLongOperation::CLongOperation(UINT nIDText, bool bStart)
:	m_bStarted(false)
,	m_hwndProgress(NULL)
{
VERIFY(m_strText.LoadString(nIDText));
if (bStart)
Start();
}
CLongOperation::CLongOperation(LPCTSTR lpszText, bool bStart)
:	m_strText(lpszText)
,	m_bStarted(false)
,	m_hwndProgress(NULL)
{
if (bStart)
Start();
}
CLongOperation::~CLongOperation()
{
if (m_bStarted)
Stop();
}
void CLongOperation::Start()
{
if (m_bStarted)
Stop();
// display text in the status bar
CWnd* pMainWnd = ::AfxGetMainWnd();
if (pMainWnd)
pMainWnd->SendMessage(WM_SETMESSAGESTRING, 0, (LPARAM)(LPCTSTR)m_strText);
// switch on wait cursor
::AfxGetApp()->BeginWaitCursor();
m_bStarted = true;
}
void CLongOperation::Stop()
{
if (!m_bStarted)
return;
if (m_hwndProgress)
{
// clean up and destroy progress bar
CStatusBar* pStatusBar = DYNAMIC_DOWNCAST(CStatusBar, CWnd::FromHandle(::GetParent(m_hwndProgress)));
ASSERT_VALID(pStatusBar);
::DestroyWindow(m_hwndProgress);
m_hwndProgress = NULL;
// remove progress bar pane
int anPart[32];
int nParts = pStatusBar->GetStatusBarCtrl().GetParts(31, anPart);
nParts--;
pStatusBar->GetStatusBarCtrl().SetParts(nParts, anPart+1);
}
// switch back to standard text in the status bar
CWnd* pMainWnd = ::AfxGetMainWnd();
if (pMainWnd)
pMainWnd->SendMessage(WM_SETMESSAGESTRING, AFX_IDS_IDLEMESSAGE, 0);
// switch off wait cursor
::AfxGetApp()->EndWaitCursor();
m_bStarted = false;
}
void CLongOperation::Step(int nPercentage)
{
if (!m_bStarted)
Start();
::AfxGetApp()->RestoreWaitCursor();
if (nPercentage >= 0)
{
ASSERT(nPercentage <= 100);
// create or update a progress control in the status bar
if (m_hwndProgress == NULL)
CreateProgressControl();
if (m_hwndProgress)
::SendMessage(m_hwndProgress, PBM_SETPOS, (WPARAM)nPercentage, 0);
}
}
void CLongOperation::SetText(LPCTSTR lpszText)
{
m_strText = lpszText;
CWnd* pMainWnd = ::AfxGetMainWnd();
if (pMainWnd)
pMainWnd->SendMessage(WM_SETMESSAGESTRING, 0, (LPARAM)(LPCTSTR)m_strText);
}
void CLongOperation::CreateProgressControl()
{
ASSERT(m_hwndProgress == NULL);
// find status bar
CWnd* pMainWnd = ::AfxGetMainWnd();
if (pMainWnd == NULL)
return;
CStatusBar* pStatusBar = DYNAMIC_DOWNCAST(CStatusBar,
pMainWnd->GetDescendantWindow(AFX_IDW_STATUS_BAR, TRUE));
if (pStatusBar == NULL || pStatusBar->m_hWnd == NULL)
return;
CRect rc; // this will be the location for the progress bar pane
pStatusBar->GetItemRect(0, rc);
if (!m_strText.IsEmpty())
{
// adjust so that the text in the leftmost pane will not be covered
CClientDC dc(pStatusBar);
dc.SelectObject(pStatusBar->GetFont());
CSize sz = dc.GetTextExtent(m_strText);
TEXTMETRIC tm;
dc.GetTextMetrics(&tm);
rc.left += sz.cx + 2*tm.tmAveCharWidth;
}
int cx = rc.Width();
if (cx < 20)
{
// no sense in displaying such a small progress bar
TRACE0("ProgressDisplay would be too small\n");
return;
}
else if (cx > 200)
{
// arbitrarily limiting progress bar width to 200 pixel
cx = 200;
rc.left = rc.right - cx;
}
// add a pane between the text and the currently leftmost pane
int anPart[32];
int nParts = pStatusBar->GetStatusBarCtrl().GetParts(31, anPart+1);
anPart[0] = rc.left;
nParts++;
pStatusBar->GetStatusBarCtrl().SetParts(nParts, anPart);
pStatusBar->GetStatusBarCtrl().GetRect(1, rc);
// create progress bar control
m_hwndProgress = ::CreateWindow(PROGRESS_CLASS, "",
WS_CHILD | WS_VISIBLE, rc.left, rc.top, rc.Width(), rc.Height(),
pStatusBar->m_hWnd, (HMENU)1, AfxGetInstanceHandle(), NULL);
pStatusBar->UpdateWindow();
}