MFC打开大数据文件等待过程状态显示实现

首先申明，本文参考"c++ - MFC 打开大文件"和"Notifying the Document"两篇文章写成。

在编写Windows软件时，打开一个Excel文件或实际计算需要耗费一定的时间，使得Windows窗口不流畅，此时在窗口显示等待过程的状态特别有意义。

一、VC++ 2022生成MFC单文档项目ReadState

二、 在菜单资源视图中，对“文件->打开”添加事件处理程序CReadStateDoc::OnFileOpen()

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 三、添加代码

1. 在resource.h中：

#define IDD_NotifyDocumentFinished        101

2. 在ReadStateDoc.h中的class CReadStateDoc : public CDocument中：

public:
	enum DocState { None, Failed, Loading, Loaded };
	DocState GetDocState() const { return m_state; }
	DocState m_state;
	void StartLoading();

3. 在ReadStateDoc.cpp中：

UINT LongRunningFunction(LPVOID param)
{
	Sleep(12000);

	HWND hWnd = AfxGetApp()->m_pMainWnd->GetSafeHwnd();

	NMHDR hdr = { hWnd, IDD_NotifyDocumentFinished, 0 };
	::SendMessage(hWnd, WM_NOTIFY, 0, reinterpret_cast(&hdr));

	return 0;
}

void CReadStateDoc::StartLoading()
{
	AfxBeginThread(&LongRunningFunction, nullptr);
}

4. 使用类向导添加函数CReadStateDoc::OnCmdMsg，并添加代码：

BOOL CReadStateDoc::OnCmdMsg(UINT nID, int nCode, void* pExtra, AFX_CMDHANDLERINFO* pHandlerInfo)
{
	// TODO: 在此添加专用代码和/或调用基类

	if (HIWORD(nCode) == WM_NOTIFY)
	{
		WORD wCode = LOWORD(nCode);
		AFX_NOTIFY* notify = reinterpret_cast(pExtra);
		if (notify->pNMHDR->idFrom == IDD_NotifyDocumentFinished)
		{
			m_state = Loaded;
			UpdateAllViews(nullptr);
		}
	}

	return CDocument::OnCmdMsg(nID, nCode, pExtra, pHandlerInfo);
}

5. 在CReadStateView::OnFileOpen()中：

	CReadStateDoc* pDoc = GetDocument();
	ASSERT_VALID(pDoc);
	if (!pDoc)
		return;

	pDoc->m_state = pDoc->Loading;
	Invalidate();
	pDoc->StartLoading();

6. 在CReadStateView::OnDraw(CDC* pDC)中：

void CReadStateView::OnDraw(CDC* pDC)
{
	CReadStateDoc* pDoc = GetDocument();
	ASSERT_VALID(pDoc);
	if (!pDoc)
		return;

	// TODO: 在此处为本机数据添加绘制代码
	CFont font;
	CFont* pFont;
	font.CreatePointFont(120, _T("Arial"));
	pFont = pDC->SelectObject(&font);

	CReadStateDoc::DocState state = pDoc->GetDocState();
	CString sstate;
	switch (state)
	{
	case CReadStateDoc::None:
		sstate = "None";
		break;
	case CReadStateDoc::Failed:
		sstate = "Failed";
		break;
	case CReadStateDoc::Loading:
		sstate = "Loading ... ";
		break;
	case CReadStateDoc::Loaded:
		sstate = "Loaded";
		break;
	}
	pDC->TextOut(50, 50, sstate);
	// Release the font object
	pDC->SelectObject(pFont);
}

四、编译运行

点击“文件->打开”，窗口出现“Loading ...”：

过一会，窗口出现“Loaded”：