MFC自定义实现CheckComboBox下拉多选

先看效果图

自定义类继承CComboBox头文件

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000


class CCheckComboBox : public CComboBox
{
public:
	CCheckComboBox();
	virtual ~CCheckComboBox();

	BOOL Create(DWORD dwStyle, const RECT& rect, CWnd* pParentWnd, UINT nID);

	// Selects all/unselects the specified item
	INT SetCheck(INT nIndex, BOOL bFlag);

	// Returns checked state
	BOOL GetCheck(INT nIndex);

	// Selects all/unselects all
	void SelectAll(BOOL bCheck = TRUE);

protected:
	// ClassWizard generated virtual function overrides
	//{
  {AFX_VIRTUAL(CCheckComboBox)
	protected:
	virtual void DrawItem(LPDRAWITEMSTRUCT lpDrawItemStruct);
	virtual void MeasureItem(LPMEASUREITEMSTRUCT lpMeasureItemStruct);
	//}}AFX_VIRTUAL

	//{
  {AFX_MSG(CCheckComboBox)
	afx_msg LRESULT OnCtlColorListBox(WPARAM wParam, LPARAM lParam);
	afx_msg LRESULT OnGetText(WPARAM wParam, LPARAM lParam);
	afx_msg LRESULT OnGetTextLength(WPARAM wParam, LPARAM lParam);
	afx_msg void OnDropDown();
	//}}AFX_MSG

	DECLARE_MESSAGE_MAP()

protected:
	// Routine to update the text
	void RecalcText();

	// The subclassed COMBOLBOX window (notice the 'L')
	HWND m_hListBox;

	// The string containing the text to display
	CString m_strText;
	BOOL m_bTextUpdated;

	// A flag used in MeasureItem, see comments there
	BOOL m_bItemHeightSet;
};

实现

#include "pch.h"
#include "CCheckComboBox.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

static WNDPROC m_pWndProc = 0;
static CCheckComboBox* m_pComboBox = 0;


BEGIN_MESSAGE_MAP(CCheckComboBox, CComboBox)
	//{
  {AFX_MSG_MAP(CCheckComboBox)
	ON_MESSAGE(WM_CTLCOLORLISTBOX, OnCtlColorListBox)
	ON_MESSAGE(WM_GETTEXT, OnGetText)
	ON_MESSAGE(WM_GETTEXTLENGTH, OnGetTextLength)
	ON_CONTROL_REFLECT(CBN_DROPDOWN, OnDropDown)
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()


//
// The subclassed COMBOLBOX message handler
//
extern "C" LRESULT FAR PASCAL ComboBoxListBoxProc(HWND hWnd, UINT nMsg, WPAR