MFC怎么在单击按钮时改变一个Icon的显示图像

//////////////////////////////////////////////////
// Controls.cpp文件



#include <windows.h>
#include "resource.h"

BOOL __stdcall DlgProc(HWND, UINT, WPARAM, LPARAM);

HBITMAP g_hBitmap1;    // 第一个图片的句柄
HBITMAP g_hBitmap2;    // 第二个图片的句柄
HICON    g_hIcon;    // 对话框图标句柄
HBRUSH    g_hBgBrush;    // 背景刷子

int __stdcall WinMain(HINSTANCE hInstance, HINSTANCE, LPSTR, int)
{
    // 从资源中加载BMP文件和图标，这些工作也可以在WM_INITDIALOG消息中进行
    g_hBitmap1 = ::LoadBitmap(hInstance, (LPCTSTR)IDB_BITMAP1);
    g_hBitmap2 = ::LoadBitmap(hInstance, (LPCTSTR)IDB_BITMAP2);
    g_hIcon = ::LoadIcon(hInstance, (LPCTSTR)IDI_MAIN);
    // 创建背景刷子
    g_hBgBrush = ::CreateSolidBrush(RGB(0xa6, 0xca, 0xf0));

    int nResult = ::DialogBoxParam(
        hInstance,        // 实例句柄
        (LPCTSTR)IDD_MAIN,    // 对话框资源ID号
        NULL,            // 父窗口句柄
        DlgProc,        // 消息处理函数
        NULL);             // 对话框初始化的值，在WM_INITDIALOG消息的lParam参数中取出

    ::DeleteObject(g_hBgBrush);

    return 0;
}

BOOL __stdcall DlgProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch(message)
    {    
    case WM_INITDIALOG:
        {
            // 设置标题栏图标
            ::SendMessage(hDlg, WM_SETICON, ICON_BIG, (long)g_hIcon);

            // 初始化显示图片的静态框架

            HWND hWndBmp = ::GetDlgItem(hDlg, IDC_BMP);
            // 设置SS_BITMAP风格
            LONG nStyle = ::GetWindowLong(hWndBmp, GWL_STYLE);
            ::SetWindowLong(hWndBmp, GWL_STYLE, nStyle | SS_BITMAP);
            // 设置图片
            ::SendDlgItemMessage(hDlg, IDC_BMP, STM_SETIMAGE, IMAGE_BITMAP, (long)g_hBitmap1);

            // 初始化复选框
            ::CheckDlgButton(hDlg, IDC_BMP1, BST_CHECKED);
        }
        break;

    case WM_COMMAND:
        switch(LOWORD(wParam))
        {
        case IDOK:    // 向列表框中添加文本
            {
                HWND hWndEdit = ::GetDlgItem(hDlg, IDC_INPUT);

                // 取得文本框中的文本
                char szText[256];
                int nLen = ::GetWindowText(hWndEdit, szText, 256);
                if(nLen > 0)
                {
                    // 向列表框控件中添加文本
                    ::SendDlgItemMessage(hDlg, IDC_LIST, LB_ADDSTRING, NULL, (long)szText);
                    // 清空文本框中的文本
                    ::SetWindowText(hWndEdit, "");
                }
            
            }
            break;

        case IDCANCEL:        // 退出程序
            ::EndDialog (hDlg, IDCANCEL);
            break;

        case IDC_TOPMOST:    // 设置对话框的Z轴位置 
            {
                HWND hWndCheck = ::GetDlgItem(hDlg, IDC_TOPMOST);
                int nRet = ::SendMessage(hWndCheck, BM_GETCHECK, 0, 0);
                if(nRet == BST_CHECKED)
                {
                    ::SetWindowPos(hDlg, HWND_TOPMOST, 0, 0, 0, 0, 
                        SWP_NOMOVE|SWP_NOSIZE|SWP_NOREDRAW);
                }
                else
                {
                    ::SetWindowPos(hDlg, HWND_NOTOPMOST, 0, 0, 0, 0, 
                        SWP_NOMOVE|SWP_NOSIZE|SWP_NOREDRAW);
                }
            }
            break;

        case IDC_BMP1:        // 更换到第一个图片
            {
                int nRet = ::IsDlgButtonChecked(hDlg, IDC_BMP1);
                if(nRet == BST_CHECKED)
                {
                    ::SendDlgItemMessage(hDlg, IDC_BMP, 
                        STM_SETIMAGE, IMAGE_BITMAP, (LPARAM)g_hBitmap1);
                }
            
            }
            break;

        case IDC_BMP2:        // 更换到第二个图片
            {
                int nRet = ::IsDlgButtonChecked(hDlg, IDC_BMP2);
                if(nRet == BST_CHECKED)
                {
                    ::SendDlgItemMessage(hDlg, IDC_BMP, 
                        STM_SETIMAGE, IMAGE_BITMAP, (LPARAM)g_hBitmap2);
                }
            }
            break;

        case IDC_HIDE:        // 更换图片的显示状态
            {
                HWND hWndBmp = ::GetDlgItem(hDlg, IDC_BMP);
                HWND hWndCheck = ::GetDlgItem(hDlg, IDC_HIDE);
                int nRet = ::SendMessage(hWndCheck, BM_GETCHECK, 0, 0);
                if(nRet == BST_CHECKED)
                    ::ShowWindow(hWndBmp, SW_HIDE);
                else
                    ::ShowWindow(hWndBmp, SW_SHOW);
            }
            break;
        }
        break;

    case WM_CTLCOLORSTATIC:    // 设置静态文本框的背景色
    case WM_CTLCOLORDLG:    // 设置对话框的背景色
        {
            HDC hdc = (HDC)wParam;

            // 为静态文本框设置文本背景色
            ::SetBkColor(hdc, RGB(0xa6, 0xca, 0xf0));

            if((HWND)lParam == ::GetDlgItem(hDlg, IDC_AUTHOR))
            {
                ::SetTextColor(hdc, RGB(0, 0, 0xff));
            }
            
            return (int)g_hBgBrush;
        }
    }

    return 0;
}