MFC和QT的消息循环机制不同，所以，要让QT写的DLL可以供MFC调用，要做一点特殊的处理

#include <qmfcapp.h>
#include <qwinwidget.h>
#include <QtGui>#include <QtGui/QMessageBox>
#include <windows.h>
#include <QTextCodec>
#include "widget.h"BOOL WINAPI DllMain( HINSTANCE hInstance, DWORD dwReason, LPVOID /*lpvReserved*/ )
{static bool ownApplication = FALSE;//加入本地语言支持QTextCodec::setCodecForTr(QTextCodec::codecForLocale());QTextCodec::setCodecForCStrings(QTextCodec::codecForLocale());if ( dwReason == DLL_PROCESS_ATTACH ){ownApplication = QMfcApp::pluginInstance( hInstance );}if ( dwReason == DLL_PROCESS_DETACH && ownApplication ){qApp->quit();delete qApp;}return TRUE;
}extern "C" __declspec(dllexport) int ShowDialog( HWND parent)
{QWinWidget win(parent, NULL, Qt::Window);win.showCentered();win.center();QHBoxLayout hbox(&win);Widget *widget = new Widget(&win);widget->setWindowFlags(Qt::Window);hbox.addWidget(widget);win.show();qApp->exec();
}