通过全局设置过滤器，就能让所有窗口都可移动，而不是都要继承指定QDialog

#include "appinit.h"
#include <QMouseEvent>
#include <QApplication>
#include <QWidget>
AppInit::AppInit(QObject *parent) : QObject(parent)
{
    mousePressed = false;
    qApp->installEventFilter(this);
}

void AppInit::load()
{

}

bool AppInit::eventFilter(QObject *obj, QEvent *evt)
{
    QWidget *w = (QWidget *)obj;
    if(evt->type () == QEvent::KeyPress)
        {
            QKeyEvent * event = static_cast<QKeyEvent *>(evt);
            if(event->key () == Qt::Key_Escape)
            {
                return true;
            }
        }

    if (!w->property("CanMove").toBool()) {
        return QObject::eventFilter(obj, evt);
    }

    QMouseEvent *event = static_cast<QMouseEvent *>(evt);
    if (event->type() == QEvent::MouseButtonPress) {
        if (event->button() == Qt::LeftButton) {
            mousePressed = true;
            mousePoint = event->globalPos() - w->pos();
            return true;
        }
    } else if (event->type() == QEvent::MouseButtonRelease) {
        mousePressed = false;
        return true;
    } else if (event->type() == QEvent::MouseMove) {
        if (mousePressed && (event->buttons() && Qt::LeftButton)) {
            w->move(event->globalPos() - mousePoint);
            return true;
        }
    }
    return QObject::eventFilter(obj, evt);
}

这个方法的最大特点是，不影响其它类层次的设计，而不必强行指定继承我的QDialog。而且在全局做任何事情都可以。