#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QKeyEvent>
class KeyBackQuit: public  QObject{
public:
    KeyBackQuit(QObject *parent=0): QObject(parent){}
    //Override
    bool eventFilter(QObject *watched, QEvent *e){
        switch (e->type()) {
            case QEvent::KeyPress:
                if(((QKeyEvent*)e)->key()==Qt::Key_Backspace){
                    //接收者处理当前事件
                    e->accept();
                    return true;
                }
                break;
            case QEvent::KeyRelease:
                if(((QKeyEvent*)e)->key()==Qt::Key_Backspace){
                    //设置事件对象的 accept 标志，等价于 setAccepted(true)
                    e->accept();
                    qApp->quit();
                    return true;
                }
                break;
            default:
                break;
        }
        //监控的组件 转发的事件 true过滤掉无需转发 false转发给watched
        return QObject::eventFilter(watched,e);
    }
};

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);
    app.installEventFilter(new KeyBackQuit);
    QQmlApplicationEngine engine;

    const QUrl url(QStringLiteral("qrc:/main.qml"));
    engine.load(url);
    return app.exec();
}