main.cpp

#include <QGuiApplication>
//#include <QQmlApplicationEngine>
#include <QQuickView>

int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling); //支援高解析度螢幕

    QGuiApplication app(argc, argv);

//    QQmlApplicationEngine engine;
//    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
 

//    if (engine.rootObjects().isEmpty())
//        return -1;
    QQuickView *view = new QQuickView();
    view->setSource(QUrl("qrc:/keys.qml"));
    view->show();

    return app.exec();
}

keys.qml

import QtQuick 2.9

DarkSquare {
    width: 400; height: 200

    GreenSquare {
        id: square
        x
 
: 8; y: 8
    }
    focus: true
    Keys.onLeftPressed: square.x -= 8
    Keys.onRightPressed: square.x += 8
    Keys.onUpPressed: square.y -= 8
    Keys.onDownPressed: square.y += 8
    Keys.onPressed: {
        switch(event.key) {
            case Qt.Key_Plus:
                square.scale += 0.2
                break
 
;
            case Qt.Key_Minus:
                square.scale -= 0.2
                break;
        }

    }
}

DarkSquare.qml

import QtQuick 2.9

Rectangle {
    width: 48
    height: 48
    color: "#3c3c3c"
    border.color: Qt.lighter(color)
}

GreenSquare.qml

import QtQuick 2.9

Rectangle {
    width: 48
    height: 48
    color: "#67c111"
    border.color: Qt.lighter(color)
}

執行結果為: