QML simple program not running

Question

I am trying to run the following, but nothing happens when I run it. How can I debug such an issue?

import QtQuick 2.0
import QtQml.Models 2.1



Item{
    id: main
    width: 1500
    height: 1500
    GridView {
        id: root
        width: 1500
        height: 1500
        cellWidth: 200; cellHeight: 200
        visible: true


        model: DelegateModel {
            model: ListModel {
                ListElement {
                    color: "blue"
                }
                ListElement {
                    color: "white"
                }
                ListElement {
                    color: "red"
                }
                ListElement {
                    color: "green"
                }
                ListElement {
                    color: "orange"
                }
                ListElement {
                    color: "yellow"
                }
                ListElement {
                    color: "grey"
                }
            }

            delegate: MouseArea {
                objectName: "mousearea"

                implicitHeight: parent.height
                implicitWidth: parent.width

                Rectangle {
                    anchors.fill: parent
                    color: model.color
                }
                drag{
                    target: parent
                }
            }
        }
    }
}

What I intend from this code is the following: create few rectangles inside a GridView and add a MouseArea to them and try dragging them around afterwards. I am not sure if my model structure is correct here.

EDIT: Adding main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>

int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);

    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    if (engine.rootObjects().isEmpty())
        return -1;

    return app.exec();
}

Answer 1

QQmlApplicationEngine expects to have a Window as the root element as indicated by the docs:

...
Unlike QQuickView, QQmlApplicationEngine does not automatically create a root window. If you are using visual items from Qt Quick, you will need to place them inside of a Window.
...

So the solution is simple, change Item by Window:

main.qml

import QtQuick 2.0
import QtQuick.Window 2.11
import QtQml.Models 2.1

Window{
    visible: true
    id: main
    width: 1500
    height: 1500
    GridView {
        id: root
        width: 1500
        height: 1500
        cellWidth: 200; cellHeight: 200
        visible: true


        model: DelegateModel {
            model: ListModel {
                ListElement {
                    color: "blue"
                }
                ListElement {
                    color: "white"
                }
                ListElement {
                    color: "red"
                }
                ListElement {
                    color: "green"
                }
                ListElement {
                    color: "orange"
                }
                ListElement {
                    color: "yellow"
                }
                ListElement {
                    color: "grey"
                }
            }

            delegate: MouseArea {
                objectName: "mousearea"

                implicitHeight: parent.height
                implicitWidth: parent.width

                Rectangle {
                    anchors.fill: parent
                    color: model.color
                }
                drag{
                    target: parent
                }
            }
        }
    }
}