- Qt 5.5
- Qt QML
- QML Plugin Example
- plugin.cpp Example File
- Qt 5.5.1 Reference Documentation

# plugin.cpp Example File

qmlextensionplugins/plugin.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** You may use this file under the terms of the BSD license as follows:
    **
    ** "Redistribution and use in source and binary forms, with or without
    ** modification, are permitted provided that the following conditions are
    ** met:
    **   * Redistributions of source code must retain the above copyright
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    **     the documentation and/or other materials provided with the
    **     distribution.
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    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
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    #include <QtQml/QQmlExtensionPlugin>
    #include <QtQml/qqml.h>
    #include <qdebug.h>
    #include <qdatetime.h>
    #include <qbasictimer.h>
    #include <qcoreapplication.h>

    // Implements a "TimeModel" class with hour and minute properties
    // that change on-the-minute yet efficiently sleep the rest
    // of the time.

    class MinuteTimer : public QObject
    {
        Q_OBJECT
    public:
        MinuteTimer(QObject *parent) : QObject(parent)
        {
        }

        void start()
        {
            if (!timer.isActive()) {
                time = QTime::currentTime();
                timer.start(60000-time.second()*1000, this);
            }
        }

        void stop()
        {
            timer.stop();
        }

        int hour() const { return time.hour(); }
        int minute() const { return time.minute(); }

    signals:
        void timeChanged();

    protected:
        void timerEvent(QTimerEvent *)
        {
            QTime now = QTime::currentTime();
            if (now.second() == 59 && now.minute() == time.minute() && now.hour() == time.hour()) {
                // just missed time tick over, force it, wait extra 0.5 seconds
                time.addSecs(60);
                timer.start(60500, this);
            } else {
                time = now;
                timer.start(60000-time.second()*1000, this);
            }
            emit timeChanged();
        }

    private:
        QTime time;
        QBasicTimer timer;
    };

    class TimeModel : public QObject
    {
        Q_OBJECT
        Q_PROPERTY(int hour READ hour NOTIFY timeChanged)
        Q_PROPERTY(int minute READ minute NOTIFY timeChanged)

    public:
        TimeModel(QObject *parent=0) : QObject(parent)
        {
            if (++instances == 1) {
                if (!timer)
                    timer = new MinuteTimer(QCoreApplication::instance());
                connect(timer, SIGNAL(timeChanged()), this, SIGNAL(timeChanged()));
                timer->start();
            }
        }

        ~TimeModel()
        {
            if (--instances == 0) {
                timer->stop();
            }
        }

        int minute() const { return timer->minute(); }
        int hour() const { return timer->hour(); }

    signals:
        void timeChanged();

    private:
        QTime t;
        static MinuteTimer *timer;
        static int instances;
    };

    int TimeModel::instances=0;
    MinuteTimer *TimeModel::timer=0;

    class QExampleQmlPlugin : public QQmlExtensionPlugin
    {
        Q_OBJECT
        Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QQmlExtensionInterface")

    public:
        void registerTypes(const char *uri)
        {
            Q_ASSERT(uri == QLatin1String("TimeExample"));
            qmlRegisterType<TimeModel>(uri, 1, 0, "Time");
        }
    };

    #include "plugin.moc"