plugin.cpp Example File

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

     ~TimeModel() override
     {
         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=nullptr;

 class QExampleQmlPlugin : public QQmlExtensionPlugin
 {
     Q_OBJECT
     Q_PLUGIN_METADATA(IID QQmlExtensionInterface_iid)

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

 #include "plugin.moc"