fingerswipegesture.cpp Example File

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 #include "fingerswipegesture.h"
 #include <QGesture>

 #include <QWidget>
 #include <QGraphicsObject>
 #include <QEvent>
 #include <QTouchEvent>
 #include <QtDebug>

 /*!
     \class FingerSwipeGestureRecognizer
     The gesture recognizer for the FingerSwipeGesture.
     \see FingerSwipeGesture
 */

 FingerSwipeGestureRecognizer::FingerSwipeGestureRecognizer()
 {
 }

 /*! \reimp
  */
 QGesture *FingerSwipeGestureRecognizer::create(QObject *target)
 {
     if (target && target->isWidgetType()) {
         QWidget *widget = static_cast<QWidget *>(target);
 // ![0]
         widget->setAttribute(Qt::WA_AcceptTouchEvents);
 // ![0]

     } else if (target) {
         QGraphicsObject *go = qobject_cast<QGraphicsObject*>(target);
         if (go) {
 // ![1]
             go->setAcceptTouchEvents(true);
 // ![1]
         }
     }
     return new FingerSwipeGesture();
 }

 /*! \reimp
  */
 QGestureRecognizer::Result FingerSwipeGestureRecognizer::recognize(QGesture *state,
                                                             QObject *,
                                                             QEvent *event)
 {
     FingerSwipeGesture *q = static_cast<FingerSwipeGesture *>(state);

     const QTouchEvent *ev = static_cast<const QTouchEvent *>(event); // only use ev after checking event->type()

     QGestureRecognizer::Result result = QGestureRecognizer::Ignore;

     switch (event->type()) {
     case QEvent::TouchBegin: {
         result = QGestureRecognizer::MayBeGesture;
         if (ev->touchPoints().size() >= 1) {
             QTouchEvent::TouchPoint p1 = ev->touchPoints().first();
             q->m_startPos = p1.startPos();
         }
         break;
     }
     case QEvent::TouchEnd: {
         if (q->m_cancelled) {
             result = QGestureRecognizer::Ignore;
         } else if (q->m_triggered) {
             result = QGestureRecognizer::FinishGesture;
         } else {
             result = QGestureRecognizer::CancelGesture;
         }
         break;
     }
     case QEvent::TouchUpdate: {
         if (!q->m_cancelled &&
             ev->touchPoints().size() >= 1) {

             QTouchEvent::TouchPoint p1 = ev->touchPoints().first();

             q->m_currentPos = p1.pos();

             // update the hot-spot to be in the middle between start and current point
             q->setHotSpot(QPointF(p1.screenPos().x() - (q->m_currentPos.x() - q->m_startPos.x()) / 2,
                                   p1.screenPos().y() - (q->m_currentPos.y() - q->m_startPos.y()) / 2));

             QPointF delta = p1.pos() - q->m_startPos;

             // -- check that the user has drawn a vertical line
             if (qAbs(delta.x()) > 25 &&
                 (qAbs(delta.y()) < qAbs(delta.x()) * 0.2) ) {
                 if (!q->m_triggered) {
                     q->m_triggered = true;
                     result = QGestureRecognizer::TriggerGesture;
                 }
             } else {
                 if (!q->m_triggered) {
                     result = QGestureRecognizer::MayBeGesture;
                 } else {
                     q->m_cancelled = true;
                     result = QGestureRecognizer::CancelGesture;
                 }
             }
             break;
         }
     }
     default:
         break;
     }
     return result;
 }

 /*! \reimp
  */
 void FingerSwipeGestureRecognizer::reset(QGesture *state)
 {
     FingerSwipeGesture *q = static_cast<FingerSwipeGesture *>(state);
     q->m_startPos = QPoint();
     q->m_lastPos = QPoint();
     q->m_currentPos = QPoint();
     q->m_triggered = false;
     q->m_cancelled = false;

     QGestureRecognizer::reset(state);
 }

 /*!
     \class FingerSwipeGesture
     This gesture detect a left to right or right to left swipe.
 */

 /*!
     \internal
 */
 FingerSwipeGesture::FingerSwipeGesture(QObject *parent)
     : QGesture(parent)
     , m_triggered(false)
     , m_cancelled(false)
 { }

 FingerSwipeGesture::~FingerSwipeGesture()
 { }

 bool FingerSwipeGesture::isLeftToRight() const
 {
     return m_startPos.x() < m_currentPos.x();
 }