knob.cpp Example File

touch/knobs/knob.cpp
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#include "knob.h" #include <QBrush> #include <QTouchEvent> Knob::Knob() : QGraphicsEllipseItem(-50, -50, 100, 100) { setAcceptTouchEvents(true); setBrush(Qt::lightGray); QGraphicsEllipseItem *leftItem = new QGraphicsEllipseItem(0, 0, 20, 20, this); leftItem->setPos(-40, -10); leftItem->setBrush(Qt::darkGreen); QGraphicsEllipseItem *rightItem = new QGraphicsEllipseItem(0, 0, 20, 20, this); rightItem->setPos(20, -10); rightItem->setBrush(Qt::darkRed); } bool Knob::sceneEvent(QEvent *event) { switch (event->type()) { case QEvent::TouchBegin: case QEvent::TouchUpdate: case QEvent::TouchEnd: { QTouchEvent *touchEvent = static_cast<QTouchEvent *>(event); if (touchEvent->touchPoints().count() == 2) { const QTouchEvent::TouchPoint &touchPoint1 = touchEvent->touchPoints().first(); const QTouchEvent::TouchPoint &touchPoint2 = touchEvent->touchPoints().last(); QLineF line1(touchPoint1.lastScenePos(), touchPoint2.lastScenePos()); QLineF line2(touchPoint1.scenePos(), touchPoint2.scenePos()); setTransform(QTransform().rotate(line2.angleTo(line1)), true); } break; } default: return QGraphicsItem::sceneEvent(event); } return true; }