Zoom Line Example▲

The example shows how to create your own custom zooming effect with QRubberBand by using a mouse and how to use touch gestures for paning and zooming.

Image non disponible
Image non disponible

Running the Example▲

To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, visit Building and Running an Example.

Customizing Zooming Effects▲

Let's first create a line series with some example data.

 
Sélectionnez
    QLineSeries *series = new QLineSeries();
    for (int i = 0; i < 500; i++) {
        QPointF p((qreal) i, qSin(M_PI / 50 * i) * 100);
        p.ry() += QRandomGenerator::global()->bounded(20);
        *series << p;
    }

Then we create a custom chart view by deriving from QChartView:

 
Sélectionnez
class ChartView : public QChartView

We override mouse and key event handling

 
Sélectionnez
protected:
    bool viewportEvent(QEvent *event);
    void mousePressEvent(QMouseEvent *event);
    void mouseMoveEvent(QMouseEvent *event);
    void mouseReleaseEvent(QMouseEvent *event);
    void keyPressEvent(QKeyEvent *event);

Then we implement a custom logic for mouse and key events. For example pressing the '+' key will zoom in and pressing the '-' key will zoom out.

 
Sélectionnez
void ChartView::keyPressEvent(QKeyEvent *event)
{
    switch (event->key()) {
    case Qt::Key_Plus:
        chart()->zoomIn();
        break;
    case Qt::Key_Minus:
        chart()->zoomOut();
        break;

We also create our own QChart:

 
Sélectionnez
class Chart : public QChart

Where we can handle the gestures:

 
Sélectionnez
bool Chart::sceneEvent(QEvent *event)
{
    if (event->type() == QEvent::Gesture)
        return gestureEvent(static_cast<QGestureEvent *>(event));
    return QChart::event(event);
}

bool Chart::gestureEvent(QGestureEvent *event)
{
    if (QGesture *gesture = event->gesture(Qt::PanGesture)) {
        QPanGesture *pan = static_cast&l