縮放綫範例

範例展示如何創建自己的自定義縮放效果。

範例展示如何創建自己的自定義縮放效果采用 QRubberBand 通過使用鼠標及如何使用觸摸手勢進行平移和縮放。

運行範例

要運行範例從 Qt Creator ，打開歡迎模式，然後選擇範例從範例。更多信息，拜訪構建和運行範例 .

定製縮放效果

讓我們首先采用一些範例數據創建綫係列。

    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 :

class ChartView : public QChartView

We override mouse and key event handling

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.

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 :

class Chart : public QChart

Where we can handle the gestures:

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<QPanGesture *>(gesture);
        QChart::scroll(-(pan->delta().x()), pan->delta().y());
    }
    if (QGesture *gesture = event->gesture(Qt::PinchGesture)) {
        QPinchGesture *pinch = static_cast<QPinchGesture *>(gesture);
        if (pinch->changeFlags() & QPinchGesture::ScaleFactorChanged)
            QChart::zoom(pinch->scaleFactor());
    }
    return true;
}

Note that you will need to call grabGesture() to both QMainWindow and QChart .

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