InteractiveCanvasComponent.java 文件源码

public void mouseWheelMoved(MouseWheelEvent e) {
    // Mouse wheel zooming takes precedence over scrolling
    if (isMouseZoomingEnabled() &&
        e.getSource() == InteractiveCanvasComponent.this) return;

    // Change the ScrollBar value
    if (e.getScrollType() == MouseWheelEvent.WHEEL_UNIT_SCROLL) {
        int unitsToScroll = e.getUnitsToScroll();
        int direction = unitsToScroll < 0 ? -1 : 1;
        if (unitsToScroll != 0) {
            int increment = scrollBar.getUnitIncrement(direction);
            int oldValue = scrollBar.getValue();
            int newValue = oldValue + increment * unitsToScroll;
            newValue = Math.max(Math.min(newValue, scrollBar.getMaximum() -
                    scrollBar.getVisibleAmount()), scrollBar.getMinimum());
            if (oldValue != newValue) scrollBar.setValue(newValue);
        }
    }
}