Code
class ViewportDragScrollListener extends MouseAdapter
implements HierarchyListener {
private static final int SPEED = 4;
private static final int DELAY = 10;
private final Cursor dc;
private final Cursor hc = Cursor.getPredefinedCursor(Cursor.HAND_CURSOR);
private final Timer scroller;
private final JComponent label;
private Point startPt = new Point();
private Point move = new Point();
public ViewportDragScrollListener(JComponent comp) {
this.label = comp;
this.dc = comp.getCursor();
this.scroller = new Timer(DELAY, new ActionListener() {
@Override public void actionPerformed(ActionEvent e) {
Container c = SwingUtilities.getAncestorOfClass(
JViewport.class, label);
if (c instanceof JViewport.class) {
JViewport vport = (JViewport) c;
Rectangle rect = vport.getViewRect();
rect.translate(move.x, move.y);
label.scrollRectToVisible(rect);
}
}
});
}
@Override public void hierarchyChanged(HierarchyEvent e) {
JComponent c = (JComponent) e.getSource();
if ((e.getChangeFlags() & HierarchyEvent.DISPLAYABILITY_CHANGED) != 0
&& !c.isDisplayable()) {
scroller.stop();
}
}
@Override public void mouseDragged(MouseEvent e) {
JViewport vport = (JViewport) e.getSource();
Point pt = e.getPoint();
int dx = startPt.x - pt.x;
int dy = startPt.y - pt.y;
Rectangle rect = vport.getViewRect();
rect.translate(dx, dy);
label.scrollRectToVisible(rect);
move.setLocation(SPEED * dx, SPEED * dy);
startPt.setLocation(pt);
}
@Override public void mousePressed(MouseEvent e) {
e.getComponent().setCursor(hc); // label.setCursor(hc);
startPt.setLocation(e.getPoint());
move.setLocation(0, 0);
scroller.stop();
}
@Override public void mouseReleased(MouseEvent e) {
e.getComponent().setCursor(dc); // label.setCursor(dc);
scroller.start();
}
@Override public void mouseExited(MouseEvent e) {
e.getComponent().setCursor(dc); // label.setCursor(dc);
move.setLocation(0, 0);
scroller.stop();
}
}
References
