Mouse Dragging ViewPort Scroll

• download example.jar
• download src.zip
• repository

Code

MouseAdapter hsl1 = new HandScrollListener();
vport.addMouseMotionListener(hsl1);
vport.addMouseListener(hsl1);

MouseAdapter hsl2 = new DragScrollListener();
label.addMouseMotionListener(hsl2);
label.addMouseListener(hsl2);

class HandScrollListener extends MouseAdapter {
  private final Cursor defCursor = Cursor.getDefaultCursor();
  private final Cursor hndCursor = Cursor.getPredefinedCursor(Cursor.HAND_CURSOR);
  private final Point pp = new Point();

  @Override public void mouseDragged(MouseEvent e) {
    JViewport vport = (JViewport) e.getComponent();
    Point cp = e.getPoint();
    Rectangle rect = vport.getViewRect();
    rect.translate(pp.x - cp.x, pp.y - cp.y);
    label.scrollRectToVisible(rect);
    pp.setLocation(cp);
  }

  @Override public void mousePressed(MouseEvent e) {
    e.getComponent().setCursor(hndCursor);
    pp.setLocation(e.getPoint());
  }

  @Override public void mouseReleased(MouseEvent e) {
    e.getComponent().setCursor(defCursor);
  }
}

class DragScrollListener extends MouseAdapter {
  private final Cursor defCursor = Cursor.getDefaultCursor();
  private final Cursor hndCursor = Cursor.getPredefinedCursor(Cursor.HAND_CURSOR);
  private final Point pp = new Point();

  @Override public void mouseDragged(MouseEvent e) {
    Component c = e.getComponent();
    Container p = SwingUtilities.getUnwrappedParent(c);
    if (p instanceof JViewport) {
      JViewport viewport = (JViewport) p;
      Point cp = SwingUtilities.convertPoint(c, e.getPoint(), viewport);
      Rectangle rect = viewport.getViewPosition();
      rect.translate(pp.x - cp.x, pp.y - cp.y);
      ((JComponent) c).scrollRectToVisible(rect);
      pp.setLocation(cp);
    }
  }

  @Override public void mousePressed(MouseEvent e) {
    Component c = e.getComponent();
    c.setCursor(hndCursor);
    Container p = SwingUtilities.getUnwrappedParent(c);
    if (p instanceof JViewport) {
      JViewport viewport = (JViewport) p;
      Point cp = SwingUtilities.convertPoint(c, e.getPoint(), viewport);
      pp.setLocation(cp);
    }
  }

  @Override public void mouseReleased(MouseEvent e) {
    e.getComponent().setCursor(defCursor);
  }
}

References

• Java Swing Tips: Mouse Drag Auto Scrolling
• Mouse Drag Auto Scrolling(Japanese)
• Mouse Dragging ViewPort Scroll(Japanese)