Code
JLabel label = new JLabel();
//"CRW_3857_JFR.jpg" > http://sozai-free.com/
label.setIcon(new ImageIcon(getClass().getResource("CRW_3857_JFR.jpg")));
JScrollPane scroll = new JScrollPane(label,
JScrollPane.VERTICAL_SCROLLBAR_NEVER, JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
//*
ViewportDragScrollListener l = new ViewportDragScrollListener(label);
JViewport v = scroll.getViewport();
v.addMouseMotionListener(l);
v.addMouseListener(l);
v.addHierarchyListener(l);
/*/
//If label has its own MouseListeners, recommended to use ComponentDragScrollListener instead of ViewportDragScrollListener:
ComponentDragScrollListener l = new ComponentDragScrollListener(label);
label.addMouseMotionListener(l);
label.addMouseListener(l);
label.addHierarchyListener(l);
//*/
add(scroll);
scroll.setPreferredSize(new Dimension(320, 320));
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 javax.swing.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 javax.swing.Timer(DELAY, new ActionListener() {
@Override public void actionPerformed(ActionEvent e) {
JViewport vport = (JViewport)label.getParent();
Point vp = vport.getViewPosition();
vp.translate(move.x, move.y);
label.scrollRectToVisible(new Rectangle(vp, vport.getSize()));
}
});
}
@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;
Point vp = vport.getViewPosition();
vp.translate(dx, dy);
label.scrollRectToVisible(new Rectangle(vp, vport.getSize()));
move.setLocation(SPEED*dx, SPEED*dy);
startPt.setLocation(pt);
}
@Override public void mousePressed(MouseEvent e) {
((JComponent)e.getSource()).setCursor(hc); //label.setCursor(hc);
startPt.setLocation(e.getPoint());
move.setLocation(0, 0);
scroller.stop();
}
@Override public void mouseReleased(MouseEvent e) {
((JComponent)e.getSource()).setCursor(dc); //label.setCursor(dc);
scroller.start();
}
@Override public void mouseExited(MouseEvent e) {
((JComponent)e.getSource()).setCursor(dc); //label.setCursor(dc);
move.setLocation(0, 0);
scroller.stop();
}
}
class ComponentDragScrollListener 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 javax.swing.Timer scroller;
private final JComponent label;
private Point startPt = new Point();
private Point move = new Point();
public ComponentDragScrollListener(JComponent comp) {
this.label = comp;
this.dc = comp.getCursor();
this.scroller = new javax.swing.Timer(DELAY, new ActionListener() {
@Override public void actionPerformed(ActionEvent e) {
Container c = label.getParent();
if(c instanceof JViewport) {
JViewport vport = (JViewport)c;
Point vp = vport.getViewPosition();
vp.translate(move.x, move.y);
label.scrollRectToVisible(new Rectangle(vp, vport.getSize()));
}
}
});
}
@Override public void hierarchyChanged(HierarchyEvent e) {
JComponent jc = (JComponent)e.getSource();
if((e.getChangeFlags() & HierarchyEvent.DISPLAYABILITY_CHANGED)!=0
&& !jc.isDisplayable()) {
scroller.stop();
}
}
@Override public void mouseDragged(MouseEvent e) {
scroller.stop();
JComponent jc = (JComponent)e.getSource();
Container c = jc.getParent();
if(c instanceof JViewport) {
JViewport vport = (JViewport)jc.getParent();
Point cp = SwingUtilities.convertPoint(jc,e.getPoint(),vport);
int dx = startPt.x - cp.x;
int dy = startPt.y - cp.y;
Point vp = vport.getViewPosition();
vp.translate(dx, dy);
jc.scrollRectToVisible(new Rectangle(vp, vport.getSize()));
move.setLocation(SPEED*dx, SPEED*dy);
startPt.setLocation(cp);
}
}
@Override public void mousePressed(MouseEvent e) {
scroller.stop();
move.setLocation(0, 0);
JComponent jc = (JComponent)e.getSource();
jc.setCursor(hc);
Container c = jc.getParent();
if(c instanceof JViewport) {
JViewport vport = (JViewport)c;
Point cp = SwingUtilities.convertPoint(jc,e.getPoint(),vport);
startPt.setLocation(cp);
}
}
@Override public void mouseReleased(MouseEvent e) {
((JComponent)e.getSource()).setCursor(dc);
scroller.start();
}
@Override public void mouseExited(MouseEvent e) {
((JComponent)e.getSource()).setCursor(dc);
move.setLocation(0, 0);
scroller.stop();
}
}
References
