Code
class RearrangingHandler extends MouseAdapter {
private static final int xoffset = 16;
private static final Rectangle R1 = new Rectangle();
private static final Rectangle R2 = new Rectangle();
private static Rectangle prevRect;
private final int gestureMotionThreshold = DragSource.getDragThreshold();
private final JWindow window = new JWindow();
private int index = -1;
private Component draggingComonent;
private Component gap;
private Point startPt;
private Point dragOffset;
public RearrangingHandler() {
super();
window.setBackground(new Color(0, true));
}
@Override public void mousePressed(MouseEvent e) {
if (((JComponent) e.getComponent()).getComponentCount() <= 1) {
startPt = null;
} else {
startPt = e.getPoint();
}
}
private void startDragging(JComponent parent, Point pt) {
Component c = parent.getComponentAt(pt);
index = parent.getComponentZOrder(c);
if (Objects.equals(c, parent) || index < 0) {
return;
}
draggingComonent = c;
Dimension d = draggingComonent.getSize();
Point dp = draggingComonent.getLocation();
dragOffset = new Point(pt.x - dp.x, pt.y - dp.y);
gap = Box.createRigidArea(d);
swapComponentLocation(parent, c, gap, index);
window.add(draggingComonent);
//window.setSize(d);
window.pack();
updateWindowLocation(pt, parent);
window.setVisible(true);
}
private void updateWindowLocation(Point pt, JComponent parent) {
Point p = new Point(pt.x - dragOffset.x, pt.y - dragOffset.y);
SwingUtilities.convertPointToScreen(p, parent);
window.setLocation(p);
}
private static int getTargetIndex(Rectangle r, Point pt, int i) {
int ht2 = (int)(.5 + r.height * .5);
R1.setBounds(r.x, r.y, r.width, ht2);
R2.setBounds(r.x, r.y + ht2, r.width, ht2);
if (R1.contains(pt)) {
prevRect = R1;
return i - 1 > 0 ? i : 0;
} else if (R2.contains(pt)) {
prevRect = R2;
return i;
}
return -1;
}
private static void swapComponentLocation(
Container parent, Component remove, Component add, int idx) {
parent.remove(remove);
parent.add(add, idx);
parent.revalidate();
parent.repaint();
}
@Override public void mouseDragged(MouseEvent e) {
Point pt = e.getPoint();
JComponent parent = (JComponent) e.getComponent();
double a = Math.pow(pt.x - startPt.x, 2);
double b = Math.pow(pt.y - startPt.y, 2);
if (draggingComonent == null &&
Math.sqrt(a + b) > gestureMotionThreshold) {
startDragging(parent, pt);
return;
}
if (!window.isVisible() || draggingComonent == null) {
return;
}
updateWindowLocation(pt, parent);
if (prevRect != null && prevRect.contains(pt)) {
return;
}
for (int i = 0; i < parent.getComponentCount(); i++) {
Component c = parent.getComponent(i);
Rectangle r = c.getBounds();
if (Objects.equals(c, gap) && r.contains(pt)) {
return;
}
int tgt = getTargetIndex(r, pt, i);
if (tgt >= 0) {
swapComponentLocation(parent, gap, gap, tgt);
return;
}
}
//System.out.println("outer");
parent.remove(gap);
parent.revalidate();
}
@Override public void mouseReleased(MouseEvent e) {
startPt = null;
if (!window.isVisible() || draggingComonent == null) {
return;
}
Point pt = e.getPoint();
JComponent parent = (JComponent) e.getComponent();
Component cmp = draggingComonent;
draggingComonent = null;
prevRect = null;
startPt = null;
dragOffset = null;
window.setVisible(false);
for (int i = 0; i < parent.getComponentCount(); i++) {
Component c = parent.getComponent(i);
if (Objects.equals(c, gap)) {
swapComponentLocation(parent, gap, cmp, i);
return;
}
int tgt = getTargetIndex(c.getBounds(), pt, i);
if (tgt >= 0) {
swapComponentLocation(parent, gap, cmp, tgt);
return;
}
}
if (parent.getParent().getBounds().contains(pt)) {
swapComponentLocation(parent, gap, cmp, parent.getComponentCount());
} else {
swapComponentLocation(parent, gap, cmp, index);
}
}
}
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