Swing/TreeDragScroll のバックアップ(No.15)

  • category: swing folder: TreeDragScroll title: JTreeの余白をドラッグしてスクロール tags: [MouseListener, MouseMotionListener, JViewport, JScrollPane, JTree, JComponent] author: aterai pubdate: 2011-12-26T14:16:38+09:00 description: JTreeの余白などをマウスでドラッグしてスクロールします。 image: https://lh3.googleusercontent.com/-8b-0M5bS9Tw/Tvf_XhVVreI/AAAAAAAABHU/BdECxkBAdzU/s800/TreeDragScroll.png

Summary

JTreeの余白などをマウスでドラッグしてスクロールします。

Screenshot

screenshot

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Source Code Examples

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

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

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

  @Override public void mouseReleased(MouseEvent e) {
    e.getComponent().setCursor(defCursor);
  }
}
View in GitHub: Java, Kotlin

Explanation

上記のサンプルでは、JTreeにMouseListenerとMouseMotionListenerを設定し、マウスドラッグをJViewportの座標に変換してscrollRectToVisible(...)メソッドを使ったスクロールをおこなっています。

MouseAdapter ma = new DragScrollListener();
tree2.addMouseMotionListener(ma);
tree2.addMouseListener(ma);
  • JScrollPaneのViewportをマウスで掴んでスクロールとほぼ同一
  • ただし、JLabelとは異なりJTreeにはデフォルトでMouseListenerとMouseMotionListenerが設定されているため、JViewportにリスナーを設定してもJTreeまでマウスイベントが伝達しない
  • 例えば以下のようにJComponent#dispatchEvent(...)でJTreeの親のJViewportにイベントを転送する必要がある
MouseAdapter ma = new HandScrollListener();
JScrollPane scroll = new JScrollPane(tree1);
JViewport vport = scroll.getViewport();
vport.addMouseMotionListener(ma);
vport.addMouseListener(ma);
MouseAdapter transparent = new MouseAdapter() {
  private void dispatchEvent(MouseEvent e) {
    JComponent c = (JComponent) e.getComponent();
    JComponent p = (JComponent) e.getComponent().getParent();
    p.dispatchEvent(SwingUtilities.convertMouseEvent(c, e, p));
  }

  @Override public void mouseDragged(MouseEvent e)  {
    dispatchEvent(e);
  }

  @Override public void mouseClicked(MouseEvent e)  {
    dispatchEvent(e);
  }

  @Override public void mouseEntered(MouseEvent e)  {
    dispatchEvent(e);
  }

  @Override public void mouseExited(MouseEvent e)   {
    dispatchEvent(e);
  }

  @Override public void mousePressed(MouseEvent e)  {
    dispatchEvent(e);
  }

  @Override public void mouseReleased(MouseEvent e) {
    dispatchEvent(e);
  }
};
tree1.addMouseMotionListener(transparent);
tree1.addMouseListener(transparent);

Reference

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