右键单击Java JTree的上下文菜单？

Question

我正在尝试在Java JTree中实现弹出菜单.我已经对DefaultTreeCellRenderer(更改节点外观)和DefaultTreeCellEditor(创建组件以附加事件侦听器)进行了细分,因为显然DefaultTreeCellRenderer.getTreeCellRendererComponent()返回的组件不能这样做吗？).我真的不想"编辑"节点,只需在节点右键单击时弹出菜单,但这是我现在想到的唯一方法......

下面是我到目前为止的代码 - 我只想弄清楚如何捕获MouseEvents.它有点工作,但很糟糕.有什么更好的方法来完成我在这里要做的事情？

private class My_TreeCellRenderer extends DefaultTreeCellRenderer { 
    My_TreeCellRenderer() {
        super ();
    }   

    public Component getTreeCellRendererComponent(JTree tree, Object value, boolean selected, boolean expanded, boolean leaf, int row, boolean hasFocus) {
        super.getTreeCellRendererComponent(tree, value, selected, expanded, leaf, row, hasFocus);

        // set label text and tool tips
        setText(((My_Object)value).getTreeLabel());
        setToolTipText(((My_Object)value).getTreeToolTip());

        return this;
    }
}

private class My_TreeCellEditor extends DefaultTreeCellEditor { 
    private MouseAdapter ma;

    My_TreeCellEditor(JTree tree, DefaultTreeCellRenderer renderer) {
        super (tree, renderer);
        ma = new MouseAdapter() {
            public void mousePressed(MouseEvent e) {
                if (e.isPopupTrigger()) {
                    System.out.println("My Popup");
                }
            }
            public void mouseReleased(MouseEvent e) {
                if (e.isPopupTrigger()) {
                    System.out.println("My Popup");
                }
            }
        };
    }

    public Component getTreeCellEditorComponent(JTree tree, Object value, boolean selected, boolean expanded, boolean leaf, int row) {
        String src_filename = null;

        // return non-editing component
        Component c = renderer.getTreeCellRendererComponent(tree, value, selected, expanded, leaf, row, true);

        // add mouse listener if it's not listening already
        MouseListener mouseListeners[] = c.getMouseListeners();
        int i;
        for (i=0; i < mouseListeners.length && mouseListeners[i] != ma; i++);
        if (i >= mouseListeners.length)
            c.addMouseListener(ma);

        return c;
    }

    protected boolean canEditImmediately(EventObject event) {
        if (event instanceof MouseEvent && ((MouseEvent)event).getClickCount() == 1)
            return true;
        else
            return false;
    }
}

Answer 1

这项任务很容易完成,以下是您所需要的:

//create a class which implements the MouseListener interface and
//implement the following in your overridden mouseClicked method

@Override
public void mouseClicked(MouseEvent e) {

    if (SwingUtilities.isRightMouseButton(e)) {

        int row = tree.getClosestRowForLocation(e.getX(), e.getY());
        tree.setSelectionRow(row);
        popupMenu.show(e.getComponent(), e.getX(), e.getY());
    }
}

然后,您可以将此自定义侦听器添加到所需的树.

Answer 2

取自JTree API

 // If you are interested in detecting either double-click events or when a user clicks on a node, regardless of whether or not it was selected, we recommend you do the following:

 final JTree tree = ...;

 MouseListener ml = new MouseAdapter() {
     public void mousePressed(MouseEvent e) {
         int selRow = tree.getRowForLocation(e.getX(), e.getY());
         TreePath selPath = tree.getPathForLocation(e.getX(), e.getY());
         if(selRow != -1) {
             if(e.getClickCount() == 1) {
                 mySingleClick(selRow, selPath);
             }
             else if(e.getClickCount() == 2) {
                 myDoubleClick(selRow, selPath);
             }
         }
     }
 };
 tree.addMouseListener(ml);

当然,您需要稍微修改它以进行右键单击而不是左键单击

Answer 3

感谢大家.当我花费大量精力实现一个简单的弹出窗口时,我知道出了什么问题.

我首先驳回了这一思路,因为使用x和y坐标找到我正在寻找的节点感觉很奇怪,但我想这是做到这一点的方法.

    // add MouseListener to tree
    MouseAdapter ma = new MouseAdapter() {
        private void myPopupEvent(MouseEvent e) {
            int x = e.getX();
            int y = e.getY();
            JTree tree = (JTree)e.getSource();
            TreePath path = tree.getPathForLocation(x, y);
            if (path == null)
                return; 

            tree.setSelectionPath(path);

            My_Obj obj = (My_Obj)path.getLastPathComponent();

            String label = "popup: " + obj.getTreeLabel();
            JPopupMenu popup = new JPopupMenu();
            popup.add(new JMenuItem(label));
            popup.show(tree, x, y);
        }
        public void mousePressed(MouseEvent e) {
            if (e.isPopupTrigger()) myPopupEvent(e);
        }
        public void mouseReleased(MouseEvent e) {
            if (e.isPopupTrigger()) myPopupEvent(e);
        }
    };

    (...)

    JTree tree = new JTree();
    tree.addMouseListener(ma);

Answer 4

渲染器只是一个瞬态的“橡皮图章”，因此在其上添加输入侦听器不会特别有帮助。正如您所指出的，编辑器只有在您做出编辑手势后才会出现。因此，您想要向 JTree 添加一个侦听器（假设它不是作为复合组件实现的）。