Java JTree 的右键单击上下文菜单？

Right-click context menu for Java JTree?

提问by

I'm trying to implement pop-up menus in Java JTree. I've sub-classed DefaultTreeCellRenderer (to change node appearance) and DefaultTreeCellEditor (to create Components to attach event listeners to, since apparently the Components that DefaultTreeCellRenderer.getTreeCellRendererComponent() returns can't do it?). I don't really want to "edit" the nodes, just be able to pop-up a menu when a node gets right-clicked, but this is the only way I can think of doing it right now...

我正在尝试在 Java JTree 中实现弹出菜单。我已经将 DefaultTreeCellRenderer（更改节点外观）和 DefaultTreeCellEditor（创建组件以将事件侦听器附加到其中，因为 DefaultTreeCellRenderer.getTreeCellRendererComponent() 返回的组件显然不能这样做？）。我真的不想“编辑”节点，只是能够在节点被右键单击时弹出一个菜单，但这是我现在能想到的唯一方法......

Below is the code that I have so far-- I'm just trying to figure out how to capture MouseEvents. It sort of works, but badly. What's a better way to accomplish what I'm trying to do here?

下面是我到目前为止的代码——我只是想弄清楚如何捕获 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;
    }
}

回答by Tom Hawtin - tackline

The Renderer is only a transient "rubber stamp", so adding an input listener on that wont be particularly helpful. The Editor, as you point out, is only there once you have gestured to edit. So you want to add a listener to the JTree (assuming it isn't implemented as a composite component).

渲染器只是一个暂时的“橡皮图章”，因此在其上添加输入侦听器不会特别有用。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，您想向 JTree 添加一个侦听器（假设它不是作为复合组件实现的）。

回答by kazanaki

Taken right out of the JTree API

直接从JTree API 中取出

 // 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);

Of course you need to modify it a bit for right click instead of left click

当然你需要稍微修改一下右键单击而不是左键单击

回答by dw.mackie

I think you're making things way harder than they need to be.
JTree has several "add_foo_Listener" methods on it. Implement one of those (TreeSelectionListener looks about right), and then you've got the currently selected node.
Implement a MouseListener so that you can detect the right-click event (and add it to the JTree, since JTree's a Component), and then you should have everything you need to post a context-sensitive menu.
Check out this tutorialfor more details.

我认为你让事情变得比他们需要的更难。
JTree 有几个“add_foo_Listener”方法。实现其中之一（TreeSelectionListener 看起来差不多），然后您就获得了当前选定的节点。
实现 MouseListener 以便您可以检测右键单击事件（并将其添加到 JTree，因为 JTree 是一个组件），然后您应该拥有发布上下文相关菜单所需的一切。
查看本教程了解更多详情。

回答by dw.mackie

Thanks everyone. I knew something was wrong when I was spending that much effort on implementing a simple popup.

谢谢大家。当我花费那么多精力来实现一个简单的弹出窗口时，我知道出了什么问题。

I dismissed this line of thought at first because it felt weird to resort to x- and y- coordinates to find the node I'm looking for, but I guess this is the way to do it.

起初我驳回了这个想法，因为求助于 x 和 y 坐标来找到我正在寻找的节点感觉很奇怪，但我想这就是这样做的方法。

    // 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);

回答by b1nary.atr0phy

This task is simple to accomplish, the following is all you need:

此任务很容易完成，您只需要以下内容：

//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());
    }
}

You can then add this custom listener to your desired tree(s).

然后，您可以将此自定义侦听器添加到所需的树中。

回答by BullyWiiPlaza

Call addRightClickListener()to add the right-click context menu listener to your JTree. Both overrides are for proper cross-platform functionality (Windowsand Linuxdiffer here).

调用addRightClickListener()以将右键单击上下文菜单侦听器添加到您的JTree. 两个覆盖是正确的跨平台功能（Windows和Linux这里不同）。

private void addRightClickListener()
{
    MouseListener mouseListener = new MouseAdapter()
    {
        @Override
        public void mousePressed(MouseEvent mouseEvent)
        {
            handleContextMenu(mouseEvent);
        }

        @Override
        public void mouseReleased(MouseEvent mouseEvent)
        {
            handleContextMenu(mouseEvent);
        }
    };

    tree.addMouseListener(mouseListener);
}

private void handleContextMenu(MouseEvent mouseEvent)
{
    if (mouseEvent.isPopupTrigger())
    {
        MyContextMenu contextMenu = new MyContextMenu();

        contextMenu.show(mouseEvent.getComponent(),
                mouseEvent.getX(),
                mouseEvent.getY());
    }
}