java 如何动态构建jtree

How to build a jtree dynamically

提问by Syed Muhammad Mubashir

The SSCCE of the problem is as follows. I am dynamically populating JTree, but nothing is happening.

问题的SSCCE如下。我正在动态填充JTree，但什么也没发生。

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Vector;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreePath;

public class DynamicTreeDemo extends JFrame
                        implements ActionListener {
private int newNodeSuffix = 1;
private static String ADD_COMMAND = "add";
private static String REMOVE_COMMAND = "remove";
private static String CLEAR_COMMAND = "clear";

private JTree jtrMainMenu;
DefaultMutableTreeNode   rootNode = null;
DefaultTreeModel treeModel;
public DynamicTreeDemo() {
    super(new BorderLayout());

    //Create the components.
    jtrMainMenu = new JTree();
    populateTree();

    JButton addButton = new JButton("Add");
    addButton.setActionCommand(ADD_COMMAND);
    addButton.addActionListener(this);

    JButton removeButton = new JButton("Remove");
    removeButton.setActionCommand(REMOVE_COMMAND);
    removeButton.addActionListener(this);

    JButton clearButton = new JButton("Clear");
    clearButton.setActionCommand(CLEAR_COMMAND);
    clearButton.addActionListener(this);

    //Lay everything out.
    jtrMainMenu.setPreferredSize(new Dimension(300, 150));
    add(jtrMainMenu, BorderLayout.CENTER);

    JPanel panel = new JPanel(new GridLayout(0,3));
    panel.add(addButton);
    panel.add(removeButton); 
    panel.add(clearButton);
add(panel, BorderLayout.SOUTH);
}


    public void populateTree() {
  Vector<Vector<String>> data =GetDataFromDB();           
 java.util.List<String> list =GetListFromDB();
        int i=0;;
 int size=list.size();
 treeModel=(DefaultTreeModel)jtrMainMenu.getModel();  

 ((DefaultMutableTreeNode)  (treeModel.getRoot())).removeAllChildren();
 treeModel.reload();
 rootNode = new DefaultMutableTreeNode("JewelleryERPApplication");
 treeModel=new DefaultTreeModel(rootNode);


 DefaultMutableTreeNode p1=null, p2=null,p3=null,p4=null,p5=null;


     while(i<size){

        if(list.get(i).length()==2){
          p1 = addObject(null, data.get(i).elementAt(1),true);  

        }else 
        if(list.get(i).length()==4){
           p2 = addObject(p1, data.get(i).elementAt(1),true);   

     }else if
       (list.get(i).length()==6){
             p3 = addObject(p2, data.get(i).elementAt(1),true);   

     }
     else if
       (list.get(i).length()==8){
             p4 = addObject(p3, data.get(i).elementAt(1),true);    

     }  
     else if
       (list.get(i).length()==10){
             p5 = addObject(p4, data.get(i).elementAt(1),true);    

     }      
         i++;
     }

    jtrMainMenu.setModel(treeModel);
   ((DefaultMutableTreeNode)  (treeModel.getRoot())).getChildCount();
    jtrMainMenu.revalidate();
    jtrMainMenu.repaint();
}


public DefaultMutableTreeNode addObject(DefaultMutableTreeNode parent,
                                        Object child, 
                                        boolean shouldBeVisible) {


          DefaultMutableTreeNode childNode = 
            new DefaultMutableTreeNode(child);



    if (parent == null) {
        parent = rootNode;
    }

//It is key to invoke this on the TreeModel, and NOT DefaultMutableTreeNode
    treeModel.insertNodeInto(childNode, parent, 
                             parent.getChildCount());

     jtrMainMenu.setModel(treeModel);

    //Make sure the user can see the lovely new node.
    if (shouldBeVisible) {
        jtrMainMenu.scrollPathToVisible(new TreePath(childNode.getPath()));
    }

    return childNode;
} 

/**
 * Create the GUI and show it.  For thread safety,
 * this method should be invoked from the
 * event-dispatching thread.
 */
private static void createAndShowGUI() {
    //Create and set up the window.
    JFrame frame = new JFrame("DynamicTreeDemo");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //Create and set up the content pane.
    DynamicTreeDemo newContentPane = new DynamicTreeDemo();
    newContentPane.setOpaque(true); //content panes must be opaque
    frame.setContentPane(newContentPane);

    //Display the window.
    frame.pack();
    frame.setVisible(true);
}

public static void main(String[] args) {
    //Schedule a job for the event-dispatching thread:
    //creating and showing this application's GUI.
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            createAndShowGUI();
        }
    });
}
}

回答by MadProgrammer

There are a number of problems with you code, but...the major problem (I think) you're having is the fact that when you reload the model, the root node is collapsed by default.

你的代码有很多问题，但是......你遇到的主要问题（我认为）是当你重新加载模型时，默认情况下根节点是折叠的。

If the root node is hidden and/or it's handle is hidden, it will appear as if nothing has been loaded.

如果根节点被隐藏和/或它的句柄被隐藏，它将看起来好像没有加载任何东西。

Unhide these elements for testing.

取消隐藏这些元素以进行测试。

You can also expand the root node once the model has been reloaded...

重新加载模型后，您还可以扩展根节点...

!! Warning !!Don't run this on your root directory !! It will scan all child directories and that could take more time then you're actually willing to wait for :P

!! 警告 ！！不要在你的根目录上运行这个！！它将扫描所有子目录，这可能需要更多时间，然后您实际上愿意等待 :P

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreePath;

public class FileTree {

    public static void main(String[] args) {
        new FileTree();
    }

    public FileTree() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private DefaultTreeModel model;
        private JTree tree;

        public TestPane() {
            setLayout(new BorderLayout());

            tree = new JTree();
            File rootFile = new File(".");
            DefaultMutableTreeNode root = new DefaultMutableTreeNode(rootFile);
            model = new DefaultTreeModel(root);

            tree.setModel(model);
            tree.setRootVisible(true);
            tree.setShowsRootHandles(true);

            add(new JScrollPane(tree));

            JButton load = new JButton("Load");
            add(load, BorderLayout.SOUTH);

            load.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {

                    DefaultMutableTreeNode root = (DefaultMutableTreeNode) model.getRoot();
                    root.removeAllChildren();
                    model.reload();
                    File rootFile = (File) root.getUserObject();

                    addFiles(rootFile, model, root);

                    tree.expandPath(new TreePath(root));

                }
            });

        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        protected void addFiles(File rootFile, DefaultTreeModel model, DefaultMutableTreeNode root) {

            for (File file : rootFile.listFiles()) {
                DefaultMutableTreeNode child = new DefaultMutableTreeNode(file);
                model.insertNodeInto(child, root, root.getChildCount());
                if (file.isDirectory()) {
                    addFiles(file, model, child);
                }
            }

        }
    }
}

Code Review

代码

You should avoid extending directly from JFrame. From the looks of you example, you weren't, but hacked it in, but it's inadvisable anyway...

您应该避免直接从JFrame. 从你的例子来看，你不是，而是入侵了它，但无论如何这是不可取的......

This...

这...

jtrMainMenu.setPreferredSize(new Dimension(300, 150));
add(jtrMainMenu, BorderLayout.CENTER);

This is inadvisable. JTreeshould be added to JScrollPane.

这是不可取的。 JTree应该添加到JScrollPane.

This...

这...

private static void createAndShowGUI() {
    //Create and set up the window.
    JFrame frame = new JFrame("DynamicTreeDemo");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //Create and set up the content pane.
    BadTree newContentPane = new BadTree();
    newContentPane.setOpaque(true); //content panes must be opaque
    frame.setContentPane(newContentPane);

    //Display the window.
    frame.pack();
    frame.setVisible(true);
}

Isn't going to work either (based on your example), as anything that extends from Windowcan not be added to any other container that extends Window

也不会工作（根据您的示例），因为任何扩展的内容Window都无法添加到任何其他扩展的容器中Window

Unless your base component is extending from JComponent, must other components are opaque (JLabelis an obvious exception), so setting the newContentPaneto opaque may be a mute point.

除非您的基础组件从 扩展JComponent，否则其他组件必须是不透明的（这JLabel是一个明显的例外），因此将 设置newContentPane为不透明可能是一个静音点。