动态更改JTree的数据模型

问题描述

我有一个小的GUI应用程序，它处理鼠标单击并将它们存储在列表中：

package test;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.ArrayList;
import java.util.List;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class TestGUI extends JFrame {

    private final List<String> objects = new ArrayList<>();
    private TestTree testTree;

    final JPanel canvas = new JPanel() {
        @Override
        public void paintComponent(final Graphics g) {
            super.paintComponent(g);
            g.clearRect(0,canvas.getWidth(),canvas.getHeight());
            g.setColor(Color.BLACK);
            for (final String object : objects) {
                final String[] parts = object.split("--");
                g.drawoval(Integer.parseInt(parts[0]),Integer.parseInt(parts[1]),5,5);
            }
        }
    };

    public TestGUI() {
        final Container cp = getContentPane();
        cp.setLayout(new BorderLayout());
        cp.add(canvas,BorderLayout.CENTER);
        testTree = new TestTree(objects);
        cp.add(testTree,BorderLayout.EAST);
        setTitle("TestGUI");
        canvas.addMouseListener(new MouseListener() {
            @Override
            public void mouseReleased(MouseEvent me) {}
            @Override
            public void mousepressed(MouseEvent me) {}
            @Override
            public void mouseExited(MouseEvent me) {}
            @Override
            public void mouseEntered(MouseEvent me) {}
            @Override
            public void mouseClicked(MouseEvent me) {
                objects.add(me.getX() + "--" + me.getY());
                testTree.update();
                canvas.repaint();
            }
        });
        setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
        setSize(500,500);
        setVisible(true);
    }

    public static void main(final String[] args) {
        SwingUtilities.invokelater(new Runnable() {
            @Override
            public void run() {
                new TestGUI();
            }
        });
    }

}

我想使用画布侧面的JTree表示列表的概述。负责JTree的类如下：

package test;

import java.util.List;

import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;

public class TestTree extends JPanel {

    final List<String> objects;

    private JTree tree;
    private final DefaultMutableTreeNode root;

    public TestTree(final List<String> theObjects) {
        objects = theObjects;

        root = new DefaultMutableTreeNode("root");
        tree = new JTree(root);

        add(new JScrollPane(tree));
    }

    private void updateTree(final List<String> objects) {
        root.removeAllChildren();
        final DefaultMutableTreeNode result = new DefaultMutableTreeNode(objects.size() + " objects");
        for (final String object : objects) {
            final DefaultMutableTreeNode objectNode = new DefaultMutableTreeNode(object);
            result.add(objectNode);
        }
        root.add(result);
        tree.updateUI();
    }

    public void update() {
        updateTree(objects);
        tree = new JTree(root);
        add(new JScrollPane(tree));
    }

}

那么，通过提交列表来更新JTree的正确方法是什么？因为单击几下后，我的应用程序为每个添加的元素渲染一棵单独的树，而不是随时间更新的一棵树：

任何建议将不胜感激。非常感谢！

解决方法

您的问题出在类update()的方法TestTree中。您一直在向JScrollPane添加另一个TestTree。您只需要一个JScrollPane。

您正确地更新了JTree的模型，这就是您要做的全部。 JTree会在模型更改时自动进行自我更新。

此外，请勿设置JFrame的大小。设置其组件的大小并调用方法pack()，这将使JFrame足够大以容纳其所有组件。

在下面的代码中，我注释掉了需要从代码中删除的行。

TestTree类

package test;

import java.awt.Dimension;
import java.util.List;

import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;

public class TestTree extends JPanel {
    final List<String> objects;

    private JTree tree;
    private final DefaultMutableTreeNode root;

    public TestTree(final List<String> theObjects) {
        objects = theObjects;
        root = new DefaultMutableTreeNode("root");
        tree = new JTree(root);
        JScrollPane scrollPane = new JScrollPane(tree);
        scrollPane.setPreferredSize(new Dimension(100,490));
        add(scrollPane);
    }

    private void updateTree() {
        root.removeAllChildren();
        final DefaultMutableTreeNode result = new DefaultMutableTreeNode(objects.size() + " objects");
        for (String object : objects) {
            final DefaultMutableTreeNode objectNode = new DefaultMutableTreeNode(object);
            result.add(objectNode);
        }
        root.add(result);
        tree.updateUI();
    }

    public void update() {
        updateTree();
//        tree = new JTree(root);
//        add(new JScrollPane(tree));
    }
}

TestGUI类

package test;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.ArrayList;
import java.util.List;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class TestGUI extends JFrame {

    private final List<String> objects = new ArrayList<>();
    private TestTree testTree;

    final JPanel canvas = new JPanel() {
        @Override
        public void paintComponent(final Graphics g) {
            super.paintComponent(g);
            g.clearRect(0,canvas.getWidth(),canvas.getHeight());
            g.setColor(Color.BLACK);
            for (final String object : objects) {
                final String[] parts = object.split("--");
                g.drawOval(Integer.parseInt(parts[0]),Integer.parseInt(parts[1]),5,5);
            }
        }
    };

    public TestGUI() {
        final Container cp = getContentPane();
        cp.setLayout(new BorderLayout());
        cp.add(canvas,BorderLayout.CENTER);
        testTree = new TestTree(objects);
        cp.add(testTree,BorderLayout.EAST);
        setTitle("TestGUI");
        canvas.addMouseListener(new MouseListener() {
            @Override
            public void mouseReleased(MouseEvent me) {}
            @Override
            public void mousePressed(MouseEvent me) {}
            @Override
            public void mouseExited(MouseEvent me) {}
            @Override
            public void mouseEntered(MouseEvent me) {}
            @Override
            public void mouseClicked(MouseEvent me) {
                objects.add(me.getX() + "--" + me.getY());
                testTree.update();
                TestGUI.this.pack();
                canvas.repaint();
            }
        });
        canvas.setPreferredSize(new Dimension(400,490));
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        pack();
//        setSize(500,500);
        setVisible(true);
    }

    public static void main(final String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new TestGUI();
            }
        });
    }
}