伙计们,

我正在尝试创建一个渐变JTree控件.除了树单元格的背景不是透明的以外,以下代码大部分可用.如果有人打电话告诉我我做错了什么,我将不胜感激.

预先感谢您的帮助.

问候,
彼得

package TestPackage;

import javax.swing.*;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeCellRenderer;
import java.awt.*;

public class Test {

    public Test() {
        JFrame frame = new JFrame();

        JPanel framePanel = new JPanel();
        framePanel.setLayout(new BorderLayout());
        frame.setContentPane(framePanel);


        DefaultMutableTreeNode rootNode = new DefaultMutableTreeNode("Item");
        DefaultMutableTreeNode childNode = new DefaultMutableTreeNode("Child");
        rootNode.add(childNode);

        GradientTree tree = new GradientTree(rootNode);
        // JTree tree = new JTree(rootNode);
        // tree.setBackground(Color.blue);
        tree.setCellRenderer(new MyRenderer());

        JScrollPane scroll = new JScrollPane(tree);
        scroll.setOpaque(false);
        framePanel.add(scroll, BorderLayout.CENTER);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);

    }

    public static void main(String[] args) {

        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new Test();
            }
        });
    }


    @SuppressWarnings("serial")
    public static class GradientTree extends JTree {

        public GradientTree(DefaultMutableTreeNode node) {
            super(node);
        }


        @Override
        protected void paintComponent(Graphics g) {

            int h = getHeight();
            int w = getWidth();

            GradientPaint gradientPaint = new GradientPaint(0, 0, Color.LIGHT_GRAY, 0, h, Color.WHITE);

            Graphics2D g2D = (Graphics2D) g;
            g2D.setPaint(gradientPaint);
            g2D.fillRect(0, 0, w, h);

            this.setOpaque(false);
            super.paintComponent(g);
            this.setOpaque(true);
        }
    }

    @SuppressWarnings({"serial" })
    private class MyRenderer extends DefaultTreeCellRenderer {
        public MyRenderer() {
            this.setOpaque(false);
            this.setForeground(Color.RED);
        }

        public Component getTreeCellRendererComponent(
                JTree tree,
                Object value,
                boolean sel,
                boolean expanded,
                boolean leaf,
                int row,
                boolean hasFocus) {

            super.getTreeCellRendererComponent(
                    tree, value, sel,
                    expanded, leaf, row,
                    hasFocus);

            return this;
        }
    }
}

解决方法:

这是一个真正的痛苦. DefaultTreeCellRenderer将忽略不透明值,并始终填充其内容.但是,有一个标志可以尝试.我过去做过,但是没有时间进行测试…

尝试UIManager.put(“ Tree.rendererFillBackground”,false).在任何东西都成为渲染器之前,但在应用任何外观设置之后,请尝试执行此操作.

更新

在创建任何树之前,设置此属性非常重要

没有|随着…

public class TestTreeRenderer {

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

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

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

        });
    }

    public class TreePane extends JPanel {

        private JTree tree;

        public TreePane() {
            // THIS IS VERY IMPORTANT
            // You must set this BEFORE creating ANY trees!!
            UIManager.put("Tree.rendererFillBackground", false);

            setLayout(new BorderLayout());
            tree = new JTree();
            tree.setBackground(Color.BLUE);

            System.out.println("Loading files...");
            File root = new File("/etc");
            DefaultMutableTreeNode rootNode = new DefaultMutableTreeNode(root.getName());
            for (File file : root.listFiles()) {
                rootNode.add(new DefaultMutableTreeNode(file.getName()));
            }
            System.out.println("Loading model");
            DefaultTreeModel model = new DefaultTreeModel(rootNode);
            tree.setModel(model);

            add(new JScrollPane(tree));
        }
    }
}