Created
February 24, 2021 19:41
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NPE with darklaf when using a custom `TreeCellRenderer`
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package com.weblogism.darklaf; | |
import com.github.weisj.darklaf.LafManager; | |
import com.github.weisj.darklaf.theme.DarculaTheme; | |
import javax.swing.*; | |
import javax.swing.tree.DefaultMutableTreeNode; | |
import javax.swing.tree.TreeCellRenderer; | |
import java.awt.*; | |
public class TreeExample extends JFrame { | |
static class LovelyTreeCellRenderer implements TreeCellRenderer { | |
@Override | |
public Component getTreeCellRendererComponent(JTree tree, Object value, boolean selected, boolean expanded, boolean leaf, int row, boolean hasFocus) { | |
final JPanel panel = new JPanel(); | |
panel.setBorder(BorderFactory.createLineBorder(Color.BLUE)); | |
final JLabel label = new JLabel(String.valueOf(value)); | |
panel.add(label); | |
return panel; | |
} | |
} | |
public TreeExample() { | |
setTitle("Lorem Ipsum"); | |
// Deliberately keep window narrow to ensure labels will not be fully visible. | |
setSize(new Dimension(100, 140)); | |
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); | |
DefaultMutableTreeNode root = new DefaultMutableTreeNode("Daft Punk"); | |
DefaultMutableTreeNode homeworkNode = new DefaultMutableTreeNode("Homework"); | |
DefaultMutableTreeNode discoveryNode = new DefaultMutableTreeNode("Discovery"); | |
DefaultMutableTreeNode humanAfterAllNode = new DefaultMutableTreeNode("Human After All"); | |
DefaultMutableTreeNode randomAccessMemoriesNode = new DefaultMutableTreeNode("Random Access Memories"); | |
root.add(homeworkNode); | |
root.add(discoveryNode); | |
root.add(humanAfterAllNode); | |
root.add(randomAccessMemoriesNode); | |
JPanel mainPanel = new JPanel(); | |
final JTree tree = new JTree(root); | |
tree.setCellRenderer(new LovelyTreeCellRenderer()); | |
mainPanel.add(new JScrollPane(tree)); | |
getContentPane().add(mainPanel, BorderLayout.CENTER); | |
setVisible(true); | |
// Once window is visible, hover over the entries in the tree, NPE occurs. | |
} | |
public static void main(String[] args) { | |
SwingUtilities.invokeLater(() -> { | |
LafManager.install(new DarculaTheme()); | |
final TreeExample frame = new TreeExample(); | |
frame.setVisible(true); | |
}); | |
} | |
} |
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