How to Display ANTLR Tree GUI

antlr, java, swing, tree, user-interface

Solution

Using ANTLR V4 (for V3 try to find out the similar API),to show a gui AST, you can use `org.antlr.v4.runtime.tree.gui.TreeViewer`.

You can get the Hello demo from ANTLR's site. Once you got it, run this simple demo:

import java.util.Arrays;
import javax.swing.JFrame;
import javax.swing.JPanel;

import org.antlr.v4.runtime.ANTLRInputStream;
import org.antlr.v4.runtime.CharStream;
import org.antlr.v4.runtime.CommonTokenStream;
import org.antlr.v4.runtime.TokenStream;
import org.antlr.v4.runtime.tree.ParseTree;
import org.antlr.v4.runtime.tree.gui.TreeViewer;

/**
 * A simple demo to show AST GUI with ANTLR
 * @see http://www.antlr.org/api/Java/org/antlr/v4/runtime/tree/gui/TreeViewer.html
 * 
 * @author wangdq
 * 2014-5-24
 *
 */
public class HelloTestDrive {
    public static void main(String[] args) {
        //prepare token stream
        CharStream stream = new ANTLRInputStream("hello antlr");
        HelloLexer lexer  = new HelloLexer(stream);   
        TokenStream tokenStream = new CommonTokenStream(lexer);
        HelloParser parser = new HelloParser(tokenStream);
        ParseTree tree = parser.r(); 

        //show AST in console
        System.out.println(tree.toStringTree(parser));

        //show AST in GUI
        JFrame frame = new JFrame("Antlr AST");
        JPanel panel = new JPanel();
        TreeViewer viewer = new TreeViewer(Arrays.asList(
                parser.getRuleNames()),tree);
        viewer.setScale(1.5); // Scale a little
        panel.add(viewer);
        frame.add(panel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
    }
}

Then you will get the AST print in the console and show in `JFrame`. more details, please refer ANTLR API.

Make sure your grammar work fine, then you can modify this demo to meet your requirement.

Update for ANTLR 4: `TreeViewer` has moved to `org.antlr.v4.gui.TreeViewer` package from ANTLR 4 Tool.

When using `maven`, `TreeViewer` requires the following dependency:

<dependency>
    <groupId>org.antlr</groupId>
    <artifactId>antlr4</artifactId>
    <version>4.7.2</version>
</dependency>

Problem

Original source