embed SWT widget into Swing JFrame

gistfile1.erl

import java.awt.BorderLayout;
import java.awt.Canvas;
import java.awt.Dimension;

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

import org.eclipse.swt.SWT;
import org.eclipse.swt.awt.SWT_AWT;
import org.eclipse.swt.browser.Browser;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

/**
 * A simple canvas that encapsulates a SWT Browser instance.
 * Add it to a AWT or Swing container and call "connect()" after
 * the container has been made visible.
 */
public class BrowserCanvas extends Canvas {

  private Thread swtThread;
  private Browser swtBrowser;

  /**
   * Connect this canvas to a SWT shell with a Browser component
   * and starts a background thread to handle SWT events. This method
   * waits until the browser component is ready.
   */
  public void connect() {
    if (this.swtThread == null) {
      final Canvas canvas = this;
      this.swtThread = new Thread() {
        @Override
        public void run() {
          try {
            Display display = new Display();
            Shell shell = SWT_AWT.new_Shell(display, canvas);
            shell.setLayout(new FillLayout());

            synchronized (this) {
              swtBrowser = new Browser(shell, SWT.NONE);
              this.notifyAll();
            }

            shell.open();
            while (!isInterrupted() && !shell.isDisposed()) {
              if (!display.readAndDispatch()) {
                display.sleep();
              }
            }
            shell.dispose();
            display.dispose();
          } catch (Exception e) {
            interrupt();
          }
        }
      };
      this.swtThread.start();
    }

    // Wait for the Browser instance to become ready
    synchronized (this.swtThread) {
      while (this.swtBrowser == null) {
        try {
          this.swtThread.wait(100);
        } catch (InterruptedException e) {
          this.swtBrowser = null;
          this.swtThread = null;
          break;
        }
      }
    }
  }

  /**
   * Returns the Browser instance. Will return "null"
   * before "connect()" or after "disconnect()" has
   * been called.
   */
  public Browser getBrowser() {
    return this.swtBrowser;
  }

  /**
   * Stops the swt background thread.
   */
  public void disconnect() {
    if (swtThread != null) {
      swtBrowser = null;
      swtThread.interrupt();
      swtThread = null;
    }
  }

  /**
   * Ensures that the SWT background thread
   * is stopped if this canvas is removed from
   * it's parent component (e.g. because the
   * frame has been disposed).
   */
  @Override
  public void removeNotify() {
    super.removeNotify();
    disconnect();
  }

  /**
   * Opens a new JFrame with BrowserCanvas in it
   */
  public static void main(String[] args) {
    // Required for Linux systems
    System.setProperty("sun.awt.xembedserver", "true");

    // Create container canvas. Note that the browser
    // widget will not be created, yet.
    final BrowserCanvas browserCanvas = new BrowserCanvas();
    browserCanvas.setPreferredSize(new Dimension(800, 600));
    JPanel panel = new JPanel(new BorderLayout());
    panel.add(browserCanvas, BorderLayout.CENTER);

    // Add container to Frame
    JFrame frame = new JFrame("My SWT Browser");
    frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
    frame.setContentPane(panel);
    frame.pack();

    // This is VERY important: Make the frame visible BEFORE
    // connecting the SWT Shell and starting the event loop!
    frame.setVisible(true);
    browserCanvas.connect();

    // Now we can open a webpage, but remember that we have
    // to use the SWT thread for this.
    browserCanvas.getBrowser().getDisplay().asyncExec(new Runnable() {
      @Override
      public void run() {
        browserCanvas.getBrowser().setUrl("http://www.google.com");
      }
    });
  }
}

It seems that panel can't display the browser on canvas

Only by this way can I see browser
Container cp = frame.getContentPane();
Canvas canvas = new Canvas();
cp.add(canvas,BorderLayout.CENTER);
frame.setVisible(true);

I want to know why.......

This is a very useful gist, but I always see native errors (at least on Linux64) when I dispose the JFrame, either X-Window errors, or warnings about plugin failures (where the URL is www.google.com).

What I had to do was get rid of the removeNotify() override (seems it is too late to disconnect() here), and instead add a WindowListener to the frame and invoke disconnect() inside the WindowClosing event. It seems to be OK, but I'm not 100% convinced.

FWIW, I wrote an alternative implementation here: https://gist.github.com/caprica/6890618

The significant differences are that my implementation uses java.util.concurrent objects for the synchronisation, and it shuts down cleanly (no fatal crashes) when the frame is disposed.