OnJava8-Examples/swt/ColorBoxes.java

// swt/ColorBoxes.java
// (c)2016 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://mindviewinc.com/Books/OnJava/ for more book information.
// SWT translation of Swing ColorBoxes.java.
import swt.util.*;
import org.eclipse.swt.*;
import org.eclipse.swt.widgets.*;
import org.eclipse.swt.events.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.layout.*;
import java.util.concurrent.*;
import java.util.*;
import onjava.*;

class CBox extends Canvas implements Runnable {
  class CBoxPaintListener implements PaintListener {
    public void paintControl(PaintEvent e) {
      Color color = new Color(e.display, cColor);
      e.gc.setBackground(color);
      Point size = getSize();
      e.gc.fillRectangle(0, 0, size.x, size.y);
      color.dispose();
    }
  }
  private static Random rand = new Random();
  private static RGB newColor() {
    return new RGB(rand.nextInt(255),
      rand.nextInt(255), rand.nextInt(255));
  }
  private int pause;
  private RGB cColor = newColor();
  public CBox(Composite parent, int pause) {
    super(parent, SWT.NONE);
    this.pause = pause;
    addPaintListener(new CBoxPaintListener());
  }
  @Override
  public void run() {
    try {
      while(!Thread.interrupted()) {
        cColor = newColor();
        getDisplay().asyncExec( () -> {
          try { redraw(); } catch(SWTException e) {}
          // SWTException is OK when the parent
          // is terminated from under us.
        });
        TimeUnit.MILLISECONDS.sleep(pause);
      }
    } catch(InterruptedException e) {
      // Acceptable way to exit
    } catch(SWTException e) {
      // Acceptable way to exit: our parent
      // was terminated from under us.
    }
  }
}

public class ColorBoxes implements SWTApplication {
  private int grid = 12;
  private int pause = 50;
  @Override
  public void createContents(Composite parent) {
    GridLayout gridLayout = new GridLayout(grid, true);
    gridLayout.horizontalSpacing = 0;
    gridLayout.verticalSpacing = 0;
    parent.setLayout(gridLayout);
    ExecutorService exec = new DaemonThreadPoolExecutor();
    for(int i = 0; i < (grid * grid); i++) {
      final CBox cb = new CBox(parent, pause);
      cb.setLayoutData(new GridData(GridData.FILL_BOTH));
      exec.execute(cb);
    }
  }
  public static void main(String[] args) {
    ColorBoxes boxes = new ColorBoxes();
    if(args.length > 0)
      boxes.grid = new Integer(args[0]);
    if(args.length > 1)
      boxes.pause = new Integer(args[1]);
    SWTConsole.run(boxes, 500, 400);
  }
}