SWT 2D Graphics Java Tutorial

  1. Home
  2. Java Tutorial
  3. SWT 2D Graphics
  4. Avoid creating a GC
You can avoid creating a GC and just use the one from the event.
In this case, you shouldn't dispose that GC.

shell.addPaintListener(new PaintListener() {
  public void paintControl(PaintEvent event) {
    event.gc.drawRectangle();
  }
});

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
public class GCFromEvent {
  public static void main(String[] args) {
    Display display = new Display();
    Shell shell = new Shell(display);
    shell.setText("Canvas Example");
    shell.setLayout(new FillLayout());
    Canvas canvas = new Canvas(shell, SWT.NONE);
    canvas.addPaintListener(new PaintListener() {
      public void paintControl(PaintEvent e) {
        e.gc.setForeground(e.display.getSystemColor(SWT.COLOR_RED));
        e.gc.drawFocus(5, 5, 200,10);
        e.gc.drawText("You can draw text directly on a canvas", 60, 60);
      }
    });
    shell.open();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch()) {
        display.sleep();
      }
    }
    display.dispose();
  }
}