以前很少用到这个类（org.eclipse.swt.events.PaintListener），利用它可以用来在control上画一些东西，基本方法是在control上 addPaintListener()一个PaintListener，然后在这个listener里做具体的画图工作，listener在control需要绘制的时候调用。

下面例子代码用来在一个composite的中央绘制一行文字。

package com.test;

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class Test3 {

    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setLayout(new FillLayout());
        final Button button = new Button(shell, SWT.PUSH);
        button.setText("This is a button");
        final Composite comp2 = new Composite(shell, SWT.BORDER);
        comp2.addPaintListener(new PaintListener() {
            public void paintControl(PaintEvent e) {
                String text = "This is a composite";
                Rectangle area = comp2.getClientArea();//client area
                int tw = calcTextWidth(e.gc, text);//text width
                int th = e.gc.getFontMetrics().getHeight();//text height
                Rectangle textArea = new Rectangle(area.x + (area.width - tw) / 2,
                        area.y + (area.height - th) / 2, 
                        tw,
                        th);//centerized text area
                e.gc.drawString(text, textArea.x, textArea.y);
                e.gc.drawRectangle(textArea);
            }

            private int calcTextWidth(GC gc, String text) {
                int stWidth = 0;
                for (int i = 0; i < text.length(); i++) {
                    char c = text.charAt(i);
                    stWidth += gc.getAdvanceWidth(c);
                }
                return stWidth;
            }
        });
        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch())
                display.sleep();
        }
        display.dispose();
    }
}

运行结果如下图：

搬家前链接：https://www.cnblogs.com/bjzhanghao/archive/2005/09/23/242837.html