Using Headless Mode in the Java SE Platform--转

import javax.imageio.*;

public class HeadlessBasics
{
public static void main(String[] args)
{
// Set system property.
// Call this BEFORE the toolkit has been initialized,that is,// before Toolkit.getDefaultToolkit() has been called.
System.setProperty("java.awt.headless","true");

    // This triggers creation of the toolkit.
    // Because java.awt.headless property is set to true,this 
    // will be an instance of headless toolkit.
    Toolkit tk = Toolkit.getDefaultToolkit();
    // Standard beep is available.
    tk.beep();

    // Check whether the application is
    // running in headless mode.
    GraphicsEnvironment ge = 
    GraphicsEnvironment.getLocalGraphicsEnvironment();
    System.out.println("Headless mode: " + ge.isHeadless());

    // No top levels are allowed.
    boolean created = false;
    try
    {
        Frame f = new Frame("Frame");
        created = true;
    }
    catch (Exception z)
    {
        z.printStackTrace(System.err);
        created = false;
    }
    System.err.println("Frame is created: " + created);

    // No other components except Canvas and Panel are allowed.
    created = false;
    try
    {
        Button b = new Button("Button");
        created = true;
    }
    catch (Exception z)
    {
        z.printStackTrace(System.err);
        created = false;
    }
    System.err.println("Button is created: " + created);

    // Canvases can be created.
    final Canvas c = new Canvas()
    {
        public void paint(Graphics g)
        {
            Rectangle r = getBounds();
            g.drawLine(0,r.height - 1);
            // Colors work too.
            g.setColor(new Color(255,0);
            // And fonts
            g.setFont(new Font("Arial",8);
        }
    };
    // And all the operations work correctly.
    c.setBounds(32,128,128);

    // Images are available.
    Image i = null;
    try
    {
        File f = new File("grapefruit.jpg");
        i = ImageIO.read(f);
    }
    catch (Exception z)
    {
        z.printStackTrace(System.err);
    }
    final Image im = i;

    // Print system is available.
    PrinterJob pj = PrinterJob.getPrinterJob();
    pj.setPrintable(new Printable()
    {
        public int print(Graphics g,int pageIndex)
        {
            if (pageIndex > 0)
            {
                return Printable.NO_SUCH_PAGE;
            }
            ((Graphics2D)g).translate(pf.getImageableX(),pf.getImageableY());

            // Paint the canvas.
            c.paint(g);

            // Paint the image.
            if (im != null)
            {
                g.drawImage(im,64,null);
            }

            return Printable.PAGE_EXISTS;
        }
    });
    try
    {
        pj.print();
    }
    catch (Exception z)
    {
        z.printStackTrace(System.err);
    }
}

}

Headless mode: true
java.awt.HeadlessException
at java.awt.GraphicsEnvironment.checkHeadless(Unknown Source)
at java.awt.Window.(Unknown Source)
at java.awt.Frame.(Unknown Source)
at HeadlessBasics.main(HeadlessBasics.java:24)
Frame is created: false
java.awt.HeadlessException
at java.awt.GraphicsEnvironment.checkHeadless(Unknown Source)
at java.awt.Button.(Unknown Source)
at HeadlessBasics.main(HeadlessBasics.java:39)
Button is created: false

【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容!