在JTabbedPane中设置背景图片

Question

I want to set a background image in a simple JTabbedPane. I used a Jlabel to set my background image. But i haven't been able to do so as i get a null pointer exception upon running. Can anyone help with some more ideas?

Here is my code:

import javax.swing.ImageIcon;
import javax.swing.JTabbedPane;
import javax.swing.JTextField;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.UIManager;
import javax.swing.UIManager.LookAndFeelInfo;

import java.awt.*;
import java.awt.event.*;

class ImageTest 
{
 JTabbedPane tp;
 JLabel lab1
 JPanel  welcome;
 JFrame frame;
 ImageIcon image2;
 public void createUI()
 {
    frame=new JFrame("JTabbedPane");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);



    welcome= new JPanel(null);
    welcome.setPreferredSize(new Dimension(1366,786));
    image2 = new ImageIcon("icloud.jpg");
    tp=new JTabbedPane();
            Container pane = frame.getContentPane();
    pane.add(tp);
    tp.addTab("Welcome", welcome);

    lab1.setIcon(image2);
    lab1.setBounds(0,0,1500,700);

    frame.setSize(500,500);
    frame.setVisible(true);
    frame.setTitle("I-Cloud");

}   
public static void main(String[] args) 
{

    try {
        for (LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (Exception e) {

    }
    ImageTest  tbp = new ImageTest ();
    tbp.createUI();     
}
   }

EDIT:

 import javax.swing.ImageIcon;
 import javax.swing.JTabbedPane;
 import javax.swing.JTextField;
 import javax.swing.JLabel;
 import javax.swing.JPanel;
 import javax.swing.JButton;
 import javax.swing.JFrame;
 import javax.swing.SwingUtilities;
 import javax.swing.UIManager;
 import javax.swing.UnsupportedLookAndFeelException;
 import javax.swing.UIManager.LookAndFeelInfo;

 import java.awt.*;
 import java.awt.event.*;

 class ImageTest 
  {
 JTabbedPane tp;
 JLabel lab1;
 JPanel  welcome,w;
 JFrame frame;
 ImageIcon image2;
 JButton b1;

public void createUI()
{
    frame=new JFrame("JTabbedPane Example");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    b1=new JButton();
    welcome= new JPanel(new GridLayout(1,1,15,15));
    w=new JPanel (new GridLayout(1, 1, 15, 15));
    welcome.setPreferredSize(new Dimension(1366,786));

    ImageIcon icon = new ImageIcon(ImageTest.class.getResource("icloud.jpg"));

    tp=new JTabbedPane();
            Container pane = frame.getContentPane();
    pane.add(tp);


    lab1=new JLabel();
    lab1.setIcon(icon);
    w.setOpaque(false);
    w.add(b1);


    b1.setVisible(true);
            welcome.add(lab1);
            welcome.add(w);
            tp.addTab("Welcome", welcome);

    frame.setSize(500,500);
    frame.pack();
    frame.setVisible(true);
    frame.setTitle("I-Cloud");

}   
public static void main(String[] args) 
{
    try {
        for (LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (Exception e) {

    }

        ImageTest w = new ImageTest();
        w.createUI();   

    }
  }

Answer 1

You may just want to paint the image onto the panel you use for the JTabbedPane (as seen below). But as MadProgammer pointed out. It's most likely you are getting a null from the file location of your image file.

Note: when passing a String to the ImageIcon you are telling it to look for image in the file system. though this may work in a development environment from your IDE, it will not work at time of deployment Instead of reading the image file from the file system, you want to load it from the class path, as should be don with embedded resources , using a URL, which can be obtained by using MyClass.class.getResource(path)

So the way you should loading your image is like this

ImageIcon icon = new ImageIcon(ImageTest.class.getResource("icloud.jpg"));

And your image file would be in the same package as ImageIcon.java . You don't have to put the image in the same package, as you can specify a different path. You can find more info from the embedded resource tag wiki link above.

But back to the option of painting the background, see the example below. Instead of using a URL web link for the image though, you would read in your image file path as specified above.

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTabbedPane;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TabBackground {

    private BufferedImage bg;

    public TabBackground() {
        try {
            bg = ImageIO.read(new URL("http://2.bp.blogspot.com/-wWANHD-Dr00/TtSmeY57ZXI/AAAAAAAABB8/t-fpXmQZ0-Y/s1600/Vector_by_Karpiu23.png"));
        } catch (IOException ex) {
            Logger.getLogger(TabBackground.class.getName()).log(Level.SEVERE, null, ex);
        }

        JPanel tabPanel = new JPanel(new GridBagLayout()) {
            @Override
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);
                g.drawImage(bg, 0, 0, getWidth(), getHeight(), this);
            }

            @Override
            public Dimension getPreferredSize() {
                return new Dimension(400, 300);
            }
        };
        JPanel buttons = new JPanel(new GridLayout(4, 1, 15, 15));
        buttons.setOpaque(false);
        for (int i = 0; i < 4; i++) {
            buttons.add(new JButton("Button"));
        }
        tabPanel.add(buttons);

        JTabbedPane tabPane = new JTabbedPane();
        tabPane.add("Panel with Bachground", tabPanel);

        JFrame frame = new JFrame("Tabbed Pane with Background");
        frame.setContentPane(tabPane);
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    Logger.getLogger(TabBackground.class.getName()).log(Level.SEVERE, null, ex);
                }
                new TabBackground();
            }
        });
    }
}

Answer 2

You can add an image like this on Jframe:

tp.addTab("Welcome",new JLabel(new ImageIcon("bksqla_xlargecover.jpg")));