我如何以小程序和应用程序的形式运行某些内容？

Question

I'm working on this project and I need it run as an applet and an application. This is what I have but I stuck on where to go because I can't find anything on the internet. Are there any resources or does someone have some quick advice to give me?

public class Project extends JApplet {

public void init() {

    try {
        URL pictureURL = new URL(getDocumentBase(), "sample.jpg");
        myPicture = ImageIO.read(pictureURL);
        myIcon = new ImageIcon(myPicture);
        myLabel = new JLabel(myIcon);
    } catch (Exception e) {
        e.printStackTrace();
    }
    add(label, BorderLayout.NORTH);

    add(bio);
    add(bio, BorderLayout.CENTER);

    pane.add(play);
    getContentPane().add(pane, BorderLayout.SOUTH);
    play.addActionListener(new  ActionListener() {
        public void actionPerformed(ActionEvent e) {
            try{
                FileInputStream FIS = new FileInputStream("sample.mp3");
                player = new Player (FIS);
                player.play();
            } catch (Exception e1) {
                e1.printStackTrace();
            }}});
}

public static void main(String args[]) {
    JFrame frame = new JFrame("");
    frame.getContentPane().add();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.show();
}

private JPanel pane = new JPanel();
private TextArea bio = new TextArea("Bio");
private JButton play = new JButton("Play");
private Image myPicture;
private ImageIcon icon;
private JLabel label;
private Player player;

}

Answer 1

When trying to run something as an applet and as an application, there are several caveats.

Applets have a certain life cycle that must be obeyed. One can add the applet to the content pane of the JFrame and manually call init() , but in general, if the applet expects its start() or stop() methods to be called, things may become tricky...

More importantly: The way how resources are handled is different between applets and applications.

Handling files in applets (eg with a FileInputStream ) may have security implications, and will plainly not work in some cases - eg when the applet is embedded into a website. (Also see What Applets Can and Cannot Do ).

Conversely, when running this as an application, calling getDocumentBase() does not make sense. There simply is no "document base" for an application.

---

Nevertheless, it is possible to write a program that can be shown as an Applet or as an Application. The main difference will then be whether the main JPanel is placed into a JApplet or into a JFrame , and how data is read.

One approach for reading data that works for applets as well as for applications is via getClass().getResourceAsStream("file.txt") , given that the respective file is in the class path.

I hesitated a while, whether I should post an example, targeting the main question, or whether I should modify your code so that it works. I'll do both:

Here is an example that can be executed as an Applet or as an Application. It will read and display a "sample.jpg". (This file is currently basically expected to be "in the same directory as the .class-file". More details about resource handling, classpaths and stream handling are beyond the scope of this answer)

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.InputStream;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JApplet;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextArea;

public class AppletOrApplicationExample extends JApplet
{
    @Override
    public void init()
    {
        add(new AppletOrApplicationMainComponent());
    }

    public static void main(String args[])
    {
        JFrame frame = new JFrame("");
        frame.getContentPane().add(new AppletOrApplicationMainComponent());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
    }
}

class AppletOrApplicationMainComponent extends JPanel
{
    public AppletOrApplicationMainComponent()
    {
        super(new BorderLayout());

        InputStream stream = getClass().getResourceAsStream("sample.jpg");
        if (stream == null)
        {
            add(new JLabel("Resource not found"), BorderLayout.NORTH);
        }
        else
        {
            try
            {
                BufferedImage image = ImageIO.read(stream);
                add(new JLabel(new ImageIcon(image)), BorderLayout.NORTH);
            }
            catch (IOException e1)
            {
                add(new JLabel("Could not load image"), BorderLayout.NORTH);
            }
        }

        JTextArea textArea = new JTextArea("Text...");
        add(textArea, BorderLayout.CENTER);

        JButton button = new JButton("Button");
        button.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                doSomething();
            }
        });
        add(button, BorderLayout.SOUTH);
    }

    private void doSomething()
    {
        System.out.println("Button was clicked");
    }
}

---

---

And here is something that is still a bit closer to your original code. However, I'd strongly recommend to factor out the actual application logic as far as possible. For example, your main GUI component should then not be the applet itself, but a JPanel . Resources should not be read directly via FileInputStream s or URLs from the document base, but only from InputStreams . This is basically the code that you posted, with the fewest modifications that are necessary to get it running as an applet or an application :

import java.awt.BorderLayout;
import java.awt.Image;
import java.awt.TextArea;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.FileInputStream;
import java.io.InputStream;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JApplet;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class Module5Assignment2 extends JApplet
{
    public void init()
    {
        try
        {
            InputStream stream = getClass().getResourceAsStream("sample.jpg");
            if (stream == null)
            {
                System.out.println("Resource not found");
            }
            else
            {
                myPicture = ImageIO.read(stream);
                icon = new ImageIcon(myPicture);
                label = new JLabel(icon);
                add(label, BorderLayout.NORTH);
            }
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }

        add(bio);
        add(bio, BorderLayout.CENTER);

        pane.add(play);
        getContentPane().add(pane, BorderLayout.SOUTH);
        play.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                try
                {
                    FileInputStream FIS = new FileInputStream("sample.mp3");
                    // player = new Player (FIS);
                    // player.play();
                }
                catch (Exception e1)
                {
                    e1.printStackTrace();
                }
            }
        });
    }

    public static void main(String args[])
    {
        JFrame frame = new JFrame("");
        // ******PRETTY SURE I NEED TO ADD SOMETHING HERE*************
        Module5Assignment2 contents = new Module5Assignment2();
        frame.getContentPane().add(contents);
        contents.init();
        // *************************************************************

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.show();
    }

    private JPanel pane = new JPanel();
    private TextArea bio = new TextArea(
        "This is the bio of Christian Sprague; he doesn't like typing things.");
    private JButton play = new JButton("Play");
    private Image myPicture;
    private ImageIcon icon;
    private JLabel label;
    // private Player player;

}