How to set an image filename

Question

I made a Java program with Swing libraries that displays text and an image. Both the text string and the image filename are set via a set method, but while the text is displayed correctly, the image is not.

If I set the filename directly in the constructor then it works, but it is not what I want to do.

I cannot find a way to pass the filename to display the image.

The intention is to periodically pass an array of strings and a set of image filenames, to have a GUI with text and image changing over time.

Here is the code simplified:

import javax.swing.*;
import java.net.URL;
class Swing extends JFrame {
 
 private JLabel label = new JLabel();
 private String imageFilename = new String();
 
 Swing()
 {
 super("Swing Test Application"); 
 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 setSize(1000, 700);
 setLayout(null);
 setLocationRelativeTo(null);
 
 label.setBounds(10, 0, 220, 100); 
 add(label);
 
 //String imageFilename = "images\\image-1.jpg"; 
 URL imageURL = getClass().getResource(imageFilename); 
 if (imageURL != null) {
 ImageIcon imageIcon = new ImageIcon(imageURL);
 JLabel imageLabel = new JLabel(imageIcon);
 imageLabel.setBounds(10, 200, 420, 420);
 add(imageLabel); // Aggiungi l'etichetta al frame
 } else {
 System.err.println("Image " + imageFilename + " not found.");
 } 
 
 setVisible(true);
 }
 
 void SetText(String strLabel, String imageFilename) 
 {
 label.setText(strLabel); 
 this.imageFilename = imageFilename;
 
 return;
 }
 
 public static void main(String arg[]) 
 { 
 Swing swing = new Swing(); 
 swing.SetText("This is string 1", "images\\image-1.jpg"); 
 }
}

• g00se: I'm guessing THIS is what you were trying to do. Run as java -jar slides.jar Source inside the jar

Answer 1

In the same way that you declared a JLabel field for the text label, you can declare another JLabel field for the image label:

private JLabel label = new JLabel();
private JLabel image = new JLabel(); // <-------
Swing()
{
 super("Swing Test Application");
 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 setSize(1000, 700);
 setLayout(null);
 setLocationRelativeTo(null);
 label.setBounds(10, 0, 220, 100);
 add(label);
 image.setBounds(10, 200, 420, 420);
 add(image);
 setVisible(true);
}

In SetText, call setIcon on the image label:

void SetText(String strLabel, String imageFilename)
{
 label.setText(strLabel);
 URL imageURL = getClass().getResource(imageFilename);
 if (imageURL != null) {
 ImageIcon imageIcon = new ImageIcon(imageURL);
 image.setIcon(imageIcon);
 } else {
 System.err.println("Image " + imageFilename + " not found.");
 }
}

• Fabio Ferro: Now I have another little problem. If I compile with javac and then call java etc... the application can load corectly the images located in the directory "images". Instead if I try to create a jar file, with the following commands: javac Swing.java jar cfe Build.jar Swing . java -jar Build.jar the application does not find the images. How can I say to the Java compiler to look for the images in the directory "images"? Thanks
• g00se: That's because you're not treating the images properly as resources, a fact which is revealed by this: //String imageFilename = "images\\image-1.jpg"; Resources are not files/file paths. Are you using any kind of IDE for doing your Java? Also, you should avoid null layouts
• Sweeper: @g00se This problem is further discussed here.
• g00se: That question should have been closed immediately as essentially a duplicate of this one. But looking at that other one, you should say what you expect your code to do as well Fabio

Answer 2

With a few modifications, your code will work as expected:

public class Swing extends JFrame {
 private JLabel imageLabel;
 private JLabel label;
 Swing() {
 super( "Swing Test Application" );
 setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
 setLocationRelativeTo(null);
 setSize( 1000, 700 );
 setLayout( null );
 
 // create both labels
 imageLabel = new JLabel();
 // we assign the initial text
 label = new JLabel( "Default text" );
 // we assign the sizes and positions only once
 imageLabel.setBounds( 10, 200, 420, 420 );
 label.setBounds( 10, 0, 220, 100 );
 
 // set icon with path to default icon
 // your IDE will probably complain that "setFrameIcon" is not "private",
 // but since it will be invoked later by other sections of the 
 // code you need it to look like this
 setFrameIcon( "images/aa.jpg" );
 add( imageLabel );
 add( label );
 setVisible( true );
 }
 public void setFrameIcon( String imageFilename ) {
 try {
 // we create the "ImageIcon" object as a resource, to be able to use 
 // it from the "Jar".
 // you must take into account that absolute routes are not accepted.
 ImageIcon icon = new ImageIcon( getClass().getResource( imageFilename ) );
 imageLabel.setIcon( icon );
 // in one line
 imageLabel.setIcon( new ImageIcon( getClass().getResource( imageFilename )));
 }
 catch( Exception e ) {
 System.err.println( "Image " + imageFilename + " not found." );
 }
 }
 public void setText( String strLabel ) {
 label.setText( strLabel );
 }
 public static void main( String arg[] ) {
 
 // we use "InvokeLater" so that the "GUI" is built on the event thread
 SwingUtilities.invokeLater( () -> {
 Swing swing = new Swing();
 } );
 }
}

• Basil Bourque: You should explain those few modifications in prose.