Re: Displaying Images

  To: comp.lang.java.gui
Sean,

This is NOT an easy problem. Especially, if you use WebStart or a
different thread/classloader needs to load the resource.

I wrote a Java Application framework about 7 years ago. One of the
first utility classes I wrote was something called IconLoader. Feel
free to use as needed.

The entire project can be found at:
https://tframe.dev.java.net/

Kind regards,
Ed Tidwell

package net.java.dev.tframe.util;

import java.awt.Frame;
import java.net.URL;

import javax.swing.*;

/**
  * This class will load an icon and add it to the control passed in.
We will
  * add more methods as they are needed to support future controls not
currently
  * implemented. If an icon is not found an error message is printed to
system
  * out to inform the caller that the icon was not located.
  *
  * Currently we have an "icons" directory in our jar file for all icons.
  * This directory should exist in your classes directory if your using
  * JBuilder to create your jar file. <recommended solution>
  *
  * Made 2.0 so you do not have to create an instance of IconLoader.
Just call
  * the static method. This is a LOT more efficient.
  *
  * Made 3.0 to work with WebStart
  *
  * @Author Ed Tidwell
  * @version 3.0
  */
public final class IconLoader {
     // this directory MUST exist in the jar AND
     // must contain all your icons
     //JBuilder note... Create this directory in your classes directory and
     //copy your icons to that location.
     public static final String ICON_PATH = "resources/icons/";

     /** All methods in this class are static - forces access through
class only */
     private IconLoader() {}

     /**
      * This helper method insures we redirect to the class loader that
loads us.
      * @param iconName path to resources
      * @return url to resource
      */
     private static URL getURL(String iconName) {
         // have to get the class to get to the classLoader that LOADED us.
         // this is so we work correctly under WebStart
         URL iconURL = Thread.currentThread().getContextClassLoader().
                       getResource(ICON_PATH + iconName);
         return iconURL;
     }

     /**
      * Give the name of an icon to look for and a JButton target for
the icon
      * IF it is found.
      * @param iconName file name
      * @param setMe button to set
      */
     public static void setIcon(String iconName, JButton setMe) {
         URL iconURL = getURL(iconName);
         if (iconURL != null) {
             setMe.setIcon(new ImageIcon(iconURL));
         } else {
             System.out.println(iconName + " not found in " + ICON_PATH);
         } // if else
     } // setIcon for JButton

     /**
      * Give the name of an icon to look for and a JLabel target for the
icon
      * IF it is found.
      * @param iconName file name
      * @param setMe button to set
      */
     public static void setIcon(String iconName, JLabel setMe) {
         URL iconURL = getURL(iconName);
         if (iconURL != null) {
             setMe.setIcon(new ImageIcon(iconURL));
         } else {
             System.out.println(iconName + " not found in " + ICON_PATH);
         } // if else
     } // setIcon for JButton

     /**
      * Give the name of an icon to look for and a Frame target for the icon
      * @param iconName of file
      * @param frame to set icon image against
      */
     public static void setIcon(String iconName, Frame frame) {
         URL iconURL = getURL(iconName);

         if (iconURL != null) {
             // set upper left hand corner icon for OS platforms that
support it
             // child applications can easily override the default
             frame.setIconImage(new ImageIcon(iconURL).getImage());
         } else {
             System.out.println(iconName + " not found in " + ICON_PATH);
         } // if else
     } // setIcon for JButton

     /**
      * Given an icon name return the icon.
      * @param iconName file name of icon
      * @return the icon if it exists. Otherwise, null.
      */
     public static ImageIcon getIcon(String iconName) {
         URL iconURL = getURL(iconName);

         if (iconURL == null) {
             System.out.println(iconName + " not found in " + ICON_PATH);
         }

         return (iconURL == null ? null : new ImageIcon(iconURL));
     } // getIcon

} //IconLoader

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