使用 URL (Java) 将图像加载到 JPanel

Question

I'm currently working on a Java school project where I have to display an image into a JPanel. I'm having some trouble loading the image. Here's my code:

public void LoadImage(String imageURL){
    panel.setLayout(new BorderLayout());

    Image image = null;
    URL url = null;
    try {
        url = new URL("https://i.ibb.co/GTTV1cm/3ad25e3ae0f6.jpg");

        image = ImageIO.read(url);
        JLabel label = new JLabel(new ImageIcon(image));
        panel.add(label, BorderLayout.CENTER);
    } catch (MalformedURLException ex) {
        System.out.println("Malformed URL");
    } catch (IOException iox) {
        System.out.println("Can not load file");
        iox.printStackTrace();
    }

    pack();
    setVisible(true);
}

And this is the error I'm getting

javax.imageio.IIOException: Can't get input stream from URL!
at java.desktop/javax.imageio.ImageIO.read(ImageIO.java:1409)
at MainScreen.LoadImage(MainScreen.java:90)
at MainScreen.<init>(MainScreen.java:35)
at MainScreen.main(MainScreen.java:105)
Caused by: java.io.FileNotFoundException: https://i.ibb.co/GTTV1cm/3ad25e3ae0f6.jpg
    at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1993)
    at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1589)
    at java.base/sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:224)
    at java.base/java.net.URL.openStream(URL.java:1161)
    at java.desktop/javax.imageio.ImageIO.read(ImageIO.java:1407)
    ... 3 more

I would greatly appreciate your help as I'm a beginner in Java!!

Answer 1

There seems to be some confusion ( at least for me and by reading the comments ) as to what the actual URL is to the image you are trying to access on the net. With the URL supplied ( https://i.ibb.co/GTTV1cm/3ad25e3ae0f6.jpg ) I get a blank black page with the following image (yes...I said image) sitting in the middle:

To me, this means there is no image at the URL provided so, the URL is invalid. Uhhhh, confusion ended.

Anyways, I just wanted to suggest that you let your loadImage() method do exactly that, load an image and leave the GUI building in another method altogether. Either have this method return an ImageIcon which can be set into a component during the GUI build or set the image to the component itself within the method by passing the component as argument after the GUI build.

The method below requires the JLabel to be passed to it in order load an image into it. The image path supplied can be from an URL, resources, or local file system. It shouldn't matter if the url is http or https . The method also contains an option to size the image to the actual JLabel or not.

/**
 * Loads an image into the supplied JLabel.<br><br>
 *
 * @param jlabel                  (JLabel) The variable name of the JLabel
 *                                to load image into<br>
 *
 * @param imagePath               (String) The full path and file name of
 *                                the image to load into JLabel. This path
 *                                can be either from the local file system
 *                                or from a from a JAR's resources or from a
 *                                http or https web link, for example:<pre>
 *
 *      "C:/My Gifs/flowers.gif"
 *
 *                OR
 *
 *      "/resources/images/flowers.gif"
 *
 *                OR
 *
 *      "https://thumbs.gfycat.com/cool.gif"</pre>
 *
 * To retrieve your images from a JAR's resources you need to ensure that
 * your resource folder is properly located during development. The resource
 * folder (resources) should be located within the source (src) folder. The
 * path tree should be:
 * <pre>
 *
 *  * PROJECT NAME
 *      * src
 *          * PACKAGE YOU NAMED IN PROJECT
 *               yourApp.java
 *          * resources
 *              * images
 *                  yourImageFile1.jpg
 *                  yourImageFile2.gif
 *                  yourImageFile3.png
 *                  yourImageFile4.jpeg
 *                  yourImageFile5.bmp
 *                  yourImageFile6.wbmp
 *              * text
 *                  myText1.txt
 *                  myText2.txt
 *                  myText3.txt
 *              * etc..........</pre>
 *
 * Whenever loading anything from resources the path must always start with
 * a forward slash (/), for example:
 * <pre>
 *
 *      loadImageToJLabel(jLabel1, "/resources/inages/yourImageFile1.jpg", true);</pre>
 *
 * @param autoSetImageToLabelSize
 */
public void loadImageToJLabel(JLabel jlabel, String imagePath, boolean... autoSetImageToLabelSize) {
    String ls = System.lineSeparator();
    boolean autoSize = false;
    if (autoSetImageToLabelSize.length > 0) {
        autoSize = autoSetImageToLabelSize[0];
    }
    javax.swing.ImageIcon image;

    try {
        if (imagePath.toLowerCase().startsWith("http")) {
            final java.net.URL url = new java.net.URL(imagePath);
            java.net.HttpURLConnection huc = (java.net.HttpURLConnection) url.openConnection();
            int responseCode = huc.getResponseCode();
            huc.disconnect();
            //Does responseCode fall into the 200 to 299 range (which are the codes for: SUCCESS)
            // If NO then....
            if (responseCode < 200 || responseCode > 299) {
                System.err.println("loadImageToJLabel() Method Error! Can not "
                        + "locate the image file specified!" + ls + "Ensure "
                        + "that your HTTP or HTTPS link exists!" + ls
                        + "Supplied Link Path:  \"" + imagePath + "\"" + ls);
                return;
            }
            image = new javax.swing.ImageIcon(url); //new URL(imagePath));
        }
        else if (imagePath.startsWith("/") || imagePath.startsWith("\\")) {
            Class currentClass = new Object() {
            }.getClass().getEnclosingClass();
            try {
                image = new javax.swing.ImageIcon(currentClass.getClass().getResource(imagePath));
            }
            catch (NullPointerException npe) {
                System.err.println("loadImageToJLabel() Method Error! Can not "
                        + "locate the Resource Path or the resource file!" + ls + "Ensure "
                        + "that your resources are properly located." + ls
                        + "Supplied Resource Path:  \"" + imagePath + "\"" + ls);
                return;
            }
        }
        else {
            java.io.File f = new java.io.File(imagePath);
            if (!f.exists()) {
                System.err.println("loadImageToJLabel() Method Error! Can not "
                        + "locate the image file specified!" + ls + "Ensure "
                        + "that your Image file exists within the local file system path provided!" + ls
                        + "Supplied File Path:  \"" + imagePath + "\"" + ls);
                return;
            }
            image = new javax.swing.ImageIcon(new java.net.URL("file:" + imagePath));
        }

        if (autoSize) {
            Image img = image.getImage();
            Image resizedImage = img.getScaledInstance(jlabel.getWidth(), jlabel.getHeight(), java.awt.Image.SCALE_SMOOTH);
            jlabel.setIcon(new ImageIcon(resizedImage));
        }
        else {
            jlabel.setIcon(image);
        }
        jlabel.validate();
    }
    catch (java.net.MalformedURLException ex) {
        System.err.println("loadImageToJLabel() Method Error! Improper Image file link supplied!" + ls
                + "Supplied Link:  \"" + imagePath + "\"" + ls);

    }
    catch (java.io.IOException ex) {
        System.err.println("loadImageToJLabel() Method Error! Can not access Image File!" + ls
                + "Supplied File Path:  \"" + imagePath + "\"" + ls);
    }
}