BlueJ Image Not Found

Question

I have a JavaFX BlueJ project. Following is the simple directory structure

As you can see that I have a Gui.java and map.png files in same directory. Following is my code

@Override
public void start(Stage primaryStage) throws Exception {

    primaryStage.setTitle("Dragon Castle");

    Game game = new Game();
    TextArea logArea = new TextArea();

    VBox vbox = new VBox(10);

    // Create maps

    Canvas canvas = new Canvas(770, 630);

    Image map = new Image("map.png"); // Here it is giving error

    GraphicsContext gc = canvas.getGraphicsContext2D();

    // Insert controls

    VBox controlsVbox = new VBox(5);
    controlsVbox.setAlignment(Pos.CENTER);

    HBox buttonHboxR1 = new HBox(5);
    buttonHboxR1.setAlignment(Pos.CENTER); .... Other code

Error:

Exception in Application start method
java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$152(LauncherImpl.java:182)
    at com.sun.javafx.application.LauncherImpl$$Lambda$7/22058848.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalArgumentException: Invalid URL: Invalid URL or resource not found
    at javafx.scene.image.Image.validateUrl(Image.java:1099)
    at javafx.scene.image.Image.<init>(Image.java:608)
    at src.Gui.start(Gui.java:46)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$159(LauncherImpl.java:863)
    at com.sun.javafx.application.LauncherImpl$$Lambda$57/5668924.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$172(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl$$Lambda$53/812813.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$null$170(PlatformImpl.java:295)
    at com.sun.javafx.application.PlatformImpl$$Lambda$55/19277439.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$171(PlatformImpl.java:294)
    at com.sun.javafx.application.PlatformImpl$$Lambda$54/26973244.run(Unknown Source)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$145(WinApplication.java:101)
    at com.sun.glass.ui.win.WinApplication$$Lambda$43/21354624.run(Unknown Source)
    ... 1 more
Caused by: java.lang.IllegalArgumentException: Invalid URL or resource not found
    at javafx.scene.image.Image.validateUrl(Image.java:1091)
    ... 16 more

Image not found. I tried same code in eclipse, its working. Also I put map.png in resources folder but its still not working in BlueJ.

Answer 1

From the Image documentation:

All URLs supported by URL can be passed to the constructor. If the passed string is not a valid URL, but a path instead, the Image is searched on the classpath in that case.

So, since you pass a simple path, the Image constructor will attempt to resolve that relative to the classpath. Looking at the stack trace, your Gui class appears to be in a package called src (really???) and your image is in the same package. Hence the path to the image should be src/map.png.

A better way to retrieve the image from the same package as the current class is to get the URL from the class object as a resource:

Image map = new Image(getClass().getResource("map.png").toExternalForm());