NullPointerException with getResource() while adding CSS to JavaFX application

Question

A little confused with a NullPointerException that I am getting. I am trying to add a .css file to my Main class. Here is the code.

        //Load FXML file
        Parent root = FXMLLoader.load(getClass().getResource("/application/HumansightFirstDraft.fxml"));

        // Create scene
        Scene scene = new Scene(root, 400, 600);

        //Load CSS
        scene.getStylesheets().add(getClass().getClassLoader().getResource("/application/application.css").toExternalForm());

        // Display application
        primaryStage.setScene(scene);
        primaryStage.show();`

The application.css is in the same place as the Main.java.

Here is my console output.

Jan 10, 2019 8:30:20 AM javafx.fxml.FXMLLoader$ValueElement processValue
WARNING: Loading FXML document with JavaFX API of version 10.0.1 by JavaFX runtime of version 8.0.191
java.lang.NullPointerException
    at application.Main.start(Main.java:22)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(LauncherImpl.java:863)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$174(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)

Here is my css. I only have one change so as to make it easier to test.

#startSurvey {

-fx-border-radius: 30;

}

Here is my directory as seen in Eclipse.

When the result of getResource(...) is null that means the resource couldn't be found at the specified location. Make sure you have the path correct and that the resource file is on the classpath. — Slaw
– Slaw, Commented Jan 10, 2019 at 14:17
I assumed that much, but the I've checked and rechecked the file path and it seems to be correct. I will include a screenshot of my folder. — Riley Fitzpatrick
– Riley Fitzpatrick, Commented Jan 10, 2019 at 14:22
What happens if you use getClass().getResource(...) instead of getClass().getClassLoader().getResource(...)? — Slaw
– Slaw, Commented Jan 10, 2019 at 14:24
The fact that the css file is included in the source folder does not automatically result in the IDE copying it to the build folders. Have you checked the folders containing the .class files for the css file? — fabian
– fabian, Commented Jan 10, 2019 at 14:27
So when I take out getClassLoader(), there is no error, but the css doesn't load. I've had a weird thing since I started JavaFX where my programs only work when I include the getClassLoader(). Where would I find these folders? — Riley Fitzpatrick
– Riley Fitzpatrick, Commented Jan 10, 2019 at 14:36

Ahmad D. Sulaiman · Accepted Answer · 2019-01-12 11:36:00Z

1

You dont nee to say /application/application.css

Just write it like this application.css

This is becsuse both the main class an the css file are in the same parent direvtory

The same as all the fxml files

Update It is also possible that the null pointer occurs in the controller of the fxml.

Update 2 Thanks to

@kleopatra

dont use getClass().getClassLoader().getResource() simply use getClass().getResource()

edited Jan 12, 2019 at 11:36

answered Jan 11, 2019 at 0:58

Ahmad D. Sulaiman

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7 Comments

Riley Fitzpatrick Over a year ago

That's what I thought too. But I tried that out and it didn't change.

kleopatra Over a year ago

beware, the getResource param interpretation is different for classloader vs class: classloader.getResource(absolutePath) - can have the leading slash or not, doesn't matter, vs. class.getResource(relativePath) without slash and absolute with slash. So something really fishy going on here ... most probably a head-on-table when found ;)

kleopatra Over a year ago

that's not what I meant (probably wasn't clear enough): we can use the one or other but must be aware of the difference :)

Riley Fitzpatrick Over a year ago

So, when I do what you said, I get no errors, but the nothing from the css is actually applied.

Riley Fitzpatrick Over a year ago

Your correction was right. The problem ended up actually being in my CSS. The -fx-border-radius characteristic does not change what I expected, so the css was applied, but in a visible way. But thank you for teaching me about the difference between class... & class.classLoader()...

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