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I am trying to write a game in javaFX and need ImageView to display a png image with a transparent background as one of the sprites. I use Main class's getClass.getResource() method to find the image's URL. the image is saved under resources/images/transparentegg.png. I have this line in the constructor of my Bullet class, which extends ImageView:

setImage(new Image(Main.getMain().getResource("images/transparentegg.png").toString()));

Main class has a static field main which is set to this in the start method. Main.getMain() method returns that static field. Main.getResource() method has this body:

public URL getResource(String name) {
        return getClass().getResource(name);
}

when I run the game with "images/transparentegg.png" as the input to getResource, I get an error and the image is not loaded. this is the error:

Exception in thread "JavaFX Application Thread" java.lang.NullPointerException: Cannot invoke "java.net.URL.toString()" because the return value of "cuphead.cuphead.Main.getResource(String)" is null at cuphead.cuphead/cuphead.cuphead.sprite.Bullet.(Bullet.java:26) at cuphead.cuphead/cuphead.cuphead.sprite.Chicken.shoot(Chicken.java:80) at cuphead.cuphead/cuphead.cuphead.controller.GameController$2.handle(GameController.java:191) at cuphead.cuphead/cuphead.cuphead.controller.GameController$2.handle(GameController.java:188) at javafx.graphics@18.0.1/com.sun.scenario.animation.shared.TimelineClipCore.visitKeyFrame(TimelineClipCore.java:239) at javafx.graphics@18.0.1/com.sun.scenario.animation.shared.TimelineClipCore.playTo(TimelineClipCore.java:180) at javafx.graphics@18.0.1/javafx.animation.Timeline.doPlayTo(Timeline.java:172) at javafx.graphics@18.0.1/javafx.animation.AnimationAccessorImpl.playTo(AnimationAccessorImpl.java:39) at javafx.graphics@18.0.1/com.sun.scenario.animation.shared.InfiniteClipEnvelope.timePulse(InfiniteClipEnvelope.java:104) at javafx.graphics@18.0.1/javafx.animation.Animation.doTimePulse(Animation.java:1189) at javafx.graphics@18.0.1/javafx.animation.Animation$1.lambda$timePulse$0(Animation.java:207) at java.base/java.security.AccessController.doPrivileged(AccessController.java:399) at javafx.graphics@18.0.1/javafx.animation.Animation$1.timePulse(Animation.java:206)

However, if I enter "images/egg.png" as the argument of getResource, the program runs without a problem. images/egg.png is another image of the egg but without a transparent background: the background is black. I am using java 17, and JavaFX 18. The program is being run on Windows 10. I will also include the aforementioned images.

egg.png transparent egg

EDIT I updated to java 18 and the issue was resolved.

Amir Kooshky
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    You should try `getResource("/images/transparentegg.png")` instead of `getResource("images/transparentegg.png")`... – khmarbaise May 26 '22 at 08:21
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    JavaFX can definitely load png images with transparent backgrounds, for instance the images in [this answer](https://stackoverflow.com/questions/72050368/javafx-combobox-with-custom-cell-factory-buggy-rendering/72050915#72050915) work. – jewelsea May 26 '22 at 08:22
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    Try this, you say egg.png works, so, when that is working, rename your transparent egg to overwrite the egg.png and see if it loads. The error is saying `images/transparentegg.png` does not exist, it is not even getting to the point where it is trying to load the image in the constuctor, it just can't find the resource. Check it is really there. See troubleshooting at [how to find JavaFX resources](https://stackoverflow.com/questions/61531317/how-do-i-determine-the-correct-path-for-fxml-files-css-files-images-and-other) and the eden guide referenced in that question. – jewelsea May 26 '22 at 08:28

0 Answers0