FXML: ClassNotFoundException

Question

I'm very new to JavaFX and I'm having problem using my custom class in FXML. The console keeps giving me this exception when trying to load main.fxml:

... 1 more
Caused by: java.lang.ClassNotFoundException: sample.View$BoardPane
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
...

I created BoardPane class as a subclass of FlowPane in package sample.View and referred to it in my FXML as the following:

<?import sample.View.BoardPane?>
...
<TitledPane expanded="true" collapsible="false" text="BoardPane" fx:id="centerTitledPane">
    <BoardPane fx:id="mechoBoardPane"/>
</TitledPane>
...

and the project structure looks like this:

• resources
  • fxml
    • main.fxml
• ...
• src
  • ...
  • sample
    • ...
    • View
      • BoardPane

Can anyone please help me on this? I've been searching for some time and haven't found any explanation.

Answer 1

The package name "View" must be lower case. In your project, as well as in the fxml.

For more details see the method loadType of FXMLLoader.class:

private Class<?> loadType(String name, boolean cache) throws ClassNotFoundException {
    int i = name.indexOf('.');
    int n = name.length();
    while (i != -1
        && i < n
        && Character.isLowerCase(name.charAt(i + 1))) {  // <<<<<<<<<
        i = name.indexOf('.', i + 1);
    }

    if (i == -1 || i == n) {
        throw new ClassNotFoundException();
    }

    String packageName = name.substring(0, i);
    String className = name.substring(i + 1);

    Class<?> type = loadTypeForPackage(packageName, className);

    if (cache) {
        classes.put(className, type);
    }

    return type;
}