Why is my JavaFX Controller Class not working?

JavaFX Controller Class Not Working

The provided code interfaces with a TextArea as a log. The goal is to update the TextArea's content from a separate class when needed. This requires creating a controller class that extends Initializable. However, the controller implementation isn't functioning correctly.

Solution

The code has a fundamental issue: the Application class is being used as a controller. This practice is discouraged because:

• There should only be one Application instance, but the loader often creates multiple instances.
• Referencing controller member objects can be confusing, as they differ in their field availability between the launched application and the loader-created application instance.

Additionally, it's recommended to complete the UI's basic functionality before implementing multi-threading.

Revised Code

Here's the corrected code using separate classes for the controller, the web importer, and the text logging sample:

Root.fxml

<code class="xml">...
fx:controller="textlogger.ImportController"
...</code>

ImportController.java

<code class="java">...
private WebImporter importer;
...</code>

WebImporter.java

<code class="java">...
private final TextArea textArea;
...</code>

TextLoggingSample.java (entry point)

<code class="java">...
Parent root = loader.load(
    getClass().getResourceAsStream(
            "Root.fxml"
    )
);
...</code>

Conclusion

By separating the controller class and using the proper approach for multi-threading, the application can now successfully update the TextArea from a separate class.

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