Скачать или смотреть Solving the Non-static method cannot be referred from a static context Error in JavaFX

Learn how to resolve the `Non-static method cannot be referred from a static context` error in JavaFX applications, particularly when dealing with event handling in your calculator app.
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This video is based on the question https://stackoverflow.com/q/72519125/ asked by the user 'Ruben Moons' ( https://stackoverflow.com/u/17317583/ ) and on the answer https://stackoverflow.com/a/72519294/ provided by the user 'James_D' ( https://stackoverflow.com/u/2189127/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Solving the Non-static method cannot be referred from a static context Error in JavaFX

If you're developing a JavaFX application and encounter the error Non-static method cannot be referred from a static context, you're not alone. This common issue tends to arise when trying to access instance methods from static contexts. In this guide, we will break down the problem and provide a clear solution to help you get past this hurdle so that your application can function smoothly.

Understanding the Problem

In Java, static methods belong to the class rather than to any specific instance of the class. This means that you cannot call instance methods (non-static) directly within static contexts. In your case, the error occurred when trying to call the keyPress(...) method from the MainWindow class.

Why Does This Happen?

In your code snippet, here's the problematic part:

[[See Video to Reveal this Text or Code Snippet]]

The method keyPress(...) is defined in the MainWindowController class as an instance method.

You're trying to invoke it in a static context (the static scope of the handle method in MainWindow). Hence, the Java compiler throws an error.

The Solution: Accessing Instance Methods Correctly

To resolve the issue, you need to access the keyPress(...) method through an instance of the MainWindowController. Luckily, you've already obtained this instance when you loaded the FXML. Here’s how to implement the solution:

Step-by-Step Implementation

Declare an Instance Variable for the Controller:

At the top of your MainWindow class, declare an instance variable for the MainWindowController.

[[See Video to Reveal this Text or Code Snippet]]

Initialize the Controller in the start Method:

After loading the FXML with FXMLLoader, get the controller instance and assign it to your instance variable.

[[See Video to Reveal this Text or Code Snippet]]

Call the keyPress Method Through the Controller Instance:

In your handle method, instead of trying to call keyPress directly on the class name, use the instance variable:

[[See Video to Reveal this Text or Code Snippet]]

Final Code Segment

Your MainWindow class should look like this after implementing the above modifications:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By recognizing the distinction between static and non-static contexts, you can avoid common pitfalls when programming in JavaFX. The solution provided helps you correctly reference instance methods from within static methods, ensuring that your calculator app responds accurately to user inputs from numpad keys.

If you have any further questions or run into similar issues while coding, feel free to ask. Happy coding!