how to call onAction(ActionEvent event) method in javafx

I am having a problem in javafx when calling onAction(ActionEvent event) method in initialize() method.

This is javafx code:

public class MainViewController implements Initializable {

    @FXML
    private Label lblHeading;

    @Override
    public void initialize(URL url, ResourceBundle rb) {
        btnLoginUserOnAction(null);
    }

    @FXML
    private void btnLoginUserOnAction(ActionEvent event) {
        String getId = ((Button) event.getSource()).getText();
        lblHeading.setText(getId);
    }

}

How i call btnLoginUserOnAction(ActionEvent event) in initialize(URL url, ResourceBundle rb). If i pass null to ActionEvent parameter then i shows execption because Event us null.

Any help???

After exploring the issue and considering the comments provided by other users, here’s the solution and explanation:

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The Problem:

In JavaFX, the ActionEvent parameter in an onAction method cannot be null if you're trying to retrieve information from the event, such as the source button. If you call the method with null, attempting to access event.getSource() will result in a NullPointerException.

The issue arises because you want to programmatically trigger the same logic defined in the onAction method, but without user interaction.

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Solution:

Instead of directly calling the btnLoginUserOnAction(null) method, you can achieve this in two professional ways:

1. Preferred Method: Use button.fire() If you have access to the Button (via @FXML injection or lookup), the fire() method is the cleanest way to simulate a button click. It programmatically triggers the onAction handler.

   @FXML
   private Button btnLoginUser; // Inject the button
   
   @Override
   public void initialize(URL url, ResourceBundle rb) {
       // Simulate a button click
       btnLoginUser.fire();
   }
   
   @FXML
   private void btnLoginUserOnAction(ActionEvent event) {
       String getId = ((Button) event.getSource()).getText();
       lblHeading.setText(getId);
   }
   

2. Alternative: Manually Create and Pass an ActionEvent If the button reference is not directly available, you can create an ActionEvent and pass it to the method. Ensure you set the correct source to avoid runtime errors.

   @FXML
   private Button btnLoginUser;
   
   @Override
   public void initialize(URL url, ResourceBundle rb) {
       // Manually create an ActionEvent
       ActionEvent event = new ActionEvent(btnLoginUser, null);
       btnLoginUserOnAction(event);
   }
   
   @FXML
   private void btnLoginUserOnAction(ActionEvent event) {
       if (event == null || event.getSource() == null) {
           System.out.println("ActionEvent or its source is null!");
           return;
       }
   
       String getId = ((Button) event.getSource()).getText();
       lblHeading.setText(getId);
   }
   

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Acknowledgments:

Thanks to the insightful comments that guided the solution:

1. @kleopatra: Suggested focusing on how buttons should work in JavaFX and the importance of learning best practices.
2. @fabian: Highlighted that creating an ActionEvent manually requires access to the button and that navigating the scene graph for the button is not ideal.
3. @SaiDandem: Asked whether buttons are predefined or dynamically loaded, helping clarify the problem.

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Key Takeaways:

• Use Button.fire() whenever possible—it’s designed for this use case and is clean and efficient.
• Avoid passing null to methods that expect an event unless you’ve handled the null scenario explicitly.
• Always design your JavaFX application to follow best practices, ensuring readability and maintainability.

I hope this explanation and solution help others facing a similar problem. Thanks again to the community for their valuable insights!