Is there a generic way of passing FXML controller references as parameters to a method?

Question

I'm writing an app that will have many data entry windows, each of which has a label for system messages.

I have a GenUtil class for common methods, one of which sets the system message in the controller that called the method.

Setting a system message works if I pass the controller reference to the method ie.

Create a reference to the data entry window controller when the FXML is loaded:

deWindowController = loader.getController();

In the data entry window controller:

genUtil.setSystemMessage(this);

In GenUtil:

public void setSystemMessage(FXMLDEWindowController deWindowController) {

    deWindowController.lblSysMsg.setText("setting the message");

}

However, the setSystemMessage method will be called from many FXML controllers I can't figure out how to "genericise" this process ie.

1) What goes in the method's parameter:

public void setSystemMessage(**<WHAT_GOES_HERE?>** controllerRef) {

2) Assuming the system message label IDs are all lblSysMsg, can I use controllerRef in the same way as before to set a message label?

I could include references to all of the controllers in the GenUtil class and in each of the controllers, pass a string containing the data entry window name when I call the setSystemMessage method. That way I could manually work out which controller to use. However, I'm trying to avoid that.

Can anyone help please?

I'm using JavaSE8 and NetBeans8.2.

Answer 1

You should not provide direct access to fields. This would allow a user of the class to do with the field including setting it to null or modifying properties other than the text property.

Declare a setSystemMessage method in a common supertype of the controller. If all of the controllers contain the same field, a abstract class would be a good choice to avoid repetition but you could also use a interface.

Use this supertype as the type of the controllerRef parameter:

public void setSystemMessage(SuperType controllerRef) {
    controllerRef.setSystemMessage("setting the message");
}

public abstract class SuperType {
    @FXML
    private Label lblSysMsg;

    public void setSystemMessage(String message) {
        lblSysMsg.setText(message);
    }
}