How can I enable a Dialog's button from an event handler method?

[Jesse Duncan]

I'm trying to learn a sprinkling of JavaFx to test the backend code of a personal project I am working on. At the moment I am trying to create a simple login dialog. I want to disable the 'ok' button until all the input fields contain valid data. I have knocked together a little example to demonstrate what I want.

For context, this is how I create the dialog:

@FXML
public void buttonClicked() throws Exception {
    URL url = getClass().getClassLoader().getResource(DIALOG);
    FXMLLoader loader = new FXMLLoader(url);
    if (url == null) {
        throw new RuntimeException("Can't load fxml");
    }
    Parent root = loader.load();

    Dialog<ButtonType> dialog = new Dialog<>();
    dialog.getDialogPane().setContent(root);
    dialog.getDialogPane().getButtonTypes().addAll(ButtonType.CANCEL, ButtonType.OK);
    dialog.getDialogPane().lookupButton(ButtonType.OK).setDisable(true);
    dialog.showAndWait();
}

and this is the fxml:

<DialogPane fx:controller="sample.Controller" xmlns="http://javafx.com/javafx/10.0.2-internal" xmlns:fx="http://javafx.com/fxml/1">
   <content>
      <TextField fx:id="textField" onKeyReleased="#validateInput"/>
   </content>
</DialogPane>

My issue is enabling the button once the input it valid. I have another method 'validateInput()' to check if the TextField contains valid data.

@FXML
public void validateInput() {
    String text;
    if (textField != null) {
        text = textField.getText();
        if (!text.isBlank()) {
            //re-enable the ok button here
        }
    }
}

I tried creating a field for the DialogPane, but calling lookUpButton(ButtonType.OK) always returns null. I also tried using a Dialog<ButtonType> field and then setting it to the Dialog object I create in buttonClicked(), instead of a local variable:

myDialogField = new Dialog<>();
dialog.getDialogPane().setContent(root);
dialog.getDialogPane().getButtonTypes().addAll(ButtonType.CANCEL, ButtonType.OK);
dialog.getDialogPane().lookupButton(ButtonType.OK).setDisable(true);
dialog.showAndWait();

The field is always null from the validateInput() method, however.

I'm more or less shooting in the dark here. There is a lot to JavaFx which I will have to get to grips with
How can I enable the button from the validateInput() method?

[Victor Apocalypse Rodrigues]

I hope you've already found a way to do this, but if not, here it goes:

You need to bind the property of the OK button to a BooleanBinding:

    Dialog<ButtonType> dialog = new Dialog<>();
    dialog.getDialogPane().setContent(root);
    dialog.getDialogPane().getButtonTypes().addAll(ButtonType.CANCEL, ButtonType.OK);
    dialog.getDialogPane().lookupButton(ButtonType.OK).setDisable(true);

    YourDialogController controller = loader.getController(); // replace with your controller class name here
    dialog.getDialogPane().lookupButton(ButtonType.OK).disableProperty().bind(
        Bindings.createBooleanBinding(
            () -> controller.getTextField().textProperty().getValue().isBlank(), // create a getter for your text field in your controller
            controller.getTextField().textProperty()
        )
    );

[Campbell Ritchie]

VAR: welcome to the Ranch

[Lou Hamers]

I started a more elaborate reply before I saw the age of the first post and realized that the OP is probably an expert by now. I guess 4 years late is better than never! Don't think I was active back then or I'd have definitely replied.

We do need some new blood injected in here, are visitors not posting because it looks inactive?

Thanks for the activity though Victor. Good to see new JFX users around.