如何将按钮添加到另一个类

Question

I have a class called Restaurant, that has an FXML file, in that class, I have a button that when pressed opens another window called tables, that also has an FXML file, I have a minimize button in tables window.

What I want is when I press the minimize button in table, a new button will be added to the Restaurant window.

But I'm getting a null exception. Can someone help me solve this.

This is the code for my minimize button:

@FXML
public void minimiza(ActionEvent event) {
     Button Tables = new Button("Mesas");
    try {
        Stage mesa = (Stage) ((Button) event.getSource()).getScene().getWindow();
        mesa.setIconified(true);
        FXMLLoader loader = new FXMLLoader();
        RestauranteController controle = loader.getController();
        controle.adicionaBotao(Tables);
    } catch (Exception e) {
        System.out.println("Not working " + e.getMessage());
    }
}

Answer 1

It's probably better to just listen to the iconified property of the Stage from the Restaurant class. If the minimized state does not match the iconified state, you could create this property in the controller for the tables window yourself.

private int windowCount;

@Override
public void start(Stage primaryStage) {

    Button btn = new Button("Show new Window");
    VBox buttonContainer = new VBox(btn);

    btn.setOnAction((ActionEvent event) -> {
        // create new window
        windowCount++;
        Label label = new Label("Window No " + windowCount);
        Stage stage = new Stage();
        Scene scene = new Scene(label);
        stage.setScene(scene);

        // button for restoring from main scene
        Button restoreButton = new Button("Restore Window " + windowCount);

        // restore window on button click
        restoreButton.setOnAction(evt -> {
            stage.setIconified(false);
        });

        // we rely on the minimize button of the stage here

        // listen to the iconified state to add/remove button form main window
        stage.iconifiedProperty().addListener((observable, oldValue, newValue) -> {
            if (newValue) {
                buttonContainer.getChildren().add(restoreButton);
            } else {
                buttonContainer.getChildren().remove(restoreButton);
            }
        });
        stage.show();
    });


    Scene scene = new Scene(buttonContainer, 200, 200);

    primaryStage.setScene(scene);
    primaryStage.show();
}

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BTW: Note that without loading a fxml, FXMLLoader will never create a controller instance, let alone without the fxml being specified. Furthermore under no circumstances would it return the same controller instance as the one used with your Restaurant window.