import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;


public class Calculator extends Application 
{
    // the calculator dimensions
    public static int CALC_WIDTH = 400;
    public static int CALC_HEIGHT = 300;

    // the calculator screen
    private TextField screen; 

    // the calculator buttons
    private Button button1;
    private Button button2;
    private Button button3;
    private Button button4;

    
    public static void main(String[] args) 
    {
        launch(args);
    }

    @Override
    public void start(Stage primaryStage) 
    {
        // create the calculator screen
        screen = new TextField(); 
       
        // create the buttons
        button1 = new Button("1");
        button2 = new Button("2");
        button3 = new Button("3");
        button4 = new Button("4");
        
        // attach a handler to process button clicks 
        ButtonHandler handler = new ButtonHandler();       
        button1.setOnAction(handler);
        button2.setOnAction(handler);
        button3.setOnAction(handler);
        button4.setOnAction(handler);
        
        // setup a grid panel for the keypad
        GridPane keypad = new GridPane();  
        keypad.setMinSize(CALC_WIDTH, CALC_HEIGHT); 
//        keypad.setPadding(new Insets(10, 10, 10, 10));  
//        keypad.setVgap(5); 
//        keypad.setHgap(5);       
        keypad.setAlignment(Pos.CENTER); 
        
        // attach the buttons to the keypad grid
        keypad.add(button1, 0, 0); 
        keypad.add(button2, 1, 0); 
        keypad.add(button3, 0, 1);       
        keypad.add(button4, 1, 1); 
        
        // put screen and keypad together
        BorderPane gui = new BorderPane();
        gui.setTop(screen);
        gui.setCenter(keypad);

        // set up the scene
        Scene scene = new Scene(gui); 
        primaryStage.setTitle("Calculator");
        primaryStage.setScene(scene);
        primaryStage.show();
    }
    
    // Handler for processing the button clicks 
    private class ButtonHandler implements EventHandler<ActionEvent>
    { 
       @Override 
       public void handle(ActionEvent e) 
       {
           if (e.getSource() == button1) {
               System.out.println("Button 1 Pressed");
           }
           else if (e.getSource() == button2) {
               System.out.println("Button 2 Pressed");
           }
           else if (e.getSource() == button3) {
               System.out.println("Button 3 Pressed");
           }
           else if (e.getSource() == button4) {
               System.out.println("Button 4 Pressed");
           }
       } 
    }  
}