Using JButtons in Frame-based Applications

Dharmesh Tailor's Random Numbers Guessing Game is a well-commented useful demonstration of the use of JButtons, JLabels and JTextFields in GUI applications. Note how he adds components to a FlowLayout instead of to a Box. We needed to remove the instruction gui.setResizable(False) in order to make the application work on our Raspberry Pi.

Application in action

You can compare this Oxygene code with the RemObjects C# version below it.

The code in jbutton_app.pas

namespace jbutton_app;
{
    Author: Dharmesh Tailor
    Application: Random Numbers Guessing Game
}
interface

uses
  java.awt.*, java.awt.event.*, javax.swing.*;

type
  JButtonApp = public class(JFrame, ActionListener)
  private      
    button : JButton;
    textField : JTextField;
    promptLabel, resultLabel, randomLabel : JLabel;

  public
    constructor;
    class method Main(args : array of String);
    method actionPerformed(e : ActionEvent);
  end;

implementation

constructor JButtonApp;
begin
  {Sets the layout - FlowLayout is the most simple where components
  are arranged one after the other. Will write a program to demonstrate
  GridLayout later.}
  setLayout(new FlowLayout);

  promptLabel := new JLabel('Enter a random number 1-10');
  add(promptLabel);

  textField := new JTextField(5);
  add(textField);

  button := new JButton('Guess!');
  button.addActionListener(self);
  add(button);

  resultLabel := new JLabel('');
  add(resultLabel);

  randomLabel := new JLabel('');
  add(randomLabel);
end;

method JButtonApp.actionPerformed(e : ActionEvent);
var
  randomNum, guess : Integer;
begin
  if e.getSource = button then
    begin
      //Generates a random number between 1 and 10
      randomNum := Integer(Math.random * 10 + 1);
      try
        //Takes the input from the textfield and tries to parse it
        guess := Integer(Double.parseDouble(textField.getText));

        if guess = randomNum then
          begin
            resultLabel.setText('You won the game!');
          end
        else
          begin
            resultLabel.setText('You lost the game. ');
          end;
        randomLabel.setText('The random number generated was: ' + randomNum);
      //If the textfield input is invalid, i.e. not a number
      except
        on Exception do
          begin
            randomLabel.setText('Please enter numbers only!');
          end;
      end;
    end;
end;

class method JButtonApp.Main(args : array of String);
begin
  var gui : JButtonApp := new JButtonApp;
  gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  gui.setVisible(True);
  gui.setSize(350, 100);
  gui.setResizable(False);
  gui.setTitle('Random Number Guessing Game');
end;

end.

The code of jbutton_app.oxygene

<?xml version="1.0" encoding="utf-8"?>
<Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003" ToolsVersion="4.0">
  <PropertyGroup>
    <OutputType>Executable</OutputType>
  </PropertyGroup>
  <ItemGroup>
    <Reference Include="rt.jar" />
  </ItemGroup>
  <ItemGroup>
    <Compile Include="jbutton_app.pas" />
  </ItemGroup>
  <Import Project="$(MSBuildExtensionsPath)\RemObjects Software\Oxygene\RemObjects.Oxygene.Cooper.targets" />
</Project>

RemObjects C# Version of Random Numbers Guessing Game

/*
   Author of original Oxygene version: Dharmesh Tailor
   Application: Random Numbers Guessing Game
   Converted to RemObjects C# by Norman Morrison 
*/

using java.util;
using java.awt;
using java.awt.@event;
using javax.swing;

namespace jbutton_app_cs
{
  public class JButtonApp  : JFrame, ActionListener
  { 
    private JButton button;
    private JTextField textField;
    private JLabel promptLabel, resultLabel, randomLabel;
    public JButtonApp()
    {
      /* 
      Sets the layout - FlowLayout is the most simple where components
      are arranged one after the other. Will write a program to demonstrate
      GridLayout later.
      */
      setLayout(new FlowLayout());

      promptLabel = new JLabel("Enter a random number 1-10");
      add(promptLabel);

      textField = new JTextField(5);
      add(textField);

      button = new JButton("Guess!");
      button.addActionListener(this);
      add(button);

      resultLabel = new JLabel("");
      add(resultLabel);

      randomLabel = new JLabel("");
      add(randomLabel);
    }

    public void actionPerformed(ActionEvent e)
    {
      Integer randomNum, guess;

      if (e.getSource() == button) 
      {
        //Generates a random number between 1 and 10
        randomNum = (Integer)(Math.random() * 10 + 1);
        try
        {
          //Takes the input from the textfield and tries to parse it
          guess = (Integer)(Double.parseDouble(textField.getText()));

          if (guess == randomNum)
            resultLabel.setText("You won the game!");
          else
            resultLabel.setText("You lost the game. ");
          randomLabel.setText("The random number generated was: " + randomNum);
        }
        
        catch (Exception) //If the textfield input is invalid, i.e. not a number
        {
          randomLabel.setText("Please enter numbers only!");
        }
      }
    }

    public static void Main(string[] args)
    {
      JButtonApp gui = new JButtonApp();
      gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      gui.setVisible(true);
      gui.setSize(350, 100);
      gui.setResizable(false);
      gui.setTitle("Random Number Guessing Game");
    }
  }
}