//********************************************************************
//  BMIGUI.java     
//
//  Computes body mass index in a GUI.
//********************************************************************

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.DecimalFormat;

public class BMIGUI
{
   private final int WIDTH = 275;
   private final int HEIGHT = 100;
   
   DecimalFormat fmt = new DecimalFormat ("0.00");

   private JFrame frame;
   private JPanel panel;
   private JLabel heightLabel, weightLabel, BMILabel, resultLabel;
   private JTextField height, weight;
   private JButton calculate;

   //-----------------------------------------------------------------
   //  Sets up the GUI.
   //-----------------------------------------------------------------
   public BMIGUI()
   {
      frame = new JFrame ("BMI Calculator");
      frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);

      //create labels for the height and weight textfields 
      heightLabel = new JLabel ("Your height in meters:");
      weightLabel = new JLabel ("Your weight in kilograms: ");

      //create a "this is your BMI" label
      BMILabel = new JLabel ("Your BMI is ") ;
      //create a result label to hold the BMI value
      resultLabel = new JLabel ("") ;

      //create a JTextField to hold the person's height in inches
      height = new JTextField (5);
      //create a JTextField to hold the person's weight in pounds
      weight = new JTextField (5) ;
	
      //create a button to press to calculate BMI
      calculate = new JButton ("calculate BMI");
      //create a BMIListener and make it listen for the button to be pressed
      calculate.addActionListener ( new BMIListener () ) ;

      //set up the JPanel to go on the JFrame 
      panel = new JPanel();
      panel.setPreferredSize (new Dimension(WIDTH, HEIGHT));
      panel.setBackground (Color.yellow);

      //add the height label and height textfield to the panel
      panel.add (heightLabel) ;
      panel.add (height) ;
      //add the weight label and weight textfield to the panel
      panel.add (weightLabel) ;
      panel.add (weight) ;
      //add the button to the panel
      panel.add (calculate) ;
      //add the BMI label to the panel
      panel.add (BMILabel) ;
      //add the label that holds the result to the panel
      panel.add (resultLabel) ;

      //add the panel to the frame 
      frame.getContentPane().add (panel);
   }

   //-----------------------------------------------------------------
   //  Displays the primary application frame.
   //-----------------------------------------------------------------
   public void display()
   {
      frame.pack();
      frame.setVisible(true);
   }

   //*****************************************************************
   //  Represents an action listener for the calculate button.
   //*****************************************************************
   private class BMIListener implements ActionListener
   {
      //--------------------------------------------------------------
      //  Compute the BMI when the button is pressed
      //--------------------------------------------------------------
      public void actionPerformed (ActionEvent event)
      {
         String heightText, weightText;
         double heightVal, weightVal, bmi;

	 //get the text from the height and weight textfields
	 heightText = height.getText();
	 weightText = weight.getText();

	 //Use Integer.parseInt to convert the text to integer values
	 heightVal = Double.parseDouble (heightText) ;
	 weightVal = Double.parseDouble (weightText) ;

	 //Calculate the bmi = 703 * weight in pounds / (height in inches)^2
	 bmi = weightVal / (heightVal*heightVal) ;

	 //Put result in result label.  Use Double.toString to convert double to string.
	 resultLabel.setText( fmt.format(bmi) ) ;

      }
   }
}