/*
    InClassGUI1.java
    CIS 160
    2014-10-28
    David Klick

    Demonstration of a GUI including a button listener.
    This GUI computes the average of three numbers.
*/

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class InClassGUI1 extends JFrame implements ActionListener {
    // Create globals so widgets can be referenced in two methods.
    private JLabel lblResult = new JLabel("Result");
    private JTextField txt1 = new JTextField("");
    private JTextField txt2 = new JTextField("");
    private JTextField txt3 = new JTextField("");
    
    // Create an object out of ourself when program starts.
    public static void main(String[] args) {
        new InClassGUI1();
    }
    
    // Create thread to setup GUI when the EDT has time.
    public InClassGUI1() {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
    
    // This method sets up the GUI and displays it.
    public void createAndShowGUI() {
        // Create containers.
        Container c = getContentPane();
        JPanel pnlCenter = new JPanel();
        JPanel pnlSouth = new JPanel();
        
        // Set layout managers.
        c.setLayout(new BorderLayout());
        pnlCenter.setLayout(new GridLayout(3, 2));
        pnlSouth.setLayout(new FlowLayout());
        
        // Create widgets.
        JButton btnCalc = new JButton("Calc Avg");
        JLabel lbl1 = new JLabel("Score 1");
        JLabel lbl2 = new JLabel("Score 2");
        JLabel lbl3 = new JLabel("Score 3");
        
        // Add listener to widget.
        btnCalc.addActionListener(this);
        
        // Add widgets to containers.
        pnlCenter.add(lbl1);
        pnlCenter.add(txt1);
        pnlCenter.add(lbl2);
        pnlCenter.add(txt2);
        pnlCenter.add(lbl3);
        pnlCenter.add(txt3);
        pnlSouth.add(lblResult);
        c.add(btnCalc, BorderLayout.NORTH);
        c.add(pnlCenter, BorderLayout.CENTER);
        c.add(pnlSouth, BorderLayout.SOUTH);
        
        // Set close operation and display GUI.
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        pack();
        setVisible(true);
    }
    
    // This method handles clicks on the Calc button.
    public void actionPerformed(ActionEvent e) {
        try{
            // Get text from text fields and convert to double values.
            double n1 = Double.parseDouble(txt1.getText());
            double n2 = Double.parseDouble(txt2.getText());
            double n3 = Double.parseDouble(txt3.getText());
            
            // Calculate average of three numbers from text fields.
            double avg = (n1 + n2 + n3) / 3.0;
            
            // Format and display the average in the result label.
            String result = String.format("%.2f", avg);
            lblResult.setText(result);
            
        } catch (NumberFormatException e2) {
            // Display an error message if input doesn't parse.
            lblResult.setText("Error");
        }
    }
}