NumberPanel.java

package gui;

import java.awt.Color;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JPanel;

import controller.NumListener;

/**
 * JPanel for the number buttons plus comma
 *
 */
public class NumberPanel extends JPanel {

	/**
	 * 
	 */
	private static final long serialVersionUID = 4992174666314388065L;

	// array for the number buttons
	private JButton[] numericButtons;

	// The action listener common to all number buttons
	private NumberHandler numberListener;

	// Create the GridbagConstraints for the layout
	private GridBagConstraints gc = new GridBagConstraints();

	/**
	 * Constructor for the number panel
	 * 
	 * @param controller
	 *            reference to the main controller that is needed for the action
	 *            listener.
	 */
	public NumberPanel(NumListener controller) {

		numberListener = new NumberHandler(controller);

		// Create the actual buttons
		createNumericButtons();

		// Add the Layout manager
		GridBagLayout gBL = new GridBagLayout();
		gBL.columnWidths = new int[] { 0 };
		gBL.rowHeights = new int[] { 0 };
		gBL.columnWeights = new double[] { Double.MIN_VALUE };
		gBL.rowWeights = new double[] { Double.MIN_VALUE };
		setLayout(gBL);

		// Add the Buttons to the panel
		setupButtons();

		validate();
	}

	/**
	 * Adds the buttons to the panel.
	 * 
	 * The panel uses a GridBagLayout to arrange the buttons in rows and columns
	 */
	private void setupButtons() {

		// Common for all grid cells
		gc.weightx = 1;
		gc.weighty = 1;
		gc.fill = GridBagConstraints.BOTH;

		// Numeric buttons
		// Individual properties per button
		for (int row = 0; row <= 2; row++) {
			for (int col = 0; col <= 2; col++) {
				addButton(col, row, 1, 1, numericButtons[(7 - row * 3) + col]);
			}
		}
		// Zero Button - spans 2 columns
		addButton(0, 3, 2, 1, numericButtons[GuiConstants.NB_ZERO]);

		// Decimal Button - spans 1 column
		addButton(2, 3, 1, 1, numericButtons[GuiConstants.NB_PERIOD]);
	}

	/**
	 * Creates the array of JButton elements and assigns the action listener
	 */
	private void createNumericButtons() {
		numericButtons = new JButton[11];
		for (int i = 0; i <= 9; i++) {
			numericButtons[i] = createButton(Integer.toString(i),
					Integer.toString(i), GuiConstants.COL_NUMBER,
					numberListener);
		}

		numericButtons[GuiConstants.NB_PERIOD] = createButton(".", ".",
				GuiConstants.COL_NUMBER, numberListener);
	}

	/**
	 * Helper routine to add the buttons to the panel
	 * 
	 * @param gridx
	 *            the x-position (column) in the grid
	 * @param gridy
	 *            the y-position (row) in the grid
	 * @param gridwidth
	 *            the column span
	 * @param gridheight
	 *            the row span
	 * @param button
	 *            the actual button object to be added to the panel
	 */
	private void addButton(int gridx, int gridy, int gridwidth, int gridheight,
			JButton button) {
		gc.gridx = gridx;
		gc.gridy = gridy;
		gc.gridwidth = gridwidth;
		gc.gridheight = gridheight;
		add(button, gc);
	}

	/**
	 * Helper routine to create and pre-set a JButton
	 * 
	 * @param label
	 *            the label on the button
	 * @param cmd
	 *            the ActionCommand of the button (a String that is evaluated by
	 *            the action listener)
	 * @param color
	 *            the button color
	 * @param actionListener
	 *            the action listener
	 * @return a pre-configured JButton
	 */
	private JButton createButton(String label, String cmd, Color color,
			ActionListener actionListener) {
		JButton btn = new JButton(label);
		btn.setActionCommand(cmd);
		btn.setBackground(color);
		if (actionListener != null) {
			btn.addActionListener(actionListener);
		}
		return btn;
	}

}

OperationPanel.java

package gui;

import java.awt.Color;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JPanel;

import controller.CmdListener;

/**
 * The JPanel for the operation buttons
 *
 */
public class OperationPanel extends JPanel {

	/**
	 * 
	 */
	private static final long serialVersionUID = -1305333779778055422L;

	// Create the GridbagConstraints for the layout
	private GridBagConstraints gc = new GridBagConstraints();

	// Array for the operation buttons
	private JButton[] operationButtons;
	// Array for the auxiliary buttons
	private JButton[] auxButtons;

	// The action listener common to all buttons
	private CmdHandler cmdHandler;

	/**
	 * Constructor for the Operation Panel
	 * 
	 * @param controller
	 *            reference to the main controller that is needed for the action
	 *            listener.
	 */
	public OperationPanel(CmdListener controller) {

		cmdHandler = new CmdHandler(controller);

		createOperatorButtons();
		createAuxButtons();

		// Add the Layout manager
		GridBagLayout gBL = new GridBagLayout();
		gBL.columnWidths = new int[] { 0 };
		gBL.rowHeights = new int[] { 0 };
		gBL.columnWeights = new double[] { Double.MIN_VALUE };
		gBL.rowWeights = new double[] { Double.MIN_VALUE };
		setLayout(gBL);

		// Add the Buttons to the panel
		setupButtons();

	}

	/**
	 * Adds the pre-created buttons to the panel
	 */
	private void setupButtons() {

		// Common for all grid cells
		gc.weightx = 1;
		gc.weighty = 1;
		gc.fill = GridBagConstraints.BOTH;

		// Auxiliary Buttons - C
		addButton(0, 0, 1, 1, auxButtons[GuiConstants.AB_CE]);

		// Auxiliary Buttons - CE
		addButton(1, 0, 1, 1, auxButtons[GuiConstants.AB_C]);

		// Auxiliary Buttons - Enter
		addButton(0, 4, 2, 1, auxButtons[GuiConstants.AB_ENTER]);

		// Operator Buttons
		for (int row = 0; row <= 2; row++) {
			for (int col = 0; col <= 1; col++) {
				addButton(col, 1 + row, 1, 1, operationButtons[(2 - row) * 2
						+ col]);
			}
		}
	}

	/**
	 * Creates the operation (+, -, *, /, +/-, 1/x) buttons
	 */
	private void createOperatorButtons() {
		operationButtons = new JButton[6];
		// "+" Button
		operationButtons[GuiConstants.OP_ADD] = createButton("+", "+",
				GuiConstants.COL_OPERATION, cmdHandler);

		// "-" Button
		operationButtons[GuiConstants.OP_SUB] = createButton("-", "-",
				GuiConstants.COL_OPERATION, cmdHandler);

		// "*" Button
		operationButtons[GuiConstants.OP_MUL] = createButton("*", "*",
				GuiConstants.COL_OPERATION, cmdHandler);

		// "/" Button
		operationButtons[GuiConstants.OP_DIV] = createButton("/", "/",
				GuiConstants.COL_OPERATION, cmdHandler);

		// "1/x" Button
		operationButtons[GuiConstants.OP_INV] = createButton("1/x", "INV",
				GuiConstants.COL_OPERATION, cmdHandler);

		// "+/-" Button
		operationButtons[GuiConstants.OP_SGN] = createButton("+/-", "SGN",
				GuiConstants.COL_OPERATION, cmdHandler);

	}

	/**
	 * Creates the auxiliary buttons (Enter, Backspace, Clear)
	 */
	private void createAuxButtons() {
		auxButtons = new JButton[3];

		// "Enter" Button
		auxButtons[GuiConstants.AB_ENTER] = createButton("Enter", "Enter",
				GuiConstants.COL_ENTER, cmdHandler);

		// "C" Button
		auxButtons[GuiConstants.AB_C] = createButton("C", "C",
				GuiConstants.COL_AUX, cmdHandler);

		// "CE" Button
		auxButtons[GuiConstants.AB_CE] = createButton("\u2190", "CE",
				GuiConstants.COL_AUX, cmdHandler);

	}

	/**
	 * Helper routine to add the buttons to the panel
	 * 
	 * @param gridx
	 *            the x-position (column) in the grid
	 * @param gridy
	 *            the y-position (row) in the grid
	 * @param gridwidth
	 *            the column span
	 * @param gridheight
	 *            the row span
	 * @param button
	 *            the actual button object to be added to the panel
	 */
	private void addButton(int gridx, int gridy, int gridwidth, int gridheight,
			JButton button) {
		gc.gridx = gridx;
		gc.gridy = gridy;
		gc.gridwidth = gridwidth;
		gc.gridheight = gridheight;
		add(button, gc);
	}

	/**
	 * Helper routine to create and pre-set a JButton
	 * 
	 * @param label
	 *            the label on the button
	 * @param cmd
	 *            the ActionCommand of the button (a String that is evaluated by
	 *            the action listener)
	 * @param color
	 *            the button color
	 * @param actionListener
	 *            the action listener
	 * @return a pre-configured JButton
	 */
	private JButton createButton(String label, String cmd, Color color,
			ActionListener actionListener) {
		JButton btn = new JButton(label);
		btn.setActionCommand(cmd);
		btn.setBackground(color);
		if (actionListener != null) {
			btn.addActionListener(actionListener);
		}
		return btn;
	}

}