Added tool panel and event system for check notification

+ GameEvent and GameEventListener
+ Check detection and notification in Board and BoardPanel
+ Tool panel in Chess with a restart button

src/dev/kske/chess/Board.java

@@ -1,8 +1,13 @@
 package dev.kske.chess;
 
+import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
+import dev.kske.chess.event.GameEvent;
+import dev.kske.chess.event.GameEvent.GameEventType;
+import dev.kske.chess.event.GameEventListener;
 import dev.kske.chess.piece.Bishop;
 import dev.kske.chess.piece.King;
 import dev.kske.chess.piece.Knight;
@@ -24,9 +29,12 @@ public class Board {
 	private Piece[][]				boardArr;
 	private Map<Color, Position>	kingPos;
 
+	private List<GameEventListener> gameEventListeners;
+
 	public Board() {
 		boardArr		= new Piece[8][8];
 		kingPos	= new HashMap<>();
+		gameEventListeners	= new ArrayList<>();
 		initializeDefaultPositions();
 	}
 
@@ -52,6 +60,13 @@ public class Board {
 				revert(move, capturePiece);
 				return false;
 			}
+
+			// TODO: detecting checkmate
+			// Check for check on the opposite team
+			Color oppositeColor = piece.getColor() == Color.WHITE ? Color.BLACK : Color.WHITE;
+			if (checkCheck(oppositeColor))
+				notifyListeners(new GameEvent(this, GameEventType.CHECK, oppositeColor));
+
 			return true;
 		}
 	}
@@ -80,6 +95,14 @@ public class Board {
 		return false;
 	}
 
+	public void registerGameEventListener(GameEventListener listener) {
+		gameEventListeners.add(listener);
+	}
+
+	private void notifyListeners(GameEvent evt) {
+		gameEventListeners.forEach(listener -> listener.onGameEvent(evt));
+	}
+
 	public Piece get(Position pos) {
 		return boardArr[pos.x][pos.y];
 	}
@@ -107,7 +130,7 @@ public class Board {
 	/**
 	 * Initialized the board array with the default chess pieces and positions.
 	 */
-	private void initializeDefaultPositions() {
+	public void initializeDefaultPositions() {
 		// Initialize pawns
 		for (int i = 0; i < 8; i++) {
 			boardArr[i][1]	= new Pawn(Color.BLACK, this);
@@ -143,6 +166,11 @@ public class Board {
 		boardArr[2][7]	= new Bishop(Color.WHITE, this);
 		boardArr[5][0]	= new Bishop(Color.BLACK, this);
 		boardArr[5][7]	= new Bishop(Color.WHITE, this);
+
+		// Clear all other tiles
+		for (int i = 0; i < 8; i++)
+			for (int j = 2; j < 6; j++)
+				boardArr[i][j] = null;
 	}
 
 	/**

src/dev/kske/chess/BoardPanel.java

@@ -13,8 +13,11 @@ import java.io.File;
 import java.util.HashMap;
 import java.util.Map;
 
+import javax.swing.JOptionPane;
 import javax.swing.JPanel;
 
+import dev.kske.chess.event.GameEvent;
+import dev.kske.chess.event.GameEventListener;
 import dev.kske.chess.piece.Piece;
 
 /**
@@ -27,7 +30,7 @@ import dev.kske.chess.piece.Piece;
  * this must be added to a parent component that allows the child to decide the
  * size.
  */
-public class BoardPanel extends JPanel {
+public class BoardPanel extends JPanel implements GameEventListener {
 
 	private static final long serialVersionUID = 6771148331334310216L;
 
@@ -37,14 +40,11 @@ public class BoardPanel extends JPanel {
 
 	private Board board;
 
-	static {
-		loadPieceTextures();
-	}
-
 	public BoardPanel(Board board) {
 		this();
 		setSize(getPreferredSize());
 		setBoard(board);
+		if (textures == null) loadPieceTextures();
 	}
 
 	public BoardPanel() {
@@ -99,6 +99,23 @@ public class BoardPanel extends JPanel {
 					g.drawImage(getPieceTexture(board.getBoardArr()[i][j]), i * tileSize, j * tileSize, this);
 	}
 
+	@Override
+	public void onGameEvent(GameEvent evt) {
+		switch (evt.getEventType()) {
+			case CHECK:
+				JOptionPane.showMessageDialog(this, evt.getColor().toString() + " in check!");
+				break;
+		}
+	}
+
+	/**
+	 * Reverts the board to its initial state
+	 */
+	public void reset() {
+		board.initializeDefaultPositions();
+		repaint();
+	}
+
 	/**
 	 * Load every PNG file inside the res/pieces directory.
 	 * The filenames without extensions are used as keys in the map textures.
@@ -140,5 +157,10 @@ public class BoardPanel extends JPanel {
 
 	public Board getBoard() { return board; }
 
-	public void setBoard(Board board) { this.board = board; }
+	public void setBoard(Board board) {
+		this.board = board;
+
+		// Register this BoardPanel as a GameEventListener to the board
+		board.registerGameEventListener(this);
+	}
 }

src/dev/kske/chess/Chess.java

@@ -3,7 +3,9 @@ package dev.kske.chess;
 import java.awt.BorderLayout;
 import java.awt.EventQueue;
 
+import javax.swing.JButton;
 import javax.swing.JFrame;
+import javax.swing.JPanel;
 
 
 /**
@@ -46,13 +48,19 @@ public class Chess {
 	private void initialize() {
 		mframe = new JFrame();
 		mframe.setResizable(false);
-		mframe.setBounds(100, 100, 729, 737);
+		mframe.setBounds(100, 100, 494, 565);
 		mframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
 		BoardPanel boardPanel = new BoardPanel(new Board());
 		boardPanel.setLayout(null);
 		mframe.getContentPane().add(boardPanel, BorderLayout.CENTER);
+
+		JPanel toolPanel = new JPanel();
+		mframe.getContentPane().add(toolPanel, BorderLayout.NORTH);
+
+		JButton btnRestart = new JButton("Restart");
+		btnRestart.addActionListener((evt) -> boardPanel.reset());
+		toolPanel.add(btnRestart);
 		mframe.pack();
 	}
-
 }

src/dev/kske/chess/event/GameEvent.java

@@ -0,0 +1,38 @@
+package dev.kske.chess.event;
+
+import java.util.EventObject;
+
+import dev.kske.chess.Board;
+import dev.kske.chess.piece.Piece.Color;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>GameEvent.java</strong><br>
+ * Created: <strong>03.07.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public class GameEvent extends EventObject {
+
+	private static final long serialVersionUID = -6783035746521826589L;
+
+	private final Board			source;
+	private final GameEventType	eventType;
+	private final Color			color;
+
+	public GameEvent(Board source, GameEventType eventType, Color color) {
+		super(source);
+		this.source		= source;
+		this.eventType	= eventType;
+		this.color		= color;
+	}
+
+	public Board getSource() { return source; }
+
+	public GameEventType getEventType() { return eventType; }
+
+	public Color getColor() { return color; }
+
+	public static enum GameEventType {
+		CHECK, CHECKMATE
+	}
+}

src/dev/kske/chess/event/GameEventListener.java

@@ -0,0 +1,12 @@
+package dev.kske.chess.event;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>GameEventListener.java</strong><br>
+ * Created: <strong>03.07.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public interface GameEventListener {
+
+	void onGameEvent(GameEvent evt);
+}