Some UI improvements

src/main/java/ultimatetictactoe/view/TicTacToeView.java

@@ -21,6 +21,7 @@ public class TicTacToeView {
         for (int i = 0; i < 9; i++) {
             var btn = new Button("");
             btn.setEnabled(false);
+            btn.setBackground(Color.GRAY);
             btn.setActionCommand(Integer.toString(i));
             btn.addActionListener(e -> {
                 viewModel.onButtonClicked(Integer.parseInt(e.getActionCommand()));
@@ -45,12 +46,14 @@ public class TicTacToeView {
     public void activate(List<Integer> btnIds) {
         for (Integer btnId : btnIds) {
             this.buttons[btnId].setEnabled(true);
+            this.buttons[btnId].setBackground(Color.GREEN);
         }
     }
 
     public void deactivate() {
         for (Button button : buttons) {
             button.setEnabled(false);
+            button.setBackground(Color.GRAY);
         }
     }
 
@@ -58,9 +61,12 @@ public class TicTacToeView {
         this.view.removeAll();
         this.view.setLayout(new BorderLayout());
         Button winnerLabel = new Button(finishString);
+        winnerLabel.setEnabled(false);
         Font font = new Font(Font.SANS_SERIF, Font.BOLD, 15);
         winnerLabel.setFont(font);
-        this.view.add(winnerLabel);
+        this.view.add(winnerLabel, BorderLayout.CENTER);
+        this.view.validate();
+        this.view.repaint();
     }
 
 }

src/main/java/ultimatetictactoe/view/UltimateTicTacToeView.java

@@ -1,5 +1,6 @@
 package ultimatetictactoe.view;
 
+import ultimatetictactoe.model.Player;
 import ultimatetictactoe.viewmodel.TicTacToePanelViewModel;
 import ultimatetictactoe.viewmodel.UltimateTicTacToePanelViewModel;
 
@@ -10,6 +11,7 @@ import java.awt.*;
 public class UltimateTicTacToeView extends JFrame {
 
     private final UltimateTicTacToePanelViewModel viewModel;
+    private final Label currentPlayerLabel;
 
     public UltimateTicTacToeView(UltimateTicTacToePanelViewModel viewModel) {
         super("Ultimate TicTacToe");
@@ -17,26 +19,45 @@ public class UltimateTicTacToeView extends JFrame {
         this.setDefaultCloseOperation(EXIT_ON_CLOSE);
 
         //Create and set up the window.
-        this.setLayout(new GridLayout(3, 3, 2, 2));
+        this.getContentPane().setLayout(new BorderLayout());
 
+        JPanel mainGamePane = new JPanel();
+        this.getContentPane().add(mainGamePane, BorderLayout.CENTER);
+        mainGamePane.setLayout(new GridLayout(3, 3, 2, 2));
         for (int i = 0; i < 9; i++) {
             TicTacToePanelViewModel subViewModel = viewModel.getSubGameViewModel(i);
-            this.add(new TicTacToeView(subViewModel).getView());
+            mainGamePane.add(new TicTacToeView(subViewModel).getView());
         }
 
+        this.currentPlayerLabel = new Label();
+        this.getContentPane().add(this.currentPlayerLabel, BorderLayout.NORTH);
+
         this.viewModel.setGameResultCallback(this::setGameResult);
+        this.viewModel.setCurrentPlayerCallback(this::setCurrentPlayer);
 
         //Display the window.
-        this.setSize(new Dimension(500, 500));
+        this.setSize(new Dimension(500, 520));
         this.setVisible(true);
     }
 
     public void setGameResult(String resultText) {
-        this.removeAll();
+        this.getContentPane().removeAll();
-        this.setLayout(new BorderLayout());
+
+        this.getContentPane().setLayout(new BorderLayout());
         Button winnerLabel = new Button(resultText);
         Font font = new Font(Font.SANS_SERIF, Font.BOLD, 15);
         winnerLabel.setFont(font);
-        this.add(winnerLabel);
+
+        this.getContentPane().add(winnerLabel);
+        this.getContentPane().validate();
+        this.getContentPane().repaint();
+    }
+
+    public void setCurrentPlayer(Player player) {
+        if (player == Player.O) {
+            this.currentPlayerLabel.setText("Current player: O");
+        } else if (player == Player.X) {
+            this.currentPlayerLabel.setText("Current player: X");
+        }
     }
 }

src/main/java/ultimatetictactoe/viewmodel/UltimateTicTacToePanelViewModel.java

@@ -1,6 +1,7 @@
 package ultimatetictactoe.viewmodel;
 
 import ultimatetictactoe.model.GameState;
+import ultimatetictactoe.model.Player;
 import ultimatetictactoe.model.TicTacToeGame;
 import ultimatetictactoe.model.UltimateTicTacToe;
 
@@ -12,6 +13,7 @@ public class UltimateTicTacToePanelViewModel {
     private final TicTacToePanelViewModel[] subGameViewModels;
     private final UltimateTicTacToe ultimateTicTacToe;
     private Consumer<String> gameResultCallback;
+    private Consumer<Player> currentPlayerCallback;
 
     public UltimateTicTacToePanelViewModel() {
         this.subGameViewModels = new TicTacToePanelViewModel[9];
@@ -34,6 +36,7 @@ public class UltimateTicTacToePanelViewModel {
         final int fieldId = this.ultimateTicTacToe.getActiveField();
         final List<Integer> availableFields = this.ultimateTicTacToe.getSubGame(fieldId).getAvailableFields();
         this.subGameViewModels[fieldId].activate(availableFields);
+        this.currentPlayerCallback.accept(this.ultimateTicTacToe.getCurrentPlayer());
     }
 
     public void onCellClicked(int cell) {
@@ -62,4 +65,8 @@ public class UltimateTicTacToePanelViewModel {
     public void setGameResultCallback(Consumer<String> gameResultCallback) {
         this.gameResultCallback = gameResultCallback;
     }
+
+    public void setCurrentPlayerCallback(Consumer<Player> currentPlayerCallback) {
+        this.currentPlayerCallback = currentPlayerCallback;
+    }
 }