Introduce own view for JFrame, Change button listener to use static number

src/main/java/de/icaotix/ultimatetictactoe/Main.java

@@ -1,22 +1,12 @@
 package de.icaotix.ultimatetictactoe;
 
-import de.icaotix.ultimatetictactoe.model.ModelFactory;
+import de.icaotix.ultimatetictactoe.view.MainWindowView;
-import de.icaotix.ultimatetictactoe.view.UltimateTicTacToeView;
-import de.icaotix.ultimatetictactoe.viewmodel.ViewModelFactory;
 
 import javax.swing.*;
 
 public class Main {
 
     public static void main(String[] args) {
-        SwingUtilities.invokeLater(() -> {
+        SwingUtilities.invokeLater(MainWindowView::new);
-
-            ModelFactory modelFactory = new ModelFactory();
-            ViewModelFactory viewModelFactory = new ViewModelFactory(modelFactory);
-
-            final var ultimateTicTacToePanelViewModel = viewModelFactory.getUltimateTicTacToePanelViewModel();
-            new UltimateTicTacToeView(ultimateTicTacToePanelViewModel);
-            ultimateTicTacToePanelViewModel.prepareNextMove();
-        });
     }
 }

src/main/java/de/icaotix/ultimatetictactoe/view/MainWindowView.java

@@ -0,0 +1,24 @@
+package de.icaotix.ultimatetictactoe.view;
+
+import de.icaotix.ultimatetictactoe.model.ModelFactory;
+import de.icaotix.ultimatetictactoe.viewmodel.ViewModelFactory;
+
+import javax.swing.*;
+import java.awt.*;
+
+public class MainWindowView extends JFrame {
+
+    public MainWindowView() throws HeadlessException {
+        super("Ultimate TicTacToe");
+        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
+
+        ModelFactory modelFactory = new ModelFactory();
+        ViewModelFactory viewModelFactory = new ViewModelFactory(modelFactory);
+
+        final var ultimateTicTacToePanelViewModel = viewModelFactory.getUltimateTicTacToePanelViewModel();
+        this.setContentPane(new UltimateTicTacToeView(ultimateTicTacToePanelViewModel));
+        ultimateTicTacToePanelViewModel.prepareNextMove();
+        this.setSize(new Dimension(500, 520));
+        this.setVisible(true);
+    }
+}

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

@@ -7,24 +7,21 @@ import javax.swing.plaf.metal.MetalButtonUI;
 import java.awt.*;
 import java.util.List;
 
-public class TicTacToeView {
+public class TicTacToeView extends JPanel {
 
     private final TicTacToePanelViewModel viewModel;
-    private final JPanel view;
     private final JButton[] buttons;
 
     public TicTacToeView(TicTacToePanelViewModel viewModel) {
         this.viewModel = viewModel;
         this.buttons = new JButton[9];
-        this.view = new JPanel(new GridLayout(3, 3, 0, 0));
+        this.setLayout(new GridLayout(3, 3, 0, 0));
-        view.setBorder(BorderFactory.createLineBorder(Color.BLACK, 2));
+        this.setBorder(BorderFactory.createLineBorder(Color.BLACK, 2));
 
         for (int i = 0; i < 9; i++) {
             var btn = new JButton("");
-            btn.setActionCommand(Integer.toString(i));
+            final int clickedButton = i;
-            btn.addActionListener(e -> {
+            btn.addActionListener(e -> viewModel.onButtonClicked(clickedButton));
-                viewModel.onButtonClicked(Integer.parseInt(e.getActionCommand()));
-            });
             btn.setUI(new MetalButtonUI() {
                 @Override
                 protected Color getDisabledTextColor() {
@@ -32,7 +29,7 @@ public class TicTacToeView {
                 }
             });
             buttons[i] = btn;
-            view.add(btn);
+            this.add(btn);
         }
         this.deactivate();
 
@@ -42,10 +39,6 @@ public class TicTacToeView {
         this.viewModel.setButtonTextCallback(this::setButtonText);
     }
 
-    public JPanel getView() {
-        return this.view;
-    }
-
     public void setButtonText(int btnId, String text) {
         this.buttons[btnId].setText(text);
     }
@@ -65,14 +58,14 @@ public class TicTacToeView {
     }
 
     public void setFinishPanel(String finishString) {
-        this.view.removeAll();
+        this.removeAll();
-        this.view.setLayout(new BorderLayout());
+        this.setLayout(new BorderLayout());
         JButton winnerLabel = new JButton(finishString);
         winnerLabel.setEnabled(false);
         winnerLabel.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 15));
-        this.view.add(winnerLabel, BorderLayout.CENTER);
+        this.add(winnerLabel, BorderLayout.CENTER);
-        this.view.validate();
+        this.validate();
-        this.view.repaint();
+        this.repaint();
     }
 
 }

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

@@ -7,48 +7,42 @@ import javax.swing.*;
 import java.awt.*;
 
 
-public class UltimateTicTacToeView extends JFrame {
+public class UltimateTicTacToeView extends JPanel {
 
     private final UltimateTicTacToePanelViewModel viewModel;
     private JLabel currentPlayerLabel;
 
     public UltimateTicTacToeView(UltimateTicTacToePanelViewModel viewModel) {
-        super("Ultimate TicTacToe");
         this.viewModel = viewModel;
-        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
-
         this.setContentToGamePane();
-
-        this.setSize(new Dimension(500, 520));
-        this.setVisible(true);
     }
 
     public void setContentToGamePane() {
-        this.getContentPane().removeAll();
+        this.removeAll();
-        this.getContentPane().setLayout(new BorderLayout());
+        this.setLayout(new BorderLayout());
 
         JPanel mainGamePane = new JPanel();
-        this.getContentPane().add(mainGamePane, BorderLayout.CENTER);
+        this.add(mainGamePane, BorderLayout.CENTER);
         mainGamePane.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
         mainGamePane.setLayout(new GridLayout(3, 3, 2, 2));
         for (int i = 0; i < 9; i++) {
             TicTacToePanelViewModel subViewModel = viewModel.getSubGameViewModel(i);
-            mainGamePane.add(new TicTacToeView(subViewModel).getView());
+            mainGamePane.add(new TicTacToeView(subViewModel));
         }
 
         this.currentPlayerLabel = new JLabel();
         this.currentPlayerLabel.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 15));
         this.currentPlayerLabel.setHorizontalAlignment(SwingConstants.CENTER);
-        this.getContentPane().add(this.currentPlayerLabel, BorderLayout.NORTH);
+        this.add(this.currentPlayerLabel, BorderLayout.NORTH);
 
         this.viewModel.setGameResultCallback(this::setGameResult);
         this.viewModel.setCurrentPlayerCallback(this::setCurrentPlayer);
     }
 
     public void setGameResult(String resultText) {
-        this.getContentPane().removeAll();
+        this.removeAll();
 
-        this.getContentPane().setLayout(new BorderLayout());
+        this.setLayout(new BorderLayout());
         JLabel winnerLabel = new JLabel(resultText);
         Font font = new Font(Font.SANS_SERIF, Font.BOLD, 20);
         winnerLabel.setFont(font);
@@ -61,10 +55,10 @@ public class UltimateTicTacToeView extends JFrame {
             this.viewModel.prepareNextMove();
         });
 
-        this.getContentPane().add(winnerLabel, BorderLayout.CENTER);
+        this.add(winnerLabel, BorderLayout.CENTER);
-        this.getContentPane().add(restartBtn, BorderLayout.SOUTH);
+        this.add(restartBtn, BorderLayout.SOUTH);
-        this.getContentPane().validate();
+        this.validate();
-        this.getContentPane().repaint();
+        this.repaint();
     }
 
     public void setCurrentPlayer(String playerText) {