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Muhamed H.
Muhamed H.

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Building a Chess Game with JavaFX: The Journey and Lessons Learned

#java #oop #chess #softwareengineering

Introduction

Although I implemented this project a little over a year ago, this project wasn’t just about creating a playable game; it was also an experience in object-oriented programming, event handling, and user interface design. I want to share this with you because you may learn something from my mistakes. I’ll walk you through the core structure of the project, some of the challenges I faced, and the lessons I learned along the way.

The Core of the Game: Figures and Their Movements

In chess, every piece has a unique way of moving across the board. To handle this, I created an abstract Figure class, from which each chess piece (pawn, bishop, knight, etc.) inherits.

The Figure class is designed to manage the core functionalities of any chess piece:

  • Movement placeholders: The class can draw possible move indicators on the grid.
  • Eat placeholders: For pieces that can capture others, special placeholders indicate valid capture positions.
  • Click handlers: Each piece has click listeners to handle user interaction and move validation.

Additionally, the class contains abstract methods such as canMoveOnClick(MouseEvent event) and canEat(VBox cell), ensuring that each piece can define its own unique movement rules.

Challenges: Coupling Business Logic with UI

One of the main challenges in this project was managing the coupling between the business logic and the user interface (UI). Since JavaFX inherently mixes UI design with interaction handling, I used the VBox JavaFX component to represent individual cells on the chessboard and attached event listeners directly to these cells.

At first, this seemed like an efficient way to handle interactions, but as the project grew, I realized that this approach tightly couples the business logic (chess rules) with the UI elements (how the game is drawn). This made it difficult to make the game scalable or add additional features without creating dependencies between UI and logic.

What I learned: Decoupling the UI from the business logic is essential for creating maintainable software.

Handling Movement and Capturing

One of the fun yet complex aspects of chess is the movement of pieces and their ability to capture opponents. In my implementation, I created placeholder elements on the board to indicate where a piece can move. Here’s a simplified version of the logic for adding move and capture placeholders:

public void drawPlaceholder(VBox cell) {
    Circle placeholder = new Circle(10);
    placeholder.setFill(Color.GRAY);
    placeholder.setOnMouseClicked(event -> moveOnClick(event));
    cell.getChildren().add(placeholder);
    listOfPlaceholders.add(cell);
}
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This method creates a visual indicator (a gray circle) on valid movement cells, making it easier for players to understand where their selected piece can go.

For capturing opponent pieces, I added an "eat" placeholder, which changes the appearance of the cell and overrides the click handler to remove the opponent’s piece:

public void drawEatPlaceholder(VBox cell) {
   saveOriginalClickHandler(cell);
   cell.getStyleClass().add("eatPozadina");
   cell.setOnMouseClicked(ev -> eatOnClick(cell));
   listOfEatPlaceholders.add(cell);
}
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What Could Be Improved

While the project was functional, there are several areas I would improve if I were to revisit this project:

  1. Decoupling the UI from Logic: The biggest improvement would be separating the chess rules and piece movements from the UI components. This would make the code more maintainable and flexible for future changes.

  2. Better Event Handling: The current method of saving and restoring event handlers for each move or capture is not ideal. A more sophisticated event handling system could reduce the complexity of managing these interactions.

Takeaways

This project provided several valuable insights into software development:

  1. Decoupling Business Logic from UI: Combining game logic with the UI initially worked, but separating them is essential for flexibility, maintainability, and scalability in future enhancements.

  2. Modular and Maintainable Code: As projects grow, tightly coupled code can lead to significant challenges. Creating modular designs helps ensure that systems can be extended or modified without widespread impact.

  3. Applying Design Patterns: The project underscored the importance of design patterns, such as MVC (Model-View-Controller), in separating concerns and enhancing the structure and maintainability of the codebase. While my implementation touched on these principles, there’s room for further refinement to fully embrace the MVC architecture.

If you're interested in seeing the full implementation of the chess game, feel free to check out the repository on GitHub.

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