KeyAdapter input in java not working

Question

I just wrote some code to make my player move in my little maze game, but nothing happens. Also my maze is not drawn correct as in the matrix input. I don't figure out why is wrong this code...any help is well appeciated. Thank you!

import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import javax.swing.*;

public class Main extends JPanel {
    private static Image white;
    private static Image black;
    private static Image finish;
    private static Image player;
    private static int x = 1;
    private static int y = 1;
    private String matrix[][];

    public Main() {
        addKeyListener(new Keys());
        setFocusable(true);
    }

    public static String[][] load(String input) {
        List<String[]> rows = new ArrayList<>();
        try (Scanner scanner = new Scanner(input)) {
            while (scanner.hasNextLine()) {
                String line = scanner.nextLine();
                String[] cols = new String[line.length()];
                for (int i = 0; i < cols.length; i++) {
                    cols[i] = line.substring(i, i + 1);
                }
                rows.add(cols);
            }
        }
        return rows.toArray(new String[rows.size()][]);
    }

    public static JFrame buildFrame() {
        JFrame frame = new JFrame("Labyrinth Game");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(900, 950);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
        return frame;
    }

    public void moveUp() {
        x += 0;
        y += -1;
    }

    public void moveLeft() {
        x += -1;
        y += 0;
    }

    public void moveDown() {
        x += 0;
        y += 1;
    }

    public void moveRight() {
        x += 1;
        y += 0;
    }

    public class Keys extends KeyAdapter {
        @Override
        public void keyPressed(KeyEvent e) {
            int keycode = e.getKeyCode();
            // repaint();
            if (keycode == KeyEvent.VK_W) {
                if (!matrix[getX()][getY() - 1].equals("1")) {
                    moveUp();
                }
            }
            if (keycode == KeyEvent.VK_A) {
                if (!matrix[getX() - 1][getY()].equals("1")) {
                    moveLeft();
                }
            }
            if (keycode == KeyEvent.VK_S) {
                if (!matrix[getX()][getY() + 1].equals("1")) {
                    moveDown();
                }
            }
            if (keycode == KeyEvent.VK_D) {
                if (!matrix[getX() + 1][getY()].equals("1")) {
                    moveRight();
                }
            }
        }

        @Override
        public void keyReleased(KeyEvent event) {
        }
    }

    public static void main(String[] args) {
        String input = "1111111111111111111111111111111111111111111\n"
                + "1000000010001000001000000010000000100000001\n"
                + "1010111010101010101111101011111010111111101\n"
                + "1010001010100010100000001010000010000010001\n"
                + "1011101010111110101111111010111111111010111\n"
                + "1000101010100000101000001000100010000010001\n"
                + "1011101011101011111011101111111010111110101\n"
                + "1010001000001010000010100000001010000010101\n"
                + "1010111111111010111110111111101011111011101\n"
                + "1010100000100010100000000000101000000000101\n"
                + "1110101111101110111110111011101011111110101\n"
                + "1000100000000010000010100010001000100010001\n"
                + "1011111111111111111011101010111111101011101\n"
                + "1000000000000000100010001010000000001010001\n"
                + "1011111111111011101110111011111111111010111\n"
                + "1000100010001000001010001000100000001010101\n"
                + "1110101011101111111010101110111110111010101\n"
                + "1000101010001000100000101000100000100010001\n"
                + "1011101010111010101111101011101110101111111\n"
                + "1000001010000010000000101000001000100010001\n"
                + "1111111011111110111111101111111011111010101\n"
                + "1000001010000010100010001000000010000010101\n"
                + "1011111010111011101010111011111110101110101\n"
                + "1010000010001010001010001000100000101010101\n"
                + "1010111111101010111011101111101111101011101\n"
                + "1000100000001010101010001000100010101000101\n"
                + "1011111011111010101010111010111010101011101\n"
                + "1010000010001000101010000010001010001000001\n"
                + "1010101110101111101011101111101011111010101\n"
                + "1010101000101000001000101000001000000010101\n"
                + "1011101011111010111110111011101111111110111\n"
                + "1000001000000010000000000010000000000010021\n"
                + "1111111111111111111111111111111111111111111\n";

        String[][] matrix = load(input);

        JFrame frame = buildFrame();
        ImageIcon img = new ImageIcon("C:/Users/Desktop/black20.png");
        black = img.getImage();
        img = new ImageIcon("C:/Users/Desktop/gri20.png");
        white = img.getImage();
        img = new ImageIcon("C:/Users/Desktop/finish20.png");
        finish = img.getImage();
        img = new ImageIcon("C:/Users/Desktop/smiley20.png");
        player = img.getImage();
        // frame.add(new Player());
        JPanel pane = new JPanel() {
            @Override
            public void paint(Graphics g) {
                super.paint(g);
                for (int i = 0; i < matrix.length; i++) {
                    for (int j = 0; j < matrix[0].length; j++) {
                        if (matrix[i][j].equals("1")) {
                            g.drawImage(black, i * 20, j * 20, null);
                        }
                        if (matrix[i][j].equals("0")) {
                            g.drawImage(white, i * 20, j * 20, null);
                        }
                        if (matrix[i][j].equals("2")) {
                            g.drawImage(finish, i * 20, j * 20, null);
                        }
                    }
                }
                g.drawImage(player, x * 20, y * 20, null);
            }
        };
        frame.add(pane);
        frame.add(new Main());
    }
}

It should look like:

Answer 1

Problems/Suggestions:

• You're adding more than one component to the JFrame in a default fashion. Since the JFrame's contentPane uses BorderLayout, only one component will display, the last one added, and the other will be completely covered and will remain invisible.
• Your Main JPanel is not being used as a true JPanel. Nothing is being added to it, and in fact it looks like it should be a logical class and not a component class.
• Rather than using KeyListeners, which are very fidgety when it comes to focus problems, use Key Bindings which will allow you to get around focus issues in a clean and higher level way.
• Don't override the JPanel's paint method but rather its paintComponent method as this will give you several advantages, including default use of double buffering for your animation.
• Don't give component classes a public int getX() and public int getY() method without care since these override key methods that place the component within its container. Since the Main class shouldn't even extend JPanel, this will end up to be a non-issue for your code, but in the future, it would mess your program up.
• When you run into similar problems, such as a KeyListener not working, remove the issue from your big program and try to reproduce it in a small separate program. This will give you a much cleaner environment for helping you to isolate and understand your problem and thereby help you fix it.
• Your program is mis-using the static modifier. Your x and y fields should not be static and should not be accessed in a static way.
• You've got way too much code within your main method, which is one of the reasons why you likely made x and y static, because you were forced to do so since you're trying to access them within main. The solution is not to make the fields static but to get all that code out of the static world and into the instance world.

---

Edit

For some reason the question intrigued me, and so I decided to try to M-V-C or Model-View-Controller it if possible and see what I could come up with. So here goes a bunch of classes that sort of work, beginning with a text file that holds the data.

The GUI looks like:

It must be in the same location as the class files since it is obtained as a resource and must have the file name "input.txt"

1111111111111111111111111111111111111111111
1000000010001000001000000010000000100000001
1010111010101010101111101011111010111111101
1010001010100010100000001010000010000010001
1011101010111110101111111010111111111010111
1000101010100000101000001000100010000010001
1011101011101011111011101111111010111110101
1010001000001010000010100000001010000010101
1010111111111010111110111111101011111011101
1010100000100010100000000000101000000000101
1110101111101110111110111011101011111110101
1000100000000010000010100010001000100010001
1011111111111111111011101010111111101011101
1000000000000000100010001010000000001010001
1011111111111011101110111011111111111010111
1000100010001000001010001000100000001010101
1110101011101111111010101110111110111010101
1000101010001000100000101000100000100010001
1011101010111010101111101011101110101111111
1000001010000010000000101000001000100010001
1111111011111110111111101111111011111010101
1000001010000010100010001000000010000010101
1011111010111011101010111011111110101110101
1010000010001010001010001000100000101010101
1010111111101010111011101111101111101011101
1000100000001010101010001000100010101000101
1011111011111010101010111010111010101011101
1010000010001000101010000010001010001000001
1010101110101111101011101111101011111010101
1010101000101000001000101000001000000010101
1011101011111010111110111011101111111110111
1000001000000010000000000010000000000010021
1111111111111111111111111111111111111111111

Next the main program, the one that creates the model, the view, and the controller, hooks them all together, and then displays the GUI:

import java.awt.BorderLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

/**
 * link: http://stackoverflow.com/a/41418250/522444
 * 
 * @author Pete
 *
 */
@SuppressWarnings("serial")
public class Main2 extends JPanel {
    private View mainPanel;

    public Main2(MatrixModel matrixModel) {
        mainPanel = new View(matrixModel);
        new Controller(matrixModel, mainPanel);

        setLayout(new BorderLayout());
        add(mainPanel, BorderLayout.CENTER);
    }

    private static void createAndShowGui(MatrixModel model) {
        Main2 mainPanel = new Main2(model);

        JFrame frame = new JFrame("Main2");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        final MatrixModel model = MatrixUtil.getInput(MatrixUtil.PATH_TO_RSC);

        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGui(model);
            }
        });
    }
}

Next a utility class with static methods for reading in the text file as a resource and converting it into a Model object:

import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class MatrixUtil {
    // again this text file must be in the jar file or the code base 
    // at the same location as the class / java files
    public static final String PATH_TO_RSC = "input.txt";

    public static MatrixModel getInput(String resourcePath) {
        InputStream is = MatrixUtil.class.getResourceAsStream(resourcePath);
        if (is == null) {
            String text = "resourcePath is not found and not loading text: " + resourcePath;
            throw new IllegalArgumentException(text);
        }
        return getInput(is);
    }

    public static MatrixModel getInput(InputStream is) {
        MatrixModel model = null;
        try (Scanner scan = new Scanner(is)) {
            List<List<MatrixPosition>> listOfLists = new ArrayList<>();
            while (scan.hasNextLine()) {
                String line = scan.nextLine();
                if (line.trim().isEmpty()) {
                    continue;
                }
                List<MatrixPosition> list = new ArrayList<>();
                for (char c : line.toCharArray()) {
                    list.add(MatrixPosition.getMatrixPosition(String.valueOf(c)));
                }
                listOfLists.add(list);
            }
            MatrixPosition[][] grid = new MatrixPosition[listOfLists.size()][];
            for (int i = 0; i < grid.length; i++) {
                List<MatrixPosition> list = listOfLists.get(i);
                grid[i] = list.toArray(new MatrixPosition[] {});
            }
            model = new MatrixModel(grid, new SpritePosition(1, 1));
        }

        return model;
    }

}

Basic enum to represent direction:

public enum Direction {
    UP, DOWN, LEFT, RIGHT
}

Another enum to represent a location point in the grid, and whether it is a wall, a coridor or the end as well as static methods to convert from number to MatrixPosition:

public enum MatrixPosition {
    WALL(1), CORRIDOR(0), END(2);

    private int value;

    private MatrixPosition(int value) {
        this.value = value;
    }

    public int getValue() {
        return value;
    }

    public static MatrixPosition getMatrixPosition(int value) {
        for (MatrixPosition position : MatrixPosition.values()) {
            if (value == position.getValue()) {
                return position;
            }
        }
        String text = "value of " + value;
        throw new IllegalArgumentException(text);
    }

    public static MatrixPosition getMatrixPosition(String strValue) {
        int value = -1;
        try {
            value = Integer.parseInt(strValue);
        } catch (NumberFormatException e) {
            String text = "NumberFormatException for strValue " + strValue;
            throw new IllegalAccessError(text);
        }
        return getMatrixPosition(value);
    }
}    

A class to represent a position of our sprite, similar to the java.awt.Point class but with row and column fields instead of x and y:

public class SpritePosition {
    int row;
    int column;

    public SpritePosition(int row, int column) {
        this.row = row;
        this.column = column;
    }

    public int getRow() {
        return row;
    }

    public void setRow(int row) {
        this.row = row;
    }

    public int getColumn() {
        return column;
    }

    public void setColumn(int column) {
        this.column = column;
    }

    public void setRowColumn(int row, int column) {
        this.row = row;
        this.column = column;
    }

}    

The model has property change support code so that it can notify any classes listening to it of any changes in its state. The controller will be the class listening to the model

import java.beans.PropertyChangeListener;
import javax.swing.event.SwingPropertyChangeSupport;

public class MatrixModel {
    public static final String SPRITE_POINT = "sprite point";
    private SwingPropertyChangeSupport pcSupport = new SwingPropertyChangeSupport(this);
    private MatrixPosition[][] grid;
    private SpritePosition spritePosition;

    public MatrixModel(MatrixPosition[][] grid, SpritePosition spritePosition) {
        this.grid = grid;
        this.spritePosition = spritePosition;
    }

    public int getRows() {
        return grid.length;
    }

    public int getColumns() {
        return grid[0].length;
    }

    public MatrixPosition getPosition(SpritePosition p) {
        return getPosition(p.row, p.column);
    }

    public MatrixPosition getPosition(int row, int col) {
        return grid[row][col];
    }

    public void setSpritePoint(SpritePosition spritePosition) {
        SpritePosition oldValue = this.spritePosition;
        SpritePosition newValue = spritePosition;
        this.spritePosition = spritePosition;
        pcSupport.firePropertyChange(SPRITE_POINT, oldValue, newValue);
    }

    public boolean isPointValid(SpritePosition p) {
        if (p.column < 0 || p.row < 0) {
            return false;
        }
        if (p.column >= grid[0].length || p.row >= grid.length) {
            return false;
        }
        return grid[p.row][p.column] == MatrixPosition.CORRIDOR;
    }

    public boolean isMoveValid(Direction direction) {
        int row = spritePosition.row;
        int column = spritePosition.column;
        switch (direction) {
        case UP:
            return isPointValid(new SpritePosition(row - 1, column));
        case DOWN:
            return isPointValid(new SpritePosition(row + 1, column));
        case LEFT:
            return isPointValid(new SpritePosition(row, column - 1));
        case RIGHT:
            return isPointValid(new SpritePosition(row, column + 1));
        default:
            return false;
        }
    }

    public void move(Direction direction) {
        if (!isMoveValid(direction)) {
            String text = "For move to " + direction + "spritePosition: " + spritePosition;
            throw new IllegalArgumentException(text);
        }
        int row = spritePosition.row;
        int column = spritePosition.column;
        switch (direction) {
        case UP:
            setSpritePoint(new SpritePosition(row - 1, column));
            break;
        case DOWN:
            setSpritePoint(new SpritePosition(row + 1, column));
            break;
        case LEFT:
            setSpritePoint(new SpritePosition(row, column - 1));
            break;
        case RIGHT:
            setSpritePoint(new SpritePosition(row, column + 1));
            break;

        default:
            break;
        }
    }

    public SpritePosition getSpritePosition() {
        return spritePosition;
    }

    public void addPropertyChangeListener(PropertyChangeListener listener) {
        pcSupport.addPropertyChangeListener(listener);
    }

    public void removePropertyChangeListener(PropertyChangeListener listener) {
        pcSupport.removePropertyChangeListener(listener);
    }

    public void addPropertyChangeListener(String name, PropertyChangeListener listener) {
        pcSupport.addPropertyChangeListener(name, listener);
    }

    public void removePropertyChangeListener(String name, PropertyChangeListener listener) {
        pcSupport.removePropertyChangeListener(name, listener);
    }
}    

Controller class, one that sets up key bindings on the view so that it can listen for key presses, checks if they represent a valid move, and if so then tells the model to make the move. It also adds a listener to the model so that when its state changes, it will tell the view to move the sprite

import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.EnumMap;
import java.util.Map;

import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JComponent;
import javax.swing.KeyStroke;

public class Controller {
    private MatrixModel model;
    private View view;
    private Map<Direction, KeyStroke> dirKeyMap = new EnumMap<>(Direction.class);

    public Controller(MatrixModel model, View view) {
        this.model = model;
        this.view = view;

        dirKeyMap.put(Direction.DOWN, KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0));
        dirKeyMap.put(Direction.UP, KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0));
        dirKeyMap.put(Direction.LEFT, KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0));
        dirKeyMap.put(Direction.RIGHT, KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0));

        model.addPropertyChangeListener(new ModelListener());
        setUpKeyBindings(view);
    }

    private void setUpKeyBindings(View view) {
        int condition = JComponent.WHEN_IN_FOCUSED_WINDOW;
        InputMap inputMap = view.getInputMap(condition);
        ActionMap actionMap = view.getActionMap();
        for (Direction dir : Direction.values()) {
            KeyStroke keyStroke = dirKeyMap.get(dir);
            hookUp(inputMap, actionMap, dir, keyStroke);
        }
    }

    private void hookUp(InputMap inputMap, ActionMap actionMap, Direction dir, KeyStroke key) {
        inputMap.put(key, key.toString());
        actionMap.put(key.toString(), new MoveAction(dir, model));
    }

    public MatrixModel getModel() {
        return model;
    }

    public View getView() {
        return view;
    }

    class ModelListener implements PropertyChangeListener {
        @Override
        public void propertyChange(PropertyChangeEvent evt) {
            if (MatrixModel.SPRITE_POINT.equals(evt.getPropertyName())) {
                SpritePosition p = model.getSpritePosition();
                view.setSpritePoint(p);
            }
        }
    }

}

@SuppressWarnings("serial")
class MoveAction extends AbstractAction {
    private Direction dir;
    private MatrixModel model;

    public MoveAction(Direction dir, MatrixModel model) {
        super(dir.toString());
        this.dir = dir;
        this.model = model;
    }

    public void actionPerformed(ActionEvent e) {
        if (model.isMoveValid(dir)) {
            model.move(dir);
        }
    }
}

Finally the View class, that extends JPanel, that displays the maze and the sprite:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import javax.swing.JPanel;

@SuppressWarnings("serial")
public class View extends JPanel {
    private static final int CELL_WIDTH = 20;
    private static final Color CORRIDOR_COLOR = Color.LIGHT_GRAY;
    private static final Color WALL_COLOR = Color.DARK_GRAY;
    private static final Color END_COLOR = Color.ORANGE;
    private static final Color SPRITE_COLOR = Color.RED;
    private static final int GAP = 1;
    private BufferedImage gridImg = null;
    private SpritePosition spritePosition;
    private JPanel mainPanel = new JPanel();

    public View(MatrixModel matrixModel) {
        gridImg = createImg(matrixModel);
        spritePosition = matrixModel.getSpritePosition();
    }

    public JPanel getMainPanel() {
        return mainPanel;
    }

    @Override
    public Dimension getPreferredSize() {
        if (isPreferredSizeSet() || gridImg == null) {
            return super.getPreferredSize();
        }
        int prefW = gridImg.getWidth();
        int prefH = gridImg.getHeight();
        return new Dimension(prefW, prefH);
    }

    public void setSpritePoint(SpritePosition spritePosition) {
        this.spritePosition = spritePosition;
        repaint();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        if (gridImg != null) {
            g.drawImage(gridImg, 0, 0, this);
        }
        g.setColor(SPRITE_COLOR);
        int y = spritePosition.row * CELL_WIDTH + GAP;
        int x = spritePosition.column * CELL_WIDTH + GAP;
        g.fillRect(x, y, CELL_WIDTH - 2 * GAP, CELL_WIDTH - 2 * GAP);
    }

    private BufferedImage createImg(MatrixModel matrixModel) {
        BufferedImage img = null;
        if (matrixModel != null && matrixModel.getRows() > 0) {
            int w = matrixModel.getColumns() * CELL_WIDTH;
            int h = matrixModel.getRows() * CELL_WIDTH;
            img = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
            Graphics2D g2 = img.createGraphics();
            for (int row = 0; row < matrixModel.getRows(); row++) {
                for (int col = 0; col < matrixModel.getColumns(); col++) {
                    MatrixPosition position = matrixModel.getPosition(row, col);
                    Color c = null;
                    switch (position) {
                    case CORRIDOR:
                        c = CORRIDOR_COLOR;
                        break;
                    case WALL:
                        c = WALL_COLOR;
                        break;
                    case END:
                        c = END_COLOR;
                        break;
                    }
                    g2.setColor(c);
                    int x = col * CELL_WIDTH;
                    int y = row * CELL_WIDTH;
                    g2.fillRect(x, y, CELL_WIDTH, CELL_WIDTH);
                }
            }
            g2.dispose();
        }
        return img;
    }

}