java - 如何使用方向键移动图像

Question

我必须为我的作业制作一个 Frog 游戏，但我的关键方法不起作用。我正在处理公共(public)无效 key ，但不知道为什么我的箭头键没有注册？ 抱歉，我是这个网站的新手。我的代码:

// FroggerComponent.java

     import java.awt.*;
     import java.awt.event.*;
     import javax.swing.*;
     import java.io.*;
    import javax.imageio.*;
    public class FroggerComponent extends JComponent {
// Size of the game grid
public static final int WIDTH = 20;
public static final int HEIGHT = 7;
// Initial pixel size for each grid square
public static final int PIXELS = 50;
// Image filenames for car, lily, and frog
public static final String[] IMAGES = new String[] { "Images/frog.png", "Images/car.png", "Images/lily.png" };
// Colors for ROAD, WATER, and DIRT
public static final Color[] COLORS = new Color[] { Color.BLACK, Color.BLUE, Color.GRAY };
// Codes to store what is in each square in the grid
public static final int EMPTY = 0;
public static final int CAR = 1;
public static final int LILY = 2;
private Image frog;
private Image car;
private Image lily;

private int[][] grid = new int[WIDTH][HEIGHT];
Row[] rows = new Row[HEIGHT];
private int x;
private int y;
int x1 = 6;
int y1 = 10;
int dx;
private int dy;

private boolean dead;

/*
 * Provided utility method to read in an Image object. If the image cannot
 * load, prints error output and returns null. Uses Java standard
 * ImageIO.read() method.
 */
private Image readImage(String filename) {
    Image image = null;
    try {
        image = ImageIO.read(new File(filename));
    } catch (IOException e) {
        System.out.println("Failed to load image '" + filename + "'");
        e.printStackTrace();
    }
    return (image);
}

private void readRow(String file) {
    try {
        FileReader fr = new FileReader(file);
        BufferedReader br = new BufferedReader(fr);
        String line = br.readLine();
        int count = 1;
        while ((line != null) && (line != "\n") && (line != "\r")) {
            Row r = new Row(line);
            rows[count] = r;
            line = br.readLine();
            count++;
        }
    } catch (IOException ex) {
        System.out.println("File not found!");
    }

}

public FroggerComponent(String filename) {
    setPreferredSize(new Dimension(WIDTH * PIXELS, HEIGHT * PIXELS));
    readRow(filename);
    /*
     * Add your code here ... readImage(...); ...
     */

    frog = readImage("images/frog.png");
    lily = readImage("Images/lily.png");
    car = readImage("Images/car-red.png");
    readRow("Images/world.txt");
    reset();

}

public void reset() {
    for (int x = 0; x < grid.length; x++)
        for (int y = 0; y < grid[x].length; y++)
            grid[x][y] = EMPTY;
    dead = false;
    x = 0;
    y = 6;
    repaint();
}

private void moveBy(int dx, int dy) {
    if ((x1 + dx >= 0 && x + dx < WIDTH) && (y1 + dy >= 0 && y1 + dy < HEIGHT)) {
        x1 += dx;
        y1 += dy;
    }
}

public boolean isWin() {
    return (y == 0);
}

public void key(int code) throws ArrayIndexOutOfBoundsException {
    /*
     * Add your code here
     */

    if (code == KeyEvent.VK_UP) {
        x1 = x1 - 1;

    } else if (code == KeyEvent.VK_DOWN) {
        x1 = x1 + 1;
    } else if (code == KeyEvent.VK_LEFT) {

        y1 = y1 - 1;
    } else if (code == KeyEvent.VK_RIGHT) {
        y1 = y1 + 1;
    }

    this.repaint();

}

public void paintComponent(Graphics g) {
    /*
     * Add your code here
     * 
     * 
     */
    // variables
    int squareWidth = getWidth() / grid.length;
    int squareHeight = getHeight() / grid[0].length;

    // paints the rows

    for (int y = 0; y < 20; y++) {
        if (grid[y][x] == EMPTY) {
            g.setColor(Color.GRAY);
            g.fillRect(squareWidth * y, squareWidth * x, squareWidth, squareHeight);
        }
    }
    x++;
    for (int y = 0; y < 20; y++) {

        if (grid[y][x] == EMPTY) {
            g.setColor(Color.BLUE);
            g.fillRect(squareWidth * y, squareWidth * x, squareWidth, squareHeight);
        }
    }
    x++;
    for (int y = 0; y < 20; y++) {

        if (grid[y][x] == EMPTY) {
            g.setColor(Color.BLACK);
            g.fillRect(squareWidth * y, squareWidth * x, squareWidth, squareHeight);
        }
    }
    x++;
    for (int y = 0; y < 20; y++) {

        if (grid[y][x] == EMPTY) {
            g.setColor(Color.BLUE);
            g.fillRect(squareWidth * y, squareWidth * x, squareWidth, squareHeight);
        }
    }
    x++;
    for (int y = 0; y < 20; y++) {

        if (grid[y][x] == EMPTY) {
            g.setColor(Color.BLUE);
            g.fillRect(squareWidth * y, squareWidth * x, squareWidth, squareHeight);
        }
    }
    x++;
    for (int y = 0; y < 20; y++) {

        if (grid[y][x] == EMPTY) {
            g.setColor(Color.BLACK);
            g.fillRect(squareWidth * y, squareWidth * x, squareWidth, squareHeight);
        }
    }
    x++;
    for (int y = 0; y < 20; y++) {

        if (grid[y][x] == EMPTY) {
            g.setColor(Color.GRAY);
            g.fillRect(squareWidth * y, squareWidth * x, squareWidth, squareHeight);
        }
    }
    // frog

    g.drawImage(frog, squareWidth * y1, squareHeight * x1, squareWidth, squareHeight, this);

    // lilypads
    g.drawImage(lily, squareWidth, squareHeight, squareWidth, squareHeight, null);
    g.drawImage(lily, squareWidth * 5, squareHeight, squareWidth, squareHeight, null);
    g.drawImage(lily, squareWidth * 10, squareHeight, squareWidth, squareHeight, null);
    g.drawImage(lily, squareWidth * 10, squareHeight * 3, squareWidth, squareHeight, null);
    g.drawImage(lily, squareWidth * 8, squareHeight * 3, squareWidth, squareHeight, null);
    g.drawImage(lily, squareWidth * 3, squareHeight * 3, squareWidth, squareHeight, null);
    g.drawImage(lily, squareWidth * 2, squareHeight * 4, squareWidth, squareHeight, null);
    g.drawImage(lily, squareWidth * 4, squareHeight * 4, squareWidth, squareHeight, null);
    g.drawImage(lily, squareWidth * 12, squareHeight * 4, squareWidth, squareHeight, null);
    g.drawImage(lily, squareWidth * 17, squareHeight * 4, squareWidth, squareHeight, null);
    // cars
    g.drawImage(car, squareWidth * 2, squareHeight * 5, squareWidth, squareHeight, null);
    g.drawImage(car, squareWidth * 5, squareHeight * 5, squareWidth, squareHeight, null);
    g.drawImage(car, squareWidth * 11, squareHeight * 5, squareWidth, squareHeight, null);
    g.drawImage(car, squareWidth * 7, squareHeight * 2, squareWidth, squareHeight, null);
    g.drawImage(car, squareWidth * 4, squareHeight * 2, squareWidth, squareHeight, null);

}

public void tick(int round) {
    /*
     * Add your code here
     */
}

}

Answer 1

您必须添加一个KeyListener来获取KeyEvents(或使用KeyBindings)。

一旦您从KeyListener获取KeyEvents(或从KeyBinding获取ActionEvents)，您就可以将这些事件委托(delegate)给您的工作方法

我将向您展示如何使用 keyBinding，这是更优雅的方法

public void addKeyBinding(){
    getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_LEFT),
                        "left")
    //map as many keys as you want
}

之后，您必须使用 ActionListener 监听这些事件

public class FroggerComponent extends JComponent  implements ActionListener { 

    //...

    @Override
    public void actionPerformed(ActionEvent e){
        if ("left".equals(e.getActionCommand()){
             key(KeyEvent.VK_LEFT)
        }
    }
}

你只需添加 ActionListener 然后

public FroggerComponent(String filename) {

    //...
    addActionListener(this);

}

另请参阅Java: Use keystroke with arrow key