Jeremy Jeremy - 1 month ago 8
Java Question

Keyboard Actionlistener

I am trying to make a space ship (PlayerShip.gif) in my game move left, right, up, and down when the coresponding keys are pressed. I know i need an keyboardListener but im having issues figuring out where it goes and how it is actually implimented. my code is as follows.

public class GamePanel extends JPanel implements KeyListener {

Timer timer1;
Timer timer2;
ArrayList<Ships> ship;
int x;
int y;
double speed;
int size;
int shipxCoord;
int shipyCoord;
int shipHeight;
int shipWidth;
int shipRise;
int shipRun;
boolean left = false;
boolean right = false;
boolean up = false;
boolean down = false;
Image enemyShip1;
Image enemyShip2;
Image playerShip;
ImageIcon ic = new ImageIcon("Ship.gif");
ImageIcon ic2 = new ImageIcon("Ship2.gif");
int width = ic.getIconWidth();
int height = ic.getIconHeight();
Image background = Toolkit.getDefaultToolkit().createImage("background.jpg");

public GamePanel(int size, double speed) {
super();

x = 450;
y = 510;
ship = new ArrayList<Ships>();
// call timer for 1st type of enemy Ship with a delay of 5 seconds between ships
enemy1Timer(5);
// call timer for 2nd type of enemy Ship with a delay of 3 seconds between ships
enemy2Timer(3);
this.size = size;
this.speed = speed;
enemyShip1 = new ImageIcon("ship.gif").getImage();
enemyShip2 = new ImageIcon("ship2.gif").getImage();
playerShip = new ImageIcon("playerShip.gif").getImage();
// this.add(image);
} // end constructor

public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(background, 0, 0, null);
for (Ships s : ship) {
s.paintComponent(g);
}

g.drawImage(playerShip, x, y, this);

//g.drawImage(enemyShip2,x,y,this);
}// end method paintComponent

public void move() {
for (Ships s : ship) {
s.moveship(this);
// s.detectCollision(ship);
}
if (left) {
x -= speed;
}
if (right) {
x += speed;
}
if (up) {
y -= speed;
}
if (down) {
y += speed;
}

if (x > getWidth() - size) {
x = getWidth() - size;
}

if (x < 0) {
x = 0;
}

if (y > getHeight() - size) {
y = getHeight() - size;
}
if (y < 0) {
y = 0;
}
}// end method move

public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == e.VK_LEFT) {
left = true;

}
if (e.getKeyCode() == e.VK_RIGHT) {
right = true;
}
if (e.getKeyCode() == e.VK_UP) {
up = true;
}
if (e.getKeyCode() == e.VK_DOWN) {
down = true;
}

} // end method keyPressed

public void keyReleased(KeyEvent e) {
if (e.getKeyCode() == e.VK_LEFT) {
left = false;
}
if (e.getKeyCode() == e.VK_RIGHT) {
right = false;
}
if (e.getKeyCode() == e.VK_UP) {
up = false;
}
if (e.getKeyCode() == e.VK_DOWN) {
down = false;
}
}

public void enemy1Timer(int seconds) {
timer1 = new Timer();
timer1.schedule(new ShipSwarm1(), 1000, seconds * 1000);
}// end method enemy1Timer

class ShipSwarm1 extends TimerTask {

public void run() {
for (int Wave = 1; Wave > 0; Wave--) {
Ships enemy = new Ships(ic, enemyShip1);
ship.add(enemy);
}// end for
}// end method run
}// end class Enemy1Swarm

public void enemy2Timer(int seconds) {
timer2 = new Timer();
timer2.schedule(new ShipSwarm2(), 3000, seconds * 1000);
}// end method enemy1Timer

class ShipSwarm2 extends TimerTask {

public void run() {
for (int Wave = 1; Wave > 0; Wave--) {
Ships enemy = new Ships(ic2, enemyShip2);
ship.add(enemy);
}// end for
}// end method run
}
}

Answer

Take a look at this link for a game impelemented in Java and it does exactly what you are looking for. Key presses - up left right and down keys.

Its the famous 15-game

enter image description here

An excerpt from that,

private void processKeys(){
    KeyboardFocusManager.getCurrentKeyboardFocusManager().addKeyEventDispatcher(
        new KeyEventDispatcher()  { 
            public boolean dispatchKeyEvent(KeyEvent e){
                if(e.getID() == KeyEvent.KEY_PRESSED){
                    handleKeyPress(e.getKeyCode());
                    if(areThingsInPlace() && !dialogShown){
                        dialogShown = true;
                        JOptionPane.showMessageDialog(null,"Congratulations!!! YOU WIN!!");
                        System.exit(1);
                    }
                }
                return false;
            } 
    });
}

The handleKeyPress() method for handling the arrow keys

private void handleKeyPress(int keyCode) {
    int emptyIndex = findEmptyIndex();
    int x = emptyIndex/SIZE;
    int y = emptyIndex%SIZE;

    switch (keyCode) {
    case 37://LEFT KEY
        if(y==SIZE-1) return;
        doSwap(x,y,x,y+1);
        break;
    case 38://UP KEY
        if(x==SIZE-1) return;
        doSwap(x,y,x+1,y);
        break;
    case 39://RIGHT KEY
        if(y==0) return;
        doSwap(x,y,x,y-1);
        break;
    case 40://DOWN KEY
        if(x==0) return;
        doSwap(x,y,x-1,y);
        break;
    }
}
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