Develop Reference

Processing, how to redraw shapes when they dissappear

Hi guys so i have this game made where the user avoids aliens coming from the right side of the screen and then they go past the left side. I need the aliens to reappear from the right side once they leave the left side of the screen. How can i go about doing this?
Here is my existing code:
EDIT:
Added alien class underneath main class
PImage background;
int x=0; //global variable background location
Alien alien1;
Alien alien2;
Alien alien3;
Defender user1;
void setup(){
size(800,400);
background = loadImage("spaceBackground.jpg");
background.resize(width,height);
alien1 = new Alien(800,100,5);
alien2 = new Alien(800,200,5);
alien3 = new Alien(800,300,5);
user1 = new Defender(10,height/2);
}
void draw ()
{
drawBackground();
alien1.move();
alien1.render();
alien2.move();
alien2.render();
alien3.move();
alien3.render();
user1.render();
}
void drawBackground()
{
image(background, x, 0); //draw background twice adjacent
image(background, x+background.width, 0);
x -=4;
if(x == -background.width)
x=0; //wrap background
}
void keyPressed()
{
if(key == CODED) {
if (keyCode == UP) {
user1.y = user1.y - 5;
}
else if (keyCode == DOWN)
{
user1.y = user1.y + 5;
}
}
}
final color Alien1 = color(0,255,0);
final color Alien2 = color(50,100,0);
class Alien
{
int x,y;
int speedX, speedY;
Alien(int x, int y, int speedX)
{
this.x = x;
this.y = y;
this.speedX = speedX;
}
void move()
{
x=x-speedX;
float stepY = random(-5,5);
y = y + (int)stepY;
}
//draw an alien
void render()
{
fill(Alien1);
ellipse(x,y,30,30);
fill(Alien2);
ellipse(x,y,50,15);
}
}

If you upload your Alien class then we can give clearer directions but the idea is that your should add the following logic in your move() method.
void move()
{
x=x-speedX;
float stepY = random(-5,5);
y = y + (int)stepY;
if(this.x < 0) {
this.x = 800; // or width, startingPosition, ...
}
}
Edit: Alien class was added so adapted my solution to the code.

How can I change the vector of a ball in breakout game made using Java?

I'm using Java to make a breakout game. The independent parts are functioning: the paddle, the ball, the bricks.
However, the ball hits a wall and then instead of changing it's vector, the ball just travels up the x-axis in a straight line at the edge of the JFrame window until it hits the top of the window and bounces back down from this corner.
The ball then gets stuck in an infinite back and forth line from the top left corner until it touches the paddle (back and forth) and will never break any of the other bricks.
How can I change my code to fix this problem?
import java.awt.Graphics;
public class Ball extends Sprite {
private int xVelocity = 1, yVelocity = -1;
// Constructor
public Ball() {
setWidth(Settings.BALL_WIDTH);
setHeight(Settings.BALL_HEIGHT);
resetPosition();
public void resetPosition() {
setX(Settings.INITIAL_BALL_X);
setY(Settings.INITIAL_BALL_Y);
}
public void update() {
x += yVelocity;
y += yVelocity;
// Bounce off left side of screen
if(x <= 0) {
x = 0;
setXVelocity(-1);
}
// Bounce off right side of screen
if(x >= Settings.WINDOW_WIDTH - Settings.BALL_WIDTH) {
x =Settings.WINDOW_WIDTH;
setXVelocity(-1);
}
// Bounce off top of screen
if(y <= 0) {
y = 0;
setYVelocity(1);
}
}
public void setXVelocity(int x) {
xVelocity = x;
}
public void setYVelocity(int y) {
yVelocity = y;
}
public int getXVelocity() {
return xVelocity;
}
public int getYVelocity() {
return yVelocity;
}
public void paint(Graphics g) {
g.fillOval(x, y, Settings.BALL_WIDTH, Settings.BALL_HEIGHT);
}
}
import java.awt.Color;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Paint;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JPanel;
import javax.swing.Timer;
public class BreakoutPanel extends JPanel implements ActionListener, KeyListener {
static final long serialVersionUID = 2L;
private boolean gameRunning = true;
private int livesLeft = 3;
private String screenMessage = "";
private Ball ball;
private Paddle paddle;
private Brick bricks[];
public BreakoutPanel(Breakout game) {
addKeyListener(this);
setFocusable(true);
Timer timer = new Timer(5, this);
timer.start();
ball = new Ball();
paddle = new Paddle();
bricks = new Brick[Settings.TOTAL_BRICKS];
createBricks();
}
private void createBricks() {
int counter = 0;
int x_space = 0;
int y_space = 0;
for(int x = 0; x < 4; x++) {
for(int y = 0; y < 5; y++) {
bricks[counter] = new Brick((x * Settings.BRICK_WIDTH) + Settings.BRICK_HORI_PADDING + x_space, (y * Settings.BRICK_HEIGHT) + Settings.BRICK_VERT_PADDING + y_space);
counter++;
y_space++;
}
x_space++;
y_space = 0;
}
}
private void paintBricks(Graphics g) {
for(int x = 0; x < Settings.TOTAL_BRICKS; x++) {
for(int y = 0; y < Settings.TOTAL_BRICKS; y++) {
bricks[y].paint(g);
}
}
}
private void update() {
if(gameRunning) {
// TODO: Update the ball and paddle
ball.update();
paddle.update();
collisions();
repaint();
}
}
private void gameOver() {
stopGame();
screenMessage = "Game Over!";
}
private void gameWon() {
stopGame();
screenMessage = "Congratulations! You have won!";
}
private void stopGame() {
gameRunning = false;
}
private void collisions() {
// Check for loss
if(ball.y > 450) {
// Game over
livesLeft--;
if(livesLeft <= 0) {
gameOver();
return;
} else {
ball.resetPosition();
ball.setYVelocity(-1);
}
}
// Check for win
boolean bricksLeft = false;
for(int i = 0; i < bricks.length; i++) {
// Check if there are any bricks left
if(!bricks[i].isBroken()) {
// Brick was found, close loop
bricksLeft = true;
break;
}
}
if(!bricksLeft) {
gameWon();
return;
}
// Check collisions
if(ball.getRectangle().intersects(paddle.getRectangle())) {
// Simplified touching of paddle
ball.setYVelocity(-1);
}
for(int i = 0; i < bricks.length; i++) {
if (ball.getRectangle().intersects(bricks[i].getRectangle())) {
int ballLeft = (int) ball.getRectangle().getMinX();
int ballHeight = (int) ball.getRectangle().getHeight();
int ballWidth = (int) ball.getRectangle().getWidth();
int ballTop = (int) ball.getRectangle().getMinY();
Point pointRight = new Point(ballLeft + ballWidth + 1, ballTop);
Point pointLeft = new Point(ballLeft - 1, ballTop);
Point pointTop = new Point(ballLeft, ballTop - 1);
Point pointBottom = new Point(ballLeft, ballTop + ballHeight + 1);
if (!bricks[i].isBroken()) {
if (bricks[i].getRectangle().contains(pointRight)) {
ball.setXVelocity(-1);
} else if (bricks[i].getRectangle().contains(pointLeft)) {
ball.setXVelocity(1);
}
if (bricks[i].getRectangle().contains(pointTop)) {
ball.setYVelocity(1);
} else if (bricks[i].getRectangle().contains(pointBottom)) {
ball.setYVelocity(-1);
}
bricks[i].setBroken(true);
}
}
}
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
ball.paint(g);
paddle.paint(g);
paintBricks(g);
// Draw lives left
// TODO: Draw lives left in the top left hand corner**
if(livesLeft != 0) {
String displayLives = Integer.toString(livesLeft);
g.setFont(new Font("Arial", Font.BOLD, 18));
g.drawString(displayLives, Settings.LIVES_POSITION_X, Settings.LIVES_POSITION_Y);
}
// Draw screen message*
if(screenMessage != null) {
g.setFont(new Font("Arial", Font.BOLD, 18));
int messageWidth = g.getFontMetrics().stringWidth(screenMessage);
g.drawString(screenMessage, (Settings.WINDOW_WIDTH / 2) - (messageWidth / 2),
Settings.MESSAGE_POSITION);
}
}
#Override
public void keyPressed(KeyEvent e) {
int key = e.getKeyCode();
if (key == KeyEvent.VK_LEFT) {
paddle.setXVelocity(-1);
}
if (key == KeyEvent.VK_RIGHT) {
paddle.setXVelocity(1);
}
}
#Override
public void keyReleased(KeyEvent e) {
if(e.getKeyCode() == KeyEvent.VK_LEFT || e.getKeyCode() == KeyEvent.VK_RIGHT) {
paddle.setXVelocity(0);
}
}
#Override
public void keyTyped(KeyEvent arg0) {
}
#Override
public void actionPerformed(ActionEvent arg0) {
update();
}
}

I made a similar game in python years ago. What I did to solve this problem was allow the player to control the direction of the ball by hitting it with different parts of the paddle.
If the player hit the ball with the absolute center of the paddle, then I would just reverse the vector as if it had hit off a wall. But if the absolute edge of the paddle hit the ball, then I would increase the x velocity in the same direction of the edge that it hit. You can make the effect continuous, so if the the ball hits the paddle halfway between the edge and the center, it increases the x velocity half as much as it would have if it had hit the absolute edge.
This way the vector will continuously change and the ball will bounce off of things in a more interesting way, as well as give the player more control so they don't have to just wait until the ball eventually hits every brick in a predefined pattern.
You can use a coefficient, or more complex function if you don't want the effect of where the ball hits the paddle to effect the x velocity in such a linear manner.
You can use a similar strategy for handling collisions with the bricks. For instance, if the ball hits the corner of a brick, you probably don't want it to react as if it had hit the bottom, or the side, but have a reaction that is somewhere in between.

How to create random monsters

I am making a game like Space Impact. In my game the rockets are working correctly, but I can't create monsters randomly. Monsters are on the screen but they aren't moving so they aren't active
How can I do this?
public class Dnm extends JFrame implements Runnable {
Graphics dbg;
Image dbImage;
Image Pik1;
Image Boss;
static ImageIcon active;
int x, y, xDirection, yDirection, BossX, BossY;
public void run() {
try {
while (true) {
move();
boss();
Thread.sleep(10);
}
} catch (Exception e) {
System.out.println("Uh-oh, something went wrong!.");
}
}
private void move() {
x += xDirection;
y += yDirection;
}
private void boss() {
while (BossX == 0) {
BossX = getX() - 1;
}
Random rastgele = new Random(getY());
BossY = rastgele.nextInt();
}
public void setXDirection(int xdir) {
xDirection = xdir;
}
public void setYDirection(int ydir) {
yDirection = ydir;
}
// KEY COMMANDS //
public class AL extends KeyAdapter {
#Override
public void keyPressed(KeyEvent e) {
int keyCode = e.getKeyCode();
if (keyCode == e.VK_LEFT) {
setXDirection(-1);
}
if (keyCode == e.VK_RIGHT) {
setXDirection(+1);
}
if (keyCode == e.VK_UP) {
setYDirection(-1);
}
if (keyCode == e.VK_DOWN) {
setYDirection(+1);
}
}
#Override
public void keyReleased(KeyEvent e) {
int keyCode = e.getKeyCode();
if (keyCode == e.VK_LEFT) {
setXDirection(0);
}
if (keyCode == e.VK_RIGHT) {
setXDirection(0);
}
if (keyCode == e.VK_UP) {
setYDirection(0);
}
if (keyCode == e.VK_DOWN) {
setYDirection(0);
}
}
#Override
public void keyTyped(KeyEvent e) {
}
}
// CONSTRUCTOR //
public Dnm() {
//Image Import
ImageIcon still = new ImageIcon("img/rocket.png");
Pik1 = still.getImage();
addKeyListener(new AL());
setTitle("Dnm");
setSize(500, 500);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setResizable(true);
setVisible(true);
x = 15;
y = 15;
}
public void paint(Graphics g) {
dbImage = createImage(getWidth(), getHeight());
dbg = dbImage.getGraphics();
paintComponent(dbg);
g.drawImage(dbImage, 0, 0, this);
}
public void paintComponent(Graphics g) {
ImageIcon background = new ImageIcon("img/space.jpeg");
Image background1 = background.getImage();
ImageIcon still1 = new ImageIcon("img/Alien.png");
Boss = still1.getImage();
g.setColor(Color.red);
g.drawImage(background1, 0, 0, this);
g.drawImage(Boss, BossX, BossY, this);
g.drawImage(Pik1, x, y, this);
g.setColor(Color.blue);
repaint();
}
public static void main(String[] args) {
Dnm game = new Dnm();
Thread t1 = new Thread(game);
t1.start();
}
}
Thank You.

With your code being incomplete, it is hard to say for sure, but this line looks suspicious:
while (BossX == 0) {
BossX = getX() - 1;
}
This code is mostly likely going to be executed once, right? If BossX is initially zero, the code executes where you change its value. On the next update, BossX is not zero (presumably), so the code doesn't execute. Since BossX is the X coordinate where you are drawing the boss, then it will not move. Instead it just gets redrawn over and over in the same spot.
To get the monster to move randomly, increment or decrement both the X and Y coordinate values randomly during each game loop. Add a second random variable to cause them to move at random speeds in the random direction (by adjusting the coordinate value by a value greater than one).
As NPE commented, you should step through the code in a debugger and find out precisely what is going on.

I am fairly a beginner at programming, but here is my best attempt:
I would create a method that is called every x seconds that generates a random number using Math.Random(). I would say
int number = .5;
if(number > Math.Random())
GenerateMonster();
Your GenerateMonster method would then create a new object with the default values for monster. In order for the monster's created to act a certain way, you need to inherit those functions wherever you defined how you want the monster to act. I don't see the code for these functions so I am assuming you just didn't list them. Hope this at least helps. Good Luck!

PacMan game movement

I am creating a pacman game in Java and I have 1 problem I can't get rid of.. The problem is as follows:
I have 4 buttons in the game screen for each way: up, down, left, right. The problem is that I can not use the buttons in the same time in x position as in the y position because I always get a value of 0 ( you understand this if you see my code below )
Below you can find my class for the pacman that i think is related to the problem ( see setBesturing(int besturing) method )
package h04PacMan;
/*
* PacMan laten bewegen
*/
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class PacMan extends JPanel implements ActionListener {
private int horizontalePlaats = 250; // x location
private int verticalePlaats = 150; // y location
private int richtingEnSnelheid = +10; // speed
private final int WACHTTIJD = 500; // DELAY
int diameter;
int waarde;
public PacMan() {
// create timer and start timer
javax.swing.Timer autoKlik = new javax.swing.Timer(WACHTTIJD, this);
autoKlik.start();
}
public int getHorPlaats() {
return horizontalePlaats;
}
// current y positie
public int getVerPlaats() {
return verticalePlaats;
}
// speed and way;
public int getRichtingEnSnelheid() {
return richtingEnSnelheid;
}
// new x position
public void setHorPlaats(int nieuweHorPlaats) {
if(nieuweHorPlaats > getWidth()) {
nieuweHorPlaats = 0;
}
else if(nieuweHorPlaats < 0) {
nieuweHorPlaats = getWidth();
}
horizontalePlaats = nieuweHorPlaats;
}
// new y position
public void setVerPlaats(int nieuweVerPlaats) {
if(nieuweVerPlaats > getHeight()) {
nieuweVerPlaats = 0;
}
else if(nieuweVerPlaats < 0) {
nieuweVerPlaats = getHeight();
}
verticalePlaats = nieuweVerPlaats;
}
public void setRichtingEnSnelheid(int nieuweRichtingEnSnelheid) {
richtingEnSnelheid = nieuweRichtingEnSnelheid;
}
//movement
public void setBesturing(int besturing) {
besturing = waarde;
if(waarde == 0) {
setVerPlaats( getVerPlaats() + richtingEnSnelheid);
}
else if(waarde == 1){
setHorPlaats( getHorPlaats() + richtingEnSnelheid);
}
}
#Override
public void actionPerformed(ActionEvent e) {
setBesturing(waarde);
System.out.println(waarde);
repaint();
}
DrawPacMan pacman = new DrawPacMan();
DrawPacMan ghost1 = new DrawPacMan();
DrawPacMan ghost2 = new DrawPacMan();
public void paintComponent(Graphics g) {
super.paintComponent(g);
// pacman movement
diameter = 75;
pacman.drawPacMan(g, getHorPlaats(), getVerPlaats(), diameter, Color.yellow);
// ghosts movement
int g1x;
for(g1x = 0; g1x < 10; g1x++) {
pacman.drawGhost(g, g1x, 40, diameter, Color.red);
}
pacman.drawGhost(g, 170, 70, diameter, Color.blue);
}
}
and this is the actionListener in my gamecontrol class
#Override
public void actionPerformed(ActionEvent e) {
if(e.getSource() == links) {
pacman.setRichtingEnSnelheid( -10 );
pacman.setBesturing(1);
System.out.println("links");
}
else if(e.getSource() == rechts) {
pacman.setRichtingEnSnelheid( +10 );
pacman.setBesturing(1);
System.out.println("rechts");
}
else if(e.getSource() == boven) {
pacman.setRichtingEnSnelheid( -10);
pacman.setBesturing(0);
System.out.println("boven");
}
else {
pacman.setRichtingEnSnelheid( +10);
pacman.setBesturing(0);
System.out.println("beneden");
}
}

Here is your problem:
//movement
public void setBesturing(int besturing) {
besturing = waarde; <-- THIS LINE
if(waarde == 0) {
setVerPlaats( getVerPlaats() + richtingEnSnelheid);
}
else if(waarde == 1){
setHorPlaats( getHorPlaats() + richtingEnSnelheid);
}
}
You are overwriting the value of besturing with the old value waarde. It should be the other way around.
//movement
public void setBesturing(int besturing) {
waarde = besturing; <-- THIS LINE
if(waarde == 0) {
setVerPlaats( getVerPlaats() + richtingEnSnelheid);
}
else if(waarde == 1){
setHorPlaats( getHorPlaats() + richtingEnSnelheid);
}
}

I think inside the method setBesturing(int besturing) should be:
waarde = besturing;

In your setBesturing method: -
besturing = waarde;
This line never changes the value of your waarde.. It is always zero.
You should do the assignment the other way : -
this.waarde = besturing;

You'll need to keep track of whether the button is pressed or not indepentently. Also, you're model doesn't support a diagonal movement at all (I'm not sure what your nederlands names exactly mean, i can interprete snelheid=Schnelligkeit=speed and some more).
You'll need to put diagonal movement into the model (e.g. give him an x and y velocity indepent from each other)

Keylisteners/Actionlisteners with Timer not working properly

I'm coding a game and I'm using Java's Swing. And right now i'm trying to get the KeyListeners and Action listeners to work.
What I'm trying to do is to make my object to move according to what key i'm pressing. (Left,Right,Up,Down), But for some reason nothing happens when i press either of these keys, but when i press 3 of them at the same time. the object is strangely moving to the left..
So here's my code for the class to create the Runner-object:
import java.awt.*;
public class Runner{
private int xpos, ypos, base, side;
public Runner(int b, int h ) {
base = b;
side = h;
}
public void setPosition(int x, int y){
xpos = x;
ypos = y;
}
public void view(Graphics g) {
int x[] = { xpos, xpos-base/2, xpos + base/2};
int y[] = { ypos, ypos + side, ypos + side };
g.setColor(Color.lightGray);
g.fillPolygon( x, y, 3 );
g.setColor(Color.darkGray);
g.drawLine(xpos, ypos, xpos, ypos + side);
}
public void shoot(Graphics g){
g.setColor(Color.red);
g.drawLine(xpos,ypos, xpos, 0);
}
}
And here's the code thats suppose to run the damn thing:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class RunningGame extends JPanel implements KeyListener, ActionListener{
Runner rs;
int x,y;
Timer t;
boolean shot = false;
boolean left = false, right = false, up = false, down = false;
public RunningGame() {
x = 100;
y = 150;
rs = new Runner(40,60);
rs.setPosition(x,y);
this.addKeyListener(this);
this.setBackground(Color.black);
t = new Timer(40, this);
t.start();
}
public void paintComponent(Graphics g){
super.paintComponent(g);
rs.view(g);
if(shot) rs.shoot(g);
}
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == 37) {left = true;}
if (e.getKeyCode() == 39) {right = true;}
if (e.getKeyCode() == 38) {up = true;}
if (e.getKeyCode() == 40) {down = true;}
if (e.getKeyCode() == 32) {shot = true;}
rs.setPosition(x,y);
this.repaint();
}
public void keyReleased(KeyEvent e){
if (e.getKeyCode() == 37) left = false;
if (e.getKeyCode() == 39) right = false;
if (e.getKeyCode() == 38) up = false;
if (e.getKeyCode() == 40) down = false;
if (e.getKeyCode() == 32) shot = false;
this.repaint();
}
public void keyTyped(KeyEvent e){}
public void actionPerformed(ActionEvent e) {
if (left) {
if(right){
right = false;
x = x - 10; shot = false;
}
}
if (right) {
if(left){
left = false;
x = x + 10; shot = false;
}
}
if (up) {
if(down){
down = false;
y = y - 10; shot = false;
}
}
if (down) {
if(up){
up = false;
y = y + 10; shot = false;
}
}
rs.setPosition(x,y);
this.repaint();
}
public static void main(String[] args) {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setSize(300, 300); f.setLocation(100,100);
f.setTitle("Running");
RunningGame p = new RunningGame();
f.add(p); f.setVisible(true);
p.requestFocus();
}
}
(This is not the final code it's just using an example with a spaceship, later i will use a different object, just wanna test the KeyListener and ActionListener so it works before proceeding.)
Anyways can anyone help me make the space ship move smoothly? and without having to release all keys to activate another? i.e If i hold left i want it to be able to press another button. so that if i press right, the space ship will start to move in that direction instead.
//MrElephants

In the blocks that look like:
if (left) {
if(right){
right = false;
x = x - 10; shot = false;
}
}
I think you should have x = x - 10; outside the second if:
if (left) {
if(right){
right = false;
shot = false;
}
x = x - 10;
}
although I'm not really sure what that inner if is for, maybe you should remove it completely (but keep the x -= 10 etc.). This should be sufficient to make the movement seem natural.