I am attempting to create my own version of the well known game Space invaders. I am using zetcode as a point of reference (not a direct copy and paste) http://zetcode.com/tutorials/javagamestutorial/spaceinvaders/
However I seem to be a bit stuck. Namely on the use of KeyAdapters and the MVC design pattern. According to zetcode tutorial, the protected int dx changes when KeyPressed is pressed and once again when it is released, however I not seeing any movement nor value change outside of the KeyPressed and Keyreleased methods.
I carried out some simple checks
1: Does the "player" graphics move without key input at all (basically do graphic updates work)? - Yes, I changed the "move()" method within player to simply do a "x--; " and visibly see movement on screen
2: Does the value "dx" change at all? - Kinda, from Keypressed method, I can use System.out.println(""+dx); to return the value and visibly see, from within the method that dx changes, but not outside of this method, suggesting that the value changes are only occurring local to this method, which in my opinion is bizarre.
My ask from the community is the following:
Is this an issue with concurrency (or should I say, 2 references to the "dx" value stored in memory but only 1 reference is getting updated or there something else funky going on in my code that I am missing?
package spaceInvaders;
import java.awt.event.KeyEvent;
public class Player extends IngameObjects implements Commons {
private int startX = 250;
private final int startY = 150;
public Player(){
initPlayer();
}
public void initPlayer(){
this.setX(startX);
this.setY(startY);
}
public int getX() {
return x;
}
public void setX(int x) {
this.x = x;
}
public void move(){
this.x += dx;
if (x <= 2) {
x = 2;
}
if (x >= 400 - 2 * 10) {
x = 400 - 2 * 10;
}
}
public void keyPressed(KeyEvent e) {
int key = e.getKeyCode();
if(key == KeyEvent.VK_LEFT){
dx = -1;
System.out.println(""+dx);
}
if(key == KeyEvent.VK_RIGHT){}
if(key == KeyEvent.VK_ESCAPE){
System.exit(0);
}
}
public void keyReleased(KeyEvent e) {
int key = e.getKeyCode();
if(key == KeyEvent.VK_LEFT){
this.x = -1;
}
if(key == KeyEvent.VK_RIGHT){}
}
}
package spaceInvaders;
public class IngameObjects {
protected int x;
private int y;
protected int dx;
public int getY() {
return y;
}
public void setY(int y) {
this.y = y;
}
}
package spaceInvaders;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Toolkit;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import javax.swing.JPanel;
public class GamePanel extends JPanel implements Runnable{
private Player player;
private Thread animator;
private boolean isRunning;
public GamePanel(){
this.setBackground(Color.BLACK);
this.setDoubleBuffered(true);
addKeyListener(new TAdapter());
setFocusable(true);
}
public void paintComponent(Graphics g){
super.paintComponent(g);
drawPlayer(g);
Toolkit.getDefaultToolkit().sync();
g.dispose();
}
public void drawPlayer(Graphics g){
g.setColor(Color.GREEN);
g.fillRect(player.getX(), player.getY(), 50, 50);
}
#Override
public void run() {
isRunning = true;
long startTime, timeDiff, sleepTime;
startTime = System.currentTimeMillis();
while(isRunning){
repaint();
gameUpdate();
timeDiff = System.currentTimeMillis() - startTime;
sleepTime = 5 - timeDiff;
try{
Thread.sleep(sleepTime);
}
catch(InterruptedException ex){
System.exit(0);
}
startTime = System.currentTimeMillis();
}
}
#Override
public void addNotify(){
super.addNotify();
startGame();
}
public void startGame(){
player = new Player();
if(animator == null || !isRunning){
animator = new Thread(this);
animator.start();
}
}
public void gameUpdate(){
player.move();
}
private class TAdapter extends KeyAdapter{
#Override
public void keyPressed(KeyEvent e) {
System.out.println(""+player.getX());
player.keyPressed(e);
}
#Override
public void keyReleased(KeyEvent e) {
player.keyReleased(e);
}
}
}
thanks for the swift responses, much appreciated. After x amount of time (leaving it as x due to embarrassment) I have actually found a problem, quite a serious one actually.
1: Duplicated TAdapter on another class which extended the JFrame
2: 2 classes (GamePanel (which extends JPanel) and class (poorly named) Main (which extends JFrame) both have setFocusable(true);
Regarding Vince's reply, yes you are correct, as an attempt to debug my own code I actually replaced what was originally dx, for x. Obviously neither worked which led me to suspect there was a coding issue elsewhere.
Regarding MadProgrammer's reply, thanks, I am not familiar with Key bindings, I have not been programming in a very long time, which is the reason why I am making my own version of space invaders, so I can not only get back into programming but improve my knowledge, I will look at key bindings, even though you don't specify what is wrong with KeyListeners, I will study the differences. Regarding dispose, yep once again, not very familiar with the uses, i thought it was another way of refreshing the graphics, I will look into this.
in summary, where did I go wrong:
Duplicated TAdapter in a dedicated class for JFrame and another one
in JPanel
Duplicated requests for "focus" setFocusable(true);
Use KeyListener instead of key bindings (not sure why: research required)
Use of the dispose() method
Changing value of x rather than dx
This question can be considered resolved at this point, thanks
Related
So I've been trying to figure out what's wrong with my code, but I've had basically no luck when it comes to finding what's wrong. I've seen plenty of folks who had similar issues but none of the fixes that were suggested helped with my problem.
I've made a video showcasing my problem, but I'll give an explanation here too: whenever I move on the screen, the tiles in my game engine don't sync up with each other in terms of positioning, and it seems to be only on the rendering end. When I do any sort of checks to see if the distance between two tiles changes, I don't get any sort of errors. I get these gaps between the tiles specifically when I'm moving up or left, and they instead merge slightly when I move down or right, as if some of the tiles are updating faster than the others.
I don't want to just start dumping my couple thousand lines of code here since that won't really help anyone, but I'm also not well versed in the game development world, so I'm not entirely sure what pieces of code are super relevant here. If there's anything that y'all would like to see, let me know and I'll happily provide it.
The main method and postInit looks like this:
public static void main (String[] args)
{
EventQueue.invokeLater(() ->{
ex = new ShootyGame();
ex.dispose();
ex.setLayout(null);
ex.setUndecorated(Settings.isFullscreen);
ex.setVisible(true);
ex.setCursor(ex.getToolkit().createCustomCursor(
new BufferedImage(1, 1, BufferedImage.TYPE_INT_ARGB), new Point(), null)); //hides the system cursor
ex.createBufferStrategy(2);
postInit();
});
}
private static void postInit()
{
//add a window listener to the main JFrame
ex.addWindowListener(new WindowAdapter()
{
/**
* Autosaves when the window is closed, then kills the game.
*/
#Override
public void windowClosing(WindowEvent e)
{
//TODO autosaving
kill();
}
});
render.start(); //these are just the two threads being started
run.start();
}
My two threads, which basically just run the step and render methods in my game class:
private static class Running extends Thread
{
boolean stop = false;
int fps = TickManager.fromFPS(Settings.FPS);
public void run()
{
while (!stop)
{
try
{
Running.sleep(fps);
}
catch(InterruptedException e)
{
System.err.println("B");
}
game.step();
}
}
}
private static class Render extends Thread
{
boolean stop = false;
int fps = TickManager.fromFPS(Settings.FPS);
public void run()
{
while (!stop)
{
try
{
Running.sleep(fps);
}
catch(InterruptedException e)
{
System.err.println("A");
}
game.render();
}
}
}
The run method in my Game class just calls the current character's step method (it'll call more later), which is what's directly used to move the Camera class' x and y position. The character step looks like this:
public void step()
{
this.calculateMove(); //gets info on which keys are being pressed, adds or subtracts an integer from dx and dy (which are also ints) based on which are being pressed
Game.cam.update(-this.dx, -this.dy); //sends the opposite movement to the camera
//change the position of the player character by the appropriate x and y amounts
this.changeX(this.dx);
this.changeY(this.dy);
this.reset(); //just sets dx and dy back to 0 after moving
}
And now to the rendering stuff here's the entire camera class since it's probably the most relevant class:
public class Camera
{
private int x;
private int y;
public Camera(int x, int y)
{
this.x = x;
this.y = y;
}
public void update(int dx, int dy)
{
moveX(dx);
moveY(dy);
}
public void moveX(int dx)
{
this.x += dx;
}
public void moveY(int dy)
{
this.y += dy;
}
/**
* Gets the top left corner of the camera's x position.
* #return The x position of the top left corner of the camera
*/
public int getCamX()
{
return this.x;
}
/**
* Gets the top left corner of the camera's y position.
* #return The y position of the top left corner of the camera
*/
public int getCamY()
{
return this.y;
}
}
And finally, the relevant code for the actual painting of the tiles:
public void render() //this is the part that the render thread calls initially
{
Toolkit.getDefaultToolkit().sync();
repaint();
}
public void paint(Graphics g) //the paint method, mostly handled in doDrawing
{
super.paint(g);
doDrawing(g);
}
private void doDrawing(Graphics g)
{
Graphics2D g2d = (Graphics2D) g;
//stuff that happens if the game isn't paused
if(!GameStates.isPaused)
{
currentMap.drawMap(g2d, this);
currentChar.draw(g2d, this);
}
}
public void drawMap(Graphics2D g2d, ImageObserver observer)
{
//for each tile in the map, call its draw method
for(int i = 0; i < this.tileArray.length; i++)
{
for(int j = 0; j < this.tileArray[0].length; j++)
{
this.tileArray[i][j].draw(g2d, observer);
}
}
}
public void draw(Graphics2D g2d, ImageObserver observer, BufferedImage image)
{
g2d.drawImage(image, this.getX() + Game.cam.getCamX(), this.getY() + Game.cam.getCamY() observer);
}
Sorry for the long winded post, I've just tried everything I can think of (and that my Googling abilities can help me think of) and I'm throwing this out as a last-ditch effort before I just move to an actual game engine. I wanted to make my own engine from scratch for the sake of getting more experience in Java, but if I can't figure this out I'd rather just move to a proper engine and actually make a game. Any help is massively appreciated :)
EDIT: capitalization
I testing to implement graphics into MVC structure but Im a bit stuck. Here is what I got so far. For now I just want to get the red ball to bounce back and forth. And use the button start to start the thread and button stop to stop the thread that runs the GameLoop in the controller.
But I think Im mixing this up a bit. Would very much appreciate some feedback!
Heres what I got so far:
GameModell
suppose to controll the bouncing. If the location of the ball is under 40 px or above 80 px - multiply the locationX with -1 to make the ball change direction
GameView
Here Im putting the labels on a JFrame. I also want to display the buttons start and stop to controll the thread but I guess they are hidden by the JPanel in TheGraphics class
GameController
Starts and stops the thread with ActionListeners. Contains the GameLoop
TheGraphics
Paints the ball and controll the direction
I guess I got a lot of thing that are all wrong but this is the best I can do at the moment. Would very much apreciate some help!
Thanks!
MAIN:
public class MVCgame {
public static void main(String[] args) {
GameModel gm = new GameModel();
GameView gv = new GameView();
GameController gc = new GameController(gm, gv);
}
}
MODEL:
public class GameModel {
private int multi = 1;
public void setMulti(int locX) {
if(locX < 40 || locX > 80) {
multi = multi * -1;
}
}
public int multi() {
return multi;
}
}
VIEW:
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class GameView extends JFrame {
private JPanel jp = new JPanel();
private JButton start = new JButton("Start");
private JButton stop = new JButton("Stop");
TheGraphics gr = new TheGraphics();
public GameView() {
add(jp);
add(gr);
jp.add(start);
jp.add(stop);
setSize(250, 250);
setVisible(true);
}
public void addListener(ActionListener theListener) {
start.addActionListener(theListener);
stop.addActionListener(theListener);
}
public JButton getStart() {
return start;
}
public JButton getStop() {
return stop;
}
// GUESS I SHOULD PUT THIS IN THE VIEW???
public void paintEllipse(Graphics theG) {
Graphics2D g2d = (Graphics2D) theG;
g2d.setColor(new Color(255, 0, 0));
g2d.fillOval(0, 0, 10, 10);
}
}
CONTROLLER:
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class GameController implements Runnable {
GameView gv;
GameModel gm;
private Thread thread;
private boolean running = false;
public GameController(GameModel gm, GameView gv) {
this.gv = gv;
this.gm = gm;
gv.addListener(theListener);
start();
}
ActionListener theListener = new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (e.getSource() == gv.getStart()) {
start();
System.out.println("PLAY = ");
} else if (e.getSource() == gv.getStop()) {
stop();
System.out.println("STOP = ");
}
}
};
public synchronized void start() {
thread = new Thread(this);
thread.start();
running = true;
}
public synchronized void stop() {
thread.interrupt();
running = false;
}
// GameLoop
public void run() {
long lastTime = System.nanoTime();
double amountOfTicks = 60.0;
double ns = 1000000000 / amountOfTicks;
double delta = 0;
long timer = System.currentTimeMillis();
int frames = 0;
while (running) {
long now = System.nanoTime();
delta += (now - lastTime) / ns;
lastTime = now;
while (delta >= 10) {
// tick();
delta--;
// repainting the graphics
gv.gr.drawer();
gm.setMulti(gv.gr.drawer());
System.out.println("gv.gr.drawer() = " + gv.gr.drawer() + " gm.multi() " + gm.multi());
// I want to use this value in the model to change the direction
}
if (running) {
}
frames++;
if (System.currentTimeMillis() - timer > 1000) {
timer += 1000;
System.out.println("FPS: " + frames);
frames = 0;
}
}
}
}
THE GRAPHICS:
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JPanel;
public class TheGraphics extends JPanel {
private int locX = 40;
public TheGraphics() {
}
public int drawer() {
locX++;
repaint();
return locX;
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(new Color(255, 0, 0));
g2d.fillOval(locX, 30, 10, 10);
}
}
GameModell suppose to controll the bouncing. If the location of the ball is under 40 px or above 80 px - multiply the locationX with -1 to make the ball change direction
public void setMulti(int locX) {
if(locX < 40 || locX > 80) {
multi = multi * -1;
}
}
Really bad idea. You should always check position and direction (sign(speed)). Otherwise, your object might get stuck out of bounds always changing direction without moving from place forever.
Apart from this, using the MVC concept is overkill in my eyes and shouldn't be used in such a small project nor in a game. In a game, you should more or less put all three together. Of course you can, but the advantages and disadvantages of the MVC concept don't fit the needs of a game in many ways (except for the GUI, perhaps).
Your main loop might look something like this (you kind of did this already, but why is the tick() commented out in your code?):
while (running) {
update(); // Update all game objects
paint(); // Paint them all
}
Each game object will have its own update() and paint() implementation. You absolutely need to separate the logic of update and paint, even if they are in the same class. So this one:
public int drawer() {
locX++;
repaint();
return locX;
}
is an absolute no-go.
Edit: (Referring your update answer)
You are using the method location() for different purposes. According to the Java name convention, you should rename it getLocation() and setLocation() depending on the use to clarify the code.
(Even if this is not really MVC anymore, I'd let GameFrame implement ActionListener instead of specifying it as variable of GameController.)
One thing you should really change is this one:
private int locX = 0;
public void location(int loc) {
this.locX = (int) loc;
}
Basically, you are duplicating the location value every frame and create unused redundant data. Another problem is, that this might work fine for only one variable, but what if you add more than the position to your model later on? Instead TheGraphics has to render on an instance of the data model, not its values. As long you are using one GameModel
private GameModel model; // set value once at initialisation
and rendering its values in paintComponent will work fine, but if you want to add more than one GameModel (handling GameModel more like a GameObjectModel), you will need to pass it as parameter in the paint method.
public void update() {
repaint();
}
Remove it and try getting around without. A method called from one place forwarding to a different method is a bad idea most of the time, especially if it obfuscates the functionality with a different name.
gv.gr.update();
gv.gr.location(gm.location());
You are first repainting your image and then setting the location? Basically, your game runs one frame behind all the time. Swap that order.
gv.gr.location(gm.location());
gv.gr.repaint();
Will be fine (I already said about location()).
This question already has answers here:
Class.getResource() returns null
(2 answers)
Closed 8 years ago.
This is my first question, I hope it's not too poorly made.
I'm definitely beginner level at java, probably lower. I'm taking most of my code from a tutorial in fact, hoping I'll learn what all the things do soon enough.
Anyway, so far, I have 3 .java files in my program, and it shows the exception to be at all 3 of them, plus one I never made.
Here's the full error:
Exception in thread "main" java.lang.NullPointerException
at javax.swing.ImageIcon.<init>(ImageIcon.java:205)
at Emilia.<init>(Emilia.java:17)
at Board.<init>(Board.java:26)
at TestGame.<init>(TestGame.java:7)
at TestGame.main(TestGame.java:18)
Here's all the code:
TestGame.java
import javax.swing.JFrame;
public class TestGame extends JFrame {
public TestGame() {
add(new Board());
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(400, 300);
setLocationRelativeTo(null);
setTitle("Project Obcasus");
setResizable(false);
setVisible(true);
}
public static void main(String[] args) {
new TestGame();
}
}
Board.java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Board extends JPanel implements ActionListener {
private Timer timer;
private Emilia emilia;
public Board() {
addKeyListener(new TAdapter());
setFocusable(true);
setBackground(Color.BLACK);
setDoubleBuffered(true);
emilia = new Emilia();
timer = new Timer(5, this);
timer.start();
}
public void paint(Graphics g) {
super.paint(g);
Graphics2D g2d = (Graphics2D)g;
g2d.drawImage(emilia.getImage(), emilia.getX(), emilia.getY(), this);
Toolkit.getDefaultToolkit().sync();
g.dispose();
}
public void actionPerformed(ActionEvent e) {
emilia.move();
repaint();
}
private class TAdapter extends KeyAdapter {
public void keyReleased(KeyEvent e) {
emilia.keyReleased(e);
}
public void keyPressed(KeyEvent e) {
emilia.keyPressed(e);
}
}
}
Emilia.java
import java.awt.Image;
import java.awt.event.KeyEvent;
import javax.swing.ImageIcon;
public class Emilia {
private String emilia = "emiliasprite.png";
private int dx;
private int dy;
private int x;
private int y;
private Image image;
public Emilia() {
ImageIcon ii = new ImageIcon(this.getClass().getResource(emilia));
image = ii.getImage();
x = 40;
y = 60;
}
public void move() {
x += dx;
y += dy;
}
public int getX() {
return x;
}
public int getY() {
return y;
}
public Image getImage() {
return image;
}
public void keyPressed(KeyEvent e) {
int key = e.getKeyCode();
if (key == KeyEvent.VK_A) {
dx = -1;
}
if (key == KeyEvent.VK_D) {
dx = 1;
}
if (key == KeyEvent.VK_W) {
dy = -1;
}
}
public void keyReleased(KeyEvent e) {
int key = e.getKeyCode();
if (key == KeyEvent.VK_A) {
dx = 0;
}
if (key == KeyEvent.VK_D) {
dx = 0;
}
if (key == KeyEvent.VK_W) {
dy = 0;
}
}
}
ImageIcon.java - Line 205
this(location, location.toExternalForm());
Again, I'm beginner level so if you guys could explain it as you would to a newcomer to java (or any programming language for that matter)
Thanks for any help. - Niblexis
path of .png file:
C:\Users\Damon\workspace\TestGame\Resources\Sprites\Player
The .png file is in the player folder. I tried to run the program via the run button in Eclipse. At least, I think it's the run button because it's what showed me the errors in the first place.
Looks like the problem is in this line:
ImageIcon ii = new ImageIcon(this.getClass().getResource(emilia));
which means most likely that you haven't placed your .png file in the right place for Java to find it.
Could you post the exact path of the .png file on disk?
More specifically: a null pointer in this line of ImageIcon.java:
this(location, location.toExternalForm());
would imply that the URL location is null (causing an exception in the method call .toExternalForm(). If you look at the docs for Class.getResource() you will see it says:
Returns: A URL object or null if no resource with this name is found
which implies that Java can't find the resource in question.
For us to help, you will need to describe your runtime environment (are you running your program from .class files or in a .jar? at the command-line or in a debugger in Eclipse / Netbeans?) so we can help you figure out why the resource isn't being found.
You're effectively calling Emilia.class.getResource("emiliasprite.png") with Emilia.java in the default (root) package, which means that you need to tell your IDE / build process to copy this file into the root of the classpath. (in the same directory that Emilia.class ends up) Otherwise, Java has no idea where to find it.
If you want to place the resource somewhere else, you need to change the path accordingly, as well as the mechanism that copies the resource from the source directory to the appropriate place on the classpath.
See this stackoverflow answer: Java in Eclipse: Where do I put files on the filesystem that I want to load using getResource? (e.g. images for an ImageIcon)
I was doing a tutorial online because I wanted to make a 2d side scroller, and I got this exact error. I have googled it but came up with nothing. I tried looking for a typo and it looks clean, its not giving me an error anywere else in the code. I do not know where to start. If you could explaing to me what the error is and how i fix it then that would be amazing.
package Main;
import GameState.GameStateManager;
import javax.swing.JPanel;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.image.BufferedImage;
public class GamePanel extends JPanel implements Runnable, KeyListener{
public static final int WIDTH = 320;
public static final int HIGHT = 240;
public static final int SCALE = 2;
//game thread
private Thread thread;
private boolean running;
private int FPS = 60;
private long targetTime = 1000/FPS;
//image
private BufferedImage image;
private Graphics2D g;
//game state manager
private GameStateManager gsm;
public GamePanel(){
super();
setPreferredSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
setFocusable(true);
requestFocus();
}
public void addNotify(){
super.addNotify();
if (thread == null) {
thread = new Thread(this);
addKeyListener(this);
thread.start();
}
}
private void init() {
image = new BufferedImage(WIDTH, HIGHT, BufferedImage.TYPE_INT_RGB);
g = (Graphics2D) image.getGraphics();
running = true;
gsm = new GameStateManager();
}
public void run(){
init();
long start, elapsed, wait;
//game loop
while(running) {
start = System.nanoTime();
update();
draw();
drawToScreen();
elapsed = System.nanoTime() - start;
wait = targetTime - elapsed / 1000000;
try
{
Thread.sleep(wait);
}
catch(Exception e)
{
e.printStackTrace();
}//end of try catch
}
}
private void update()
{
gsm.update();
}
private void draw()
{
gsm.draw(g);
}
private void drawToScreen()
{
Graphics g2 = getGraphics();
g2.drawImage(image, 0, 0, null);
g2.dispose();
}
public void KeyPressed(KeyEvent key)
{
gsm.keyPressed(key.getKeyCode());
}
public void KeyReleased(KeyEvent key)
{
gsm.keyReleased(key.getKeyCode());
}
}
The compiler error message tells you exactly what's wrong: your class implements the KeyListener interface but does not implement all the necessary methods of the interface. Solution: be sure to implement all the necessary methods as per the KeyListener API. Also be sure to use the #Override annotation to make sure that your overrides are correct.
Having said that, I'm going to recommend that you not use KeyListeners for most key board input with Swing applications, that it is a low-level listener and should be avoided in favor of higher level constructs such as key bindings. Also, Swing GUI's should avoid use of update(...) method overrides as that is more of an AWT construct.
Your KeyReleased(KeyEvent key) method must start with small letter 'k' like keyReleased(KeyEvent key). Java is case sensitive.
You may also required to override other methods of KeyListener interface.
Also add #Override annotation (as suggested by #Hovercraft Full Of Eels) to the method when you want to override a super method. That way IDE's will give you hint's while coding.
Im on to create a little "game", something like an 2d AirForce Shooter.
So, i have a problem with deleting unused enemys.
An Enemy is an simple JPanel, which is saved in the main logic as an array List.
public static ArrayList<Enemy> enemys = new ArrayList<Enemy>();
The Enemy run logic does the following:
while(!destroyed){
if(Game.running){
x--;
if(getBounds().intersects(Field.player.getBounding())){
Player.death = true;
}
if(x < 0){
Field.deleteEnemy(this);
}
setBounds((int) x, (int) y, 100, 50);
try{Thread.sleep(10);}catch(InterruptedException e){}
}
}
So you can seem there i already tried to call the method deleteEnemy, and just give it the unused Enemy.
But it isnt possible - when i just do this:
public static void deleteEnemy(Enemy e){
System.out.println("test");
enemys.remove(e);
}
It will be just removed from the list, but coninues existing on the Main JPanel.
And i cannot say
remove(e);
Because then i try to call a non static function in a static.
So, how could i delete an Enemy? Someone knows?
Thanks for help!
The hole code: (Game.java)
And, Enemy.java:
package Game;
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
public class Field extends JPanel implements Runnable{
public static Player player = new Player();
public static ArrayList<Enemy> enemys = new ArrayList<Enemy>();
private Thread moveBackground = new Thread(this);
private boolean bgMoving = false;
public static boolean addMob = false;
private int x = 0;
private int bgSpeed = -1;
public Field(){
setBounds(0, 0, 800, 600);
setFocusable(true);
setLayout(null);
addKeyListener(new Handler());
add(player);
}
public void paintComponent(Graphics g){
Field.super.paintComponent(g);
g.drawImage(Images.images[0], x, 0, this);
}
public static void deleteEnemy(Enemy e){
System.out.println("test");
enemys.remove(e);
}
public void run(){
while(!Player.death){
if(bgMoving){
bgMoving = true;
x += bgSpeed;
if(x < -(Images.images[0].getWidth(this) - this.getWidth() - 20)){
bgMoving = false;
}
repaint();
try { Thread.sleep(20); } catch (InterruptedException e) {}
}
if(addMob){
enemys.add(new Enemy());
add(enemys.get(enemys.size() - 1));
addMob = false;
}
}
JOptionPane.showMessageDialog(null, "DIED!");
}
public class Handler extends KeyAdapter {
public void keyPressed(KeyEvent e) {
player.KeyPressed(e);
if(!bgMoving){
if(Game.running){
bgMoving = true;
if(moveBackground.getState().toString() == "NEW"){
moveBackground.start();
}
}
}
}
public void keyReleased(KeyEvent e) {
player.KeyReleased(e);
}
}
}
And, Enemy.java:
package Game;
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;
public class Enemy extends JPanel implements Runnable{
Thread t = new Thread(this);
private double x = Game.width();
private double y = Math.random() * Game.height();
private double xF = 0, yF = 0;
private boolean destroyed = false;
public Enemy(){
setBounds((int) x, (int) y, 100, 50);
setOpaque(false);
t.start();
}
public void paintComponent(Graphics g){
Enemy.super.paintComponent(g);
g.setColor(Color.GREEN);
g.drawImage(Images.images[2], 0, 0, this);
}
public void run() {
while(!destroyed){
if(Game.running){
x--;
if(getBounds().intersects(Field.player.getBounding())){
Player.death = true;
}
if(x < 0){
Field.deleteEnemy(this);
}
setBounds((int) x, (int) y, 100, 50);
try{Thread.sleep(10);}catch(InterruptedException e){}
}
}
}
}
After removing you will need to call revalidate() and repaint()
[Too long for a comment]
I think the problem is in your logic on removing an Enemy/JPanel:
You are removing it from the ArrayList only, what about the containing JPanel/JFrame you added it to?
You must remove the JPanel from its container (maybe another JPanel or the JFrame) not just the ArrayList via Component#remove(Component c).
If you drew the Enemy images directly in paintComponent(...) of your container via iterating the ArrayList; removing it from the ArrayList would be sufficient, as it will no longer be in the Array and thus no longer drawn on the next repaint().
+1 to #Optional, you may need to call revalidate() and repaint() on the container for the affects of the removed JPanel/Enemy to be shown.
Also as #darijan mentioned, the use of static variables along with instance is not really a great design (though for certain designs this may be fine).
In your case if you need access to an instance method of another class, within another class, simply pass the instance of the class whos method you would like to access to the object which will access it.
Here is some psuedo code expressing much of the above mentioned problems / solutions:
public class Field extends JPanel {
private ArrayList<Enemy> enemies;
public Field() {
...
enemies.add(new Enemy(this));//create a new enemy and pas it the JPanel instance so it may access instance methods of this class
}
//ONLY USED IF JPanel for Enemy is ommited and Enemy class created which represents Enemy object and not Enemy object and aJPanel
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
ArrayList<Enemy> enemiesClone = new ArrayList<>(enemies);//copy array into another so we don't get a ConcurrentModificaton exception if removeEnemy is called while iterating the list
if(!enemiesClone.isEmpty())
for(Enemy e:enemiesClone) {//iterate through array of images
draw(e.getImage(),e.getX(),e.getY(),this);
}
}
public void removeEnemy(Enemy e) {
enemies.remove(e);//remove from the array
//ONLY USED IF JPanels are used as Enemy
remove(e);//remove from the JPanel
//so the changes of removed panel can be visible seen
revalidate();
repaint();
}
}
class Enemy extends JPanel //extends JPanel should be ommited for paintComponent method of drawing an enemy onscreen
{
private int x,y;
private BufferedImage image;
private Field f;
public Enemy(Field f) {//constructor accepts Field instance to access instance method for the class
this.f=f;
}
public void update() {
if(offscreen||dead) {
f.removeEnemy(this);//call removeEnemy which is an instance method of Field
}
}
//BELOW METHODS ONLY USED WHEN Enemy represents object and not a JPanel which can draw its image itself (and update position by simply changing co-ordinates)
public BufferedImage getImage() {
return image;
}
public int getX() {
return x;
}
public int getY() {
return y;
}
}
For a more detailed look check Game Development Loop, Logic and Collision detection Java Swing 2D I made which will give you the basics needed for most 2D games. However I do not use JPanels rather draw directly to a container.
Where do you add an Enemy to JPanel?
Basically, you should call remove on Field JPanel:
public void deleteEnemy(Enemy e){
System.out.println("test");
enemys.remove(e);
this.remove(e);
}
The method should not be static.