Develop Reference

Java - Graphics pixels aren't correctly updating?

Right now I just wanted to get my game window shown on the screen and I thought all would be well, except for the fact that the color red isn't shown on the whole window. Not sure why, I've gone over my code a few times and can't figure anything out. This is my code:
package game;
import java.awt.BorderLayout;
import java.awt.Canvas;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferInt;
import javax.swing.JFrame;
public class Game extends Canvas implements Runnable {
private final String GAME_NAME;
private final int GAME_WIDTH;
private final int GAME_HEIGHT;
private final int SCALE;
private boolean isRunning;
private JFrame frame;
private BufferedImage image;
private int[] pixels;
public Game(String name, int width, int aspectRatio[], int scale) {
// Variabe Initialization
this.GAME_NAME = name;
this.GAME_WIDTH = width;
this.GAME_HEIGHT = width / aspectRatio[0] * aspectRatio[1];
this.SCALE = scale;
this.image = new BufferedImage(GAME_WIDTH, GAME_WIDTH, BufferedImage.TYPE_INT_RGB);
this.pixels = ((DataBufferInt)image.getRaster().getDataBuffer()).getData();
this.frame = new JFrame(GAME_NAME);
Init();
}
private void Init() {
// Frame Setup
setMinimumSize(new Dimension(GAME_WIDTH * SCALE, GAME_HEIGHT * SCALE));
setMaximumSize(new Dimension(GAME_WIDTH * SCALE, GAME_HEIGHT * SCALE));
setPreferredSize(new Dimension(GAME_WIDTH * SCALE, GAME_HEIGHT * SCALE));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(this, BorderLayout.CENTER);
frame.pack();
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
private void Start() {
isRunning = true;
new Thread(this).start();
}
private void Stop() {
isRunning = false;
}
#Override
public void run() {
long lastTime = System.nanoTime();
long timer = System.currentTimeMillis();
final double ns = 1000000000d / 60d;
double delta = 0d;
int frames = 0;
int updates = 0;
while (isRunning) {
long now = System.nanoTime();
delta += (now - lastTime) / ns;
lastTime = now;
while (delta >= 1) {
updates++;
Update();
delta--;
}
Render();
frames++;
if (System.currentTimeMillis() - timer > 1000) {
timer += 1000;
frame.setTitle(GAME_NAME + " | " + updates + " ups, " + frames + " fps");
updates = 0;
frames = 0;
}
}
}
public void Update() {
for (int y = 0; y < GAME_HEIGHT; y++) {
for (int x = 0; x < GAME_WIDTH; x++) {
pixels[x + y * GAME_WIDTH] = 0xffff0000;
}
}
}
public void Render() {
BufferStrategy bs = getBufferStrategy();
if (bs == null) {
createBufferStrategy(3);
requestFocus();
return;
}
Graphics g = bs.getDrawGraphics();
{
g.drawImage(image, 0, 0, getWidth(), getHeight(), null);
}
g.dispose();
bs.show();
}
public static void main(String[] args) {
new Game("Game", 160, new int[]{12, 9}, 1).Start();
}
}

You've accidentally passed GAME_WIDTH as the height argument of the BufferedImage constructor call:
public Game(String name, int width, int aspectRatio[], int scale) {
// Variabe Initialization
this.GAME_NAME = name;
this.GAME_WIDTH = width;
this.GAME_HEIGHT = width / aspectRatio[0] * aspectRatio[1];
this.SCALE = scale;
this.image = new BufferedImage(GAME_WIDTH, GAME_WIDTH, BufferedImage.TYPE_INT_RGB);
// ^^^^^^^^^^
this.pixels = ((DataBufferInt)image.getRaster().getDataBuffer()).getData();
this.frame = new JFrame(GAME_NAME);
Init();
}
You probably meant to use GAME_HEIGHT:
this.image = new BufferedImage(GAME_WIDTH, GAME_HEIGHT, BufferedImage.TYPE_INT_RGB);

Created a game where the Frame's width is accurate after I run it but the height never updates

I'm learning to make games using a a tutorial on youtube. Everything seems fine except when I run the program. A frame shows up with the accurate width I want but the height looks like it sets to a default no matter what value I give it.
package ca.vanzeben.game;
import java.awt.BorderLayout;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferInt;
import javax.swing.JFrame;
public class Game extends Canvas implements Runnable {
private static final long serialVersionUID = 1L;
public static final int WIDTH = 160;
public static final int Height = WIDTH/ 12*9;
public static final int SCALE = 3; // able to move screen
public static final String NAME = "Juego";
private JFrame frame;
public boolean running = false;
public int tickCount = 0;
private BufferedImage image = new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);
private int[] pixels = ((DataBufferInt)image.getRaster().getDataBuffer()).getData();
public Game() { //game constructor
setMinimumSize(new Dimension(WIDTH*SCALE,HEIGHT*SCALE));
setMaximumSize(new Dimension(WIDTH*SCALE,HEIGHT*SCALE));
setPreferredSize(new Dimension(WIDTH*SCALE,HEIGHT*SCALE));
frame = new JFrame(NAME);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // closes game completely
frame.setLayout(new BorderLayout());
frame.add(this,BorderLayout.CENTER); //adds canvas to JFrame and centers it
frame.pack();//keeps everything sized correctly
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public synchronized void start() {//so u can start from the applet
running = true;
new Thread(this).start();
}
public synchronized void stop(){
running = false;
}
public void run() {
long lastTime = System.nanoTime();
double nsPerTick = 1000000000.0/60; //nanoseconds per tick or per update
int ticks = 0;
int frames = 0;
long lastTimer = System.currentTimeMillis();
double delta = 0.0; //how many unprocessed nano seconds
while(running){
long now = System.nanoTime();
delta+=(now-lastTime)/nsPerTick;
lastTime = now;
boolean shouldRender = true;
while(delta>=1){
ticks++;
tick();
delta -= 1;
shouldRender = true;
}
try{
Thread.sleep(2);
}catch(InterruptedException e){
e.printStackTrace();
}
if(shouldRender){
frames++;
render();
}
if(System.currentTimeMillis()-lastTimer>=1000){
lastTimer += 1000;
System.out.println(frames + " frames " + ticks + " ticks ");
frames = 0;
ticks = 0;
}
}
}
public void tick(){ //updates the game, updates the logic
tickCount++;
for(int i =0;i<pixels.length;i++){
pixels[i] = i + tickCount;
}
}
public void render(){ //prints out ^
BufferStrategy bs = getBufferStrategy();
if(bs == null){
createBufferStrategy(3);
return;
}
Graphics g = bs.getDrawGraphics();
g.drawImage(image, 0, 0, getWidth(), getHeight(), null);
g.setColor(Color.BLACK);
g.drawRect(0, 0, getWidth(), getHeight());
g.dispose();
bs.show();
}
public static void main(String[] args){
new Game().start();
}
}

You defined Height and used HEIGHT. Change it to:
public static final int HEIGHT = WIDTH / 12 * 9;
This is how it looked like to me:
Before:
After:

Java - NullPointerException with graphics [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 7 years ago.
I was trying to draw a simple rectangular on a JFrame but when I tried to draw it it gave me a NullPointerException. I could not find the problem because it is one of my codes that I already used. The object that is Null is a Graphics object that I got from the super class. Can someone help me with this?
Error:
Exception in thread "Thread-2" java.lang.NullPointerException
at com.daansander.game.Game.render(Game.java:83)
at com.daansander.game.Game.run(Game.java:76)
at java.lang.Thread.run(Thread.java:745)
Full Code:
package com.daansander.game;
import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferStrategy;
/**
* Created by Daan on 12-9-2015.
*/
public class Game extends Canvas implements Runnable {
public static final int WIDTH = 500;
public static final int HEIGHT = WIDTH / 12 * 9;
public static final int SCALE = 2;
public static final String NAME = "2DGame";
private JFrame frame;
private volatile boolean running;
public Game() {
setMinimumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
setMaximumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
setPreferredSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
frame = new JFrame(NAME);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(this, BorderLayout.CENTER);
frame.pack();
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
new Game().start();
}
public synchronized void start() {
running = true;
new Thread(this).start();
}
public synchronized void stop() {
}
#Override
public void run() {
long lastTime = System.currentTimeMillis();
long current;
long delta = 0;
int frames = 0;
// int ticks = 0;
while (running) {
current = System.currentTimeMillis();
delta += current - lastTime;
lastTime = current;
frames++;
if (delta > 1000) {
delta -= 1000;
System.out.println("FRAMES " + frames);
frames = 0;
}
try {
Thread.sleep(2);
} catch (InterruptedException e) {
e.printStackTrace();
}
render();
}
}
public void render() {
BufferStrategy bs = getBufferStrategy();
Graphics g = bs.getDrawGraphics(); // <----- Line of error
// g.setColor(Color.black);
// g.drawRect(0, 0, 5, 5);
//
// g.dispose();
// bs.show();
}
public void tick() {
}
public void init() {
}
}

getBufferStrategy() is returning null. As fabian linked to above:
public BufferStrategy getBufferStrategy()
Returns the BufferStrategy used by this component. This method will return null if a BufferStrategy has not yet been created or has been disposed.
You need to create a BufferStrategy first.

Program Terminates Instantly in Eclipse

I am creating a java program in eclipse but whenever I try to run it it terminates instantly please help. In the console next to where it says the java location it says terminated
Main Code:
package com.revert.main;
import java.awt.Canvas;
public class Game extends Canvas implements Runnable {
private static final long serialVersionUID = -2457117434114507933L;
public static final int WIDTH = 640, HEIGHT = WIDTH /12 * 9;
private Thread thread;
private boolean running = false;
public Game(){
new Window(WIDTH, HEIGHT, "Death By Block", this);
}
public synchronized void start(){
thread = new Thread(this);
thread.start();
running = true;
}
public synchronized void stop(){
try{
thread.join();
running = false;
}catch(Exception e){
e.printStackTrace();
}
}
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 >= 1){
tick();
delta--;
}
if(running)
render();
frames++;
if(System.currentTimeMillis() - timer > 1000){
timer += 1000;
System.out.println("FPS: " + frames);
frames = 0;
}
}
stop();
}
private void tick(){
}
private void render(){
}
public static void main(String args[]){
}
}
Window Code:
package com.revert.main;
import java.awt.Canvas;
import java.awt.Dimension;
import javax.swing.JFrame;
public class Window extends Canvas {
private static final long serialVersionUID = 5224458545146664877L;
public Window(int width, int height, String title, Game game){
JFrame frame = new JFrame(title);
frame.setPreferredSize(new Dimension(width, height));
frame.setMinimumSize(new Dimension(width, height));
frame.setMaximumSize(new Dimension(width, height));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.add(game);
frame.setVisible(true);
game.start();
}
}

Try this
public static void main(String args[]) {
new Game();
}

2D Top-Down Java (1.8) Game from Scratch(nothing)

So, first of all this is my first time posting and I am trying to make a top-down game with java(1.8) and IntelliJ, nothing else. I have all of my code good and done(for making the sprite show up), I test it and it keeps giving me error messages saying that certain parts are invalid. It is supposed to display an image (character) on the screen in the top right here is all code and please keep in mind that I do not have this fully finished:
Game.java
package main;
import main$entities.Player;
import main$gfx.ImageLoader;
import main$gfx.SpriteSheet;
import javax.swing.*;
import java.awt.*;
import java.awt.image.*;
import java.lang.*;
public class Game extends Canvas implements Runnable {
private static final long serialVersionUID = 1L;
public static final int WIDTH = 700, HEIGHT = 400, SCALE = 1;
public static boolean running = false;
public Thread gameThread;
private BufferedImage spriteSheet;
private Player player;
public void init(){
ImageLoader loader = new ImageLoader();
spriteSheet = loader.load("./spritesheet.png");
SpriteSheet ss = new SpriteSheet(spriteSheet);
player = new Player(0, 0, ss);
}
public synchronized void start(){
if(running)return;
running = true;
gameThread = new Thread(this);
gameThread.start();
}
public synchronized void stop(){
if(!running)return;
running = false;
try {
gameThread.join();
} catch (InterruptedException e) {e.printStackTrace();}
}
public void run(){
long lastTime = System.nanoTime();
final double amountOfTicks = 60D;
double ns = 1000000000 / amountOfTicks;
double delta = 0;
while(running){
long now = System.nanoTime();
delta += (now - lastTime) / ns;
lastTime = now;
if(delta >= 1){
tick();
delta--;
}
render();
}
stop();
}
public void tick(){
player.tick();
}
public void render(){
BufferStrategy bs = this.getBufferStrategy();
if(bs == null){
createBufferStrategy(3);
return;
}
Graphics g = bs.getDrawGraphics();
// Render Here
g.fillRect(0, 0, WIDTH * SCALE, HEIGHT * SCALE);
player.render(g);
// End Render
g.dispose();
bs.show();
}
public static void main(String[] args){
Game game = new Game();
game.setPreferredSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
game.setMaximumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
game.setMinimumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
JFrame frame = new JFrame("Tile RPG");
frame.setSize(WIDTH *SCALE, HEIGHT * SCALE);
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setResizable(false);
frame.add(game);
frame.setVisible(true);
game.start();
}
}
ImageLoader.java
package main$gfx;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.IOException;
public class ImageLoader {
public BufferedImage load(String path){
try {
return ImageIO.read(getClass().getResource(path));
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
SpriteSheet.java
package main$gfx;
import java.awt.image.BufferedImage;
public class SpriteSheet {
private BufferedImage sheet;
public SpriteSheet(BufferedImage sheet){
this.sheet = sheet;
}
public BufferedImage crop(int col, int row, int w, int h){
return sheet.getSubimage(col * 16, row * 16, w, h);
}
}
Player.java
package main$entities;
import main.Game;
import main$gfx.SpriteSheet;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
public class Player implements KeyListener{
private int x, y;
private SpriteSheet ss;
private boolean up = false, dn = false, lt = false, rt = false;
private final int SPEED = 3;
public Player(int x, int y, SpriteSheet ss){
this.x = x;
this.y = y;
this.ss = ss;
}
public void tick(){
if(up){
y -= SPEED;
}
if(dn){
y += SPEED;
}
if(lt){
x -= SPEED;
}
if(rt){
x += SPEED;
}
}
public void render(Graphics g){
g.drawImage(ss.crop(0 ,0, 16, 16), x, y, 16 * Game.SCALE, 16 * Game.SCALE, null);
}
public void keyTyped(KeyEvent e) {}
public void keyPressed(KeyEvent e) {
}
public void keyReleased(KeyEvent e) {
}
}
The error messages(It gives me multiple messages, each time is different // = what is on that line, so you don't have to find it by counting, your welcome):
First time I run the Game.java:
Exception in thread "Thread-2" java.lang.NullPointerException
at main.Game.tick(Game.java:64) // player.tick();
at main.Game.run(Game.java:56) // tick();
at java.lang.Thread.run(Thread.java:745) // this is in the JDK itself
Process finished with exit code 0
Second(and all that proceed) time I run the Game.java:
Exception in thread "Thread-2" java.lang.NullPointerException
at main.Game.render(Game.java:77) // player.render(g);
at main.Game.run(Game.java:59) // render();
at java.lang.Thread.run(Thread.java:745) // this is in the JDK itself
Process finished with exit code 0

That game.start(); takes all the responsibility. Your Game class is not extending a Thread, the thread itself will start automatically right after you instantiate your game's class, since the thread is created inside the game class.
So remove :
game.start();
Btw you fall on trap :
public static final int WIDTH = 700, HEIGHT = 400;
won't work, because those fields hide another fields, why? because
WIDTH & HEIGHT is preserved arguments for
.fillRect(...);

It's because you never call the init() method and, therefore the player and the spriteheet never gets created
You can add a constructor to the Game class like this:
public Game() {
init();
}
Or you can add the following line in the main method:
public static void main(String[] args){
Game game = new Game();
game.setPreferredSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
game.setMaximumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
game.setMinimumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
JFrame frame = new JFrame("Tile RPG");
frame.setSize(WIDTH *SCALE, HEIGHT * SCALE);
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setResizable(false);
frame.add(game);
frame.setVisible(true);
// Add this line
game.init();
game.start();
}
}
But I prefer the first way