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Graphics (java.awt.Graphics) not working on call

I am new to programming in Java, but I have coded in other languages. I've got a problem whereby I am unable to call my Paint() method which contains some drawing instructions. I want to be able to call it inside a timer function. The code's bellow:
package main;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.Timer;
import java.util.TimerTask;
import java.awt.Canvas;
import javax.swing.JPanel;
public class Player extends JPanel implements KeyListener, ActionListener{
// does the same as inheritiing methods and attributes from "JPanel" class type.
private static final long serialVersionUID = 1L;
private static long UUID;
// Time to set game-state values
#SuppressWarnings("unused")
private boolean isPlaying = false;
private int startingScore = 0;
#SuppressWarnings("unused")
private int currScore = startingScore;
// currScore should equal startingScore for correct start score when starting each game.
#SuppressWarnings("unused")
private int TotalBricks = 21;
private static Timer timer = new Timer();
private int delay = 5;
// Player Start Pos
private int PlayerX = 310;
private int PlayerY = 550; // TODO Change PlayerY Value
// Player Dimensions from Start Coords
private int PlayerMinX = PlayerX - 50;
private int PlayerMaxX = PlayerX + 50;
private int PlayerMinY = PlayerY - 4;
private int PlayerMaxY = PlayerY + 4;
// Ball Start Pos
#SuppressWarnings("unused")
private int BallX = 120;
#SuppressWarnings("unused")
private int BallY = 350;
// Ball Velocities
#SuppressWarnings("unused")
private int BallVelX = -1;
#SuppressWarnings("unused")
private int BallVelY = -2;
public Player(){
super();
this.setBackground(Color.white);
addKeyListener(this);
setFocusable(true);
setFocusTraversalKeysEnabled(false);
setVisible(true);
MyTimer();
//TODO Get the bricks to display on screen
}
public void MyTimer() {
TimerTask timerTask;
timerTask = new TimerTask() {
#Override
public void run() {
while (true) {
// TODO Get Paint() function working in here
}
}
};
timer.schedule(timerTask, 0, delay);
}
public void Paint(Graphics g){
// linear functions - colour precedes draw, can be overriden without affecting previous statements
// background
g.setColor(Color.black);
g.fillRect(1, 1, 692, 592);
// border of window
g.setColor(Color.yellow);
g.fillRect(0,0,3,592);
g.fillRect(0,0,692,3);
g.fillRect(691,0,3,592);
// no underside border
// paddle settings
g.setColor(Color.green);
g.fillRect(PlayerMinX, PlayerMinY, PlayerMaxX, PlayerMaxY);
//TODO Check if this works
// ball settings
g.setColor(Color.yellow);
g.fillRect(BallX, BallY, 20, 20);
}
public void actionPerformed(ActionEvent arg0) {
}
public void keyPressed(KeyEvent arg0) {
if (arg0.getKeyCode() == KeyEvent.VK_RIGHT)
{
}
else if (true){
}
}
public void keyReleased(KeyEvent arg0) {}
public void keyTyped(KeyEvent arg0) {}
}
Any help would be greatly appreciated. Also, any tips you guys could provide would also help. Thanks for any help you can provide in advance.

Custom painting is done by overriding paintComponent(...) not paint(...). You also need to invoke super.paintComponent(g) as the first statement to make sure the background get painted.
Java is case sensitive, so you need to make sure you override the proper method. You should always use #Override on the line before the method you override. If you make a typing error the compiler will tell you.
You should be using a Swing Timer for animation. Updates to Swing components should be done on the Event Dispatch Thread (EDT). The Swing Timer will automatically execute the code on the EDT.
Don't use a while (true) loop in the Timer. The point of using a Timer is that the Timer becomes the loop. You just execute your code every time the Timer fires.
In the ActionListener of your Timer you change the value of your variables to provide the animation and then you invoke repaint() which will cause your panel to be repainted.
Variable names should NOT start with an upper case character. Notice how the forums highlights your variable names because it thinks they are class names. This is confusing. Learn Java conventions and follow them.
Read the Swing Tutorial for Swing basics. There are section on a) Concurrency in Swing b) How to Use Swing Timers c) Custom Painting.

Swing animation flickers and makes GUI slow to respond

I'm trying to write a simple program: a bouncing ball that appears and starts bouncing after you press the "Start" button on the screen. The program should be closed by pressing "X".
For some reason, it runs very slowly. The ball is blinking, and I have to wait for a long time after I press the "X" for program to close.
Here is the code:
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.*;
import javax.swing.*;
public class Bounce
{
public static void main(String[] args)
{
JFrame frame = new BounceFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.show();
}
}
class BounceFrame extends JFrame
{
public BounceFrame()
{
setSize(WIDTH, HEIGHT);
setTitle("Bounce");
Container contentPane = getContentPane();
canvas = new BallCanvas();
contentPane.add(canvas, BorderLayout.CENTER);
JPanel buttonPanel = new JPanel();
addButton(buttonPanel, "Start", new ActionListener()
{
public void actionPerformed(ActionEvent evt)
{
addBall();
}
});
contentPane.add(buttonPanel, BorderLayout.SOUTH);
}
public void addButton(Container c, String title, ActionListener listener)
{
JButton button = new JButton(title);
c.add(button);
button.addActionListener(listener);
}
public void addBall()
{
try
{
Ball b = new Ball(canvas);
canvas.add(b);
for (int i = 1; i <= 10000; i++)
{
b.move();
Thread.sleep(10);
}
}
catch (InterruptedException exception)
{
}
}
private BallCanvas canvas;
public static final int WIDTH = 300;
public static final int HEIGHT = 200;
}
class BallCanvas extends JPanel
{
public void add(Ball b)
{
balls.add(b);
}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g;
for (int i = 0; i < balls.size(); i++)
{
Ball b = (Ball)balls.get(i);
b.draw(g2);
}
}
private ArrayList balls = new ArrayList();
}
class Ball
{
public Ball(Component c) { canvas = c; }
public void draw(Graphics2D g2)
{
g2.fill(new Ellipse2D.Double(x, y, XSIZE, YSIZE));
}
public void move()
{
x += dx;
y += dy;
if (x < 0)
{
x = 0;
dx = -dx;
}
if (x + XSIZE >= canvas.getWidth())
{
x = canvas.getWidth() - XSIZE;
dx = -dx;
}
if (y < 0)
{
y = 0;
dy = -dy;
}
if (y + YSIZE >= canvas.getHeight())
{
y = canvas.getHeight() - YSIZE;
dy = -dy;
}
canvas.paint(canvas.getGraphics());
}
private Component canvas;
private static final int XSIZE = 15;
private static final int YSIZE = 15;
private int x = 0;
private int y = 0;
private int dx = 2;
private int dy = 2;
}

The slowness comes from two related problems, one simple and one more complex.
Problem #1: paint vs. repaint
From the
JComponent.paint docs:
Invoked by Swing to draw components.
Applications should not invoke paint directly, but should instead use the repaint method to schedule the component for redrawing.
So the canvas.paint() line at the end of Ball.move must go.
You want to call
Component.repaint
instead...
but just replacing the paint with repaint will reveal the second problem, which prevents the ball from even appearing.
Problem #2: Animating inside the ActionListener
The ideal ActionListener.actionPerformed method changes the program's state and returns as soon as possible, using lazy methods like repaint to let Swing schedule the actual work for whenever it's most convenient.
In contrast, your program does basically everything inside the actionPerformed method, including all the animation.
Solution: A Game Loop
A much more typical structure is to start a
javax.swing.Timer
when your GUI starts, and just let it run
"forever",
updating your simulation's state every tick of the clock.
public BounceFrame()
{
// Original code here.
// Then add:
new javax.swing.Timer(
10, // Your timeout from `addBall`.
new ActionListener()
{
public void actionPerformed(final ActionEvent ae)
{
canvas.moveBalls(); // See below for this method.
}
}
).start();
}
In your case, the most important
(and completely missing)
state is the
"Have we started yet?"
bit, which can be stored as a boolean in BallCanvas.
That's the class that should do all the animating, since it also owns the canvas and all the balls.
BallCanvas gains one field, isRunning:
private boolean isRunning = false; // new field
// Added generic type to `balls` --- see below.
private java.util.List<Ball> balls = new ArrayList<Ball>();
...and a setter method:
public void setRunning(boolean state)
{
this.isRunning = state;
}
Finally, BallCanvas.moveBalls is the new
"update all the things"
method called by the Timer:
public void moveBalls()
{
if (! this.isRunning)
{
return;
}
for (final Ball b : balls)
{
// Remember, `move` no longer calls `paint`... It just
// updates some numbers.
b.move();
}
// Now that the visible state has changed, ask Swing to
// schedule repainting the panel.
repaint();
}
(Note how much simpler iterating over the balls list is now that the list has a proper generic type.
The loop in paintComponent could be made just as straightforward.)
Now the BounceFrame.addBall method is easy:
public void addBall()
{
Ball b = new Ball(canvas);
canvas.add(b);
this.canvas.setRunning(true);
}
With this setup, each press of the space bar adds another ball to the simulation.
I was able to get over 100 balls bouncing around on my 2006 desktop without a hint of flicker.
Also, I could exit the application using the 'X' button or Alt-F4, neither of which responded in the original version.
If you find yourself needing more performance
(or if you just want a better understanding of how Swing painting works),
see
"Painting in AWT and Swing:
Good Painting Code Is the Key to App Performance"
by Amy Fowler.

I would suggest you to use 'Timer' class for running your gameloop.It runs infinitely and you can stop it whenever you want using timer.stop()
You can also set its speed accordingly.

Java Physics loop (repaint on interval) is choppy unless mouse is moving

I have a simple physics loop that does a calculation for a time interval, waits for the interval to pass, and then renders the results on the screen. It's very simple code (even though the timing is probably wrong, but that's exactly what I'm trying to learn about) and works well when I am moving the mouse around the screen.
package physicssim;
import java.awt.Graphics;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class PhysicsSim extends JFrame {
private static class PhysicsObject {
public PhysicsObject(double x, double y, double v_x, double v_y) {
this.x = x;
this.y = y;
this.v_x = v_x;
this.v_y = v_y;
}
public double x;
public double y;
public double v_x;
public double v_y;
}
PhysicsObject particle;
boolean running = true;
DrawPane drawPane;
public PhysicsSim() {
particle = new PhysicsObject(10,10, .1, .2);
drawPane = new DrawPane(particle);
this.setSize(800,600);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setContentPane(drawPane);
this.setVisible(true);
}
private static class DrawPane extends JPanel {
PhysicsObject p;
public DrawPane(PhysicsObject p) {
this.p = p;
}
#Override
public void paint(Graphics g) {
super.paint(g); //To change body of generated methods, choose Tools | Templates.
g.fillOval((int)p.x, (int) p.y, 10, 10);
}
}
public void start() {
int FPS = 60;
long TIME_BETWEEN_FRAMES_NS = 1000000000/FPS;
// Initial draw
drawPane.repaint();
long lastDrawTime = System.nanoTime();
while(running) {
// Update physics
particle.x+=particle.v_x*(TIME_BETWEEN_FRAMES_NS*.0000001);
particle.y+=particle.v_y*(TIME_BETWEEN_FRAMES_NS*.0000001);
// While there is time until the next draw wait
while(TIME_BETWEEN_FRAMES_NS > (System.nanoTime()-lastDrawTime)) {
try {
Thread.sleep(1);
} catch (InterruptedException ex) {
Logger.getLogger(PhysicsSim.class.getName()).log(Level.SEVERE, null, ex);
}
}
drawPane.repaint();
long currentTime = System.nanoTime();
System.out.println(currentTime - lastDrawTime);
lastDrawTime = currentTime;
}
}
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
PhysicsSim sim = new PhysicsSim();
sim.start();
}
}
The last bit about printing the time difference was just a sanity check to make sure that it was in fact calling around the requested interval. The results are fairly consistent so I don't see why there should be any choppiness.
As I mentioned above, this code works great if I a moving the mouse around the screen, everything is smooth.
If I am not moving the mouse it becomes very choppy until I start moving the mouse over the application.
I assume this is something simple, but I hope that you guys can help me. Thank you.

Alright, it looks like my problem was I was drawing directly to g in paint(). After replacing with the following everything worked correctly.
#Override
public void paint(Graphics g) {
BufferedImage img = new BufferedImage(800, 600, BufferedImage.TYPE_3BYTE_BGR);
img.getGraphics().fillOval((int) p.x, (int) p.y, 10, 10);
g.drawImage(img, 0, 0, null);
}
I was considering deleting this code snippet because it's rough and shameful, but maybe it will help someone else. Happy coding.

Main.GamePanel is not abstract and does not override abstract method keyReleased(java.awt.event.KeyEvent) in java.awt.event.KeyListener

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.

Java Lang nullpointer exception in animation example?

import java.awt.*;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
public class Images extends JFrame {
public static void main(String[] args) {
DisplayMode dm = new DisplayMode(800,600,32, DisplayMode.REFRESH_RATE_UNKNOWN);
Images I = new Images();
I.run(dm);
}
private Screen s;
private Image bg;
private Image pic;
private boolean nLoaded;
Animation a;
public void run(DisplayMode dm)
{
nLoaded = false;
s = new Screen();
try{
s.Setfullscreen(dm, this);
LoadPics();
MovieLoop();
try{
Thread.sleep(50000);
}catch(Exception ex){}
}finally{
s.restoreScreen();
}
}
public void MovieLoop(){
long startingtime = System.currentTimeMillis();
long cumTime = startingtime;
while(cumTime-startingtime < 5000)
{
long timepassed = System.currentTimeMillis() - cumTime;
cumTime += timepassed;
a.update(timepassed);
Graphics g = s.getFullScreenWindow().getGraphics();
draw(g);
g.dispose();
try{
Thread.sleep(20);
}catch(Exception ex){}
}
}
public void draw(Graphics g)
{
g.drawImage(bg, 0,0, null);
g.drawImage(a.getImage(),0,0,null); }
//Create Load Pictures
public void LoadPics()
{
bg = new ImageIcon("C:\\Gamepics\\BackgroundImage.jpg").getImage();
pic = new ImageIcon("C:\\Gamepics\\SmileyIcon3.png").getImage();
nLoaded = true;
repaint();
}
public void paint(Graphics g){
if(g instanceof Graphics2D){
Graphics2D g2 = (Graphics2D)g;
g2.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
}
if(nLoaded)
{
g.drawImage(bg, 0, 0, null);
g.drawImage(pic, 300,300, null);
}
}
}
Im not understanding what I did wrong ive overlooked everything the best I can. Im just practicing a simple animation and I keep getting 3 null pointer exceptions.
Ive researched the best I can and apparently NullPointerExceptions in java have to do with trying to get the size of null arrays? The compiler hasn't marked any of my lists as problems so im a little confused. Any help would be greatly appreciated. All of the errors are commented out. There are three of them and they are in the Images class
Errors:
Exception in thread "main" java.lang.NullPointerException
at Images.MovieLoop(Images.java:45)
at Images.run(Images.java:26)
at Images.main(Images.java:8)
Animation Class
import java.awt.Image;
import java.util.*;
public class Animation {
private ArrayList scenes;
private int sceneindex;
private long movietime;
private long totaltime;
//CONSTRUCTOR
public Animation(){
scenes = new ArrayList();
totaltime =0;
start();
}
//Add scene to array list and sets time for each scene
//For example. If you have 3 scenes you would add t to total time three times. So if you had
//3 Scenes, one for 1s, one for 2s, one for 3s. Total time would be 6s. and you would call addscene 3 times
public synchronized void addScene(Image i, long t)
{
totaltime+=t;
scenes.add(new OneScene(i, totaltime));
}
//start animation from beggininign inignngingingnig
public synchronized void start(){
movietime = 0;
sceneindex = 0;
}
//change scenes
//movie time is the sum of all the time passed from last update
//If you have more than one scene. timepassed gets added to movietime.
//if movietime is greater than or equal to total time(ie. animation is complete) restart the animation
public synchronized void update(long timepassed)
{
if(scenes.size() > 1){
movietime += timepassed;
if(movietime >= totaltime)
{
movietime = 0;
sceneindex = 0;
}
while(movietime > getScene(sceneindex).endTime)
{
sceneindex++;
}
}
}
public synchronized Image getImage(){
if(scenes.size() == 0){
return null;}
else{
return getScene(sceneindex).pic;
}
}
//Getscene
private OneScene getScene(int x){
return (OneScene)scenes.get(x);
}
//Scenes are gonna be
private class OneScene{
Image pic;
long endTime;
public OneScene(Image pic, long endTime)
{
this.pic = pic;
this.endTime = endTime;
}
}
}
I included the animation class because the compiler is highlighting these three method calls as the source of the problem
a.update(timepassed);
MovieLoop();
I.run(dm);

Please Note: This is a really long comment
Let's start with Graphics g = s.getFullScreenWindow().getGraphics(); - getGraphics is NEVER a good idea, this can return null.
You should NEVER try and update any UI component from any thread other the EDT and you should NEVER draw directly to it in this manner, instead, you should be using paintComponent.
You should NEVER dispose of any Graphics context that you did not create yourself, this will prevent other components from been painted.
You should avoid overriding paint, especially of a top level container, if for no other reason, it's not double buffered (the top level container), and you will also be painting over any other child components.
Check out Performing Custom Painting for more details.
You should try using ImageIO instead of ImageIcon. ImageIO will throw exceptions if it can't read the file, where as ImageIcon simply fails silently, no very helpful.