I am trying to draw an image on a JPanel that requires thousands of calculations, and I want to animate the progression of the drawing. I.e., instead of doing all 100K iterations of drawing in one go, and then repainting the JPanel, I want to repaint after each iteration, then pause for a fraction of a second, so the user sees the image gradually appearing. However, each refresh of the JPanel erases previous drawings, so my method doesn't work. How can I do this without replicating all (1..N-1) calculations on the Nth iteration?
Consider this example: I want "snow" to gradually appear on the screen. However, this code will only show the 100,000th "snowflake" as all previous ones get erased each time repaint() is called.
import javax.swing.*;
import java.awt.*;
import java.util.Random;
class spanel extends JPanel{
public void paintComponent(Graphics g){
super.paintComponent(g);
g.drawLine(snow.x, snow.y, snow.x, snow.y);
}
}
class snow extends Thread {
static int x,y;
Random r = new Random();
public void run(){
JFrame sboard = new JFrame();
sboard.setSize(600,600);
sboard.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
spanel mypanel = new spanel();
sboard.add(mypanel);
sboard.setVisible(true);
for (int i=0;i<100000;i++){
x=r.nextInt(600);
y=r.nextInt(600);
sboard.repaint();
try {
snow.sleep((long)10);
} catch (InterruptedException e) {};
}
}
}
public class SnowAnim {
public static void main(String[] args) {
(new snow()).start();
}
}
Custom Painting Approaches shows how to draw on a BufferedImage. There are also plenty of other examples in the forum.
Also, when doing animation you should use a Swing Timer to schedule the animation.
How can I do this without replicating all (1..N-1) calculations on the Nth iteration?
Add them to a BufferedImage as seen in this example.
You should probably do your painting on a buffer, then draw the current state of the buffer in paintComponent();
You could also skip the call to super.paintComponent(g);, but then you would have to worry about other elements getting visually "stuck" in your panel.
Thanks all! I figured it out. BufferedImage solves it. For the record, here is my updated code. It also implements camickr's suggestion to use a Swing timer instead of a thread to schedule the animation. I also made some aesthetic changes to make the output look more like snow :-) Thanks again!
import javax.swing.*;
import java.awt.*;
import java.awt.image.*;
import java.util.Random;
import java.awt.event.*;
class spanel extends JPanel{
int x,y,rad,i;
static Random r = new Random();
BufferedImage image;
Graphics2D g2d;
Timer timer;
spanel(){
image = new BufferedImage(600, 600, BufferedImage.TYPE_INT_ARGB);
g2d = (Graphics2D)image.getGraphics();
setBackground(Color.black);
g2d.setColor(Color.white);
i=0;
ActionListener listener = new ActionListener() {
public void actionPerformed(ActionEvent ae) {
iterate();
}
};
timer = new Timer(10, listener);
timer.start();
}
public void iterate(){
x=r.nextInt(600);
y=r.nextInt(600);
rad=r.nextInt(5)+5;
g2d.fillOval(x, y, rad, rad);
repaint();
i++;
if (i==1000){timer.stop();}
}
public void paintComponent(Graphics g){
super.paintComponent(g);
g.drawImage(image,0,0,null);
}
}
public class SnowAnim {
public static void main(String[] args) {
JFrame sboard = new JFrame();
sboard.setSize(600,600);
sboard.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
spanel mypanel = new spanel();
sboard.add(mypanel);
sboard.setVisible(true);
}
}
Related
I'm trying this very simple code. It runs but doesn't show the animation. I'm new to animations, so I don't know what I'm missing.
package sample;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class Sample extends JPanel implements ActionListener {
Timer tm = new Timer(5, this);
int x = 0, Velx = 5;
public void paint(Graphics g) {
g.setColor(Color.RED);
g.fillRect(x, 30, 50, 50);
tm.start();
}
public void actionPerformed(ActionEvent e) {
x = x + Velx;
repaint();
}
public static void main(String[] args) {
Sample X = new Sample();
JFrame a = new JFrame();
a.setTitle("Rectangle RED");
a.setSize(500,500);
a.setVisible(true);
}
}
Sample X = new Sample();
X is never added to the frame. See first tip (the bold part) for how to add X to the frame.
Other tips:
Sample should #Override the getPreferredSize() method to return a sensible size for the canvas. Then we can dispense with a.setSize(500,500); and instead a.add(X); a.pack(); to get the frame to be the exact right size to display the rendering.
The Timer should be started in some place other than the paint methods! I'd go for the constructor.
Custom painting in any JComponent should be done in the paintComponent(Graphics) method.
In all custom painting, we should immediately call the super method to ensure that previous drawings are erased by painting the BG and border of the container.
Please learn common Java nomenclature (naming conventions - e.g. EachWordUpperCaseClass, firstWordLowerCaseMethod(), firstWordLowerCaseAttribute unless it is an UPPER_CASE_CONSTANT) and use it consistently.
JFrame a = new JFrame(); a.setTitle("Rectangle RED"); could be shortened to JFrame a = new JFrame("Rectangle RED");
I am trying to write a simple 2d animation engine in Java for visualizing later programming projects. However, I am having problems with the window refresh. On running, the frame will sometimes display a blank panel instead of the desired image. This begins with a few frames at a time at apparently random intervals, worsening as the program continues to run until the actual image only occasionally blinks into view. The code for processing each frame is run, but nothing in the frame is actually displayed. I believe the problem may come from my computer more than my code (certainly not from bad specs though), but am not sure. Help much appreciated.
Three classes. Code here:
package animator;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.applet.AudioClip;
public class APanel extends JPanel
{
public APanel(int l, int h){
setPreferredSize(new Dimension(l,h));
setLocation(80, 80);
setVisible(true);
setFocusable(true);
}
public Graphics renderFrame(Graphics g){
return g;
}
public void paintComponent(Graphics g) {
requestFocusInWindow();
renderFrame(g);
}
}
package animator;
import java.awt.*;
public class Animator extends APanel
//extending the APanel class allows you to code for different animations
//while leaving the basic functional animator untouched
{
public static final int SCREEN_X = 700;
public static final int SCREEN_Y = 700;
int frameNum;
public Animator() {
super(SCREEN_X, SCREEN_Y);
frameNum = 0;
}
public Graphics renderFrame(Graphics g) {
frameNum++;
g.drawString(""+frameNum,5,12);
return g;
}
}
package animator;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.Timer;
public class Runner {
int framerate = 30;
Animator a = new Animator();
JFrame j = new JFrame();
public Runner(){
j.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
j.add(a);
start();
j.setSize(a.getPreferredSize());
j.setVisible(true);
}
public void start() {
Timer t = new Timer(1000/framerate, new ActionListener() {
public void actionPerformed(ActionEvent e){
j.getComponent(0).paint(j.getComponent(0).getGraphics());
//The following line of code keeps the window locked to a preferred size
// j.setSize(j.getComponent(0).getPreferredSize());
}
});
t.start();
}
public static void main(String[] args){
Runner r = new Runner();
}
}
There are some serious mistakes in your code which could be the cause or a factor of your problem...
j.setSize(a.getPreferredSize()); is irrelevant, simply use JFrame#pack, you get better results as it takes into account the frame decorations
j.setSize(j.getComponent(0).getPreferredSize()); use JFrame#setResizable and pass it false instead...
NEVER do j.getComponent(0).paint(j.getComponent(0).getGraphics()); this! You are not responsible for the painting of components within Swing, that's the decision of the RepaintManager. Just call j.repaint()
super(SCREEN_X, SCREEN_Y);...just override the getPreferredSize method and return the size you want.
setLocation(80, 80); irrelevant, as the component is under the control of a layout manager
setVisible(true); (inside APanel)...Swing components are already visible by default, with the exception of windows and JInternalFrames
And finally...
public void paintComponent(Graphics g) {
requestFocusInWindow();
renderFrame(g);
}
There is never any need for this method to be made public, you NEVER want someone to be able to call it, this will break the paint chain and could have serious ramifications in the ability for the component to paint itself properly.
You MUST call super.paintComponent before performing any custom painting, otherwise you could end up with all sorts of wonderful paint artifacts and issues
Never modify the state of a component from within a paint method...while it "might" not be an immediate issue calling requestFocusInWindow(); within your paintComponent could have side effects you don't know about...
Instead, it should look more like...
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
renderFrame(g);
}
Hi I have just been messing about polygons and awt. I have created a Jframe and can draw the polygons ok and have one of them move with keypresses.
I'm wondering how to start a gameloop thread(and where to put it!) that will update the jframe independently.
From googling im led to believe that I should have one thread for user input and one for the game itself.
At the moment I have implemented KeyListener on the board class(code shown below),should I put that out into its own class and make it implement runnable?As the code stands I repaint the JFrame in the keypressed() method just so i can see that it moves correctly
Being at it most of the day and I have myself very very confused :)
As always any help much appreciated!
Also while im at it from online tutourials should I use JPanel instead of JFrame and paintComponent() instead of paint()?
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.geom.AffineTransform;
import javax.swing.JFrame;
public class Board extends JFrame implements KeyListener{
AffineTransform identity = new AffineTransform();
Graphics2D g2d;
Ship ship = new Ship();
public static final int ALIENS = 3;
Alien[] alien = new Alien[ALIENS];
Board(){
super("The Board");
setSize(1280,1024);
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
getContentPane().setBackground(Color.BLACK);
for(int x=0;x<ALIENS;x++){
alien[x]=new Alien();
}
}
public void paint(Graphics g){
super.paint(g);
addKeyListener(this);
//draw ship
g2d = (Graphics2D)g;
g2d.setTransform(identity);
g2d.translate(ship.getxPos(),ship.getyPos());
g2d.scale(2,2);
g2d.setColor(Color.ORANGE);
g2d.fill(ship.getShape());
g2d.setColor(Color.BLACK);
g2d.draw(ship.getShape());
// draw aliens
for(int x=0;x<ALIENS;x++){
//if alien alive
if(alien[x].isAlive()){
//draw alien
g2d = (Graphics2D)g;
g2d.setTransform(identity);
g2d.translate(alien[x].getxPos(),alien[x].getyPos());
g2d.scale(2,2);
g2d.setColor(Color.BLUE);
g2d.fill(alien[x].getShape());
g2d.setColor(Color.BLACK);
g2d.draw(alien[x].getShape());
}
}
}//end paint
/*****************************************************
* key listener events
*****************************************************/
public void keyReleased(KeyEvent k) { }
public void keyTyped(KeyEvent k) { }
public void keyPressed(KeyEvent k) {
int keyCode = k.getKeyCode();
switch (keyCode) {
case KeyEvent.VK_A:
//move ship left
if(ship.getxPos()<20){
ship.setxPos(20);
}else
ship.setxPos(ship.getxPos()-1);
break;
case KeyEvent.VK_D:
if(ship.getxPos()>1260){
ship.setxPos(1260);
}else
ship.setxPos(ship.getxPos()+1);
}
repaint();
}//end keypressed event
public static void main(String[] args){
new Board();
}
}
These answers depend somewhat on what kind of game you're trying to create.
From googling I'm led to believe that I should have one thread for user input and one for the game itself.
You create one main game loop, which runs in its own thread. In psudeocode
while (running) {
update game model
draw game
wait x milliseconds
}
Your user input would update the game model directly. The game loop updates the game model if the computer is required to make moves or react to your moves. Then, the game loop reads the game model and draws the game based on the values in the model.
At the moment I have implemented KeyListener on the board class(code shown below),should I put that out into its own class and make it implement runnable?
Yes, you should put KeyListener into its own class. No, you don't have to make it a separate thread.
To save yourself future trouble, your Swing components should be defined and used on the Event Dispatch thread.
Here's how you do that.
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new Board();
}
});
}
Should I use JPanel instead of JFrame and paintComponent() instead of paint()?
Yes.
You should have a JPanel inside of a JFrame. The JPanel is where you perform the draw game psudeocode, using the paintComponent method.
Some people are going to disagree with me, but I've found it best if every object in the game has a draw method to draw itself.
public void draw(Graphics g)
The game model would also have a draw method, which draws all of the objects in the model.
The JPanel paintComponent method would look like this:
public void paintComponent(Graphics g) {
super.paintComponent(g);
gameModel.draw(g);
}
I am making an Animated ProgressBar, in which i used multiple fillRect() method of class javax.swing.Graphics.
To put a delay after each rectangle is painted, I am using Thread.sleep(500) method for making a delay, (Suggested by many Forums, for making a delay).
The Problem is, instead of making a delay of 0.5sec after each Rectangle box is displayed, it takes the whole delay required by all the rectangles, in the start, and then displays the final image, thats the Progress Bar.
Question 1
TO make a delay for every single bar, i put the delay "Thread.sleep(500)" along with the bars "fillRect()" in a single for() loop, i would like to know, Why does it takes all the delay in the beginning and then dislplays the completed ProgressBar.
Question 2
How can i change my code, so that the delay can occur simultaneously with each rectangle bar, so when i run the program it should generate an Animated Progress Bar.
Code:
import javax.swing.JOptionPane;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.Color;
class DrawPanel extends JPanel
{
public paintComponent(Graphics g)
{
super.paintComponent(g);
g.setColor(new Color(71,12,3));
g.fillRect(35,30,410,90);
for ( int i=1; i<=40; i+=2)
{
Color c = new Color (12*i/2,8*i/2,2*i/2);
g.setColor(c);
g.fillRect( 30+10*i,35,20,80);
try
{ Thread.sleep(500); }
catch(InterruptedException ex)
{ Thread.currentThread().interrupt(); }
}
}
}
class ProgressBar
{
public static void main (String []args)
{
DrawPanel panel = new DrawPanel();
JFrame app = new JFrame();
app.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
app.add(panel);
app.setSize(500,200);
app.setVisible(true);
}
}
Your help is highly appreciated, Thankyou.
Don't block the EDT (Event Dispatch Thread) - the GUI will 'freeze' when that happens. Instead of calling Thread.sleep(n) implement a Swing Timer for repeated tasks. See Concurrency in Swing for more details. Also be sure to check the progress bar tutorial linked by #Brian. It contains working examples.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class DrawPanel extends JPanel
{
int i = 0;
public DrawPanel() {
ActionListener animate = new ActionListener() {
public void actionPerformed(ActionEvent ae) {
repaint();
}
};
Timer timer = new Timer(50,animate);
timer.start();
}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
g.setColor(new Color(71,12,3));
g.fillRect(35,30,410,90);
Color c = new Color (12*i/2,8*i/2,2*i/2);
g.setColor(c);
g.fillRect( 30+10*i,35,20,80);
i+=2;
if (i>40) i = 0;
}
}
class ProgressBar
{
public static void main (String []args)
{
DrawPanel panel = new DrawPanel();
JFrame app = new JFrame();
app.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
app.add(panel);
app.setSize(500,200);
app.setVisible(true);
}
}
I really wouldn't do this. The Swing refresh thread isn't supposed to be used like this. You're much better off using another thread (perhaps using a TimerTask) and redrawing rectangles upon demand.
Check out the Oracle ProgressBar tutorial for more info, code etc.
I'm new to java. I do have a java class but I want to get ahead. I really like it! This is my problem. I'm trying to draw the two paddles needed for the game. I did create 2 objects for them, and they both "Show" but the following happens:
Main Runner
import javax.swing.JFrame;
public class PongRunner {
public static void main (String[] args)
{
new PongRunner();
}
public PongRunner()
{
JFrame PongFrame= new JFrame();
PongFrame.setSize(800,600);
PongFrame.add(new PaddleB());
PongFrame.add(new PaddleA());
PongFrame.setLocationRelativeTo(null);
PongFrame.setTitle("My Pong Game");
PongFrame.setResizable(false);
PongFrame.setVisible(true);
PongFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
PaddleA and PaddleB are both drawRect Graphics and draw a specific rectangle.
The graphics that I tell JFrame to add first are the only ones visible. The one under it doesnt get added into the Frame I wanted to know why,and how i can draw both paddles in the same JFrame... I'm reading my book and looking over the internet as much as possible, but no luck within these 2 days. Some help would be nice. I just started learning java and I think I'm making progress. Some tips would be nice too thanks :), specialy on actionListener since im going to have to use them to move the paddles!
SOURCE CODE OF BOTH PADDLES:
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JPanel;
import javax.swing.Timer;
public class PaddleA extends JPanel implements ActionListener
{
private Timer timer;
public void timer()
{
timer = new Timer(25, this);
timer.start();
}
public void actionPerformed(ActionEvent e)
{
repaint();
}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
g.setColor(Color.RED);
g.fillRect(70,200,20,100);
}
}
PaddleB:
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JPanel;
import javax.swing.Timer;
public class PaddleB extends JPanel implements ActionListener
{
private Timer timer;
public void timer()
{
timer = new Timer(25, this);
timer.start();
}
public void actionPerformed(ActionEvent e)
{
repaint();
}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
g.setColor(Color.BLUE);
g.fillRect(500, 200, 20, 100);
}
}
As you've added the 2 paddles into the same BorderLayout.CENTER location of the main PongFrame, only the second paddle will be displayed.
This type of painting is more easily done using one Graphics object on one JComponent.
Swing components aren't really designed to be used like this. Each of your paddle JPanels is trying to paint a rectangle, but the container (the JFrame) and its layout manager will control the size and location of the JPanels. So the rectangle they paint may be outside their bounds, and won't appear at all.
Some Layout Managers will only show one of the JPanels if you add them one after another like this - see answer by Reimus.
To do animated graphics like this, you probably need to start with a single JComponent (e.g. a JPanel) that fills the JFrame, and paint both paddles as rectangles onto it.
This is because you add the first paddle and then add the second paddle over the first thus replacing them:
PongFrame.add(new PaddleB());
PongFrame.add(new PaddleA());
try using LayoutManagers here is just a quick sample:
PongFrame.getContentPane().add(new PaddleB(),BorderLayout.WEST);
PongFrame.getContentPane().add(new PaddleA(),BorderLayout.EAST);
also your g.fillRect(...); has x and y co-ordinates that are too large for the JFrame and thus are not displayed. Change it like so:
g.fillRect(0,0, 20, 100);
Not related though:
dont use JFrame.add() rather JFrame.getContentPane().add()
UPADTE:
As others have mentioned the logic for the game is a bit off. You should have a single drawing panel which is added to the JFrame and all drawing is done on the single JPanel using Graphics and not JPanels. Here is a small example:
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class PongRunner {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new PongRunner();
}
});
}
public PongRunner() {
JFrame PongFrame = new JFrame();
PongFrame.setTitle("My Pong Game");
PongFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
PongFrame.setResizable(false);
PongFrame.setSize(400,400);
//PongFrame.setLocationRelativeTo(null);
PongFrame.getContentPane().add(new DrawingPanel());
PongFrame.setVisible(true);
}
}
class DrawingPanel extends JPanel {
Rect rect1, rect2;
public DrawingPanel() {
super(true);
rect1 = new Rect(80, 80, 20, 100, Color.yellow);
rect2 = new Rect(100, 200, 20, 100, Color.red);
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(rect1.getColor());
g.fillRect(rect1.getX(), rect1.getY(), rect1.getWidth(), rect1.getHeight());
g.setColor(rect2.getColor());
g.fillRect(rect2.getX(), rect2.getY(), rect2.getWidth(), rect2.getHeight());
}
}
class Rect {
private Color color;
private int x, y, height, width;
Rect(int x, int y, int width, int height, Color color) {
this.x = x;
this.y = y;
this.height = height;
this.width = width;
this.color = color;
}
public Color getColor() {
return color;
}
public int getX() {
return x;
}
public int getY() {
return y;
}
public int getWidth() {
return width;
}
public int getHeight() {
return height;
}
public Rectangle getBounds() {
return new Rectangle(x, y, width, height);
}
}
Please note this snippet is not perfect and merely demonstrates the stereotypical logic needed for drawing rectangles to form a game of sorts
I don't have time to try running your code, but try setting the size and position of the "paddle" objects, or set them as non-opaque. I believe that Swing tries to speed up rendering by not drawing components which are completely covered by another opaque component. It may not be drawing one of your paddles for that reason.
If you do set the size and position of your paddles, you may have to modify your paintComponent methods: if my memory is correct, I think the Graphics object which is passed in is clipped to the area of the component, so 0,0 would be the top-left corner of the component.
you shouldn't add your JPanels to your JFrame by the JFrame#add(Component) method. Better add them to the contentPane: frame.getContentPane().add(panel); You should although read about LayoutManagers. They can help you by positining Components in your Frame or mess things up if you use them incorrect.