Develop Reference

JPanels not showing up, kinda

I am an in-school amateur making a snake game in java, it is not complete and i have run into a problem that i cant seem to fix. the first and second parts of the body show up just fine after eating the target, but after that they do not.
code that adds a body part:
public void addBody(int x, int y) {
snekBody.add(new JPanel());
snekBody.get(snekBody.size() - 1).setBackground(new Color(new Random().nextInt(255), new Random().nextInt(255), new Random().nextInt(255)));
snekBody.get(snekBody.size() - 1).setVisible(true);
snekBody.get(snekBody.size() - 1).setBounds(x*score, y*score, BODY_WIDTH, BODY_HEIGHT);
game.add(snekBody.get(this.snekBody.size() - 1));
revalidate();
}
}
code that moves the body parts(moveUp, moveDown, etc.:
public synchronized void moveRight(int x, int y) {
timer++;
while (!this.right) {
try {
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
head.setBounds(x, y, 20, 20);
xCoords.add(x);
yCoords.add(y);
//snekBody is an ArrayList of type JPanel
for(int i = 0; i < snekBody.size(); i++) {
if (i > 0) {
snekBody.get(i).setBounds(xCoords.get(timer-(10*score)), yCoords.get(timer-(10*score))+5, BODY_WIDTH, BODY_HEIGHT);
} else {
snekBody.get(i).setBounds(xCoords.get(timer-10), yCoords.get(timer-10)+5, BODY_WIDTH, BODY_HEIGHT);
}
}
repaint();
notifyAll();
revalidate();
}
code that calls addBody:
if (snek.up) {
snek.addBody(snek.xCoords.get(snek.timer-20), snek.yCoords.get(snek.timer-20));
the second picture is the snake when more than two targets have been eaten. the panels for the body just stop showing up.
The first picture is the snake when two targets have been eaten

Turns out that the panels were showing up on top of each other, thus why i could not see them.

Print String character one by one using threads

I am trying to print characters one by one on the animated banner, but i can't get the desired result.
I am getting the result with my code but not the one I am looking for. I am getting the banner and result of characters also.
But those characters are overlapping one another.
Please check below code
import java.awt.*;
import java.io.*;
//Banner class
class Banner extends Frame implements Runnable
{
boolean stop=false;
String str="Sreedhar Practice seassion";
//constructor
public Banner()
{
setLayout(null);
setBackground(Color.cyan);
setForeground(Color.blue);
}//end of constructor
//image paint settings methosd
public void paint(Graphics g)
{
Font f=new Font("Courier",Font.BOLD,40);
g.setFont(f);
for (int i=0;i<=str.length() ;i++ )
{
char ch=str.charAt(i);
String c=String.valueOf(ch);
g.drawString("\t"+c,10,100);
try
{
Thread.sleep(100);
}
catch (InterruptedException ie)
{
}
//char ch=str.carAt(0);
//str=str.substring(1,str.length());
//str=str+ch;
if (stop)
{
return;
}
}
}//image paint settings methosd end
//start of run method
public void run()
{
if (stop)
{
return;
}
}
}//end of run method
//main method starting
public static void main(String[] args)throws IOException
{
Banner b=new Banner();
b.setSize(400,400);
b.setTitle("Sreedhar Banner");
b.setVisible(true);
Thread t=new Thread(b);
t.start();
System.in.read();
b.stop=true;
}//end of main method
}//end of class Banner
This is my code, but am not getting the desired result what i want.

few bugs over here
first:
}//end of run method
one curly brace is redundant
second:
for (int i=0;i<=str.length() ;i++ )
should be:
for (int i=0; i < str.length(); i++)
third:
g.drawString("\t" + c, 10 + PRINT_FACTOR * i, 100);
where PRINT_FACTOR should be counted or choosed by expirement

It seems like in your call to g.drawString("\t"+c,10,100); the coordinates remain the same. Looks like it should somehow move along x axis depending on letter number. Try this:
int xLetterDifference = 6;
g.drawString("\t"+c, 10 + xLetterDifference * i ,100);
And alter value of xLetterDifference to adjust distance between letters

Java JButtons doesnt appear on the JFrame

Here's the significant fragment of JFrame HidingOperationView:
hideBtn.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent arg0){
currentPixelInImageToHide.setVisible(true);
pixelOfToHideTable.setVisible(true);
nextStep.setVisible(true);
doAll.setVisible(true);
SteganographyOperationsUtil.hidingOperation(
getSelectedFirstImageModel(), copyOfToHide, posterisation);
}
});
nextStep.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent arg0){
SteganographyOperationsUtil.key=1;
}
});
doAll.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent arg0){
SteganographyOperationsUtil.key2=1;
}
});
key and key2 are my controlers in the class SteganographyOperationsUtil, when to wait within the loop:
int key = 1
int key2 = 0
Key controled by the button 'next step', so the loop would go only once forward, show the results in the JTables and wait for another click.
Key2 controled by the button 'doAll', which allows the loop run till the end without stopping.
in the hiding operation:
for (int x = 0; x < hiding.getWidth(); ++x) {
for (int y = 0; y < hiding.getHeight(); ++y) {
if(temp < header.length()){
...
}else{
while (key!=1){
sleep(100);
}
key=key2;
...
if (key2 == 0){
throwToTable(HidingOperationView.pixelOfToHideTable,
colorOfToHideBinary);
}
}
}
}
The problem is that the buttons that control the loop doesn't appear at all,
they only do, when i comment the line:
SteganographyOperationsUtil.hidingOperation( getSelectedFirstImageModel(), copyOfToHide, posterisation);
Maybe it's not best way to control the loop, but i have no clue, how to do it otherwise.

How can you make your program sleep so that the GUI can catch up to what's happening?

I'm making a snake game(for those who don't know) where the snake is controlled by an AI using different algorithms to catch the food. The difference with the regular game is that the snake doesn't move unless a command has been sent by the AI.
My problem is that as soon as I run the AI, the AI creates a stack of commands to be executed to catch the food but my GUI just freezes; probably because it can't keep up with the amount of repaints that the move stacks cause. Through console logs, I can see that AI and the game logic is still running.
I tried to do Thread.sleep() after each move but I guess this just makes the entire program including the GUI sleep. I also have a Timer for my paintComponent but that doesn't seem to change anything.
How can you make your program sleep so that the GUI can catch up to what's happening?
EDIT:
Ok guys, I tried your solutions and it's still not working as it should. I don't really want to just dump the code here but I'm really lost. I have a timer that should repaint on a 140 millisecond interval(that's the value of DELAY), the commands are sent on a different thread which goes to sleep after each key press for 1000 milliseconds and I call repaint() after each call to move()... Here is relevant code(the original code without my modifications here):
private void initGame() {
dots = 5;
for (int z = 0; z < dots; z++) {
x[z] = 50 - z * 10;
y[z] = 50;
}
locateApple();
for (int k = blockNb - 1; k > 0; k--) {
locateBlock(k, apple_x, apple_y);
}
if (blocks) {
locateBlock(0, apple_x, apple_y);
}
timer = new Timer(DELAY, this);
timer.start();
startAi();
}
// AI CONTROLLER
public void startAi() {
Ai theAi = new Ai();
String move = "";
switch (ai) {
case "BFS":
move = theAi.bfs(this);
break;
}
//AI returns a string where each char is a move command
autoMove(move);
}
public void autoMove(String move) {
try {
Robot robot = new Robot();
System.out.println(move);
if (move != "#No") {
Thread thread = new Thread(new Runnable() {
public void run() {
for (int j = 0; j < move.length(); j++) {
if (move.charAt(j) == 'l') {
robot.keyPress(KeyEvent.VK_LEFT);
robot.keyRelease(KeyEvent.VK_LEFT);
}
if (move.charAt(j) == 'r') {
robot.keyPress(KeyEvent.VK_RIGHT);
robot.keyRelease(KeyEvent.VK_RIGHT);
}
if (move.charAt(j) == 'u') {
robot.keyPress(KeyEvent.VK_UP);
robot.keyRelease(KeyEvent.VK_UP);
}
if (move.charAt(j) == 'd') {
robot.keyPress(KeyEvent.VK_DOWN);
robot.keyRelease(KeyEvent.VK_DOWN);
}
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
});
thread.run();
}
} catch (AWTException e) {
e.printStackTrace();
}
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
doDrawing(g);
}
private void doDrawing(Graphics g) {
if (inGame) {
g.drawImage(apple, apple_x, apple_y, this);
for (int j = 0; j < blockNb; j++) {
g.drawImage(block, block_x[j], block_y[j], this);
}
for (int z = 0; z < dots; z++) {
if (z == 0) {
g.drawImage(head, x[z], y[z], this);
} else {
g.drawImage(ball, x[z], y[z], this);
}
}
Toolkit.getDefaultToolkit().sync();
} else {
// gameOver(g);
}
}
private void move() {
for (int z = dots; z > 0; z--) {
x[z] = x[(z - 1)];
y[z] = y[(z - 1)];
}
if (leftDirection) {
x[0] -= DOT_SIZE;
}
if (rightDirection) {
x[0] += DOT_SIZE;
}
if (upDirection) {
y[0] -= DOT_SIZE;
}
if (downDirection) {
y[0] += DOT_SIZE;
}
}
#Override
public void actionPerformed(ActionEvent e) {
if (inGame) {
repaint();
}
}
private class TAdapter extends KeyAdapter {
#Override
public void keyPressed(KeyEvent e) {
int key = e.getKeyCode();
if ((key == KeyEvent.VK_LEFT) && (!rightDirection)) {
leftDirection = true;
upDirection = false;
downDirection = false;
}
if ((key == KeyEvent.VK_RIGHT) && (!leftDirection)) {
rightDirection = true;
upDirection = false;
downDirection = false;
}
if ((key == KeyEvent.VK_UP) && (!downDirection)) {
upDirection = true;
rightDirection = false;
leftDirection = false;
}
if ((key == KeyEvent.VK_DOWN) && (!upDirection)) {
downDirection = true;
rightDirection = false;
leftDirection = false;
}
move();
checkApple();
checkCollision();
repaint();
}
}
EDIT 2: Also, I just wanted to point out that I tried to move without relying on a robot but to no avail.

Part 1:
Difference bettween Thread.sleep:
When you use it in main Thread(the Thread which java use to run the program)
then your whole program just freeze for that reason.
When you use A Thread for example(follow code)
new Thread(new Runnable(){
public void run(){
//do something...
while(flag==false)
Thread.sleep(a given time) //it need and try catch
else
//do your move
});
then only this Thread freeze (for a given time) or (Whatever you transform it to freeze).
In your case you can use a flag so every time a commant is hitten by user
the flag is going true and then again false to keep stopped the part of the
game you want but the main Thread your programms need to work still works
(if it is a window or anything...)
Part 2:(Basic form of your Thread)(The flag i use must be seen by all Methods)(public or private)
new Thread(new Runnable() {
public void run() {
flag=true;
while(flag==true){
if(move.equals("yes")){
//your code
move="no";
}else
Thread.sleep(20); //Sleep For a While(and then check again)
}
//That means that your Thread will run all over your game
//until game over (when game over just do the flag=false;)
//and The Thread will stop-exit
}});
*About Repaint Method(Dont call the repaint method too fast)
Call it only when the player make a move(this is the time that the frame
need to be repainted[Ok if you have .gif images in your game just dont see this]
Part 3:(When i made a similar game what i did)
Before some months i tried a similar game.The basic idea was a player who must past a labirinth so....
For each level i had one class like this...
public abstarct class Level2(){
//The game was into a panel like your.
//Here i added .setFocusable and .addKeyListener to panel
//Here it was an
public void actionListener(){
//The actionListener checked if the player found the door(for next level)
//Here it was the repaint so every time something happened repaint()
repaint();
}//End of Action Listener
//Use the paint or paintComponent what you need..
public void paint[or paintComponent](Graphics g){
//the 'squares' and the icons the had to be *repainted* again
}
//Here i had an extra class into this for the KeyListeners
//And I added the KeyListener like your game(up,down,left,right)
//I i said before i added this KeyListener to the panel
private class TAdapter extends KeyAdapter {
//KeyPressed,Released...etc
}
}
Thats the basic idea and for your game i think.
The Thread it's an extra option i can't help more you must find the way...

You should have a single "update" looped, from which your execute update commands and repaint request.
A simple approach would be to use a Swing Timer, which can trigger updates to a listener at regular intervals. It has the benefit of been triggered within the context of the EDT making it safe to update the UI from within. See How to use Swing Timers for more details
A more complex approach would be to use a Thread, which contained some kind of loop. This would perform the required updates and schedule repaint, but you'd need to insert Thread.sleep in to allow time for the updates to occur at a regular bases. The problem with this is you will need to synchronise your updates so that you don't update the model while painting is occurring as well synchronise you updates to the UI with the EDT

You need to have some sort of game scheduler loop and an understanding of how it works.
Here is some example code for java swing:
http://staticvoidgames.com/tutorials/swing/swingTimers
Another way to simplify things along with the scheduler is to make your game turn based at first. That is when the player moves 1turn (ie input) the game does all its processing and blocks on user input till the processing is done (ie single loop).

Every time your game AI outputs a new move, you need to call paint, but you also need to wait for whatever event is called when the painting is done before you output your next move, and you may want to wait like a second longer or something, play around with it
pseudo code
def fun 0 // entry point for program
// hook paint done event to func 1
call fun 2
def fun 1 // event handler method for when painting done
call fun 2
def fun 2 // function that does AI work
// do game logic
// call paint

Swing components freezing (Java)

I've coded a complex Snake game using Swing components.
I have a timer (call it moveRate) that calls repaint(); every x ms (x is changed during game and never goes below 50).
Now for the issue: I'm successful playing like 4 min or so before the whole frame freezes.
MoveRate class:
class MoveRate extends Timer{
private Date dateCreated=new Date();
private long timeLast=0;
public MoveRate(){
super(190, null);
dateCreated=new Date();
addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if(getWidth()>0 && getHeight()>0){
if(points.get(0).x+HOPS>getWidth() || points.get(0).x<0 ||
points.get(0).y+HOPS>getHeight() || points.get(0).y<0)
if(!crosswalls && !cheats){
moveRate.stop();
prizeRate.stop();
GameOver();
}
else{
if(points.get(0).y<0)
points.get(0).y=sp.getHeight()-HOPS;
else if(points.get(0).y+HOPS>sp.getHeight())
points.get(0).y=0;
else if(points.get(0).x<0)
points.get(0).x=sp.getWidth()-HOPS;
else
points.get(0).x=0;
}
timeLast=(System.currentTimeMillis()-dateCreated.getTime())/SECONDS;
score+=timeLast*(200/moveRate.getDelay());
}
if(prize!=null)
if(points.get(0).x==prize.x && points.get(0).y==prize.y){
int newX = points.get(points.size()-1).x-(points.get(points.size()-1).x - points.get(points.size()-2).x);
int newY = points.get(points.size()-1).y-(points.get(points.size()-1).y - points.get(points.size()-2).y);
points.add(new Point(newX, newY));
if(moveRate.getDelay()>50)
moveRate.setDelay(moveRate.getDelay()-5);
prize.createPrize(PU_NONE);
prizeRate.restart();
score+=timeLast*20*eatmultiplier;
}
if(powerup!=null)
if(points.get(0).x==powerup.x && points.get(0).y==powerup.y){
int newX = points.get(points.size()-1).x-(points.get(points.size()-1).x - points.get(points.size()-2).x);
int newY = points.get(points.size()-1).y-(points.get(points.size()-1).y - points.get(points.size()-2).y);
//points.add(new Point(newX, newY)); //if powerup should increase size
powerUpPerform(powerup.getType());
if(moveRate.getDelay()>50)
moveRate.setDelay(moveRate.getDelay()-5);
//powerUpRate.restart();
score+=timeLast*20*eatmultiplier;
powerup=null;
}
p.setScore(score);
repaint();
}
});
}
}
Basically MoveRate is responsible for animation aswell "eat moves" for prizes & powerups and checks for Game Over situations.
Some other notes:
I thought this has something to do with threads which I haven't learned yet so I added this:
new Thread(new Runnable() {
public void run() {
moveRate=new MoveRate();
moveRate.start();
powerUpRate.start();
prizeRate.start();
}
}).start();
Frame still freezes.
System.gc(); doesn't work neither if I time it every 30 seconds.
Be easy with me because I'm junior student with Java :>
EDIT
I've tried to reproduce the "bug" by making the snake longer (much longer - using my final int SNAKE_INITIAL_LENGTH=200). doesn't seem to have any effect on the problem.