I'm attempting to "animate" a die roll in Java. I currently have an icon (called "diceImage") set up that, when a button is clicked (called "diceRoll"), updates to a new random image of a die face. What I would like to do is have it change image (to a random die face) numerous times over a couple of seconds before stopping on a final image.
The problem I have is not with generating a random number, or rolling it numerous times, it's with the updating the image numerous times within a loop. The code below, which rolls the die 10 times is what I have so far:
private void diceRollActionPerformed(java.awt.event.ActionEvent evt) {
for (int i = 1; i <= 10; i++) {
rollDice();
pause(100);
}
}
This links to the following two methods (the first of which generates the random number, and sets the icon image):
private void rollDice() {
Random r = new Random();
int randomNumber = r.nextInt(6) + 1;
diceImage.setIcon(new javax.swing.ImageIcon(getClass().getResource("/Game/Images/Dice " + randomNumber + ".png")));
}
The method below is "supposed" to pause the programme briefly between updating the image (this was taken from a programming course I was on where we had to animate an image of a car moving across the screen):
private void pause(int sleepTime) {
try {
Thread.sleep(sleepTime);
} catch (InterruptedException e) {
System.exit(-1);
}
}
All this programme seems to do is pause and then print the final dice roll. It doesn't show any of the "intermediate" faces. Does anyone have any ideas on why this isn't working?
Any help is greatly appreciated.
This question is asked several times a day. If you sleep in the event dispatch thread, you're preventing it from doing its job: react to events and repaint the screen.
Your animation should be done in another thread. Read the tutorial about concurrency in Swing, and use a Swing Timer.
The pause() you are using is when u need to animate moving stuff like a car for example , but just changing the icon of a JLabel which is the dice here doesn't need pause ( unless you just want it to be delayed a bit) ...
but anyways , to solve your issue , you need to call repaint() on that JLabel or updateGraphics(). Setting the Icon for the JLabel doesn't make the new Icon get displayed , you just need to repaint() it .
of course like JB Nizet said , for the app not to hang you need to call repaint on a new Thread .Thought you have to learn how to use Thread well cuz it can be very tricky at times .
good luck
Related
Recently i added that enemy shoots but unfortunately i cannot randomize delay of Shooting for every object.
Project 60 times in second :
update (all code here is connected to this part)
draw
sleep
Fragment of code :
Fragment of code.
public void createNewEnemyBullet(){
for(Enemy enemy: enemies){
EnemyBullet enemyBullet = new EnemyBullet(getResources());
randomShot = random.nextInt(60-40)+40;
System.out.println("Randomowy shot :"+ randomShot);
enemyBullet.x = (int) (((enemy.x+enemy.widthEnemy/2)-18)*screenRatioX);
enemyBullet.y= enemy.y+20;
enemyBullets.add(enemyBullet);
}
System.out.println("\n\n");
}
Screenshot of my result
enter image description here
Use Math.random(). It'll be your friend here. Compare (Math.random() <= epsilon) the output of random() with some number epsilon you want as your threshold for making an enemy shooting decision.
If enemyBullets is what the UI code uses to draw bullets, you may want to add a Thread.sleep(Math.random()) to add variable delay in adding them.
Solution for generating random delay of bullet is to change this delay when a enemy starship is shot.
I have a problem with my java game. I’m beginner, but i have to write it as a school project.
Game is called „Birthday Cake” there is 7 candles on the cake and randomly one of it is showing for let say 30s and during this time u have to click on it to get point, if u don’t click on it during this time next candle will show. Game end when 10 candle shows.
I made for loop and i tried to make it work for sooo long that I’m dying from frustration
my for loop works but it is so fast that i use Thread.sleep(1000), i tried lots of solutions it looks ok. BUT when i start my game nothing is happening and after few seconds all 7 candles shows and quickly disappear. I think I’m doing something wrong, but i have no idea what.
if(Dane.start){
int liczbaLosowa = 0;
for(int i=0; i<10 ;i++){
liczbaLosowa = (int)(Math.random()*7);
this.wspX= wspX_p[liczbaLosowa];
this.wspY= wspY_p[liczbaLosowa];
g2d.drawImage(plomienImg, wspX, wspY,null);
Toolkit.getDefaultToolkit().sync();
try {
Thread.sleep(1000);
} catch (Exception ex) { }
//repaint();
}
Dane.start=false;
}
this loop is inside JPanel paintComponent...
Never,
Never,
NEVER
call Thread.sleep(...) inside of paintComponent ever. Please understand that this method largely determines the perceived responsiveness of your program and anything that slows it down or freezes it will severely slow down and freeze your GUI. In fact you should never call Thread.sleep inside the code of most Swing programs (all that runs on the Swing event thread) but doing so in paintComponent is an even worse sin. The solution is to use a Swing Timer, and put code that you want to be called repeatedly at regular intervals inside of the Timer's ActionListener's actionPerformed code. Within this method, change the value held by fields within your class, for instance wspX and wspY, call repaint(), and then use those fields inside of paintComponent to determine what gets painted where.
Thread.sleep() is a bad call which can lead into many problems. i was told to never use it. instead i will show you the way i do my game loops. it might not be the perfect game loop but it is good.
i recommand implemets runnable and putting your loop in your run method.
public void run(){
init(); //initialisation of images, sound..etc. will be executed once only
int fps = 60 //number of update per second.
double tickPerSecond = 1000000000/fps;
double delta = 0;
long now;
long lastTime = System.nanoTime();
while(running){
now = System.nanoTime();
delta += (now - lastTime)/tickPerSecond;
lastTime = now;
if(delta >= 1){
tick();
render();
delta--;
}
}
}
private void init(){
//initialisation image, sound, loading world, generate maps....etc
}
private void tick(){
//tick player, world, entities..etc
}
private void render(){
//render graphics.
}
also dont forget to create start and stop method for the thread. you can change the fps to what number you would like, no need to go higher than 60.
I'm a beginner in Java programming and have come across an issue (probably an easy one to solve).
I am experimenting with Java GUI and wish to create a window in which the colours of an array are cycled through until there are no more colours. I believe I can do this using a for loop and cycling through the array, however I do not know how to loop through the background colour.
Any help and explanation would be appreciated.
public void flashColor() {
Color [] color = { Color.red,Color.orange,Color.green };
int i = 0;
for(i=0;i<color.length;i--){
getContentPane().setBackground(Color(i));
}
}
This line tells me:
getContentPane().setBackground(Color(i));
that yours appears to be a Swing GUI (a key bit of information that you left out of your question!), and so you need to take Swing threading into consideration. Your current code will in fact loop through all the colors, but it will do so immediately, and on the Swing thread so that the GUI will have no way to paint any of the colors other than the last one. The solution: use a Swing Timer and not a for loop. Inside the timer advance an index int variable and use it to show the color.
Something like:
getContentPane().setBackground(colorArray[0]);
int delay = 1000; // for 1 second
Timer myTimer = new Timer(delay, new ActionListener() {
int index = 0;
public void actionPerformed(ActionEvent e) {
index++;
if (index >= colorArray.length) {
((Timer)e.getSource()).stop(); // stop the timer
} else {
getContentPane().setBackground(colorArray[index]);
}
}
});
myTimer.start();
The code has not been tested, and you'll want to read the Swing Timer tutorial for the details.
Note the key here is that yes you need to loop, and to pause (so that the color can be seen) but you need to do your looping and pausing in a thread thread is off of the Swing event dispatch thread (or EDT). Yes you could do this using a SwingWorker, but that is a way more difficult way to do this. It is far easier to use a Swing Timer to do this for you. Note that it uses a background thread invisibly for you.
I'm having a problem I'm making a pool game and I need the ballos to react when I simulate a hit, the program works like this, you click the direction and power to hit the ball and the click go, the go button is in the GUI class where my labels are created, the button calls a method from my main class that recieves the parameter and then with a while in it, changes the X and Y of the ball till the power is reduced to 0 and then stops, the code is working, but the ball moves until the while stops. So the while works and when the power int is 0 the while goes out and then the new X,Y are painted.
This is the funcion that the button calls, the button sends all the parameters
public void golpe(int pbola, int pvelocidad, String pdireccion, JLabel[] listalabels) throws InterruptedException{
listabolas[pbola].setVelocidad(pvelocidad);
listabolas[pbola].setDireccion(pdireccion);
while (listabolas[pbola].getVelocidad() > 0) {
moverBola(pbola, listalabels);
//System.out.println(listabolas[pbola].getPosX());
//System.out.println(listabolas[pbola].getPosY());
Thread.sleep(500);
//This line is supposed to change the X and Y of the object over and over
//but only does it till the end
listalabels[pbola].setLocation(listabolas[pbola].getPosX(), listabolas[pbola].getPosY());
}
}
Here is the function moverbola(), only copied one "if" so that the code doesn't look to big
private void moverBola(int pbola, JLabel[] listalabels) {
if (listabolas[pbola].getDireccion().equals("SE")) {
int pposX = listabolas[pbola].getPosX();
listabolas[pbola].setPosX(pposX + 1);
int pposY = listabolas[pbola].getPosY();
listabolas[pbola].setPosY(pposY + 1);
}
Swing is a single threaded framework. That is, all interactions with UI are expected to occur from within a single thread, known as the Event Dispatching Thread.
Any action that blocks this thread, will prevent the EDT from updating the screen or processing any new events.
Your while-loop is blocking the EDT, preventing it from painting any updates until after the while-loop is completed.
Take a look at Concurrency in Swing for more details.
There are a number of approaches you could take...
You could use a Thread, but this causes problems as you need to ensure that any changes you make to the UI are re-synced back to the EDT and this can become messy...
For example
You could use a javax.swing.Timer that ticks at a regular interval and you would update any internal parameters from within it's assigned ActionListener. Because the tick events occur within the EDT, it is save to update the screen from within it.
For example
You could use a SwingWorker to run the task in the background. It has methods for re-syncing updates back to the EDT, but might be a little over kill for your purposes...
Updated with a possible Timer example
Caveat- It is very hard to produce a reasonable example with only a code snippet, but, something like this might work
public void golpe(final int pbola, int pvelocidad, String pdireccion, final JLabel[] listalabels) throws InterruptedException{
listabolas[pbola].setVelocidad(pvelocidad);
listabolas[pbola].setDireccion(pdireccion);
Timer timer = new Timer(40, new ActionListener() {
public void actionPerformed(ActionEvent evt) {
if (listabolas[pbola].getVelocidad() == 0) {
((Timer)evt.getSource()).stop();
} else {
moverBola(pbola, listalabels);
}
}
});
timer.setRepeats(true);
timer.start();
}
public void actionPerformed(ActionEvent e) {
String sp1="Player 1's turn. ";
String sp2="Player 2's turn. ";
System.out.println("Mouse entered for rating " + index); //helps me track the cards
ori=new ImageIcon(getClass().getResource(index+1+".png")); //set the image to the card
ori.setDescription("ori"); //It's weird that I cannot directly flip the card, so I used this method to flip the cards.
tail.setDescription("tail");//http://stackoverflow.com/questions/13557561/the-method-about-imageicons-does-not-work
if (((ImageIcon) bt[index].getIcon()).getDescription()=="ori")
bt[index].setIcon(tail);
else
bt[index].setIcon(ori);
count++;
System.out.printf("Action Performed %d times \n",count);
if(count==1){ //if the card is clicked for once, the card should not flip and the index is stored in record.
record=index;
countS++;
}
String turnS=Integer.toString(countS);//parse the int and printout the turn
// text3.setText(sp1+"This is turn "+turnS);
if(count==2){
int match1=record/4; //Since every four cards have the same rank, I used this to get the rank very easily
int match2=index/4;
if(match1==match2&&record!=index){ //compare the two cards clicked
p1++;
score1=Integer.toString(p1);
text1.setText("Player 1: "+score1); //display the score
text3.setText(sp2+"This is turn "+turnS);
bt[index].setEnabled(false);//remove the cards that match
bt[record].setEnabled(false);
}
if(record==index){
text3.setText(sp2+"This is turn "+turnS);//designed for the situation that the user clicks the same card
}
if(match1!=match2){//designed for the situation that the two cards do not match
//time.schedule(taskFlip1,500);//delay the flip so that the user can see the cards
//time.schedule(taskFlip2,500);
try{ **//This part is problematic!**
Thread.currentThread().sleep(4000);
flip(index);
flip(record);
}
catch(Exception ie){
}
}
text3.setText(sp2+"This is turn "+turnS);
}
When I click on the button, the button is supposed to change the ImageIcon. It works fine without the sleep. But after I add sleep, when I click on the button, the program pauses without changing the ImageIcon! Can you tell me why? Thank you!
The actionPerformed() method runs in the event dispatching thread. So does the repaint system. If you sleep, you are deferring painting, and everything else. You should never sleep in this thread. If you want a deferred paint, use SwingWorker or javax.swing.Timer to start a deferred task.
The action is executed by the very thread which also does handle the drawing. You block this thread. You see nothing. Game over.
This is the reason why YOU SHALL NOT BLOCK NOR DELAY THE EVENT-DISPATCHER THREAD.
Searching for the term "Event Dispatcher Thread" and "blocking" you find plenty of stuff explaining the gory details.
ActionPerformed is run in the event-dispatcher thread. Sleeping in there will stop the UI from updating.
You can use a Swing Timer instead to delay an action.