I'm creating a little game as a project for my studies using Java with Libgdx.
The game is really simple: 2D, side view, controled with the arrowpad and everything is seen like in a grid divided in units (player is 1 unit tall, environment tides are 1 unit tall, ...).
The problem is that the movement of the character is quick (and it has to be) so it's really hard to move only 1 unit to the left or to the right.
I was wondering if it's possible to create a delay between two inputs from the keyboard because the movement part is in an "update" method so everytime I press a key it creates like 5 or 10 inputs.
I tried to handle it with java timers (like 0.2 or 0.3 sec) that happened everytime I press a key and unable the programm to listen to the keyboard until the timer is done. But I find it really dirty so i'm asking for your help to lead me on a more decent way to do this. Thanks.
You can easily implement a cooldown kind of thing, by comparing the last time of use by the current time.
double coolDownInMillis = 1200;
double lastTime = 0;
public void move() {
double now = System.currentTimeMillis();
if(lastTime - now > coolDownInMillis && pressingTheRightKey()){
//do what you want
lastTime = System.currentTimeMillis();
}
}
Or something like this.
Related
I want to animate some text thats in an arraylist that gets changed often but I can't figure out how to animate it on the Y-Axis as it needs to move up and down and I've only set it up for obj.renderY += 10 * deltaTime but I need it to smoothly animate to the position wanted without overcomplciating it.
The current setup for animating the Y-Axis of the text is obj.renderY = (obj.renderY * (speed - 1) + offset) / speed and this is frame dependent and I haven't figured out how I would implement deltaTime into it properly most of the times I've tried it just breaks it. This current setup I have animates it to the position I want it to be on the Y-Axis even if its above or below the wanted position.
The offset is just equal to 2 + count * (fontHeight + 1) I don't know if that would help but sure I'll include it anyway. Thanks for taking your time and reading this post.
Example of trying to animate the texts movement:
float speed = 14;
obj.renderY = (obj.renderY * (speed - 1) + offset) / speed
The class that is used to get deltaTime (Updates every frame):
public class Time {
public static float deltaTime = 0;
private static long lastTime = System.nanoTime();
public static void update() {
long currentTime = System.nanoTime();
deltaTime = (currentTime - lastTime) / 1000000000.0F;
lastTime = currentTime;
}
}
Use javax.swing.Timer. It was literally built to solve this exact problem.
Timer(int delay, ActionListener listener)
delay - Place the amount of time you want the timer to wait before kicking things off. Please note - this does NOT mean the amount of time between each task, only the amount of time before starting each task.
listener - Place your actual task here.
Then, all you need to do is use the start() method, and that should be it. You can configure the timer in other ways, but that is the basics.
EDIT - I imagine that many people who are asking this question are game developers trying to make some part of their game run at 60 frames per second.
You can use a timer, but you might be better off using something from a game engine instead.
In short, you probably want something more feature rich than a simple timer. Timers are effective, but they can be hard to manage, and may not kick off at the exact frame that you want them to, leading to issues. Timers are meant to be a simple tool to make kicking off a task at a certain frequency easier. But it's rarely as simple as that when making a game.
I would discourage you from using this timer for anything other than a basic repetitive task that only needs to start and stop after a certain event. If you want something with precision, stick to using the tools found in some of your game engines. They specialize in getting certain actions to kick off at the exact times you want them to.
I'm kinda new to the dev scene, I'm in the middle of an Android project.
I am trying to utilise the mobile phone camera flash. I'm trying to make it flash on and off in a repetitive motion. Below is a clip from my .java file.
public void clickGo(View view) {
Bundle newtempo = getIntent().getExtras();
int tempo = newtempo.getInt("tempoData");
int scaledTempo = 60000/tempo;
while (true) {
long futureTime1a = System.currentTimeMillis() + (100);
long futureTime1b = System.currentTimeMillis() + (scaledTempo - 100);
while (System.currentTimeMillis() < futureTime1a) {
setFlashlightOn();
}
while (System.currentTimeMillis() < futureTime1b) {
setFlashlightOff();
}
}
Let me explain what's going on...
So I've gained data from another activity then scaled it to a milleseconds value.
I've put the rest of the algorithm in a while(true) loop, just until I can get it working properly. I set two times, one with 100 milliseconds, and one with the scaled millesecond value MINUS the 100 milliseconds.
I then apply these two timings to turn the flash on then off.
In theory, this should work. I have data inputted from another activity which scales the number into milliseconds as shown. The concept does work, as lower numbers and higher numbers make the flash beat slower and quicker on my phone. However, the precision is my issue. When I play a click beat to the same time of the app, it's easy to tell that some flashes come in slower, or last longer.etc. I was wondering what this could possibly be? I've stripped down most of the code to a completely bare script (as I thought it could be a processing issue). It could also be the way I've implemented the time feature - if anyone else has a more efficient way, I would love to hear it!
As I said at the beginning, I'm relatively new to the dev scene, so I would appreciate it if you could answer with this in mind :)
Thank you very much!
The internal clock for computers is somewhat unreliable in quick successions like what you want. I would recommend using a timer to achieve what you want.
So, I'm creating a isometric game in JAVA; to put it simply, it has a map made of tiles, and when the user drag the mouse on the screen, the map moves. To give you guys an idea, it currently looks like this:
Before the actual prototype version, I built a small java application that had no "Game Loop" per se; the only thing updating the tile-map position was the event listeners for the mouse dragging, and it called the repaint() method after the movement update. It worked fine, and I could select Tiles and move the map without a problem.
Since then, I rebuild the prototype thinking in developing something more like a real game engine, with a Game States Manager and a real Game Loop; the Game Loop code looks like this:
init();
long start;
long elapsed;
long wait;
while(running){
start = System.nanoTime();
update();
draw();
drawToScreen();
elapsed = System.nanoTime() - start;
wait = targetTime - elapsed / 1000000;
if(wait < 0)wait = 5;
try{
Thread.sleep(wait);
} catch(Exception e) {
e.printStackTrace();
}
}
A GameStateManager is acessed with the update() and draw() methods, so I can draw the map just fine, like the older prototype. The problem happened when I dragged the mouse on the screen so the map could move; the animation became VERY croppy, in the extent that I could actually see the black background between the tiles moving before the final position of all tiles.
At first I thought the problem was in a concurrency between the Game Loop thread and the event listeners of the main class, because the mouseDragged event could be called while the JPanel was trying to draw what the map was like a moment ago; then I tested this on my game loop code:
SwingUtilities.invokeLater(new Runnable(){
public void run(){
draw();
drawToScreen();
}
});
//draw();
//drawToScreen();
And now the prototype is working just fine.
So, my question is, is this performance heavy, or just a bad practice in Java? Also, was my "concurrency" assumption right? This is my first time dealing with threads in Java, so I don't really know if I dealed with the problem the right way.
obs: This is the entire class I made in which the game loop is in:
http://pastebin.com/RMRHYc5X
obs2: If someone is interested, the game loop logic I worked in was based on a youtube java tutorial made by pj644 named "2D Game Programming in Java".
obs3: Sorry if the question became too big, this is my first time posting a question on this site!
Swing isn't really a great technology for writing games, it updates slowly and is quite limited in a number of ways.
Having said that yes calling invokeLater or using a SwingWorker would be the correct way to update the screen when your game thread has done its work.
Before you go too much further though I really suggest looking at a 2d or 3d java graphics and game framework. You will be able to get much better results that way and a lot of the work in terms of setting up the game loop, updates, managing frame rates, etc will be done for you.
I looked up many threads on how to use delta time and I can't figure it out.
I want my guy to move at a constant speed every time I run the game.
So I have:
timer = new Timer(9, this);
timer.start();
then the paint method.
I tried doing start time at the beginning of the paint method and then a current time at the end of it. How would I make it affect the timer's speed or how far the player moves. I've tried multiplying the time delta by the increment to the x. nHeroX = dx*deltaTIme;
I feel like it's very simple I just need someone to tell me straight what to do please.
Traditionally, game programming relies on a continuous loop.
Anyway, all I have realized.
In this loop, you should separate model update and graphic update.
In your snipset, you seem to try mixing the two things.
In this loop :
- In a first time, you let the model to update.For example : guy's move from x to x1.
- In a second time, you must refresh the graphics to allow the guy to have a new position in the screen.
The speed of your guy depends on the guy model (ex: constant in your guy class).
But the speed of another type of guy could be different.
The general speed of your game relies on the FPS set in your main loop.
You can see an example on this post :
Java Main Game Loop
Good luck
Get the system time from the System object.
Get it again during your animation. Delta time is nothing more than subtraction.
Get rid of the JavaScript tag. The languages are completely different.
I am developing a game, and just wanted to test it on a different computer to check if the resolutions are ok and all that stuff but noticed one big problem, the game runs in slow motion for some reason... Not laggy, but slow motion..
My game loop is a temporary:
while(gameisRunnin){
doStuff();
Thread.sleep(1000/60);
But after the test, I've tried to check how much time does it take to do the doStuff(); code and I tested it like this:
while(gameisRunnin){
long startT = System.currentTimeMillis();
doStuff();
long stopT = System.currentTimeMillis();
System.out.println(stopT-startT);
Thread.sleep(1000/60);
The result it gives me is 0, on both computers, (On the one I am developing the game which runs in the perfect speed, and on the pc that it runs in slow motion..
Also I tested it with nano time, it gives me like 50000-80000 on both computes too (pretty much same result.
Seriously what's up? Could a superman save me?
UPDATE:
Ok so when I run the game on the other computer NOT on full screen, it's runs fine, but when it is on full screen, it's slowmotion
Update:
Looks like I am the superhero here, I've set the displaymode the refresh rate to unknown, I guess that was the whole problem...
You've to use something what is usually called "delta time". Basically it means, that you measure how long it takes to do one iteration of the game loop and then use this number for all the movements.
This is because of the different count of FPS on different computers. Instead of moving objects for just constant amount of pixels, you're defining speed and calculating the actual size of movement dynamically.
Short example:
public void gameLoop() {
long initialTime = System.nanoTime();
game.redraw();
game.update(System.nanoTime() - initialTime);
}
// inside the class Game
public void update(long deltaTime) {
someObject.moveToRight(deltaTime * speed);
}
The answer is that the refresh rate of the game wasn't supported by the monitor, changing the refresh-rate from 60 to DisplayMode.REFRESH_RATE_UNKNOWN fixes the slowmotion problem.
Read this article: click here
Also, as a side note, use System.nanoTime() because System.getTimeMillis() isn't as accurate.