Java Programming: Let's Build a Game #5

Have fun learning!

In this video we take care of full on collision within our game and also a particle trail effect. If you have any questions then be sure to leave a comment or contact me on twitter; realtutsgml. If you learned something then be sure to leave a like, comment, and favorite.

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[daemon]

It's literally the best feeling when you fix an annoying bug in your code.

[robinvik]

Tipp: Add handler to the constructor of GameObject, and have it do
this.handler=handler;
handler.addObject(this) ;
That way you don't have to add every object to the handler yourself with "handler.addObject(New Player(x, y, etc))", instead you can just use "new Player(x, y, etc)" and it will automatically add itself to the handler.

[irubberduck]

"I hope that makes sense." That was by far the clearest explanation anyone could provide on the matter, lol. Love the tutorials, very easy to follow. Great job!

[youraveragejoe]

For anyone having trouble with key inputs, (pressing multiple keys at once causes the player to stop moving in the correct direction) here are the correct functions for the KeyInput class

public void keyPressed(KeyEvent e) {
int key = e.getKeyCode();

for(int i = 0; i < handler.object.size(); i++) {
GameObject tempObject = handler.object.get(i);

if(tempObject.getId() == ID.Player) {
//key events for player

if(key == KeyEvent.VK_W)
if(key == KeyEvent.VK_A)
if(key == KeyEvent.VK_S)
if(key == KeyEvent.VK_D)
tempObject.setVelY(Game.clamp(tempObject.getVelY(), -5, 5));
tempObject.setVelX(Game.clamp(tempObject.getVelX(), -5, 5));
}
}

if(key == KeyEvent.VK_ESCAPE) System.exit(1);
}

public void keyReleased(KeyEvent e){
int key = e.getKeyCode();

for(int i = 0; i < handler.object.size(); i++) {
GameObject tempObject = handler.object.get(i);

if(tempObject.getId() == ID.Player) {
//key events for player

if(key == KeyEvent.VK_W)
if(key == KeyEvent.VK_A)
if(key == KeyEvent.VK_S)
if(key == KeyEvent.VK_D)
tempObject.setVelY(Game.clamp(tempObject.getVelY(), -5, 5));
tempObject.setVelX(Game.clamp(tempObject.getVelX(), -5, 5));
}
}

}

[SetGacia]

Seeing things starting to feel alive is amazing (in a way words cannot fully explain). Thank you so much for this tutorial, I should have started a long time ago.

[woah]

Trying to keep up with the furious typing is actually really fun to do

[codebitcookie]

also if u did not understand the tick method here it is:



public void tick() {
//alpha AKA the transparency is 1 and life is what we set in parameters and if it is less then 1
//(if it's not then it's just going to not show the trail going to the else statement)
//then it's going to keep on subtracting from life so the transparency is slowly going to fade
//and then it's also going to reach the else statement if it's faded so when the alpha = 0

if(alpha > life){
alpha -= (life);
}

else{
handler.removeObject(this);
}

}

[Кукусик-еэ]

🔥From this cool project I found out that I will not use for-each loops anymore. And here is why:

I tried using a for-each loop in Handler class when looping thru the LinkedList objects (instead of the standard for-loop as for(int i = 0; ...) as shown in this tutorial).

My loop code was:

for(GameObject go : objects) {
GameObject tempObject = go;
tempObject.tick();
}

This enhanced for-loop worked well UNTIL we added in BasicEnemy class tick() method a line:

handler.addObject(new Trail(x, y

With this ☝ line I got a
(If intrested, you may try it by yourself).
It took me a while to figure out why!

The reason of that exception is due to LinkedList iterator interface which in its next() method calls checksForComodification() method which checks if modCount equals to expectedModCount.

This code ☝ checks whether the LinkedList (or ArrayList) was updated in its size while being looped thru, and it doesn't allow that kind of update.
And as far as we exactly update our LinkedList in the Handler class for enemy object trailing ... it's not possible to use for-each looping. 📯

Whereas the standard for loop works perfect!

✨Conclusion: do not use for-each loops with Collections if there is a chance of their modifying (adding or removing objects) while looping thru them!

[jimmyrustles]

This is the best resource I've found for Java game creation.
It's extremely helpful for my college level Java class!
Thanks for this. Your videos are great and you do an excellent job of explaining things.

[XXBearcat]

Totally been using these videos for an FBLA State competition learning tool!

[felix.__k]

if you get a change your enhanced loop to the one he's using

[oomphgordon]

Making Your Trail 1 less than the size of the object makes a really coll commet effect

[hernandopenados]

I'm understanding these methods now... slowly but surely...

[skuul]

ok so im pretty new to this whole programming thing, and I managed to set the ID of the trail to BasicEnemy. This caused a collision issue where the trail was colliding with the enemy square due to the nature of the collision method and how it loops through the whole object list. I was able to locate and remedy the issue after about 10 minutes, and it felt so damn good.

[guigrillo]

Using graphics2D transparency your fps drops a lot.I recommend using diferent images or use pixel manipulation changing manually your RGB values ;)

Also instead of creating new objects in every update, create only once at your inicialization and then update like this this:

for(int i = trail.lenght-1; i > 0; i--){
   trail[i].x = trail[i-1].x;
  trail[i].y = trail[i-1].y;
}

and then at position 0 of the array you move.

[Thegenfy]

Could you do a tutorial on random dungeon generation? That would be awesome.

[bryangomez]

Can you explain what is actually going on inside of the 'trail' class? What does alpha mean? AlphaComposite? Etc.

[Zeriver]

12:58 IMG_1081 is this (and more photos like this) a selfie? You been pumping bro?

[barsailles]

If someone is still watching this series (like me) and getting an error like:
Exception in thread "Thread-0"

Try this: object = new CopyOnWriteArrayList<>();
Instead of this: LinkedList<GameObject> object = new LinkedList <>();

on your BasicEnemy class. This method worked for me!

[someonelol]

I don t know anything about programming and I still wached this video instead of doing my homework