Thread: collision detection moving objects

I have the 2d 2 state game set up. menu and play are my states.

the play state has a guy who can walk around a map. I have a .png of a pig I would like to add as an enemy and I want to give my character the ability to shoot the enemy. if he runs in to the enemy I want him to die.

1. what is the best way to implement my enemy, considering it should come on the screen randomly and as the players score increases the enemy comes more frequently and moves faster.

2. how to give character the ability to shoot.

3 an explanation of adding collision detection on moving objects as well as a radius around an area on the map such as a tree or a building.

this is what i have so far.

  package javagame;
 
import org.lwjgl.input.Mouse;
import org.newdawn.slick.*;
import org.newdawn.slick.state.*;
 
public class Play extends BasicGameState{
 
	Animation bucky, movingUp, movingDown, movingLeft, movingRight;
	Image worldMap;
	boolean quit = false;
	int [] duration = {200,200};
	float buckyPositionX = 0;
	float buckyPositionY = 0;
	float shiftX = buckyPositionX + 360;
	float shiftY = buckyPositionY + 160;
 
	public Play(int state){
 
	}
 
	public void init(GameContainer gc, StateBasedGame sbg) throws SlickException{
		worldMap = new Image("res/world.png");
		Image[] walkUp = {new Image("res/buckysBack.png"), new Image("res/buckysBack.png")};
		Image[] walkDown = {new Image("res/buckysFront.png"), new Image("res/buckysFront.png")};
		Image[] walkLeft = {new Image("res/buckysLeft.png"), new Image("res/buckysLeft.png")};
		Image[] walkRight = {new Image("res/buckysRight.png"), new Image("res/buckysRight.png")};	
 
		movingUp = new Animation(walkUp, duration, false);
		movingDown = new Animation(walkDown, duration, false);
		movingLeft = new Animation(walkLeft, duration, false);
		movingRight = new Animation(walkRight, duration, false);
		bucky = movingDown;
	}
 
	public void render(GameContainer gc, StateBasedGame sbg, Graphics g) throws SlickException{
	worldMap.draw(buckyPositionX, buckyPositionY);
	bucky.draw(shiftX, shiftY);
	g.drawString("Buckys X: " + buckyPositionX +"\nBuckys Y: " +buckyPositionY, 500, 50);
 
	if(quit==true){
		g.drawString("Resume (R)", 250, 100);
		g.drawString("Main Menu (M)", 250, 150);
		g.drawString("Quit (Q)", 250, 200);
		if(quit==false){
			g.clear();
		}
	}
	}
 
	public void update(GameContainer gc, StateBasedGame sbg, int delta) throws SlickException{
		Input input = gc.getInput();
 
		//Up
 
		if(input.isKeyDown(Input.KEY_UP)){
			bucky = movingUp;
			buckyPositionY += delta * .1f;
			if(buckyPositionY>161){
				buckyPositionY -= delta * .1f;
			}
		}
 
		//Down
		if(input.isKeyDown(Input.KEY_DOWN)){
			bucky = movingDown;
			buckyPositionY -= delta * .1f;
		if(buckyPositionY<-598){
			buckyPositionY += delta * .1f;
			}
		}
 
		//Left
		if(input.isKeyDown(Input.KEY_LEFT)){
			bucky = movingLeft;
			buckyPositionX += delta * .1f;
			if(buckyPositionX>358){
				buckyPositionX -= delta * .1f;
			}
		}
 
		//Right
		if(input.isKeyDown(Input.KEY_RIGHT)){
			bucky = movingRight;
			buckyPositionX -= delta * .1f;
		if(buckyPositionX<-796){
			buckyPositionX += delta * .1f;
			}
		}
 
		//Up
		if(input.isKeyDown(Input.KEY_W)){
			bucky = movingUp;
			buckyPositionY += delta * .1f;
		if(buckyPositionY>161){
			buckyPositionY -= delta * .1f;
			}
		}
		//Down
		if(input.isKeyDown(Input.KEY_S)){
			bucky = movingDown;
			buckyPositionY -= delta * .1f;
		if(buckyPositionY<-598){
			buckyPositionY += delta * .1f;
			}
		}
		//Left
		if(input.isKeyDown(Input.KEY_A)){
			bucky = movingLeft;
			buckyPositionX += delta * .1f;
			if(buckyPositionX>358){
				buckyPositionX -= delta * .1f;
			}
		}
 
		//Right
		if(input.isKeyDown(Input.KEY_D)){
			bucky = movingRight;
			buckyPositionX -= delta * .1f;
			if(buckyPositionX<-796){
				buckyPositionX += delta * .1f;
 
			}
	}
		//escape
		if(input.isKeyDown(Input.KEY_ESCAPE)){
			quit = true;
		}
		//quit menu
		if(quit==true){
			if(input.isKeyDown(Input.KEY_R)){
				quit = false;		
			}
			if(input.isKeyDown(Input.KEY_M)){
				sbg.enterState(0);
		}
			if(input.isKeyDown(Input.KEY_Q)){
				System.exit(0);
			}
		}
	}
	public int getID(){
		return 1;
	}
}

i see you are doing bucky tutorial i did the same...not sure how to do the enemy but for collision detection on the trees and such you can do the same as the sides of the map

Awesome you can relate! thanks for your response. I was thinking that but wouldn't it need to be a radius around the tree? or would each tree have 4 collision points? 1 for each side of the tree or building????

im not soooo good at it so the 4 points is the only way i know of but maybe or hopefully someone answers how to do it a better way because i would love to know too

so are you stuck at the same point as me? and how is this forum? I am sick of being stuck all the time... lol I need to find a forum will people actually help. its actually because of this recent project ive been making a point to answer questions on forums cause it drives me crazy that its so hard to get people to answer my questions

The worst thing is that the tutorial we both followed stopped where it did... I mean why not finish the game and teach us everything? now we both are skilled enough to build a game half way... yay for us being half way useful java developers lol.

hahahaha yeap stuck at same spot...he said he was supposed to finish it but i guess he never got to it lol

this forum is great they dont usually give you the answer outright but they do help you to learn it and point you in a nice direction to get it done...you should stick around i have learned a ton here

awesome thanks for your input. I like java a lot I wish I would of started with programming instead of websites. I will let you know when I figure the solution out. and I hope you will do the same for me.

If you want to learn about collition, look into the Rectangle clas. And for more gameprograming tutorials look at:
The Cherno - YouTube
He has some really good 2D game programming tutorials.

awesome thank you!

--- Update ---

question... for learning java is making games a good way to learn? or is making other programs better for learning in order to become professional and be able to build anything. I want to learn java to the point I can build anything off the top of my head. will sticking to game tutorials limit me or make it easier?

If you are already started with java its better to stick with it. Otherwise you might get confused between diffrent langauges. Java is easier to make games in then C++, C++ is really hard to learn.
For learning stuff, there are certain tricks for certain things(entity for example). But once you learned those and you're a bit creative you can make litearly games out of your head.
I make random short games in computer science classes atm(I have finised all my work and i am programming why more advanced then the rest). And these games are just random ideas or copies of other games.

currently I am switching back and forth between objective C and Java. What I meant was is programming games good enough practice to teach me enough about Java to build anything such as understanding classes and ojects. Or am I going to need to see some tutorials on building other types of applications as well in order to really get a full grasp of Java?

I think so but searching up tutorials is allways good

cool thanks for your input