Mike B Mike B - 5 months ago 43
Java Question

Collision Detection between two images in Java

I have two characters displayed in a game I am writing, the player and the enemy. defined as such:

public void player(Graphics g) {
g.drawImage(plimg, x, y, this);
}

public void enemy(Graphics g) {
g.drawImage(enemy, 200, 200, this);
}


Then called with:

player(g);
enemy(g);


I am able to move player() around with the keyboard, but I am at a loss when trying to detect a collision between the two. A lot of people have said to use Rectangles, but being a beginner I cannot see how I would link this into my existing code. Can anyone offer some advice for me?

Answer

I think your problem is that you are not using good OO design for your player and enemies. Create two classes:

public class Player
{
    int X;
    int Y;
    int Width;
    int Height;

    // Getters and Setters
}

public class Enemy
{
    int X;
    int Y;
    int Width;
    int Height;

    // Getters and Setters
}

Your Player should have X,Y,Width,and Height variables.

Your enemies should as well.

In your game loop, do something like this (C#):

foreach (Enemy e in EnemyCollection)
{
    Rectangle r = new Rectangle(e.X,e.Y,e.Width,e.Height);
    Rectangle p = new Rectangle(player.X,player.Y,player.Width,player.Height);

    // Assuming there is an intersect method, otherwise just handcompare the values
    if (r.Intersects(p))
    {
       // A Collision!
       // we know which enemy (e), so we can call e.DoCollision();
       e.DoCollision();
    }
}

To speed things up, don't bother checking if the enemies coords are offscreen.