Question

Sorry if the title is a little… vague. Anyway, I’m making a platformer using java and I’ve been trying to create a pressure plate triggered dispenser that shoots poisoned darts. The game is pretty much split up into a grid system, with each block being a spot on the grid. so far I’ve made it so that when the pressure plate is activated, it looks as if it’s pressed down. I’ve also been able to draw it to the screen but it does not move or anything. This is the code I use to draw it to the screen:

public void drawDart(Graphics g) {
    if(Component.isPressed) {
        for(int x = 0; x < block[0].length; x++) {
            for (int y=0; y < block[0].length; y++) {
                if(x == 91 && y == 35) {
                    block[x][y] = new Block(new Rectangle(x * Tile.tileSize, y * Tile.tileSize, Tile.tileSize, Tile.tileSize), Tile.poisonDart); 
                }
            }
        }
    }
}

Unfortunately, with this code when I step on the pressure plate, the dart is drawn, but will not move. I’ve tried using x++ before but that doesn’t move the dart at all.

Another problem is that I would like the dart to look like it’s affected by gravity, which is hard to do when the game is split into a large grid system. Either way, what do you guys think?

Moderator edit (moved from OP comment):

block[x][y] = new Block(new Rectangle(x * Tile.tileSize, y * Tile.tileSize,
    Tile.tileSize, Tile.tileSize), Tile.poisonDart); 

Answer 1

Have you implemented the “game loop” for your game? It looks like this (pseudo code):

while (gameRunning) {
  for (GameEntity e in gameWorldEntities) {
    e.update(timePassed);  
  }
  for (GameEntity e in gameWorldEntities) {
    e.draw();
  }
}

Each dart object should know its position in the game world, and the Dart class’s update() method should update its position, including moving it horizontally if it’s been launched and making it fall due to gravity. Keeping track of its horizontal and vertical velocity is a good idea unless you are using a separate physics engine, which it sounds like you’re not. Then the draw() method just needs to draw it on the screen in the right place.