[Tutorial] Guns

Hello! This is a tutorial on how to add guns to spigot. In particular, we will be looking at launching projectiles, the PlayerInteractEvent and the ProjectileHitEvent.

1: Starting
I assume you know how to create a basic spigot plugin. We're going to do that, and add event handlers for PlayerInteractEvent and ProjectileHitEvent.

Code (Text):

package me.konsolas.guns;

import org.bukkit.Bukkit;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.entity.ProjectileHitEvent;
import org.bukkit.event.player.PlayerInteractEvent;
import org.bukkit.plugin.java.JavaPlugin;

public class Guns extends JavaPlugin implements Listener{
    private List<Integer> bullets = new ArrayList<>();

    public void onEnable() {
        Bukkit.getServer().getPluginManager().registerEvents(this, this);
    }
 
    @EventHandler
    public void onPlayerInteract(PlayerInteractEvent e) {
     
    }
 
    @EventHandler
    public void onProjectileHit(ProjectileHitEvent e) {
     
    }
}
 

The list 'bullets' will be used later.

2: PlayerInteractEvent
In our case, the 'Gun' will be diamond horse armor. We will be using the PlayerInteractEvent to get when the player right-clicks with the gun.

Code (Text):

@EventHandler
    public void onPlayerInteract(PlayerInteractEvent e) {
        // If the player right clicks
        if(e.getAction().equals(Action.RIGHT_CLICK_AIR)) {
            // If the player was holding diamond horse armour
            if(e.getPlayer().getItemInHand().getType().equals(Material.DIAMOND_BARDING)) {
                Player player = e.getPlayer();
                // Launch the snowball where the player is looking
                Snowball bullet = player.launchProjectile(Snowball.class, player.getLocation().getDirection());
                // Save the launched snowball's id
                bullets.add(bullet.getEntityId());
            }
        }
    }

As you can see, we check if the player right clicks, and if he was holding a piece of diamond horse armor. We launch the projectile and add it's entity id to the bullets list. This is so we can refer back to it when the projectile hits something.

3: The hit.
We're using the ProjectileHitEvent to detect when a snowball hits something. We will check if the projectile is a snowball, and if it's id is in our 'bullets' list. If so, we will create an explosion at it's location.

Code (Text):

@EventHandler
    public void onProjectileHit(ProjectileHitEvent e) {
        // If the projectile was a snowball
        if(e.getEntity() instanceof Snowball) {
            int entityId = e.getEntity().getEntityId();
         
            // If this snowball is a bullet
            if(bullets.contains(entityId)) {
                // Clear this entity id
                bullets.remove((Integer) entityId);
             
                // Create an explosion where the snowball hit
                e.getEntity().getWorld().createExplosion(e.getEntity().getLocation(), 2F);
            }
        }
    }

So that was a small tutorial on managing projectiles and when they hit. You could implement different guns by adding seperate lists for each one. e.g: save bullets made with gold horse armor in an 'incendiaryBullets' list, and setting the entity on fire when the projectile hits as opposed to blowing things up

 

the remove method is overloaded with remove(int) and remove(Object).

I have to cast the int to an integer to call the second version of remove, which removes an object based on its value and not its index.

 

I don't typically do that, but I seem to find it in every plugin I decompile. Thanks for the advice, removed.