Custom Plugin

Hi, I'm quite new to making a bukkit plugin and I'm having 1 small issue... I made a bandage plugin (when you right click with a piece of paper you get a potion effect and it also deletes 1 item for the stack, ) I did that myself but....


Everything works fine until I hit a block it comes up with a huge error here. Here's the PLUGIN code

Code:

package me.kieran.bandage;
 
import java.util.logging.Logger;
import org.bukkit.ChatColor;
import org.bukkit.Material;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.PlayerInteractEvent;
import org.bukkit.inventory.ItemStack;
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.potion.PotionEffect;
import org.bukkit.potion.PotionEffectType;
 
public class Bandages extends JavaPlugin implements Listener {
    private static final Logger log = Logger.getLogger("Minecraft");
    public static Bandages plugin;
   
    @Override
    public void onEnable(){
        log.info("Bandages has been enabled.");
        getServer().getPluginManager().registerEvents(this, this);
       
    }
   
    @Override
    public void onDisable(){
        log.info("Bandages has been disabled.");
       
    }
   
    @EventHandler
    public void onPlayerInteract(PlayerInteractEvent event) {
        if(event.getItem().getType() == Material.PAPER) {
            Player player = event.getPlayer();
           
            player.addPotionEffect(new PotionEffect(PotionEffectType.REGENERATION, 50, 1));
            player.sendMessage(ChatColor.GREEN + "You have applied a bandage");
           
            player.getInventory().removeItem(new ItemStack[] { new ItemStack(339, 1) });
           
        }
       
       
    }
}

And here's the error.

Code:

[SEVERE] Could not pass event PlayerInteractEvent to Bandages v1.0
org.bukkit.event.EventException
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:427)
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
    at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462)
    at org.bukkit.craftbukkit.v1_5_R3.event.CraftEventFactory.callPlayerInteractEvent(CraftEventFactory.java:186)
    at net.minecraft.server.v1_5_R3.PlayerInteractManager.interact(PlayerInteractManager.java:370)
    at net.minecraft.server.v1_5_R3.PlayerConnection.a(PlayerConnection.java:631)
    at net.minecraft.server.v1_5_R3.Packet15Place.handle(SourceFile:58)
    at net.minecraft.server.v1_5_R3.NetworkManager.b(NetworkManager.java:292)
    at net.minecraft.server.v1_5_R3.PlayerConnection.d(PlayerConnection.java:109)
    at net.minecraft.server.v1_5_R3.ServerConnection.b(SourceFile:35)
    at net.minecraft.server.v1_5_R3.DedicatedServerConnection.b(SourceFile:30)
    at net.minecraft.server.v1_5_R3.MinecraftServer.r(MinecraftServer.java:581)
    at net.minecraft.server.v1_5_R3.DedicatedServer.r(DedicatedServer.java:226)
    at net.minecraft.server.v1_5_R3.MinecraftServer.q(MinecraftServer.java:477)
    at net.minecraft.server.v1_5_R3.MinecraftServer.run(MinecraftServer.java:410)
    at net.minecraft.server.v1_5_R3.ThreadServerApplication.run(SourceFile:573)
Caused by: java.lang.NullPointerException
    at me.kieran.bandage.Bandages.onPlayerInteract(Bandages.java:34)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:425)
    ... 16 more

I've seen problems with NullPointerException on other plugins how can I fix this?

Thanks!

 

kieranmclean You get a null pointer exception, when you try to perform an illegal operation on a null pointer (such as trying to invoke a method on it). You can avoid the null pointer exception by checking if the return value of a method is null before you invoke a method.

 

Thanks man.

So I have to add == null? If so what line

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

Read the stack trace, it tells you what line it encountered the NPE

 

You never defined what to do if the if statement isn't true on line 34

 

kieranmclean Just make an if statement before the one checking if the item is paper saying this:

Code:

if(event.getItem() != null)
{
   if(event.getItem().equals(Material.PAPER))
   {
      //DO STUFF
   }
}

 

It would be better to check the action first, then use the player's item in hand. Don't want people consuming paper when going over a pressure plate.

 

Code:

package me.kieran.bandage;
 
import java.util.ArrayList;
import java.util.logging.Logger;
 
import org.bukkit.Bukkit;
import org.bukkit.ChatColor;
import org.bukkit.Material;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.PlayerInteractEvent;
import org.bukkit.inventory.ItemStack;
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.potion.PotionEffect;
import org.bukkit.potion.PotionEffectType;
 
public class Bandages extends JavaPlugin implements Listener {
    private static final Logger log = Logger.getLogger("Minecraft");
    public static Bandages plugin;
   
    @Override
    public void onEnable(){
        log.info("Bandages has been enabled.");
        getServer().getPluginManager().registerEvents(this, this);
       
    }
   
    @Override
    public void onDisable(){
        log.info("Bandages has been disabled.");
       
    }
   
    ArrayList<Player> cooldown = new ArrayList<Player>();
 
    @EventHandler
    public void onPlayerInteract(PlayerInteractEvent event) {
        if (event.getItem() != null && event.getItem().getType() == Material.PAPER){
            final Player player = event.getPlayer();
           
            if(cooldown.contains(player)) {
                player.sendMessage(ChatColor.RED + "You cannot apply another bandage just yet.");
                return;
            }
           
            cooldown.add(player);
            Bukkit.getServer().getScheduler().scheduleSyncDelayedTask(this, new Runnable(){
               
                public void run(){
                    cooldown.remove(player);
                    player.sendMessage(ChatColor.GREEN + "You can now apply another bandage.");
                }
            }, 180);
           
            player.addPotionEffect(new PotionEffect(PotionEffectType.REGENERATION, 100, 1));
            player.sendMessage(ChatColor.GREEN + "You have applied a bandage to yourself.");
           
            player.getInventory().removeItem(new ItemStack[] { new ItemStack(339, 1) });
        }
    }
}

This is what I got now, anything I could do to make it better?

 

add another if at the very beginning of the method, with:

Code:

if(event.getAction() == Action.RIGHT_CLICK_AIR || event.getAction() == Action.RIGHT_CLICK_BLOCK)

 

Ah Thank you! just added it.

Oh, and also how would I be able to rename the item so when people come across it they know it's a bandage and not just a piece of paper

EDIT by Moderator: merged posts, please use the edit button instead of double posting.