Java NullPointErexception Bukkit 插件

Question

尝试在我的 bukkit 服务器中加载插件时出现 NullPointerException，但在 Eclipse 中没有错误。我的插件是一个 Rush pluing，很多东西没有使用/丢失。错误是这样的:

[18:11:10] [Server thread/ERROR]: Could not load 'plugins\rush.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.NullPointerException
at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:182) ~                          [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:308) ~  [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:231) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
at org.bukkit.craftbukkit.v1_7_R1.CraftServer.loadPlugins(CraftServer.java:255) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
at org.bukkit.craftbukkit.v1_7_R1.CraftServer.<init>(CraftServer.java:233) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
at net.minecraft.server.v1_7_R1.PlayerList.<init>(PlayerList.java:63) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
at net.minecraft.server.v1_7_R1.DedicatedPlayerList.<init>(SourceFile:14) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
at net.minecraft.server.v1_7_R1.DedicatedServer.init(DedicatedServer.java:126) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java:424) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:617) [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
Caused by: java.lang.NullPointerException
at me.mailh.Rush.MainRush.<init>(MainRush.java:62) ~[?:?]
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[?:1.7.0_45]
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) ~[?:1.7.0_45]
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) ~  [?:1.7.0_45]
at java.lang.reflect.Constructor.newInstance(Unknown Source) ~[?:1.7.0_45]
at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:178) ~  [craftbukkit.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
... 9 more

这是我的代码:

package me.mailh.Rush;

import java.io.File;
import java.util.logging.Logger;

import org.bukkit.Bukkit;
import org.bukkit.ChatColor;
import org.bukkit.Location;
import org.bukkit.World;
import org.bukkit.WorldCreator;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.EntityType;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.entity.PlayerDeathEvent;
import org.bukkit.event.player.PlayerQuitEvent;
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.scoreboard.Scoreboard;
import org.bukkit.scoreboard.ScoreboardManager;
import org.bukkit.scoreboard.Team;

public  class  MainRush extends JavaPlugin implements Listener{


public final Logger logger = Logger.getLogger("Minecraft");
public static MainRush plugin;





public void onEnable(){
    this.logger.info("Rush is enabled.");
    getServer().getPluginManager().registerEvents(this, this);
}


    private  ScoreboardManager manager = Bukkit.getScoreboardManager();
    private Scoreboard board = manager.getNewScoreboard();
    private  Team bleu = board.registerNewTeam("bleu");
    private  Team orange = board.registerNewTeam("orange");


public void onDisable(){
    this.logger.info("Rush is disabled.");
}



public boolean onCommand(CommandSender s, Command c, String lbl, String[] args){
    Player pl = (Player) s;
    if (lbl.equalsIgnoreCase("rush")){
        if (args.length == 0){ 
        World w = Bukkit.getWorld("rush");


        Location rush = new Location( w, -210, 51, -8 );
        pl.sendMessage(ChatColor.GOLD + "Teleportation...");
        pl.teleport(rush);
        } 

        if (args[0].equalsIgnoreCase("bleu")){
            board.resetScores(pl.getPlayer());
            orange.removePlayer(pl.getPlayer());
            bleu.addPlayer(pl.getPlayer());
            pl.sendMessage(ChatColor.AQUA + "Vous êtes dans l'équipe bleu");
            bleu.setAllowFriendlyFire(false);

            }
        if (args[0].equalsIgnoreCase("leave")){
            board.resetScores(pl.getPlayer());
            bleu.removePlayer(pl.getPlayer());
            orange.removePlayer(pl.getPlayer());
            pl.sendMessage(ChatColor.RED + "Vous avez quitté votre équipe");

        }
        if (args[0].equalsIgnoreCase("orange")){
            board.resetScores(pl.getPlayer());
            bleu.removePlayer(pl.getPlayer());
            orange.addPlayer(pl.getPlayer());
            pl.sendMessage(ChatColor.GOLD + "Vous êtes dans l'équipe orange");
            orange.setAllowFriendlyFire(false);

        }

        }


    return true; 
    }
public  void rollback(){
if(Bukkit.getServer().unloadWorld("rush",false))
{
new File("rush").delete();
Bukkit.getServer().createWorld(new WorldCreator("rush"));
}
}




 @EventHandler
 public void onLeave(PlayerQuitEvent e){
 Player p = (Player) e.getPlayer();
    bleu.removePlayer(p);
    orange.removePlayer(p);
    board.resetScores(p);

 }
 @EventHandler
 public void Death(PlayerDeathEvent event){
 if (event.getEntityType() == EntityType.PLAYER){
 Player player = event.getEntity();
    Team team = board.getPlayerTeam(player);
 if(team.equals(bleu)){
 player.sendMessage("did it work? bleu");  
 }
 else if (team.equals(orange)){
 player.sendMessage("did it work orange?");
 }
 }
 }
 }

Answer 1

看来这段代码:

private ScoreboardManager manager = Bukkit.getScoreboardManager();
private Scoreboard board = manager.getNewScoreboard();

原因是您没有在方法内部声明这些变量，因此，它们会在您的 onEnable() 方法被调用之前加载，这样您就什么也得不到使用 Bukkit，因为 Bukkit 尚未初始化。

我建议做的是在任何方法之外做这样的事情:

private ScoreboardManager manager;
private Scoreboard board;

然后在您的 onEnable() 中执行此操作:

manager = Bukkit.getScoreboardManager();
board = manager.getNewScoreboard();

所以你会得到这样的东西:

public class MainRush extends JavaPlugin implements Listener{

    private ScoreboardManager manager;
    private Scoreboard board;

    @Override
    public void onEnable(){
        //plugin enabled
        manager = Bukkit.getScoreboardManager();
        board = manager.getNewScoreboard();
    }
}

这样做，您就消除了在加载插件时出现 NullPointerException 的可能性。作为一般经验法则，您永远不应从 bukkit 获取方法之外的任何内容。