Hello. I'm playing around with the AttachCapabilitiesEvent<Entity>. I'm trying to attach something to the player, but right now I'm just seeing if I can get the player object. I'm getting a NullPointerException though when I try to do this. Here is the relevant code: 

public class PortalGun extends Item{
	public PortalGun() {
        super(new Item.Properties().group(ItemGroup.TOOLS));
        MinecraftForge.EVENT_BUS.register(this);
    }

	@SubscribeEvent
    public void onAttachCapabilities(AttachCapabilitiesEvent<Entity> event) {
        if (event.getObject() instanceof PlayerEntity) {
			// do something with Player
        }
    }
}

When the player loads into the game, I get the following error:

[02:05:50] [Server thread/ERROR] [minecraft/MinecraftServer]: Encountered an unexpected exception
net.minecraft.crash.ReportedException: Ticking memory connection
	at net.minecraft.network.NetworkSystem.tick(NetworkSystem.java:154) ~[?:?] {re:classloading}
	at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:899) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:821) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:84) ~[?:?] {re:classloading,pl:runtimedistcleaner:A}
	at net.minecraft.server.MinecraftServer.func_240802_v_(MinecraftServer.java:664) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at net.minecraft.server.MinecraftServer.lambda$func_240784_a_$0(MinecraftServer.java:233) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_181] {}
Caused by: java.lang.NullPointerException
	at net.minecraft.entity.player.PlayerEntity.getName(PlayerEntity.java:1793) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at net.minecraft.entity.Entity.toString(Entity.java:2362) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at java.lang.String.valueOf(String.java:2994) ~[?:1.8.0_181] {}
	at net.minecraftforge.fml.loading.TracingPrintStream.println(TracingPrintStream.java:65) ~[forge-1.16.5-36.1.0_mapped_snapshot_20200514-1.16-launcher.jar:36.1] {}
	at com.namarino41.portalgunforge.items.PortalGunItem.onAttachCapabilities(PortalGunItem.java:106) ~[main/:?] {re:classloading}
	at net.minecraftforge.eventbus.ASMEventHandler_2_PortalGunItem_onAttachCapabilities_AttachCapabilitiesEvent.invoke(.dynamic) ~[?:?] {}
	at net.minecraftforge.eventbus.ASMEventHandler.invoke(ASMEventHandler.java:85) ~[eventbus-4.0.0.jar:?] {}
	at net.minecraftforge.eventbus.EventBus.post(EventBus.java:302) ~[eventbus-4.0.0.jar:?] {}
	at net.minecraftforge.eventbus.EventBus.post(EventBus.java:283) ~[eventbus-4.0.0.jar:?] {}
	at net.minecraftforge.event.ForgeEventFactory.gatherCapabilities(ForgeEventFactory.java:579) ~[?:?] {re:classloading}
	at net.minecraftforge.event.ForgeEventFactory.gatherCapabilities(ForgeEventFactory.java:573) ~[?:?] {re:classloading}
	at net.minecraftforge.common.capabilities.CapabilityProvider.gatherCapabilities(CapabilityProvider.java:48) ~[?:?] {re:classloading}
	at net.minecraftforge.common.capabilities.CapabilityProvider.gatherCapabilities(CapabilityProvider.java:44) ~[?:?] {re:classloading}
	at net.minecraft.entity.Entity.<init>(Entity.java:221) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at net.minecraft.entity.LivingEntity.<init>(LivingEntity.java:207) ~[?:?] {re:classloading}
	at net.minecraft.entity.player.PlayerEntity.<init>(PlayerEntity.java:160) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at net.minecraft.entity.player.ServerPlayerEntity.<init>(ServerPlayerEntity.java:182) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at net.minecraft.server.management.PlayerList.createPlayerForUser(PlayerList.java:419) ~[?:?] {re:classloading}
	at net.minecraft.network.login.ServerLoginNetHandler.tryAcceptPlayer(ServerLoginNetHandler.java:122) ~[?:?] {re:classloading}
	at net.minecraft.network.login.ServerLoginNetHandler.tick(ServerLoginNetHandler.java:66) ~[?:?] {re:classloading}
	at net.minecraft.network.NetworkManager.tick(NetworkManager.java:244) ~[?:?] {re:classloading}
	at net.minecraft.network.NetworkSystem.tick(NetworkSystem.java:151) ~[?:?] {re:classloading}
	... 6 more

How can I work around this and get the player? Thanks.

1 hour ago, diesieben07 said:

The player is being constructed during this event, it is not safe to do much with it. Simply attach your capability, that is what the event is for.

Hmm, I'm trying to get the player though. Anyway I can do that? 

21 minutes ago, diesieben07 said:

What do you mean by "get the player"? What do you want to achieve?

Well basically I need to create an object using the player and the world. 

5 hours ago, diesieben07 said:

You can access the player from the event and you can also get its world.

Yeah but doing that results in that exception I noted above. 

1 minute ago, diesieben07 said:

It shows you trying to print out the player object, which needs access to its name, which is not present yet. Like I said, you cannot do most things with the player at this stage.

Interesting, I wasn't trying to print out the player. So is there another way to get the fully initialized player? 

Just now, diesieben07 said:

Show the actual code then that you had when you got this crash. Because it sure looks like it:

 

Not in AttachCapabilitiesEvent.

I was trying to initialize another object using the player. 

https://github.com/namarino41/portalgun_forge/blob/ef13a032415f9a0a484005c847eae5b8ae5a7782/src/main/java/com/namarino41/portalgunforge/util/PortalManager.java#L35

5 minutes ago, diesieben07 said:

Not in AttachCapabilitiesEvent

Clearly...how can I do it then? 

1 hour ago, diesieben07 said:

That code in the repository does not at all match the stacktrace you posted.

@SubscribeEvent
    public void onAttachCapabilities(AttachCapabilitiesEvent<Entity> event) {
        if (event.getObject() instanceof PlayerEntity) {
            PlayerEntity playerEntity = (PlayerEntity) event.getObject();
            playerEntityPortalManagerMap.put(playerEntity,
                    new PortalManager(playerEntity.getEntityWorld(), playerEntity));
        }
    }

public PortalManager(World worldIn, Entity playerIn) {
        this.portalCommands = new PortalCommands(
                worldIn.getServer().getCommandSource()
                                   .withPermissionLevel(2)
                                   .withEntity(playerIn)
                                   .withFeedbackDisabled(),
                worldIn.getServer().getCommandManager());

        PORTAL_1_ID = "portal_1_" + playerIn.getUniqueID();
        PORTAL_2_ID = "portal_2_" + playerIn.getUniqueID();
    }

Here's the exception: 

net.minecraft.crash.ReportedException: Ticking memory connection
	at net.minecraft.network.NetworkSystem.tick(NetworkSystem.java:154) ~[?:?] {re:classloading}
	at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:899) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:821) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:84) ~[?:?] {re:classloading,pl:runtimedistcleaner:A}
	at net.minecraft.server.MinecraftServer.func_240802_v_(MinecraftServer.java:664) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at net.minecraft.server.MinecraftServer.lambda$func_240784_a_$0(MinecraftServer.java:233) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_181] {}
Caused by: java.lang.NullPointerException
	at net.minecraft.entity.player.PlayerEntity.getName(PlayerEntity.java:1793) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at net.minecraft.command.CommandSource.withEntity(CommandSource.java:75) ~[forge-1.16.5-36.1.0_mapped_snapshot_20200514-1.16-recomp.jar:?] {re:classloading}
	at com.namarino41.portalgunforge.util.PortalManager.<init>(PortalManager.java:39) ~[main/:?] {re:classloading}
	at com.namarino41.portalgunforge.items.PortalGunItem.onAttachCapabilities(PortalGunItem.java:108) ~[main/:?] {re:classloading}
	at net.minecraftforge.eventbus.ASMEventHandler_3_PortalGunItem_onAttachCapabilities_AttachCapabilitiesEvent.invoke(.dynamic) ~[?:?] {}
	at net.minecraftforge.eventbus.ASMEventHandler.invoke(ASMEventHandler.java:85) ~[eventbus-4.0.0.jar:?] {}
	at net.minecraftforge.eventbus.EventBus.post(EventBus.java:302) ~[eventbus-4.0.0.jar:?] {}
	at net.minecraftforge.eventbus.EventBus.post(EventBus.java:283) ~[eventbus-4.0.0.jar:?] {}
	at net.minecraftforge.event.ForgeEventFactory.gatherCapabilities(ForgeEventFactory.java:579) ~[?:?] {re:classloading}
	at net.minecraftforge.event.ForgeEventFactory.gatherCapabilities(ForgeEventFactory.java:573) ~[?:?] {re:classloading}
	at net.minecraftforge.common.capabilities.CapabilityProvider.gatherCapabilities(CapabilityProvider.java:48) ~[?:?] {re:classloading}
	at net.minecraftforge.common.capabilities.CapabilityProvider.gatherCapabilities(CapabilityProvider.java:44) ~[?:?] {re:classloading}
	at net.minecraft.entity.Entity.<init>(Entity.java:221) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at net.minecraft.entity.LivingEntity.<init>(LivingEntity.java:207) ~[?:?] {re:classloading}
	at net.minecraft.entity.player.PlayerEntity.<init>(PlayerEntity.java:160) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at net.minecraft.entity.player.ServerPlayerEntity.<init>(ServerPlayerEntity.java:182) ~[?:?] {re:classloading,pl:accesstransformer:B}
	at net.minecraft.server.management.PlayerList.createPlayerForUser(PlayerList.java:419) ~[?:?] {re:classloading}
	at net.minecraft.network.login.ServerLoginNetHandler.tryAcceptPlayer(ServerLoginNetHandler.java:122) ~[?:?] {re:classloading}
	at net.minecraft.network.login.ServerLoginNetHandler.tick(ServerLoginNetHandler.java:66) ~[?:?] {re:classloading}
	at net.minecraft.network.NetworkManager.tick(NetworkManager.java:244) ~[?:?] {re:classloading}
	at net.minecraft.network.NetworkSystem.tick(NetworkSystem.java:151) ~[?:?] {re:classloading}
	... 6 more

withEntity calls toString which is causing the error. Again, is there a way I can get the fully initialized player?

6 minutes ago, diesieben07 said:

You have to create the command source later, not during the event. The easiest way to do that would be to lazily initialize it when it is first needed.

Ah I never thought about that, great idea. Thanks for the suggestion dude.