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[1.8] Packet Query and Null Pointer


loawkise

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I set up my packet like in Diesieben's tutorial for my custom entity, but get an null pointer when I try sending one. I am not entirely sure how to set it up for entities, as don't know what to do in the onMessage() method, and this is where the error occurs.

 

public class GolemAttackTimerMessage implements IMessage
{   
private EntityGolem golem;
private float attackTimer; 

private NBTTagCompound tag;

public GolemAttackTimerMessage()
{

}

public GolemAttackTimerMessage(EntityGolem golem, float attackTimer)
{
	this.golem = golem;
	this.attackTimer = attackTimer;

	tag = new NBTTagCompound();
    }

@Override
public void fromBytes(ByteBuf buf)
{
	tag = ByteBufUtils.readTag(buf);
	attackTimer = tag.getFloat("attackTimer");
    }

@Override
public void toBytes(ByteBuf buf)
{
	ByteBufUtils.writeTag(buf, tag);
	tag.setFloat("attackTimer", attackTimer);
    }

public static class Handler implements IMessageHandler<GolemAttackTimerMessage, IMessage>
{
	@Override
	public IMessage onMessage(GolemAttackTimerMessage message, MessageContext ctx)
	{
		message.golem.setAttackTimer(message.attackTimer);
		return null; 
        }
    }
}

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The side that sends the packet knows about the golem entity, but the side that receives it is a new instance of your message class and doesn't know about anything until it reads in the packet data.

 

For an entity like that, you need to send the entity Id (i.e. entity.getEntityId()) with the packet as well, then read that integer in during read, and retrieve the entity from the world when the packet processes.

Entity entity = player.worldObj.getEntityById(this.entityId);
if (entity instanceof EntityGolem) {
// continue processing
} else {
// log error message
}

Get the player from the current context via your proxy classes: see here and the ClientProxy implementation as well.

 

That said, if all you want to do is set the attack timer on the client side for your golem entity, use worldObj.setEntityState(customFlag) and handleHealthUpdate(byte flag) - they work in tandem to send byte flags to the client side, allowing the entity to do different things like display heart particles when in love or set the attack timer for the arm-swing animation like golems.

 

You can see how the vanilla golems do it just like that, and I prefer that to a packet when I can (though it sends a packet in the background) because it keeps everything encapsulated in the class.

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Thanks for the responses :) I have now got everything set up like this, but the value of message.entityID is 0 so I must be doing something wrong somewhere, any ideas?

 

public class GolemAttackTimerMessage implements IMessage
{   
private int entityID;
private float attackTimer; 

private NBTTagCompound tag;

public GolemAttackTimerMessage()
{

}

public GolemAttackTimerMessage(int entityID, float attackTimer)
{
	tag = new NBTTagCompound();
	this.entityID = entityID;
	this.attackTimer = attackTimer;
    }

@Override
public void fromBytes(ByteBuf buf)
{
	tag = ByteBufUtils.readTag(buf);
	entityID = tag.getInteger("ID");
	attackTimer = tag.getFloat("attackTimer");
    }

@Override
public void toBytes(ByteBuf buf)
{
	ByteBufUtils.writeTag(buf, tag);
	tag.setInteger("ID", entityID);
	tag.setFloat("attackTimer", attackTimer);
    }

public static class Handler implements IMessageHandler<GolemAttackTimerMessage, IMessage>
{
	@Override
	public IMessage onMessage(GolemAttackTimerMessage message, MessageContext ctx)
	{
		Entity entity = null;

		if(ctx.side.isClient())
		{
			entity = golems.proxy.getPlayerEntity(ctx).worldObj.getEntityByID(message.entityID);

			System.out.println(message.entityID);
		}

		if(entity instanceof EntityGolem)
		{
			EntityGolem golem = (EntityGolem) entity;

			golem.setAttackTimer(message.attackTimer);
		}
		else
		{

		}

		return null; 
        }
    }
}

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