[1.7.10]How to check actual entity type with Check Spawn event

jabelar · January 27, 2015

I want to do something when specific entity types spawn. But if I check for instanceof on the event.entityLiving field, it always fails (e.g. checking for instanceof EntitySheep). However, checking for instanceof EntityLiving checks as true.

So I guess the event.entityLiving is cast as an EntityLiving and the actual type (EntitySheep or whatever) is lost. And in fact I see that if I trace back the call hierarchy for the post to the event bus, the parameter passed is indeed cast to EntityLiving.

I think that is a shame and not sure it is really necessary -- I'm pretty sure Java would have allowed them to pass EntitySheep in since they inherit from EntityLiving...

Anyway, this greatly weakens the usefulness of the CheckSpawn event since all you know is that some EntityLiving has spawned but have no way to check what exactly it was.

Does anyone have an idea on how I can acheive what I want -- detecting when certain entities spawn? Is there another event, like maybe a chunk event where I can scan for entities that have appeared along with a new chunk or something?

I suppose another way to solve it would be to remember the location of the spawn and then search for the entity in a bounding box around that point a few ticks later. But that seems kinda kludgy...

Am I wrong in thinking that the entity passed to the CheckSpawn would be more useful if it is not cast to EntityLiving? Should I put in a bug report for this?

jabelar · January 27, 2015

I should mention that I also had trouble with EntityConstructing event because that occurs before the position of the entity is set (posX is 0.0D, etc.) and I also need to know the position of the entity as well as its type.

So CheckSpawn gives location (the event actually passes x, y, z) but casts to EntityLiving and the EntityConstructing event gives the entity type without casting, but there is no position information!

So I need help figuring out a way to know the position of certain type of vanilla entity when it spawns? Anyone have an idea of an event or scheme for doing that?

jabelar · January 27, 2015

I'm thinking that what I'll have to do is use EntityConstructing but in the even handler just check for entity type and if I find it then will put it in a public list of recently spawned entities. Then in the ServerTick event I'll go through those entities and do my handling there once they have a non-zero position. I'm pretty sure I can get that to work, but it is a lot messier than it should be.

coolAlias · January 27, 2015

Casting to a type doesn't remove the true type. Try it:

// let's try with an EntityPlayer since those are easy to come by, and we'll get it from a method parameter
EntityLivingBase entity = (EntityLivingBase) player;
if (entity instanceof EntityPlayer) {
System.out.println("It's still a player!");
}

Are you sure you are getting EntitySheep in the CheckSpawnEvent?

As an aside, anytime you have an entity (such as in EntityConstructingEvent, though it is probably zero there), you automatically have its position:

entity.posX, entity.posY, entity.posZ

You could always use EntityJoinWorldEvent.

jabelar · January 27, 2015

Casting to a type doesn't remove the true type. Try it:
// let's try with an EntityPlayer since those are easy to come by, and we'll get it from a method parameter
EntityLivingBase entity = (EntityLivingBase) player;
if (entity instanceof EntityPlayer) {
System.out.println("It's still a player!");
}
Are you sure you are getting EntitySheep in the CheckSpawnEvent?

As an aside, anytime you have an entity (such as in EntityConstructingEvent, though it is probably zero there), you automatically have its position:
entity.posX, entity.posY, entity.posZ
You could always use EntityJoinWorldEvent.

I know I can get the position of the entity, except during the constructing position is always 0.0D, 0.0D, 0.0D. If you look at the Entity constructor it explicitly sets the position to that just before posting the event. So that doesn't work.

EntityJoinWorldEvent only seems to fire occasionally. I think maybe it fires once per entity type? It certainly doesn't fire for every sheep.

Back to the casting question -- I thought it should be preserved.

However, I found a weird thing -- checking for EntityLiving, EntityLivingBase, EntityCreature all test true. However testing for EntityAnimal, or EntitySheep, etc. I just cant get a hit.

I'm pretty sure that there are entity sheep spawning because I see them and I'm recreating the world each time.

Do this test if you have time. Put code like this in:

    	if (event.entityLiving instanceof EntityCreature)
    	{
    		System.out.println("EntityCreature spawning");
    	}
    	if (event.entityLiving instanceof EntityAnimal)
    	{
    		System.out.println("EntityAnimal spawning");
    	}
    	if (event.entityLiving instanceof EntitySheep)
    	{
    		System.out.println("EntitySheep spawning");
    	}

When I do I get a ton of "EntityCreature spawning messages", but nothing else. I wondered if there were just lots of non-animal creatures spawning but if I comment out that test then nothing prints out.

Do you see the same?

Draco18s · January 27, 2015

Aside from neither EntityJoinWorldEvent nor EntityConstructing having a entityLiving field, here's some of what I got (used EntityConstructing as I already had that event subscribed).

...
EntityCreature spawning

EntityAnimal spawning

EntitySheep spawning

EntityCreature spawning

EntityAnimal spawning

EntitySheep spawning

EntityCreature spawning

EntityAnimal spawning

EntitySheep spawning

EntityCreature spawning

...

coolAlias · January 27, 2015

EntityJoinWorldEvent fires once for each individual entity as it spawns, not once per type or only sometimes, but every single time.

A class instance in Java (and most other OOP languages) will always check true for every class from which it inherits, all the way up to Object, so EntitySheep will return true for instanceof in all of the following cases (in addition to any interfaces any of those types implement): EntitySheep->EntityAnimal->EntityAgeable->EntityCreature->EntityLiving->EntityLivingBase->Entity->Object

What you can do to see the current class that is spawning:

// prints the actual class, i.e. the most specific type, e.g. EntitySheep
System.out.println("Spawning: " + event.entity.getClass().getSimpleName());

EDIT: When I print that out, I literally get spammed with console messages. Perhaps yours are buried amidst other entities?

@SubscribeEvent
public void onEntityJoinWorld(EntityJoinWorldEvent event) {
if (!event.entity.worldObj.isRemote && event.entity instanceof EntitySheep) {
	ZSSMain.logger.info("Sheep spawned");
}
}

// Output:
[08:34:26] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:26] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:26] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:26] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:26] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
[08:34:27] [server thread/INFO] [zeldaswordskills]: Sheep spawned
// and on and on

Draco18s · January 27, 2015

(It also returns true for every Interface it implements at every point along the chain, too. So IShearable and IAnimals)

coolAlias · January 27, 2015

(It also returns true for every Interface it implements at every point along the chain, too. So IShearable and IAnimals)

I already mentioned that, but yes. Should I have put it in bold?

Draco18s · January 27, 2015

(It also returns true for every Interface it implements at every point along the chain, too. So IShearable and IAnimals)

I already mentioned that, but yes. Should I have put it in bold?

Oops, missed the aside.

jabelar · January 27, 2015

Draco, I can get EnititySheep detected with EntityConstructing just fine. The problem is that the position is always 0, 0, 0 in that event.

I'll try EntityJoinWorldEvent. Note another thing I didn't like about the join event is that I want to prevent some of the entities from spawning, which is easy with setting check spawn to Result.DENY. With EntityJoinWorldEvent, I think I have to set dead which will I think last time I tried it showed a visible blip where the entity is visible for a tick before disappearing. Ultimately I'd like to prevent the spawn altogether.

But can one of you try the CheckSpawn event to see if you see what I'm seeing?

Draco18s · January 27, 2015

I checked CheckSpawn:

EntityCreature spawning
EntityAnimal spawning

EntitySheep spawning

EntityCreature spawning

EntityAnimal spawning

EntitySheep spawning

jabelar · January 27, 2015

Okay, I don't know what went wrong for me then. Maybe a typo or something.

Using EntityJoinedWorldEvent seems to mostly work for me, with the exception that I get the visual glitch I mentioned where if I use spawn egg the entity briefly appears before being killed (I'm trying to prevent the spawn).

Draco18s · January 27, 2015

Likely because the creature is spawned client side and it is not aware that the event is being canceled server side.

jabelar · January 27, 2015

The Check Spawn is still driving me crazy though. I can detect things like Zombies fine.

If I have this code:

    	String name = event.entityLiving.getClass().getSimpleName();
    	if (name.equals("EntityCow"))
    	{
    		System.out.println("Check spawn event for "+event.entityLiving.getClass().getSimpleName());
    	}
    	if (event.entityLiving instanceof EntityCow)
    	{
    		System.out.println("EntityCow spawning");
    	}
    	if (name.equals("EntityZombie"))
    	{
    		System.out.println("Check spawn event for "+event.entityLiving.getClass().getSimpleName());
    	}
    	if (event.entityLiving instanceof EntityZombie)
    	{
    		System.out.println("EntityZombie spawning");
    	}

Then I get following console output (which happily reports zombies, but doesn't show any cows):

[10:28:50] [server thread/INFO]: Player383[local:E:2d50233a] logged in with entity id 256 at (-145.5, 73.0, 249.5)

[10:28:50] [server thread/INFO] [sTDOUT]: [com.blogspot.jabelarminecraft.magicbeans.MagicBeansEventHandler:onEvent:566]: NameFormat event for username = Player383

[10:28:50] [server thread/INFO]: Player383 the Ugly joined the game

[10:28:50] [server thread/INFO] [sTDOUT]: [com.blogspot.jabelarminecraft.magicbeans.MagicBeansWorldData:get:86]: MagicBeansWorldData didn't exist so creating it

[10:28:50] [server thread/INFO] [sTDOUT]: [com.blogspot.jabelarminecraft.magicbeans.MagicBeansFMLEventHandler:onEvent:124]: MagicBeansWorldData hasCastleSpawned =false, familyCowHasGivenLead =false

[10:28:50] [server thread/INFO] [sTDOUT]: [com.blogspot.jabelarminecraft.magicbeans.MagicBeansEventHandler:onEvent:427]: Check spawn event for EntityZombie

[10:28:50] [server thread/INFO] [sTDOUT]: [com.blogspot.jabelarminecraft.magicbeans.MagicBeansEventHandler:onEvent:431]: EntityZombie spawning