Detect entity you're looking at

[Poseidon_22]

Hello,
I want to damage an entity when I right click it from a distance.
I saw in the RayTraceResult class that there is something with entityHit.
So I suppose I have to use RayTraceResult. Though I'm doing something
wrong.

@Override
public ActionResult<ItemStack> onItemRightClick(World worldIn, EntityPlayer playerIn, EnumHand handIn) {
  if(!worldIn.isRemote) {
  	RayTraceResult ray = playerIn.rayTrace(100,20);
	Entity entity = ray.entityHit;
	entity.setDead();
  	return new ActionResult(EnumActionResult.SUCCESS, new ItemStack(this));
  	} else {
  	return new ActionResult(EnumActionResult.FAIL, new ItemStack(this));
}
}

What am I doing wrong?
Thanks
 

[Matryoshika]

If you look at Entity::rayTrace in your IDE, you can see that the method is annotated with @SideOnly(Side.CLIENT). This means this piece of code only exists on the client (it was moved to the client because it was never used on the server, by the deobfuscation process)

You have to copy the logic inside of Entity::rayTrace and put it somewhere in your own code, and call that instead.

[Poseidon_22]

Thanks for your reply.
So this is where I ended up with.

@Override
public ActionResult<ItemStack> onItemRightClick(World worldIn, EntityPlayer playerIn, EnumHand handIn) {
	onclick(worldIn, playerIn, handIn);
	return new ActionResult(EnumActionResult.SUCCESS, new ItemStack(this));
}
      
@SideOnly(Side.CLIENT)
  private void onclick(World worldIn, EntityPlayer playerIn, EnumHand handIn){
  	 RayTraceResult ray = new RayTraceResult(playerIn);
   	 Entity entity = ray.entityHit;
     if(entity == null){
     } else
     entity.onKillCommand();
    }
}

It kills me instead of the entity.
 

[jabelar]

By the way I already have a tutorial that explains this (making weapons with extended reach) here: http://jabelarminecraft.blogspot.com/p/minecraft-modding-extending-reach-of.html

 

You cannot just override the on right click method on the server side because that only gets called after the normal reach is processed on the client. So you have to process the right click on the client to check the extended reach. Basically the approach is to make a copy of the mouse over method on the client to find entities at a longer distance and then send a custom packet that triggers an attack the same as normal attack on the server.

[Draco18s]

3 hours ago, Poseidon_22 said:

 

  	RayTraceResult ray = playerIn.rayTrace(100,20);
	Entity entity = ray.entityHit;
	entity.setDead();

 

*Right clicks air*

*Crashes game*

[Differentiation]

9 hours ago, Poseidon_22 said:

Entity entity = ray.entityHit;

This will throw a NullPointerException since there is (most of the time) no hit entity! 

You are running the item right click method...

[larsgerrits]

1 hour ago, Differentiation said:

This will throw a NullPointerException

It will throw an NPE, however, not in the line you quoted. It's actually the next line, when entity is being used (entity.setDead()).

[Differentiation]

3 hours ago, larsgerrits said:

It will throw an NPE, however, not in the line you quoted. It's actually the next line, when entity is being used (entity.setDead()).

Yes, Entity entity = ray.entityHit; is the starting line that is wrong in his code that would lead to further errors.

You're correct, that's the cause of the exception.

[jabelar]

1 hour ago, Differentiation said:

Yes, Entity entity = ray.entityHit; is the starting line that is wrong in his code that would lead to further errors.

You're correct, that's the cause of the exception.

The reason why largerrits corrected you is because it is okay for something to be null, so that line is not really an error and is a perfectly valid line of code. It is only an error if/when later you dereference it to access something within the null instance. In programming it is important to be precise.

 

The whole null thing can be a pain though especially in a situation like modding where you didn't write the rest of the code so it isn't always clear when something may be null. You can be safe and check everything for null before using it but that is unwieldy and seems like a waste of code (imagine if in every method you had to test every parameter for null). That is why the Nullable and Non-Null annotation is a welcome addition to Forge -- it really makes it clear when you should handle the null case. 

 

Tip: In fact you can usually configure your IDE to analyze this for you -- so if the entityHit() method was annotated with Nullable annotation it would have warned him (warning or error depending on how you configure your preferences) when he tried to use setDead().

Edited December 4, 2017 by jabelar