[SOLVED] Change block properties in an if statement.

[Flayr]

EDIT: Thanks for all the help and support, I got everything in my mod working now and am going to release it after some testing.

 

My goal is to create a block that cannot be interacted with at all unless you are holding a specific item. I already have this in my Block class:

@Override
public MovingObjectPosition collisionRayTrace(World par1World, int par2, int par3, int par4, Vec3 par5Vec3, Vec3 par6Vec3)
{
return null;
}

What I cant figure out is how to make it so that it only returns null when a certain item is held but returns how it normally would otherwise. The biggest problem is that if i do make a basic if statement that will be true to test it I don't know what to return to make it normal. (because I already used @Override).

[ss7]

Hello,

 

You can get the normal ray-trace by returning this:

 

return super.collisionRayTrace(par1World, par2, par3, par4, par5Vec3, par6Vec3);

 

That should give it the behaviour of a normal block.

 

Is it that what you want?:

 

 

ss7

[Draco18s]

His problem is figuring out if the player is holding a given item.

 

Which is harder.

 

Your best bet is to poll the world for all Players in interaction range (4 blocks) and then check their active item.

 

Here's the hard part:

 

AxisAlignedBB aabb = AxisAlignedBB.getAABBPool().getAABB(xCoord-32, yCoord-32, zCoord-32, xCoord+32, yCoord+32, zCoord+32);
		List w = worldObj.getEntitiesWithinAABB(EntityPlayer.class, aabb);
		if(w.size() > 0) {
		     //at least one player in range
		     EntityPlayer player;
		     for(int i = 0; i < w.size; i++) {
		         player = w.get(i);
		         player.getHeldItem();//active item as ItemStack
		     }
		}

[Flayr]

I was actually having trouble with both things, although checking the players held item was a bigger one. The return statement works perfectly find, but I cannot seem to get it to read the closest player's held item. Could you explain in a bit more what the implementation of this code would be?

 

AxisAlignedBB aabb = AxisAlignedBB.getAABBPool().getAABB(xCoord-32, yCoord-32, zCoord-32, xCoord+32, yCoord+32, zCoord+32);
		List w = worldObj.getEntitiesWithinAABB(EntityPlayer.class, aabb);
		if(w.size() > 0) {
		     //at least one player in range
		     EntityPlayer player;
		     for(int i = 0; i < w.size; i++) {
		         player = w.get(i);
		         player.getHeldItem();//active item as ItemStack
		     }
		}

[Draco18s]

That locates every player inside a 65x65x65 cube (I meant to make it smaller, forgot) and then loops through the list of players inside that volume, and gets their currently active item.

 

All you have to do then is look at that item and decide if that's the item you want to have break the block or not.

[Flayr]

Here is the method that i am working on:

	@Override
	public MovingObjectPosition collisionRayTrace(World par1World, int x, int y, int z, Vec3 par5Vec3, Vec3 par6Vec3)
	{
		AxisAlignedBB aabb = AxisAlignedBB.getAABBPool().getAABB(x-4, y-4, z-4, x+4, y+4, z+4);
		List w = par1World.getEntitiesWithinAABB(EntityPlayer.class, aabb);
		if(w.size() > 0) {
		     //at least one player in range
		     EntityPlayer player;
		     for(int i = 0; i < w.size(); i++) {
[b]			         player = w.get(i);[/b]
		     }
		     if(player.getHeldItem() == new ItemStack(MagicLights.lightStaff)){
		    	 return null; 
		     }else{return super.collisionRayTrace(par1World, x, y, z, par5Vec3, par6Vec3);}
	    }else{return super.collisionRayTrace(par1World, x, y, z, par5Vec3, par6Vec3);}
	}

First, is this correct, second I am getting an error on the line "player = w.get(i);"

[Draco18s]

This is where your IDE comes in.  If you look at the error it tells you that the objects don't match and to add a cast.

 

player = (EntityPlayer) w.get(i);

[Flayr]

Well, it is error free now but when I run minecraft i cannot select the block regardless of weather I am holding the staff or not. Here is my current code.

	@Override
	public MovingObjectPosition collisionRayTrace(World par1World, int x, int y, int z, Vec3 par5Vec3, Vec3 par6Vec3)
	{
		AxisAlignedBB aabb = AxisAlignedBB.getAABBPool().getAABB(x-4, y-4, z-4, x+4, y+4, z+4);
		List w = par1World.getEntitiesWithinAABB(EntityPlayer.class, aabb);
		if(w.size() > 0) {
		     //at least one player in range
		     EntityPlayer player;
		     for(int i = 0; i < w.size() {
		    	 player = (EntityPlayer) w.get(i);
			     if(player.getHeldItem() == new ItemStack(MagicLights.lightStaff)){
			    	 return super.collisionRayTrace(par1World, x, y, z, par5Vec3, par6Vec3);
			     }else{return null;}
		     }
		     return null;
	    }else{return null;}
	}

[Draco18s]

if(player.getHeldItem() == new ItemStack(MagicLights.lightStaff)){

 

That is not how you check to see if two item stacks are equal.  You need to use the ItemStack.equal(stack, stack) function.

[Flayr]

It works now, thank you very much for the help!

[ItsTheRuski]

I tried this same approach, but I am getting a  java.util.ConcurrentModificationException when I try to access the list. Here is my code for a custom potioneffect that collects all the entities that: 1.are not the players and 2.extend EntityLivingBase. Then I simply print out what their names with the entity.getName() method i.e. (Zombie, Pig, Cow, Sheep)

 

 

package eclipse.MoreApples.potion;

import java.util.ArrayList;
import java.util.List;

import net.minecraft.entity.Entity;
import net.minecraft.entity.EntityLivingBase;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.potion.PotionEffect;
import net.minecraft.util.AxisAlignedBB;

public class FriendlyPotionEffect extends PotionEffect{

private EntityPlayer p;
private boolean shouldCheck;
private List<Entity> list;
private AxisAlignedBB aabb;

public FriendlyPotionEffect(int par1, int par2) {
	super(par1, par2);
	shouldCheck = true;
	// TODO Auto-generated constructor stub
}

@Override
public boolean onUpdate(EntityLivingBase par1EntityLivingBase)
{
	p = (EntityPlayer) par1EntityLivingBase;
	aabb = AxisAlignedBB.getAABBPool().getAABB(p.posX-8, p.posY-8, p.posZ-8, p.posX+8, p.posY+8, p.posZ+;
	list = p.worldObj.getEntitiesWithinAABBExcludingEntity(p, aabb);
	for(Entity e : list)
	{
		if(!(e instanceof EntityLivingBase) || e instanceof EntityPlayer)
			list.remove(e);
	}
	for (Entity b : list)
	{
		p.addChatMessage("A " + b.getEntityName() + " is near you");	
	}


	if(duration <= 1)
	{
		p.addChatMessage("Potion effect ending");
	}
	return super.onUpdate(par1EntityLivingBase);
}


}

 

 

I am getting the error

java.util.ConcurrentModificationException

on the line

for(Entity e : list)

and the description says

net.minecraft.util.ReportedException: Ticking player

 

Thanks for helping! =)

[TheGreyGhost]

Hi

 

are you accessing server-side objects from client-side code by any chance?  The client and the server run in different threads, and if they try to access the same object at the same time, you will get this error.

 

Cheers

  TGG

[ItsTheRuski]

I am not sure. I am getting a list of all entities of EntityLivingBase that are around the player. I am not sure how to check what is a server-side object.

[Draco18s]

I am not sure. I am getting a list of all entities of EntityLivingBase that are around the player. I am not sure how to check what is a server-side object.

 

if(!this.worldObj.isRemote) {

  //I am on the server, therefore all objects I can see are on the server

}

[TheGreyGhost]

Hi

 

I'm not sure but I think the PotionEffect.onUpdate might be run on both the client and the server.  If your custom code runs on the client it will cause problems.

 

Try putting this as the first line of your method

 

if (this.worldObj.isRemote) {  // Don't run entity search on client side

  return super.onUpdate(par1EntityLivingBase);   

}

 

-TGG

[Flayr]

EDIT:

This was solved earlier but then I ran into a problem that stems from this one.

So the block that needed to be unelectable when a certain item was held  also needs to change what type of tile entity is spawned when this item is held. The problem is that that method does not have x, y and z as parameters so I cannot use the same code. How would I do this? Also, if it would be easier to put the detecting in the renderer to change the texture that would work too. The current code for the original method:

	@Override
	public MovingObjectPosition collisionRayTrace(World par1World, int x, int y, int z, Vec3 par5Vec3, Vec3 par6Vec3)
	{
		AxisAlignedBB aabb = AxisAlignedBB.getAABBPool().getAABB(x-4, y-4, z-4, x+4, y+4, z+4);
		List w = par1World.getEntitiesWithinAABB(EntityPlayer.class, aabb);
		if(w.size() > 0) {
		     //at least one player in range
		     EntityPlayer player;
		     for(int i = 0; i < w.size() {
		    	 player = (EntityPlayer) w.get(i);
		    	 ItemStack stack = player.getHeldItem();
		    	 ItemStack stack2 = new ItemStack(MagicLights.lightStaff);
			     if(ItemStack.areItemStacksEqual(stack, stack2)){
			    	 return super.collisionRayTrace(par1World, x, y, z, par5Vec3, par6Vec3);
			     }else{return null;}
		     }
		     return null;
	    }else{return null;}
	}

[TheGreyGhost]

Hi

 

I would suggest repeating your "are any players nearby" code in the place you spawn the TileEntity.  You must have access to the [x,y,z] somehow because otherwise how can you spawn the TileEntity in the right place?

 

You could put the code in the TileEntity renderer instead but it would have a different effect - i.e.

do you want the appearance to change when the special item moves in or out of the vicinity?  Or do you want it to stay fixed after the initial placement, depending on whether the item was in the vicinity at the time it was place?

 

-TGG

[Draco18s]

I would suggest repeating your "are any players nearby" code in the place you spawn the TileEntity.  You must have access to the [x,y,z] somehow because otherwise how can you spawn the TileEntity in the right place?

 

You haven't actually used a TileEntity have you?

When you (the modder) creates one, you don't have block coordinates.  You only have the world:

 

	@Override
public TileEntity createNewTileEntity(World world) {
	return new MyTileEntity();
}

 

Vanilla code handles the rest.

[Flayr]

I would suggest repeating your "are any players nearby" code in the place you spawn the TileEntity.  You must have access to the [x,y,z] somehow because otherwise how can you spawn the TileEntity in the right place?

 

You haven't actually used a TileEntity have you?

When you (the modder) creates one, you don't have block coordinates.  You only have the world:

 

	@Override
public TileEntity createNewTileEntity(World world) {
	return new MyTileEntity();
}

 

Vanilla code handles the rest.

That is the problem I have, how would i best do the same thing I did with the MovingObjectPosition collisionRayTrace method in a CreateNewTileEntity method because it only has the parameter world.

[Draco18s]

Use block metadata.  When the block is placed, set its metadata to a value based on its position (etc.etc.) and then create a tile entity based on the metadata using:

 

public TileEntity createTileEntity(World world, int metadata) { }

[TheGreyGhost]

Hi Draco & Flayr

 

I guess I phrased my reply a bit confusingly.  What I meant was that the code responsible for placing the Block and associated TileEntity must know its location in the World.  You are right that this isn't directly accessible from inside createNewTileEntity.  Fortunately there are at least two other ways, for example

* if you only have a few different TileEntity types, you could set the Block metadata and use that in overridden Block.createTileEntity to decide what to create.  Or

* after creating the block, you can manually place (or replace) the TileEntity at your target [x,y,z] with the correct type - see the vanilla code in setBlockIDWithMetadata.

 

this.worldObj.setBlockTileEntity(j2, par2, k2, tileentity);

 

Personally I've never needed to do either of them, I used a single TileEntity and modified its data to make it act in different ways.  I have seen the first method used before.  Rumour has it that the second way works, have never tried it myself.

 

-TGG

 

[Flayr]

		AxisAlignedBB aabb = AxisAlignedBB.getAABBPool().getAABB(x-4, y-4, z-4, x+4, y+4, z+4);
		List w = par1World.getEntitiesWithinAABB(EntityPlayer.class, aabb);
		if(w.size() > 0) {
		     //at least one player in range
		     EntityPlayer player;
		     for(int i = 0; i < w.size() {
		    	 player = (EntityPlayer) w.get(i);
		    	 ItemStack stack = player.getHeldItem();
		    	 ItemStack stack2 = new ItemStack(MagicLights.lightStaff);
			     if(ItemStack.areItemStacksEqual(stack, stack2)){

 

So I wrote code that did change the TileEntity but it was kind of glitchy, I could go back to that but it seems like it would be better to put the code in the Renderer. How would I implement it in the renderer? The only problem is that there is no world object parameter in the renderer method, how would I change this code to work with entities instead of blocks?

[TheGreyGhost]

Hi

 

I think the best way forward is if you could describe more exactly what you're trying to do, i.e. a paragraph describing what this item is, what effects it has, on which blocks.  For example

 

"The staff of opening causes all wooden and iron doors within a 10m radius of the player to spontaneously open while the player is nearby."

 

At the moment I can't really give you any advice because it's not clear to me the behaviour you need, and hence whether you need TileEntities or not, whether the renderer is the best place, whether you can use metadata or you need something else, etc.

 

-TGG

 

[Flayr]

Hi

 

I think the best way forward is if you could describe more exactly what you're trying to do, i.e. a paragraph describing what this item is, what effects it has, on which blocks.  For example

 

"The staff of opening causes all wooden and iron doors within a 10m radius of the player to spontaneously open while the player is nearby."

 

At the moment I can't really give you any advice because it's not clear to me the behavior you need, and hence whether you need TileEntities or not, whether the renderer is the best place, whether you can use metadata or you need something else, etc.

 

-TGG

Sorry, have not been on the forums lately so this response is a bit late.

 

First, here is the GitHub for my sourcecode: https://github.com/TheJawrey/Magic-Lights/

Basically, what the mod does so far is add a single item, Staff of Light(lightStaff in the code) that on right click creates the block Light. The block light can be walked through, seen through and is also not editable without holding the Staff of Light, the object Light also creates a tile entity TileEntityLight that renderers a 2D object witch rotates to face the player. What I need to do is make it so that when you are holding the staff the rendered objects are visible and when the staff is not held they are invisible, basically acting like air that makes light.

[TheGreyGhost]

Hi

 

OK, that's much clearer now.

 

I have some suggestions on how you could go about it - some of this I've never tried before so it might take a bit of work to get it right.

 

(1) Create a BlockLight that is

  (a)  renderAsNormalBlock false

  (b) isOpaqueCube false

  ©  public AxisAlignedBB getCollisionBoundingBoxFromPool(World par1World, int par2, int par3, int par4)

    {

        return null;

    }

  (d) collisionRayTrace - return super.collisionRayTrace if player is holding the staff, NULL otherwise

(2) Have a single TileEntity associated with the block.  In the custom renderer for the TileEntity, check if the player has the staff equipped  and if so, render the TileEntity using the player's coordinates to determine which way the object should face.

 

Do you want the Light block to act like a torch when the staff is held (i.e. light up nearby blocks)?  That is a bit trickier because it means you would need to force an update of the blocklight map when you equip/unequip the item.

 

This is a bit different to some of your earlier posts, where the blocks would be interactable by any player, if there is another player holding the staff nearby.  What I've written above only allows the player holding the staff to interact, which is what I think you wanted?

 

-TGG