I'm trying to create a block that saves an array of textures into a TileEntity, and when you right click it with a particular Item, it cycles through its different textures. In the method GetIcon it reads the TileEntity, and based on the data read, it chooses the appropriate texture. The problem is that the method GetIcon is called only on client side.

In fact, everything works fine when I play in Singleplayer mode, but if I play in Multiplayer mode, the game crashes.

This happens because in order to read the TileEntity, I use the Server instance world, in this way:

MinecraftServer.getServer().getEntityWorld().getTileEntity(x, y, z);

So given that the method GetIcon is called only on client side, when I'm playing in multiplayer mode, the client side think that the server instance is null and this generates a Null Pointer exception.

Is there a way to read in client-side mode a TileEntity from a dedicated server? Do I need to use packets?

If I have to use packets I think they should be sent by the server to the client, and then the client should read the TileEntity from its client world: Minecraft.getMinecraft().theWorld.getTileEntity(x, y, z).

 

My Block class is here:

public class AdditionalOresStairsMulti extends BlockStairs implements ITileEntityProvider {

Block[] modelBlocks;
int[] modelMetadatas;

public AdditionalOresStairsMulti(Block[] _modelBlocks, int[] _modelMetadatas) {
	super(_modelBlocks[0], _modelMetadatas[0]);
	modelBlocks = _modelBlocks;
	modelMetadatas = _modelMetadatas;
	setCreativeTab(AdditionalOres.tabBlocks);
	setLightLevel(0.0F);
	setLightOpacity(255);//Min = 0: Transparent; Max = 255: Opaque             
	useNeighborBrightness = true;
}


/**
     * Gets the block's texture. Args: IBlockAccess, posX, posY, posZ, side
     */
    @Override
    @SideOnly(Side.CLIENT)
    public IIcon getIcon(IBlockAccess block, int x, int y, int z, int side)
    {
    	//Read the TileEntity data from the server instance
    	TileEntityStairsMulti teStairs = (TileEntityStairsMulti) MinecraftServer.getServer().getEntityWorld().getTileEntity(x, y, z);
    	if (teStairs != null)
        {
    		int index = teStairs.getIndex();
    		return modelBlocks[index].getIcon(side, modelMetadatas[index]);
        }
        return this.getIcon(side, block.getBlockMetadata(x, y, z));
    }
    

@Override
public boolean onBlockActivated(World world, int x, int y, int z, EntityPlayer entityPlayer, int par6, float par7, float par8, float par9)
    {
	if(!world.isRemote)
	{
		ItemStack equippedItem = entityPlayer.getCurrentEquippedItem();
		if(equippedItem != null && equippedItem.getItem() == AdditionalOres.hammer)
    	{
    		TileEntityStairsMulti teStairs = (TileEntityStairsMulti) world.getTileEntity(x, y, z);
    		teStairs.increaseIndex(world, this, modelMetadatas.length);
    		//Update the block render in order to update the client texture
    		Minecraft.getMinecraft().renderGlobal.markBlockForRenderUpdate(x, y, z);
    		return true;
    	}	
	}
	return false;
    }


@Override
public void breakBlock(World world, int x, int y, int z, Block block, int meta)
    {
	TileEntityStairsMulti teStairs = (TileEntityStairsMulti) MinecraftServer.getServer().getEntityWorld().getTileEntity(x, y, z);
    	if (teStairs != null)
    		world.removeTileEntity(x, y, z);
    }


@Override
    public boolean hasTileEntity(int metadata)
    {
        return true;
    }
    

    @Override
    public TileEntity createNewTileEntity(World world, int var2)
    {
        try
        {
            return new TileEntityStairsMulti();
        }
        catch (Exception var3)
        {
            throw new RuntimeException(var3);
        }
    } 

}

 

My TileEntity is here:

public class TileEntityStairsMulti extends TileEntity{

byte index = 0;

    public void increaseIndex(World world, Block block, int maxTextures) 
    {
    	if(index < (maxTextures - 1))
    		index++;
    	else
    		index = 0;
    	world.notifyBlockChange(xCoord, yCoord, zCoord, block);
    }
       
    
    public int getIndex()
    {
    	return index;
    }
    
    public void setIndex(byte newIndex)
    {
    	index = newIndex;
    }
    
        
    @Override
    public void readFromNBT(NBTTagCompound nbt)
    {
        super.readFromNBT(nbt);
        this.index = nbt.getByte("index");
    }

    @Override
    public void writeToNBT(NBTTagCompound nbt)
    {
        super.writeToNBT(nbt);
        nbt.setByte("index", this.index);
    }

}

Just use IBlockAccess#getBlockTileEntity(x, y, z).

And, remember that MinecraftServer.getServer() returns null in client, where rendering happens.

I tried to use IBlockAcces to get the TileEntity but it gets only the client side TileEntity, and everytime I shut down Minecraft all its data is reset.

MinecraftServer.getServer() doesnt return always null, even on clent side. As I said, it works fine but only in SinglePlayer mode. In Multiplayer mode return null as you said.

Any other help would be appreciated.

Ah, then you have to use the packets.

You have to send the tileentity information of the server to client using packets,

so you can get the property from the client side TileEntity.

 

This tutorial might be help:

http://www.minecraftforge.net/wiki/Tile_Entities#Sending_Tile_Entity_Data_From_Server_to_Client

Ok, thanks. That tutorial has been very useful, now my block works also on multiplayer mode, but it isn't updated properly.

When I right click it, sometimes its texure changes and sometimes not.

I think this happens because the method "markBlockForUpdate" is called before the client receives the packet from the server.

Is there any method in the Block class  (something like "onUpdate" as for Items) that is called very often?

I could use it to update the texture after the client receives the packet from the server containing the TileEntity.

You can simply put the markBlockForUpdate() method at the end of the onDataPacket() method that way it will run after the client receives and processes the packet.

 

@Override
public void onDataPacket(NetworkManager net, S35PacketUpdateTileEntity pkt) {
readFromNBT(pkt.func_148857_g());
worldObj.markBlockForUpdate(xCoord, yCoord, zCoord);
}

Thanks brandon for the suggestion, I was just thinking about something similar, but instead of using markBlockForUpdate I used "Minecraft.getMinecraft().renderGlobal.markBlockForRenderUpdate(xCoord, yCoord, zCoord)", that updates the block texture.

Thanks to both of you, Abastro you've pointed me in the right direction with that useful tutorial and Brandon you've helped me with your suggestion.

Now all works perfectly, on singleplayer and on multiplayer.

This is the updated code, if someone else needs to create a Block that changes texture when righ clicked:

public class AdditionalOresStairsMulti extends BlockStairs implements ITileEntityProvider 
{
Block[] modelBlocks;
int[] modelMetadatas;

public AdditionalOresStairsMulti(Block[] _modelBlocks, int[] _modelMetadatas) 
{
	super(_modelBlocks[0], _modelMetadatas[0]);
	modelBlocks = _modelBlocks;
	modelMetadatas = _modelMetadatas;
	setCreativeTab(AdditionalOres.tabBlocks);
	setLightLevel(0.0F);
	setLightOpacity(255);//Min = 0: Transparent; Max = 255: Opaque             
	useNeighborBrightness = true;
}


/**
     * Gets the block's texture. Args: IBlockAccess, posX, posY, posZ, side
     */
    @Override
    @SideOnly(Side.CLIENT)
    public IIcon getIcon(IBlockAccess block, int x, int y, int z, int side)
    {
    	TileEntityStairsMulti teStairs = (TileEntityStairsMulti) block.getTileEntity(x, y, z);
    	if (teStairs != null)
        {
    		int index = teStairs.getIndex();
    		return modelBlocks[index].getIcon(side, modelMetadatas[index]);
        }
    	return this.getIcon(side, block.getBlockMetadata(x, y, z));
    }
    

@Override
public boolean onBlockActivated(World world, int x, int y, int z, EntityPlayer entityPlayer, int par6, float par7, float par8, float par9)
    {
	if(!world.isRemote)
	{
		ItemStack equippedItem = entityPlayer.getCurrentEquippedItem();
		if(equippedItem != null && equippedItem.getItem() == AdditionalOres.hammer)
    	{
    		TileEntityStairsMulti teStairs = (TileEntityStairsMulti) world.getTileEntity(x, y, z);
    		teStairs.increaseIndex(modelMetadatas.length);
    		world.markBlockForUpdate(x, y, z);
    		return true;
    	}	
	}
	return false;
    }


@Override
public void breakBlock(World world, int x, int y, int z, Block block, int meta)
    {
	TileEntityStairsMulti teStairs = (TileEntityStairsMulti) world.getTileEntity(x, y, z);
    	if (teStairs != null)
    		world.removeTileEntity(x, y, z);
    }


@Override
    public boolean hasTileEntity(int metadata)
    {
        return true;
    }
    

    @Override
    public TileEntity createNewTileEntity(World world, int var2)
    {
        try
        {
            return new TileEntityStairsMulti();
        }
        catch (Exception var3)
        {
            throw new RuntimeException(var3);
        }
    } 

}

 

And this is the TileEntity:

 

public class TileEntityStairsMulti extends TileEntity{

byte index = 0;

    public void increaseIndex(int maxTextures) 
    {
    	if(index < (maxTextures - 1))
    		index++;
    	else
    		index = 0;
    }
       
    public int getIndex()
    {
    	return index;
    }
    
    public void setIndex(byte newIndex)
    {
    	index = newIndex;
    }
     
    
    @Override
    public void readFromNBT(NBTTagCompound nbt)
    {
        super.readFromNBT(nbt);
        this.index = nbt.getByte("index");
    }

    @Override
    public void writeToNBT(NBTTagCompound nbt)
    {
        super.writeToNBT(nbt);
        nbt.setByte("index", this.index);
    }
    
    @Override
    public Packet getDescriptionPacket() 
    {
    	NBTTagCompound tagCompound = new NBTTagCompound();
        writeToNBT(tagCompound);
        return new S35PacketUpdateTileEntity(xCoord, yCoord, zCoord, 1, tagCompound);
    }
    
    @Override
    //Other Forge release use Packet132TileEntityData instead of S35PacketUpdateTileEntity
    public void onDataPacket(NetworkManager net, S35PacketUpdateTileEntity packet) 
    {
    	//read the packet data from NBT 
        readFromNBT(packet.func_148857_g());
        //Update the block render in order to update the client texture
        Minecraft.getMinecraft().renderGlobal.markBlockForRenderUpdate(xCoord, yCoord, zCoord);
    }
    
}