Hi. I'm writing a really simple test mod to create an item that teleports the player upwards.

 

Here is the relevant code:

 public ItemStack onItemRightClick(ItemStack par1ItemStack, World par2World, EntityPlayer par3EntityPlayer)
        {
        	par1ItemStack.stackSize--;
        	((EntityPlayerMP)par3EntityPlayer).setPositionAndUpdate(par3EntityPlayer.posX, par3EntityPlayer.posY, par3EntityPlayer.posZ + 5 );

            return par1ItemStack;
        }

 

It throws a ClassCastException because the player entity object is not of the type it requires. I'm sure that this isn't the right way to do this (I just found the line that throws the exception on another website), my question is, what is the correct way to do this?

 

Thanks!

check before you cast

It's because the method is called twice - once for client side and once for server side. And EntityPlayer cannot always be cast to EntityPlayerMp (but I don't remember, on which side).

 

Do a side (FMLCommonhandler.instance.getSide()) or instanceof check

the first answer as the correct, the second its a little correct...

do

public ItemStack onItemRightClick(ItemStack par1ItemStack, World par2World, EntityPlayer par3EntityPlayer)
        {
        //only the server needs to know the position of the player        
if(!par2World.isRemote && par3EntityPlayer instanceof EntityPlayerMP){
//is instance of entity player mp?
    ((EntityPlayerMP)par3EntityPlayer).setPositionAndUpdate(par3EntityPlayer.posX, par3EntityPlayer.posY, par3EntityPlayer.posZ + 5 );
  return --par1ItemStack;
}
else{
            return par1ItemStack;
}
        }

.....

Wuut?

Do a side (FMLCommonhandler.instance.getSide()) or instanceof check

the get side returns dedicated server or client(integrated one)

I had serious problems in multiplayer in 1.4.7 with moving a player like you posted. When I run that code it did teleport the player, but chunks weren't send to him so he could see massive holes in a world (had to relog every time to "fix" this). If you encounter this problem, use playerNetServerHandler.setPlayerLocation of EntityPlayerMP .