I have method that is called on only the server side that result

player.inventory.addItemStackToInventory(item)

be called if all conditions are meet, but because it is only called on the server side the client does not update util you click in the slot it put in. If there away to invoke this update, right after

player.inventory.addItemStackToInventory(item)

is called.

Send packet from server to client with ItemStack and slotID and on client put ItemStack in that slot.

Call

Container#detectAndSendChanges

on

EntityPlayer#inventoryContainer

to sync the player's inventory to their client.

 

If you make a large amount of changes to an inventory, consider calling

EntityPlayerMP#sendContainerToPlayer

instead. This sends a single packet with the whole inventory instead of sending an individual packet for each slot that changed.

So i am guessing

player.inventory.addItemStackToInventory(item)
player.inventory.detectAndSendChanges()

 

not being at my development environment although it end yo being something more like this 

if (player.inventory.addItemStackToInventory(item)) {
    player.inventory.detectAndSendChanges()
}
else{
    playerMP.worldObj.spawnEntityInWorld(new EntityItem(playerMP.worldObj, playerMP.posX, playerMP.posY, playerMP.posZ, item));
                        }

Call

Container#detectAndSendChanges

on

EntityPlayer#inventoryContainer

to sync the player's inventory to their client.

 

EntityPlayer#inventory

is an

InventoryPlayer

, not a

Container

.

 

Use

ItemHandlerHelper.giveItemToPlayer

to give an item to a player or drop it at their feet if there wasn't room for it in their inventory.

So got this and it works

if (player.inventory.addItemStackToInventory(rewrad)){
                            player.inventoryContainer.detectAndSendChanges();
                        }
                        else{
                            playerMP.worldObj.spawnEntityInWorld(new EntityItem(playerMP.worldObj, playerMP.posX, playerMP.posY, playerMP.posZ, rewrad));
                        }

 

but will look into ItemHandlerHelper.giveItemToPlayer when i get an chance.