I have a Container with 2 slots; one for input and one for output.

 

The Output Slot is a custom-made Slot and here is it's code:

import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.inventory.IInventory;
import net.minecraft.item.ItemStack;
import net.minecraftforge.items.IItemHandler;
import net.minecraftforge.items.SlotItemHandler;

public class CompactorOutputSlot extends SlotItemHandler{

	private int removeCount;
	
	public CompactorOutputSlot(IItemHandler itemHandler, int index, int xPosition, int yPosition) {
		super(itemHandler, index, xPosition, yPosition);
	}

	@Override
	public ItemStack onTake(EntityPlayer thePlayer, ItemStack stack) {
		this.onCrafting(stack);
		super.onTake(thePlayer, stack);
		return stack;
	}

	@Override
	public boolean isItemValid(ItemStack stack) {
		return false;
	}

	@Override
	public ItemStack decrStackSize(int amount) {
		if(this.getHasStack()) this.removeCount += Math.min(amount, this.getStack().getCount());
		return super.decrStackSize(amount);
	}
	
}

 

How can I specify which of the two slots the hopper can take?

You do it by exposing the TileEntity's item stack handler capability by side. If the hopper can only take the output slot, then you only let it access the output slot when the side being accessed is DOWN.

 

https://github.com/Draco18s/ReasonableRealism/blob/1.12.1/src/main/java/com/draco18s/ores/entities/TileEntitySifter.java#L153-L155

 

Vice versa for the input slot.

 

https://github.com/Draco18s/ReasonableRealism/blob/1.12.1/src/main/java/com/draco18s/ores/entities/TileEntitySifter.java#L150-L152

Edited June 27, 20196 yr by Draco18s

On 6/27/2019 at 5:44 PM, Draco18s said:

You do it by exposing the TileEntity's item stack handler capability by side. If the hopper can only take the output slot, then you only let it access the output slot when the side being accessed is DOWN.

 

https://github.com/Draco18s/ReasonableRealism/blob/1.12.1/src/main/java/com/draco18s/ores/entities/TileEntitySifter.java#L153-L155

 

Vice versa for the input slot.

 

https://github.com/Draco18s/ReasonableRealism/blob/1.12.1/src/main/java/com/draco18s/ores/entities/TileEntitySifter.java#L150-L152

Is it the same on a block without the facing property?

That is a block without a facing parameter. If you mean one that has a facing property:

 

https://github.com/Draco18s/ReasonableRealism/blob/1.12.1/src/main/java/com/draco18s/farming/entities/TileEntityTanner.java#L136