Yesterday I started with creating mods and atm I got an ore-block, a brick-Block and an item, that gets dropped by the ore-block when breaking. Now I wanted to go further and create a block that looks like an end portal frame, and when I click on that block with my item in hand, the Item gets "inserted" like the eye of ender in the portal frame. I don't need a 3D texture, I just wanted to change the texture when the block gets activated with an item. I haven't found good Tutorials yet, so I'm asking here

You will still need to mess around with the block's model, when an item gets inserted into it, if you want to make it similar looking to the portal frame. Otherwise you won't. But most importantly, it should hold any item, or only one specific like the portal frame? Because the easiest way of doing this is to override the onBlockActivated() method, so it detects if it's clicked with your item and replace your block with an activated one. If thats what you want, I will be able to make an example for it.

	@Override
	public boolean onBlockActivated(World world, BlockPos pos, IBlockState state, EntityPlayer player, EnumHand hand, EnumFacing side, float hitX, float hitY, float hitZ) {
		if (!world.isRemote) {
			TileEntityPedestal tile = getTileEntity(world, pos);
			IItemHandler itemHandler = tile.getCapability(CapabilityItemHandler.ITEM_HANDLER_CAPABILITY, side);
			if (!player.isSneaking()) {
				if (heldItem.isEmpty()) {
					player.setHeldItem(hand, itemHandler.extractItem(0, 64, false));
				} else {
					player.setHeldItem(hand, itemHandler.insertItem(0, heldItem, false));
				}
				tile.markDirty();
			} else {
				ItemStack stack = itemHandler.getStackInSlot(0);
				if (!stack.isEmpty()) {
					String localized = TutorialMod.proxy.localize(stack.getUnlocalizedName() + ".name");
					player.addChatMessage(new TextComponentString(stack.getCount() + "x " + localized));
				} else {
					player.addChatMessage(new TextComponentString("Empty"));
				}
			}
		}
		return true;
	}

From https://shadowfacts.net/tutorials/forge-modding-112/tile-entities-inventory/

It only works if he wants a tileEntity, and he has everything needed in that tutorial. That's not what he asked for. Let's wait until he respond instead of copy pasting random code.

You don't need a tile entity for this. All that happens when you insert an eye of ender into an end portal frame is that the block changes state. As a result, it changes models.

 

This can all be done with the JSON blockstate system.

 

{
    "variants": {
        "eye=false,facing=south": { "model": "end_portal_frame_empty" },
        "eye=false,facing=west": { "model": "end_portal_frame_empty", "y": 90 },
        "eye=false,facing=north": { "model": "end_portal_frame_empty", "y": 180 },
        "eye=false,facing=east": { "model": "end_portal_frame_empty", "y": 270 },
        "eye=true,facing=south": { "model": "end_portal_frame_filled" },
        "eye=true,facing=west": { "model": "end_portal_frame_filled", "y": 90 },
        "eye=true,facing=north": { "model": "end_portal_frame_filled", "y": 180 },
        "eye=true,facing=east": { "model": "end_portal_frame_filled", "y": 270 }
    }
}