How would I make it so that the item only glows when it's held and doesn't glow when it's not held?

 

@SideOnly(Side.CLIENT)
    @Override
    public boolean hasEffect(ItemStack stack) {
        return true;
    }

You could always wait for the item to be held in the item update method, then when the status changes, write it to the ItemStack's NBT. Then, read that NBT from the ItemStack in the hasEffect method.

This is the method

    public void onUpdate(ItemStack stack, World worldIn, Entity entityIn, int itemSlot, boolean isSelected)

Probe around the isSelected flag. You'll probably need to be hacky to make sure you can revert the effect flag though.

You'll probably need to be hacky to make sure you can revert the effect flag though.

I'm pretty sure it's just reading from NBT, so nothing really hacky here.

I'm pretty sure it's just reading from NBT, so nothing really hacky here.

I'm more getting at how to turn the flag off when the item ceases to be held such as when thrown, moved in inventory, on player death, etc. I'm not aware of whether or not a final tick is sent to the item somewhere before it's unequipped though

Ahh yeah, I can see how putting into an inventory and such could be a bit tricky.

It would also show up in item frames in the "enchanted" state because putting an item into an item frame calls nothing.  The stack is cloned (storing the clone in the item frame) and deleted from your inventory.  That's it.

Hence me saying to use the system time. You can check if more than X milliseconds have passed in the hasEffect method.

 

Oh ho, that's clever.

Oh ho, that's clever.

You know what they say about clever programming. I am not proud of this one

 

Nah, it's more along the lines of having gotten so used to using system time being the absolutely wrong tool for the job (for various reasons, depending on platform) so remembering that it's there in certain edge cases can actually be useful.

Since it's a client-only method, it may be possible to directly check the player's held item to see if it's the same stack as the argument.

Okay then instead of making it glow how would I do it so on held it changes to another item and when that other item is stopped being held it changes to the original item?

Wrong question.

 

The answer is "it doesn't matter because only the currently held item is relevant."

 

If the item is currently held: glow

If the item is not currently held: don't glow

 

Two different items apply this same rule independently.