Keys para listas estables y rápidas

By default, Compose identifies each row by its position in the list. Item zero is item zero, item one is item one, and so on.

When you insert or remove a row, every item below shifts position. Compose now thinks those rows are different and rebuilds them needlessly.

Rebuilt rows lose their state and animations. A removed item can make the whole list flicker as Compose reshuffles everything below it.

A key is a stable, unique value that names each item by identity, not position. Then Compose follows items even as they move.

The best key is a true unique id from your data, like a database id. It stays the same no matter where the item sits.

Every key in the list must be different. Duplicate keys throw a runtime error, so never key items by a value two rows might share.

Using the index as a key defeats the purpose, since indexes shift just like position. Reach for it only when you truly have no id.

With stable keys, a row's remembered state travels with it. A checkbox stays checked even after items above it are deleted.

Stable keys let Compose animate items moving, appearing, or leaving. Without them, it can't tell a move from a rebuild.

The itemsIndexed builder also accepts a key lambda. You still get the index, plus stable identity for every row.

For any list that can change, adding keys is a tiny effort with a big payoff: correct state, smooth animations, and fewer rebuilds.

Keys give items identity beyond position. Use a real unique id, keep keys unique, and your state and animations just work. ✨