rememberSaveable เมื่อหมุนหน้าจอ

Rotate the screen and your tap counter snaps back to zero. That is because a configuration change recreates the whole Activity.

remember survives recomposition, but not Activity recreation. When the Activity restarts, remembered state is gone for good.

Rotation, language switches, and dark-mode toggles are configuration changes. Each one tears down and rebuilds your UI from scratch.

rememberSaveable works like remember but also saves the value into the saved instance state, so it survives recreation.

Often the fix is a one-word change: replace remember with rememberSaveable and your counter now keeps its value after rotation.

It saves types that fit in a Bundle out of the box: Int, String, Boolean, and other primitives. Most simple state just works.

For your own classes, give rememberSaveable a Saver that tells it how to store and restore the object as bundle-safe data.

For Kotlin data classes you can use the mapSaver or listSaver helpers, or annotate with Parcelize, to make saving simple.

rememberSaveable survives rotation and brief backgrounding, but not a full app kill. For permanent data you still need storage.

Use rememberSaveable for transient UI state you want to keep through rotation, like a counter, a typed query, or a tab index.

Rule of thumb: use remember for cheap or recomputable values, and rememberSaveable when losing the value on rotation would annoy the user.

Which API keeps state through a screen rotation?

You learned that rememberSaveable keeps transient UI state alive through rotation and config changes, while remember does not. Nicely done! 🎉