Understanding `remember` vs `rememberSaveable` in Jetpack Compose

When developing Android apps using Jetpack Compose, state management is a critical aspect of ensuring your app behaves as expected. Two commonly used tools for managing state are `remember` and `rememberSaveable`. While they might seem similar at first glance, they serve different purposes. In this blog post, we’ll explore the differences between these two and provide examples to illustrate when to use each.

What is `remember`?

The `remember` function in Jetpack Compose allows you to store a value in the composition, which means the value is retained across recompositions. However, the value is not retained across configuration changes, such as screen rotations or when the app goes to the background and comes back.

Example:

@Composable
fun Counter() {
    var count by remember { mutableStateOf(0) }

    Button(onClick = { count++ }) {
        Text("Count: $count")
    }
}

In the above example, the `count` value is remembered during recompositions, meaning if the UI is redrawn, the `count` value will be retained. However, if you rotate the device, the `count` will reset because `remember` does not survive configuration changes.

What is `rememberSaveable`?

`rememberSaveable` works similarly to `remember`, but with an important difference: it retains the state across configuration changes, such as device rotations. It does this by saving the value to a Bundle and restoring it when needed.

Example:

@Composable
fun Counter() {
    var count by rememberSaveable { mutableStateOf(0) }

    Button(onClick = { count++ }) {
        Text("Count: $count")
    }
}

In this example, the `count` value will persist even after the device is rotated or the app is temporarily stopped and restarted. This makes `rememberSaveable` the better choice when you need to retain state across configuration changes.

When to Use `remember` vs `rememberSaveable`

- Use `remember` when you need to store temporary state that doesn’t need to survive configuration changes, such as UI state that can be recalculated or doesn’t impact the user experience if lost.

- Use `rememberSaveable` when the state is important to the user experience and should be preserved across configuration changes, such as form inputs or progress tracking.

Conclusion

Understanding when to use `remember` and `rememberSaveable` is crucial for effective state management in Jetpack Compose. `remember` is great for temporary state during recompositions, while `rememberSaveable` ensures that state survives configuration changes, enhancing the resilience of your app’s UI.

By choosing the appropriate state management tool, you can create a more robust and user-friendly app.