How to save and restore navigation state in Jetpack Compose?

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05-10-2024

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Navigating with Confidence: Saving and Restoring State in Jetpack Compose

Jetpack Compose offers a powerful and declarative way to build Android UIs. However, managing navigation state across different screens can be tricky. Losing navigation progress when the app is closed or the device is rotated can be frustrating for users. This article explores how to save and restore navigation state in Jetpack Compose for a seamless user experience.

The Problem: Losing Your Way

Imagine a multi-screen app where the user navigates through a series of screens, filling out forms or making selections. Suddenly, the device rotates or the app is closed. When the user returns, they're back at the starting point, losing all their progress. This is a common issue with state management in apps, and it can lead to user frustration and a diminished app experience.

The Solution: Saving and Restoring Navigation State

Jetpack Compose provides a solution through its SavedStateHandle class. This powerful tool allows you to store and retrieve data associated with a specific composable. We can leverage this mechanism to store the current navigation stack, ensuring it's restored upon app restart or configuration change.

Code Example:

import androidx.compose.runtime.Composable
import androidx.compose.runtime.saveable.rememberSaveable
import androidx.compose.ui.tooling.preview.Preview
import androidx.navigation.NavHostController
import androidx.navigation.compose.NavHost
import androidx.navigation.compose.composable
import androidx.navigation.compose.rememberNavController

@Composable
fun MyApp() {
  val navController = rememberNavController()
  val navigationState = rememberSaveable { mutableStateListOf<String>() } // Store navigation stack

  NavHost(navController = navController, startDestination = "screen1") {
    composable("screen1") {
      Screen1(navController, navigationState)
    }
    composable("screen2") {
      Screen2(navController, navigationState)
    }
  }
}

@Composable
fun Screen1(navController: NavHostController, navigationState: MutableList<String>) {
  // Navigate to Screen2 and update navigation state
  Button(onClick = {
    navController.navigate("screen2")
    navigationState.add("screen2")
  }) {
    Text("Go to Screen 2")
  }
}

@Composable
fun Screen2(navController: NavHostController, navigationState: MutableList<String>) {
  // Handle back navigation and remove state entry
  Button(onClick = {
    navController.popBackStack()
    navigationState.removeLastOrNull()
  }) {
    Text("Go back")
  }
}

Explanation:

1. We use rememberSaveable to create a mutable list navigationState that stores the navigation stack. This list will persist across app restarts and configuration changes.
2. In each screen (Screen1 and Screen2), we update the navigationState list whenever navigation occurs.
3. When the app restarts or a configuration change happens, the saved state is automatically restored, including the navigationState list.
4. We can use the restored navigation stack to rebuild the navigation graph and navigate to the correct screen.

Further Considerations:

• State Persistence: Depending on your app's requirements, you can use other data structures like a map or a set to store navigation state.
• Advanced Navigation: For more complex scenarios, explore libraries like compose-navigation-ktx or Navigation-compose for advanced navigation features and state management.
• Data Serialization: If you're storing complex data structures in the saved state, ensure you're using a suitable serialization mechanism (like Gson or Kotlin serialization) to convert the data to a format that can be saved and restored.

Conclusion:

By leveraging the power of SavedStateHandle, you can easily save and restore navigation state in Jetpack Compose, making your app more resilient to app restarts and device rotations. This approach ensures a seamless user experience, allowing users to resume their navigation journey where they left off, leading to greater user satisfaction and engagement.