How to hide bottom navigation bar while scrolling down and show it while scrolling up in jetpack compose?

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05-10-2024

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Mastering the Scrolling Navigation Bar in Jetpack Compose

Have you ever wished your bottom navigation bar in your Jetpack Compose app would subtly disappear while scrolling down and reappear gracefully when scrolling up? This behavior, commonly seen in popular apps like Instagram or YouTube, enhances the user experience by maximizing screen space and providing a more immersive scrolling experience.

Let's dive into how you can achieve this elegant effect using Jetpack Compose.

The Problem: A Persistent Navigation Bar

Imagine you have a beautiful Jetpack Compose screen with a scrollable list of items. Your bottom navigation bar, while essential for navigation, is always present, obstructing the content when scrolling. This can feel intrusive and detract from the user experience.

The Solution: Dynamically Hiding and Showing the Navigation Bar

We can use a combination of composables and state management to achieve the desired effect:

@Composable
fun MyScreen() {
    val scrollState = rememberScrollState()
    var showNavigationBar by remember { mutableStateOf(true) }

    // Wrap your content inside a Column and use the scrollState
    Column(
        modifier = Modifier.fillMaxSize(),
        verticalArrangement = Arrangement.spacedBy(16.dp),
        verticalScrollState = scrollState,
    ) {
        // Your content here
        // ... 
    }

    // Observe scroll state changes and update the showNavigationBar state
    LaunchedEffect(key1 = scrollState.value) {
        if (scrollState.value > 100) { // Adjust threshold value
            showNavigationBar = false 
        } else if (scrollState.value <= 0) {
            showNavigationBar = true 
        }
    }

    // Conditional rendering of the Navigation Bar
    if (showNavigationBar) {
        BottomNavigation(
            modifier = Modifier.padding(bottom = 8.dp),
            // ... your navigation items 
        )
    }
}

Explanation:

1. rememberScrollState: We create a ScrollState to track the scroll position of our scrollable content.
2. remember { mutableStateOf(true) }: We use remember to create a MutableState to manage the visibility of the navigation bar. Initially, it's set to true (visible).
3. LaunchedEffect: This composable allows us to observe the scroll state changes and update the navigation bar visibility. The key1 = scrollState.value ensures the effect is triggered only when the scroll state changes.
4. scrollState.value > 100: We set a threshold value (100 in this example) to trigger hiding the navigation bar. Adjust this value based on your content and desired behavior.
5. if (showNavigationBar): We conditionally render the BottomNavigation based on the showNavigationBar state.

Key Considerations and Enhancements

• Threshold Value: The threshold value (e.g., 100 in the example) determines how much the user needs to scroll before the navigation bar hides. Experiment with different values to find what works best for your app.
• Animation: You can add smooth animations to the appearance and disappearance of the navigation bar using AnimatedVisibility or custom animation solutions. This can significantly improve the user experience.
• Edge Cases: Consider scenarios where the content might not be scrollable or the user might quickly scroll back up. You can implement logic to handle these edge cases and ensure the navigation bar behaves as expected.
• Platform Specific Behaviors: You might want to customize the behavior based on platform differences. For instance, on Android, you can use WindowInsets to manage system-level navigation bar interactions.

Conclusion

By dynamically hiding and showing the bottom navigation bar during scrolling, you can create a more immersive and visually appealing user experience in your Jetpack Compose application. This technique improves the usability of your app by maximizing screen space when scrolling and providing a seamless visual flow. Remember to experiment with different threshold values, animations, and edge case handling to optimize the experience for your specific app.