Fixing Rounded Navigation Bar Corner Padding in Jetpack Compose

When implementing a rounded bottom navigation bar in Jetpack Compose, you might encounter an issue where the system padding becomes visible in the corners, disrupting the clean, rounded appearance you're aiming for. Let's break down the root cause and how to resolve this common UI problem.

The Cause

In the image below, you can see unwanted edges in the corners that aren't clipped by the navigation bar. These edges are caused by the scaffold padding (innerPadding), which is used to manage the padding for the bottom bar, top bar, and system bars, ensuring UI elements don't overlap. While this padding is useful for layout adjustments, it interferes with achieving a seamless, rounded design for the bottom navigation bar.

Cases and Solutions

1. Using a LazyColumn Inside Another Container:

• Cause: The issue often arises when using a LazyColumn inside another container, such as a Column, where the height of the LazyColumn is constrained by the parent container defined in the Scaffold. Consider the following example:

Scaffold(
    containerColor = Color(0xFFC9E4FD),
    topBar = { AppBar() },
    bottomBar = { BottomBar() }
) { innerPadding ->
    Column(
        verticalArrangement = Arrangement.spacedBy(8.dp),
        modifier = Modifier.padding(innerPadding)
    ) {
        Box(
            modifier = Modifier
                .padding(8.dp)
                .background(
                    Color.DarkGray,
                    shape = RoundedCornerShape(16.dp)
                )
                .width(200.dp)
                .height(100.dp)
        ) {
            Greeting("Android")
        }
        LazyColumn(
            contentPadding = PaddingValues(8.dp),
            verticalArrangement = Arrangement.spacedBy(8.dp)
        ) {
            items(10) {
                Box(
                    modifier = Modifier
                        .background(
                            Color(0xFF001E30),
                            shape = RoundedCornerShape(16.dp)
                        )
                        .fillMaxWidth()
                        .height(100.dp)
                ) {
                    Greeting("Android")
                }
            }
        }
    }
}

• Solution: To remove the extra padding, adjust the innerPadding values:

val topPadding = innerPadding.calculateTopPadding()
var bottomPadding = innerPadding.calculateBottomPadding()
if (bottomPadding > 0.dp) bottomPadding -= 15.dp

Column(
    modifier = Modifier.padding(top = topPadding, bottom = bottomPadding)
) {
    // Your UI components here
}

This solution reassigns the value of the bottom padding to remove the extra padding. The if condition ensures the padding value remains non-negative, preventing errors like this:

FATAL EXCEPTION: main
Process: com.example.bottombar, PID: 25016
java.lang.IllegalArgumentException: Padding must be non-negative

• Complete Code for the First Solution:

Scaffold(
    containerColor = Color(0xFFC9E4FD),
    topBar = { AppBar() },
    bottomBar = { BottomBar() }
) { innerPadding ->
    val topPadding = innerPadding.calculateTopPadding()
    var bottomPadding = innerPadding.calculateBottomPadding()
    if (bottomPadding > 0.dp) bottomPadding -= 10.dp

    Column(
        modifier = Modifier.padding(
           top = topPadding,
           bottom = bottomPadding
        )
    ) {
        Box(
            modifier = Modifier
                .padding(8.dp)
                .background(
                    Color.DarkGray,
                    shape = RoundedCornerShape(16.dp)
                )
                .width(200.dp)
                .height(100.dp)
        ) {
            Greeting("Android")
        }
        LazyColumn(
            contentPadding = PaddingValues(
                top = 8.dp,
                bottom = 20.dp,
                start = 8.dp,
                end = 8.dp
            ),
            verticalArrangement = Arrangement.spacedBy(8.dp)
        ) {
            items(10) {
                Box(
                    modifier = Modifier
                        .background(
                            Color(0xFF001E30),
                            shape = RoundedCornerShape(16.dp)
                        )
                        .fillMaxWidth()
                        .height(100.dp)
                ) {
                    Greeting("Android")
                }
            }
        }
    }
}

---

2. Assigning innerPadding to LazyColumn:

• Cause: If you assign the innerPadding directly to the LazyColumn using Modifier.padding(), it can cause the same issue. Here's an example:

Scaffold(
    containerColor = Color(0xFFC9E4FD),
    topBar = { AppBar() },
    bottomBar = { BottomBar() }
) { innerPadding ->
    LazyColumn(
        verticalArrangement = Arrangement.spacedBy(8.dp),
        modifier = Modifier.padding(innerPadding)
    ) {
        items(10) {
            Box(
                modifier = Modifier
                    .background(
                        Color(0xFF001E30),
                        shape = RoundedCornerShape(16.dp)
                    )
                    .fillMaxWidth()
                    .height(100.dp)
            ) {
                Greeting("Android")
            }
        }
    }
}

• Solution: Instead of applying innerPadding directly to the LazyColumn's modifier, assign it to the contentPadding parameter:

Scaffold(
    containerColor = Color(0xFFC9E4FD),
    topBar = { AppBar() },
    bottomBar = { BottomBar() }
) { innerPadding ->
    LazyColumn(
        contentPadding = innerPadding,
        verticalArrangement = Arrangement.spacedBy(8.dp),
        modifier = Modifier.padding(8.dp)
    ) {
        items(10) {
            Box(
                modifier = Modifier
                    .background(
                        Color(0xFF001E30),
                        shape = RoundedCornerShape(16.dp)
                    )
                    .fillMaxWidth()
                    .height(100.dp)
            ) {
                Greeting("Android")
            }
        }
    }
}

By assigning innerPadding to contentPadding, this fixes the problem and ensures that the padding is handled correctly without affecting the rounded corners of your bottom navigation bar.

---

Final Result

Conclusion

These two solutions address the common issue of visible system padding interfering with the rounded corners of a bottom navigation bar in Jetpack Compose. By either adjusting the padding for the whole layout or assigning innerPadding to contentPadding, you can achieve a clean, rounded appearance without the unwanted white edges.

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