Android Compose Task App Implementation Series: Bottom Bar with a FAB

Production App

Anothertask Version 1.0.0 is available here if you are interested 😉

Objective

Recreate the Bottom Bar with a Floating Action Button (FAB) from the Taskose UI design kit I acquired, utilizing Android Jetpack Compose.

Environment

• Android Studio Iguana | 2023.2.1
• Compose version: composeBom = "2023.08.00"
• Pixel 6 API 30 Emulator
• Project Minimum SDK: 27

Implementation

Step 1

Download the needed icons here, and add them to res/drawable directory.

Step 2

Create BottomBarItem.kt file with the following content.

// Your package ...

import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Spacer
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.size
import androidx.compose.material3.Icon
import androidx.compose.material3.IconButton
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.graphics.vector.ImageVector
import androidx.compose.ui.res.vectorResource
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.Dp
import androidx.compose.ui.unit.dp
// import YOUR_PACKAGE_PATH.R

data class BottomBarItemData(
    val drawableId: Int = 0,
    val selected: Boolean = false,
    val onClick: () -> Unit = {}
)

@Composable
fun BottomBarItem(
    itemData: BottomBarItemData,
    selectedColor: Color = Color(0xFF7980FF),
    nonSelectedColor: Color = Color(0xFF464D61).copy(alpha = 0.7f),
    iconSize: Dp = 24.dp
) {
    IconButton(onClick = { itemData.onClick() }) {
        Icon(
            imageVector = ImageVector.vectorResource(id = itemData.drawableId),
            contentDescription = null,
            tint = if (itemData.selected) selectedColor else nonSelectedColor,
            modifier = Modifier.size(iconSize)
        )
    }
}

@Preview
@Composable
fun BottomBarItemPreview() {
    val mockOnClick = {}
    Column(
        verticalArrangement = Arrangement.Center,
        horizontalAlignment = Alignment.CenterHorizontally,
        modifier = Modifier
            .fillMaxSize()
            .background(Color(0xFF000000))
    ) {
        Text("Selected", color = Color.White)
        Spacer(modifier = Modifier.height(8.dp))
        BottomBarItem(
            itemData = BottomBarItemData(
                onClick = mockOnClick,
                drawableId = R.drawable.ic_dashboard,
                selected = true
            ),
        )
        Spacer(modifier = Modifier.height(16.dp))
        Text("Not Selected", color = Color.White)
        Spacer(modifier = Modifier.height(8.dp))
        BottomBarItem(
            itemData = BottomBarItemData(
                onClick = mockOnClick,
                drawableId = R.drawable.ic_profile,
                selected = false
            ),
        )
    }
}

Step 3

Create BottomBar.kt file with the following content.

// Your package ...

import android.widget.Toast
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.Spacer
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.size
import androidx.compose.foundation.shape.CircleShape
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.material3.Card
import androidx.compose.material3.CardDefaults
import androidx.compose.material3.FloatingActionButtonDefaults
import androidx.compose.material3.Icon
import androidx.compose.material3.LargeFloatingActionButton
import androidx.compose.runtime.Composable
import androidx.compose.runtime.mutableIntStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.graphics.vector.ImageVector
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.res.vectorResource
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.Dp
import androidx.compose.ui.unit.dp
// import YOUR_PACKAGE_PATH.R
// import YOUR_PACKAGE_PATH.BottomBarItem
// import YOUR_PACKAGE_PATH.BottomBarItemData

@Composable
fun BottomBar(
    barHeight: Dp = 60.dp,
    fabColor: Color = Color(0xFF7980FF),
    fabSize: Dp = 64.dp,
    fabIconSize: Dp = 32.dp,
    cardTopCornerSize: Dp = 24.dp,
    cardElevation: Dp = 8.dp,
    fabDrawableId: Int = R.drawable.ic_add,
    buttons: List<BottomBarItemData> = listOf(
        BottomBarItemData(drawableId = R.drawable.ic_dashboard),
        BottomBarItemData(drawableId = R.drawable.ic_tasks),
        BottomBarItemData(drawableId = R.drawable.ic_chat),
        BottomBarItemData(drawableId = R.drawable.ic_profile)
    ),
    fabOnClick: () -> Unit = {}
) {
    require(buttons.size == 4) { "BottomBar must have exactly 4 buttons" }
    Box(
        modifier = Modifier
            .fillMaxWidth()
            .height(barHeight + fabSize / 2)
    ) {
        Card(
            modifier = Modifier
                .fillMaxWidth()
                .height(barHeight)
                .align(Alignment.BottomCenter),
            colors = CardDefaults.cardColors(containerColor = Color.White),
            elevation = CardDefaults.cardElevation(defaultElevation = cardElevation),
            shape = RoundedCornerShape(
                topStart = cardTopCornerSize,
                topEnd = cardTopCornerSize,
                bottomEnd = 0.dp,
                bottomStart = 0.dp
            )
        ) {
            Row(
                modifier = Modifier.fillMaxSize(),
                verticalAlignment = Alignment.CenterVertically,
                horizontalArrangement = Arrangement.SpaceAround
            )
            {
                BottomBarItem(buttons[0])
                BottomBarItem(buttons[1])
                Spacer(modifier = Modifier.size(fabSize))
                BottomBarItem(buttons[2])
                BottomBarItem(buttons[3])
            }
        }
        LargeFloatingActionButton(
            modifier = Modifier
                .size(fabSize)
                .align(Alignment.TopCenter),
            onClick = { fabOnClick() },
            shape = CircleShape,
            containerColor = fabColor,
            elevation = FloatingActionButtonDefaults.bottomAppBarFabElevation(defaultElevation = 0.dp)
        ) {
            Icon(
                imageVector = ImageVector.vectorResource(id = fabDrawableId),
                contentDescription = null,
                tint = Color.White,
                modifier = Modifier.size(fabIconSize)
            )
        }
    }
}

@Preview
@Composable
fun BottomBarPreview() {
    val context = LocalContext.current
    val items = listOf(
        R.drawable.ic_dashboard,
        R.drawable.ic_tasks,
        R.drawable.ic_chat,
        R.drawable.ic_profile
    )

    // Use a single state to track the currently selected item's index
    val selectedIndex = remember { mutableIntStateOf(0) }

    // Dynamically generate the buttons based on the items list
    val buttons = items.mapIndexed { index, drawableId ->
        BottomBarItemData(
            drawableId = drawableId,
            selected = index == selectedIndex.intValue,
            onClick = { selectedIndex.intValue = index } // Update the selected index on click
        )
    }

    Box(
        modifier = Modifier.fillMaxSize(),
        contentAlignment = Alignment.BottomCenter
    ) {
        BottomBar(buttons = buttons, fabOnClick = {
            Toast.makeText(context, "FAB clicked", Toast.LENGTH_SHORT).show()
        })
    }
}

Preview Result

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