Jetpack Compose: Snackbar dismiss listener

Understanding the Snackbar Dismiss Listener in Jetpack Compose

Snackbar messages in Android applications are a useful way to provide short, transient feedback to users. Jetpack Compose, the modern toolkit for building native Android UIs, has made it simpler and more intuitive to implement such UI components. However, one challenge developers often face is handling the dismissal of a Snackbar, especially if specific actions or updates need to occur when it is dismissed. The example discussed in this article demonstrates how to display a Snackbar with a dismiss listener using Jetpack Compose and Kotlin.

This tutorial is particularly useful for those looking to gain a deeper understanding of managing state, coroutines, and user feedback in a Compose-based application. Let's walk through how this example efficiently utilizes coroutines and state management to handle the appearance and dismissal of a Snackbar, ensuring a smooth user experience.

Overview of the Implementation

The core functionality revolves around a simple screen interface with a TopAppBar and a central button. When the user clicks the button, a Snackbar is displayed at the bottom of the screen. The most significant feature here is the listener that detects when the Snackbar is dismissed, which triggers an update to a status message displayed on the screen. The whole application structure is built using Jetpack Compose components like Scaffold, Box, and Column.

The entry point of the application starts in the MainActivity class, where the setContent method is used to define the UI layout with a composable function named GetScaffold. This design encapsulates the app's structure, making it modular and easy to extend. The Scaffold composable provides the essential framework for implementing a top bar, content area, and Snackbar functionality.

Setting Up the Scaffold and Top Bar

The GetScaffold function plays a pivotal role in setting up the application's basic structure. It creates a ScaffoldState object, which is essential for controlling the Snackbar. The Scaffold composable itself is configured to include a TopAppBar, which displays a simple title at the top of the screen. This top bar adds a touch of visual polish while also demonstrating how easily Compose allows developers to incorporate Material Design elements.

Additionally, the background color of both the TopAppBar and the overall Scaffold is customized, giving the application a distinct look. These design choices show how developers can quickly modify UI components using Compose's built-in theming system.

Handling Snackbar Display and Dismissal

The MainContent composable is where the core logic for the Snackbar is implemented. It uses a Box to center its contents and a Column to arrange elements vertically. The rememberCoroutineScope function is utilized to manage the coroutine that handles the display of the Snackbar.

A key feature in this setup is the state variable snackBarStatus, which keeps track of the Snackbar's current state. Initially, it displays a message indicating that the Snackbar is inactive. When the user presses the button, the coroutine launches, triggering the showSnackbar method to display a message.

The real magic happens when a listener monitors the Snackbar’s state. Using the when statement, the application listens for the SnackbarResult.Dismissed event, updating the snackBarStatus message to indicate that the Snackbar has been dismissed. This kind of event-driven behavior is essential for creating responsive user interfaces, where changes in state trigger updates in real time.

Enhancing User Interactions

One of the benefits of using Jetpack Compose is how it simplifies handling user interactions. In this example, the button click initiates a coroutine that shows the Snackbar and waits for user interaction or automatic dismissal. The showSnackbar method, combined with the SnackbarResult object, makes it effortless to determine how the Snackbar was closed.

Additionally, by using mutableStateOf, the app can efficiently recompose when the state changes, ensuring that the UI remains in sync with the underlying data. This responsiveness is one of the key advantages of Compose over the traditional View-based approach, as it avoids complex lifecycle handling and provides a more intuitive way to update the UI.

Summary

This example serves as a practical demonstration of how to leverage Jetpack Compose for building dynamic and interactive Android UIs. By utilizing Scaffold, coroutines, and state management, the application demonstrates how to handle Snackbar display and dismissal events in an elegant and efficient manner. The use of a dismiss listener not only enhances user experience but also opens up possibilities for further customizations, such as executing additional actions upon dismissal.

For developers exploring Jetpack Compose, this project showcases essential techniques that can be extended to more complex scenarios. Whether you're adding Snackbar notifications to your app or learning how to manage state with coroutines, this approach provides a solid foundation to build upon.

MainActivity.kt


package com.cfsuman.jetpackcompose

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.*
import androidx.compose.material.*
import androidx.compose.runtime.*
import androidx.compose.ui.graphics.Color
import androidx.compose.material.Text
import androidx.compose.material.TopAppBar
import androidx.compose.material.icons.filled.*
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp
import kotlinx.coroutines.launch


class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            GetScaffold()
        }
    }


    @Composable
    fun GetScaffold(){
        val scaffoldState: ScaffoldState = rememberScaffoldState(
            snackbarHostState = SnackbarHostState()
        )

        Scaffold(
            scaffoldState = scaffoldState,
            topBar = {
                TopAppBar(
                    title = { Text(
                        text = "Compose - Snackbar Dismiss Listener"
                    )},
                    backgroundColor = Color(0xFFC0E8D5),
                )
            },
            content = {MainContent(scaffoldState)},
            backgroundColor = Color(0xFFEDEAE0),
        )
    }


    @Composable
    fun MainContent(scaffoldState: ScaffoldState){
        val scope = rememberCoroutineScope()
        var snackBarStatus by remember {
            mutableStateOf("Snackbar status")
        }

        Box(
            modifier = Modifier.fillMaxSize(),
            contentAlignment = Alignment.Center
        ){
            Column(
                verticalArrangement = Arrangement.spacedBy(24.dp),
                horizontalAlignment = Alignment.CenterHorizontally
            ) {
                Text(
                    text = snackBarStatus,
                    style = MaterialTheme.typography.h5
                )

                Button(onClick = {
                    scope.launch{
                        snackBarStatus = "Snackbar is showing"
                        val snackbarResult = scaffoldState
                            .snackbarHostState.showSnackbar(
                                message = "This is a snackbar",
                            )

                        when(snackbarResult){
                            SnackbarResult.Dismissed -> {
                                snackBarStatus = "Snackbar dismissed"
                            }
                        }
                    }
                }) {
                    Text(text = "Show Snackbar")
                }
            }
        }
    }
}