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Jetpack Compose -Android App Development Course with Jetpack


Jetpack Compose -Android App Development Course with Jetpack

Jetpack Compose Course - an app that illustrates ViewModel, State, Flow, Room and DI with Hilt and Dagger - pdichone/JetNoteApp.

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Jetpack Compose is the modern toolkit for building native Android UIs, fundamentally transforming the way developers create user interfaces. Developed by Google, Jetpack Compose is designed to simplify and accelerate UI development on Android. This course will guide you through the essential concepts and practical applications of Jetpack Compose, empowering you to build responsive, flexible, and efficient Android applications.

What is Jetpack Compose?

Jetpack Compose is a UI toolkit that leverages Kotlin’s powerful features, offering a declarative approach to building user interfaces. Unlike the traditional XML-based UI development, Jetpack Compose allows you to describe your UI in Kotlin code, providing a more intuitive and seamless way to create complex and dynamic user interfaces.

Key Features of Jetpack Compose

  1. Declarative UI: Jetpack Compose uses a declarative approach, meaning you describe the UI state, and Compose takes care of updating the UI when the state changes.
  2. Kotlin Integration: As a Kotlin-first framework, Compose leverages Kotlin’s language features like extension functions, coroutines, and more.
  3. Reusable Components: Components, or Composables, can be reused across different parts of the app, enhancing modularity and maintainability.
  4. UI State Management: Compose provides robust state management, allowing for seamless handling of state changes.
  5. Interoperability: Jetpack Compose is fully interoperable with existing Android views, enabling gradual migration from XML to Compose.

Setting Up Your Development Environment

To get started with Jetpack Compose, you need to set up your development environment. This involves installing Android Studio and configuring it for Compose development.

  1. Download and Install Android Studio: Ensure you have the latest version of Android Studio.
  2. Create a New Project: Start a new project with an Empty Compose Activity template.
  3. Configure Dependencies: Ensure your project’s build.gradle files are set up with the necessary Compose dependencies.
groovy
dependencies { implementation "androidx.compose.ui:ui:1.0.0" implementation "androidx.compose.material:material:1.0.0" implementation "androidx.compose.ui:ui-tooling-preview:1.0.0" androidTestImplementation "androidx.compose.ui:ui-test-junit4:1.0.0" }

Basic Concepts of Jetpack Compose

Composables

Composables are the building blocks of Jetpack Compose. They are functions annotated with @Composable that define the UI components.

kotlin
@Composable fun Greeting(name: String) { Text(text = "Hello, $name!") }

State Management

State management is crucial in Compose. Use remember and mutableStateOf to manage state within your Composable functions.

kotlin
@Composable fun Counter() { var count by remember { mutableStateOf(0) } Button(onClick = { count++ }) { Text("Clicked $count times") } }

Layouts

Compose offers various layout Composables like Column, Row, and Box to arrange your UI components.

kotlin
@Composable fun LayoutsExample() { Column { Text("Item 1") Text("Item 2") Text("Item 3") } }

Advanced Concepts

Get Started

Custom Composables

You can create custom Composables to encapsulate complex UI logic.

kotlin
@Composable fun CustomCard(content: @Composable () -> Unit) { Card(elevation = 4.dp) { content() } }

Animations

Jetpack Compose simplifies animations with built-in support for animations using animate* functions.

kotlin
@Composable fun AnimatedBox() { var expanded by remember { mutableStateOf(false) } val size by animateDpAsState(targetValue = if (expanded) 200.dp else 100.dp) Box( Modifier .size(size) .background(Color.Red) .clickable { expanded = !expanded } ) }

Interoperability with XML

Jetpack Compose allows you to use existing XML-based UI components alongside Compose.

kotlin
@Composable fun XmlInteropExample() { AndroidView( factory = { context -> LayoutInflater.from(context).inflate(R.layout.xml_layout, null, false) } ) }

Building a Sample App

Step 1: Project Setup

Create a new project with an Empty Compose Activity in Android Studio. Ensure you have configured the necessary dependencies.

Step 2: Create Composables

Start by creating simple Composables for different parts of your app.

kotlin
@Composable fun AppScreen() { Column { Greeting("Compose") Counter() } }

Step 3: Navigation

Jetpack Compose supports navigation through the navigation-compose library.

kotlin
@Composable fun NavigationExample() { val navController = rememberNavController() NavHost(navController, startDestination = "home") { composable("home") { HomeScreen(navController) } composable("details") { DetailsScreen() } } } @Composable fun HomeScreen(navController: NavController) { Button(onClick = { navController.navigate("details") }) { Text("Go to Details") } } @Composable fun DetailsScreen() { Text("Details Screen") }

Step 4: State Management with ViewModel

Integrate ViewModel for more complex state management.

kotlin
class MyViewModel : ViewModel() { private val _text = MutableLiveData("Hello, ViewModel!") val text: LiveData<String> = _text fun updateText(newText: String) { _text.value = newText } } @Composable fun ViewModelExample(viewModel: MyViewModel = viewModel()) { val text by viewModel.text.observeAsState("") Column { Text(text) Button(onClick = { viewModel.updateText("Updated Text!") }) { Text("Update Text") } } }

Step 5: Themes and Styles

Jetpack Compose allows you to define themes and styles to maintain a consistent look and feel.

kotlin
@Composable fun MyAppTheme(content: @Composable () -> Unit) { MaterialTheme( colors = darkColors( primary = Color.Blue, secondary = Color.Green ), typography = Typography( body1 = TextStyle(fontWeight = FontWeight.Bold, fontSize = 18.sp) ), shapes = Shapes(small = RoundedCornerShape(8.dp)) ) { content() } }

Step 6: Testing

Jetpack Compose supports UI testing using compose-test library.

kotlin
@get:Rule val composeTestRule = createComposeRule() @Test fun testButton() { composeTestRule.setContent { MyAppTheme { Counter() } } composeTestRule.onNodeWithText("Clicked 0 times").assertExists() composeTestRule.onNodeWithText("Clicked 0 times").performClick() composeTestRule.onNodeWithText("Clicked 1 times").assertExists() }

Conclusion

Jetpack Compose represents a significant shift in Android UI development, providing a more intuitive and efficient way to build modern user interfaces. By following this course, you’ve learned the basics of setting up a Compose project, creating and managing Composables, handling state, navigating between screens, and integrating ViewModel for state management. With these skills, you are well-equipped to build sophisticated and responsive Android applications using Jetpack Compose. Keep exploring and experimenting with Compose to fully harness its potential and create amazing Android apps.