All You Need To Know About Jetpack Compose

Presented by Google at I/O in 2019, Jetpack Compose will revolutionize Android user interface development by moving away from the XML files to let you specify UI in code instead.

Similar to Flutter widgets and SwiftUI, Compose takes a modular and declarative approach to develop your UI in Kotlin code.

What is JetPack Compose?

Jetpack Compose is a cutting-edge toolkit for creating native Android UI. With powerful tools and intuitive Kotlin APIs, it simplifies and accelerates UI development for Android. You can also write less code with Jetpack Compose than the existing view-building approach, implying fewer bugs.

Why Do We Need Jetpack Compose?

JetPack combines a reactive programming model with the conciseness and ease of use of the Kotlin programming language. It is fully declarative, meaning you describe your UI by calling a series of functions that transform data into a UI hierarchy. Ultimately, Jetpack plans to replace the traditional way of imperative UI design.

Why should I use Jetpack Compose?

• It’s easier from XML and Kotlin
• Declarative UI is more readable, cleaner, and faster than Imperative UI.
• In comparison to XML, Compose allows you to achieve more with less code.
• It’s easy to use Compose. All you need to do is tell Compose what you want to show the user.
• All of your previous code is compatible with Compose: Compose code can be called from Views, and Views can be called from Compose.
• It’s also compatible with several Jetpack Libraries.
• Compose shortens your build time and reduces the size of your APK.

Code and output sample

Imperative programming vs Declarative programming

Imperative UI

This is the most common thought. It entails creating a different UI prototype/model for the app. The design is more concerned with how than what. XML layouts on Android are a good example. The widgets and components shown for the user to see and interact with can be designed by us.

Imperative UI sample code:

Xml:

<TextView

android:id=”@+id/tv_name”

android:layout_width=”match_parent”

android:layout_height=”wrap_content” />

Java:

public class MainActivity extends AppCompatActivity {

TextView tvName;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_checkbox);

tvName = findViewById(R.id.tv_name);

tvName.setText(“Hello World”);

}

}

Declarative UI

This pattern is an emerging trend that permits developers to design the user interface based on the data received. Declarative UI, on the other hand, focuses on what. This design paradigm uses one programming language to create an entire application.

class MainActivity : ComponentActivity() {

override fun onCreate(savedInstanceState: Bundle?) {

super.onCreate(savedInstanceState)

setContent {

Text(text = “Hello World”)

}

}

}

No xml code is needed in Jetpack Compose; instead, we can create views using composable.

Advantages of JetPack Compose

• Speedy and offers a smooth performance.
• Simple to learn.
• Interoperate with an imperative approach.
• A more suitable way to implement loose coupling principles.
• 100% made in Kotlin, making it a modern approach in Android development.

Key points of declarative UI pattern of Jetpack compose

• Accelerate development: As you begin development, you want to have more time writing business logic than spending time on animations and color changes. Jetpack Compose provides all of it out of the box without any work. This makes the apps developed with Compose material designed with less effort.
• Less Code: Jetpack does more with less code and avoids entire classes of bugs, so code is simple and easy to maintain.
• Powerful Tools: You create attractive apps with access to the Android platform APIs.
• Intuitive: Just define your user interface, and Compose will take care of the rest. The UI is automatically updated if the state changes.

State Management

“State in an app is any value that can vary over time.”- Google

Because Compose is declarative, the only way to change it is to call it with new arguments.

• Initial Composition: Design a Composition by running composables for the first time.
• Recomposition: Re-running composables to revamp the Composition when data (state) changes.
• Store a data with remember: val data by remember { mutableStateOf(INITIAL_VALUE) }

Conclusion

Jetpack Compose is a revolution in Android UI development. With less code and more understandable code, a declarative UI approach and a managing state, you can speed up the whole development cycle and reduce the size of the app. This will eventually result in less expensive, higher-quality software that better fits the needs of businesses in a competitive mobile software marketplace. Happy coding!