Jetpack Compose is a modern toolkit for building native Android UIs. It simplifies and accelerates UI development by providing a declarative way to build UI components, making it easier to create complex layouts and animations.

Unlike the traditional Android View system, Jetpack Compose is built on Kotlin, which allows for easier integration with the rest of the Android ecosystem. With Jetpack Compose, developers can create beautiful, responsive, and performant UIs in less time and with less code.

Declarative UI:

Jetpack Compose provides a declarative way of building UI components, which makes it easier to create complex layouts and animations with less code.

XML :

<LinearLayout
   android:id="@+id/my_linearlayout"
   android:layout_width="match_parent"
   android:layout_height="wrap_content"
   android:orientation="vertical">

   <TextView
       android:id="@+id/textview1"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:text="TextView 1" />

   <TextView
       android:id="@+id/textview2"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:text="TextView 2" />

</LinearLayout>

Compose :

Column {
   Text("TextView 1")
   Text("TextView 2")
}

Example 2 :

XML:

<androidx.recyclerview.widget.RecyclerView
   android:id="@+id/my_recyclerview"
   android:layout_width="match_parent"
   android:layout_height="match_parent" />

val recyclerView = findViewById<RecyclerView>(R.id.my_recyclerview)
val adapter = MyAdapter(data)
recyclerView.adapter = adapter

Then further another 60-80 lines of code for vidwHolder, Adapter, item blah blah.

Compose:

val data = listOf("Item 1", "Item 2", "Item 3")

LazyColumn {
   items(data) { item ->
      Text(text = item)
   }
}

Kotlin Integration

Jetpack Compose is built on Kotlin, which allows for easier integration with the rest of the Android ecosystem, and leveraging all the power of Kotlin while creating composable Functions.

It uses various Kotlin features such as extension functions, operator overloading, and lambda expressions to create composable functions that can be reused and combined to build complex UIs.

For example, Compose provides composable functions like Text(), Button(), and Column() that can be used to create UI components.

These functions can be combined to create more complex UIs and layouts. Additionally, Compose uses Kotlin's type inference and null safety features to reduce boilerplate code and catch errors at compile time.

@Composable
fun MyScreenContent(names: List<String> = listOf("Android", "there")) {
    Column(modifier = Modifier.padding(16.dp)) {
        Text(text = "Hello, ${names.first()}!")
        LazyColumn {
            items(names) { name ->
                Greeting(name = name)
                Divider(color = Color.Black)
            }
        }
    }
}

@Composable
fun Greeting(name: String) {
    Text(text = "Hello $name!", modifier = Modifier.padding(24.dp))
}

Improved Performance:

Jetpack Compose is designed to be more performant than traditional XML-based UI development, with faster rendering times and improved memory usage.

it improves performance by reducing the number of UI updates, which results in faster rendering times and improved memory usage.

This is achieved through the use of a unidirectional data flow architecture, where state changes are propagated from a single source of truth to the UI components that depend on them.

As a result, only the affected UI components are re-rendered, instead of the entire UI hierarchy. This approach can lead to significant performance improvements, especially for complex UIs with many dynamic elements.

Simplified UI Development:

Jetpack Compose simplifies and accelerates UI development, making it easier to create beautiful, responsive, and performant UIs in less time and with less code.

No need to create multiple XML files and go back and forth. One single file will likely contain everything that is responsible for the specific screen.

---

With Compose, bringing movement and life to your apps through animations is quick and easy to implement: “Animations are so easy to add in Compose that there’s very little reason not to animate things like colour/size/elevation changes” (Monzo), “you can make animations without requiring anything special -- it’s no different than showing a static screen” - Square

With Compose, you build small, stateless components that are not tied to a specific activity or fragment. That makes them easy to reuse and test: “We set a goal for ourselves to deliver a new set of UI components that were stateless, easy to use and maintain, and intuitive to implement/extend/customize. Compose really provided a solid answer for us in this.” - Twitter

---

In the Next blog, we will see how Compose draws UI internally.

If you found this article helpful, please give it a thumbs up. Thanks for reading.