Jetpack Compose is Android’s modern toolkit for building native UI.
- It's declarative UI framework, you decide what your UI should contain and compose handle the rest.
- It simplifies and accelerates UI development on Android.
- Quickly bring your app to life with less code, powerful tools, and intuitive Kotlin APIs.
- It requires less code to implement a UI compared to the Android View system, which makes your app easier to maintain.
- It's a good practice to provide a default Modifier to all composable functions, as it increases reusability. It should appear as the first optional parameter in the parameter list, after all required parameters.
- In a real app, string should be added as string resources in the strings.xml file and referenced using Compose's stringResource API.
- To display a scrollable column we use a LazyColumn. LazyColumn renders only the visible items on screen, allowing performance gains when rendering a big list.
- LazyColumn and LazyRow are equivalent to RecyclerView in Android Views.
- LazyColumn API provides an items element within its scope, where individual item rendering logic is written
- Make sure you import
androidx.compose.foundation.lazy.itemsas Android Studio will pick a different items function by default. - LazyColumn doesn't recycle its children like RecyclerView. It emits new Composable as you scroll through it and is still performant, as emitting Composable is relatively cheap compared to instantiating Android Views.
- The remember function works only as long as the composable is kept in the Composition. When you rotate, the whole activity is restarted so all state is lost.
- This also happens with any configuration change and on process death.
- Instead of using remember you can use rememberSaveable. This will save each state surviving configuration changes (such as rotations) and process death.