kotlin android app development course, introduction to Jetpack and androidx

Android app development has evolved over time, and in recent years, Kotlin has become a popular language among developers. Kotlin’s concise and modern syntax makes Android development much easier. However, to effectively utilize Kotlin, it is important to understand various libraries and tools for Android app development. In this course, we will explore Android Jetpack and AndroidX.

1. What is Android Jetpack?

Android Jetpack is a library that collectively provides various components necessary for Android app development. This library helps with app structure, simplifies lifecycle management, and integrates various tools needed for data storage and UI composition. Android Jetpack can be broadly divided into three main components:

  • Architecture Components: Includes ViewModel, LiveData, and Room framework, allowing for more efficient design and management of the app’s architecture.
  • UI Components: UI-related components such as Navigation, Fragment, and ViewPager that help design the user interface easily.
  • Behavior Components: Including WorkManager and Paging Library, which help efficiently manage asynchronous tasks and data paging.

1.1 Architecture Components

Architecture components are designed for app development following the MVVM (Model-View-ViewModel) pattern. These components provide various functionalities such as lifecycle awareness, data observation, and database operations.

1.1.1 ViewModel

ViewModel is responsible for storing and managing UI-related data. Since ViewModel preserves data regardless of the Activity or Fragment’s lifecycle, it is useful during screen rotations or other lifecycle changes.

class MainViewModel : ViewModel() {
    private val _text = MutableLiveData()
    val text: LiveData get() = _text

    fun updateText(newText: String) {
        _text.value = newText
    }
}

1.1.2 LiveData

LiveData is an object that allows data to be observed in accordance with the lifecycle. The UI subscribes to LiveData, and it updates automatically when data changes.

viewModel.text.observe(this, Observer { newText ->
    textView.text = newText
})

1.1.3 Room

Room is an ORM library that makes it easier to work with SQLite databases. With Room, you can insert, update, and delete data without writing SQL queries.

@Entity(tableName = "users")
data class User(
    @PrimaryKey val id: Int,
    val name: String
)

@Dao
interface UserDao {
    @Query("SELECT * FROM users")
    fun getAllUsers(): List
    
    @Insert
    fun insertUser(user: User)
}

1.2 UI Components

UI components play a significant role in managing the flow and navigation of the user interface. The Navigation Component allows for easy connection of various screens, improving user experience through Fragment and ViewPager.

1.2.1 Navigation Component

The Navigation Component is a library that helps easily implement navigation within an app. You can define a navigation graph and manage transitions between different screens.

val navController = findNavController(R.id.nav_host_fragment)
navController.navigate(R.id.action_firstFragment_to_secondFragment)

1.2.2 Fragment

Fragment is a component that encapsulates a portion of the user interface for reuse. Fragments manage their lifecycle separately from Activities.

1.2.3 ViewPager

ViewPager is a component that helps to navigate by sliding between multiple Fragments. You can manage the pages through a PagerAdapter.

class ViewPagerAdapter(fm: FragmentManager) : FragmentPagerAdapter(fm) {
    override fun getItem(position: Int): Fragment {
        return when (position) {
            0 -> FirstFragment()
            1 -> SecondFragment()
            else -> FirstFragment()
        }
    }

    override fun getCount(): Int {
        return 2
    }
}

1.3 Behavior Components

Behavior components help manage business logic such as background tasks and data loading.

1.3.1 WorkManager

WorkManager is a framework that allows you to perform tasks in the background as needed. This enables delays or periodic execution of tasks.

val workRequest = OneTimeWorkRequestBuilder()
    .setInputData(workDataOf("key" to "value"))
    .build()

WorkManager.getInstance(context).enqueue(workRequest)

2. What is AndroidX?

AndroidX is a library that includes a new package of libraries for Android. Google has improved the management and updating of various libraries through AndroidX. AndroidX has the following features:

  • Modularity: Each feature is provided as an independent library, allowing you to choose only the libraries you need.
  • Version Management: Google regularly provides updates to AndroidX libraries, making it easy to utilize the latest features.
  • Consistent Naming for all APIs: The AndroidX library provides a consistent naming convention for all APIs.

2.1 AndroidX Components

AndroidX consists of various components, some of which include:

  • AppCompat: Provides various UI components that support compatibility.
  • ConstraintLayout: A layout that helps easily arrange UI elements.
  • RecyclerView: A component that can efficiently display large amounts of data.
  • Room: As mentioned earlier, it is an ORM library that assists in working with database operations.

2.2 Example of Using AndroidX

Below is a simple example of displaying a list using AndroidX’s RecyclerView.

2.2.1 build.gradle Setup

dependencies {
    implementation "androidx.recyclerview:recyclerview:1.2.1"
}

2.2.2 RecyclerView Adapter

class MyAdapter(private val items: List) : RecyclerView.Adapter() {

    class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val textView: TextView = itemView.findViewById(R.id.textView)
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        val view = LayoutInflater.from(parent.context)
            .inflate(R.layout.item_layout, parent, false)
        return ViewHolder(view)
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.textView.text = items[position]
    }

    override fun getItemCount() = items.size
}

2.2.3 RecyclerView Setup

val recyclerView = findViewById(R.id.recyclerView)
recyclerView.layoutManager = LinearLayoutManager(this)
recyclerView.adapter = MyAdapter(listOf("Item 1", "Item 2", "Item 3"))

3. Conclusion

Android Jetpack and AndroidX are essential elements in Android app development, enabling developers to build higher quality apps more quickly. I hope this lecture has helped you understand the various components of Android Jetpack and the importance of AndroidX. I will return with more in-depth Kotlin Android app development courses in the future!