Android SDK

Native Android development with Kotlin and Java.

When to Use

• Native Android apps
• System-level integrations
• Background services
• Performance-critical features

Quick Start

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val textView = findViewById<TextView>(R.id.text_view)
        textView.text = "Hello Android!"
    }
}

Core Concepts

Activity Lifecycle

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        // Initialize UI
    }

    override fun onStart() {
        super.onStart()
        // Visible to user
    }

    override fun onResume() {
        super.onResume()
        // Interactive
    }

    override fun onPause() {
        super.onPause()
        // Save state
    }

    override fun onStop() {
        super.onStop()
        // Release resources
    }

    override fun onDestroy() {
        super.onDestroy()
        // Cleanup
    }
}

Intents

// Start activity
val intent = Intent(this, DetailActivity::class.java).apply {
    putExtra("USER_ID", userId)
}
startActivity(intent)

// Get result
val launcher = registerForActivityResult(
    ActivityResultContracts.StartActivityForResult()
) { result ->
    if (result.resultCode == RESULT_OK) {
        val data = result.data
    }
}

Common Patterns

ViewModel

class UserViewModel(
    private val repository: UserRepository
) : ViewModel() {

    private val _user = MutableStateFlow<User?>(null)
    val user: StateFlow<User?> = _user.asStateFlow()

    fun loadUser(id: String) {
        viewModelScope.launch {
            _user.value = repository.getUser(id)
        }
    }
}

Permissions

private val permissionLauncher = registerForActivityResult(
    ActivityResultContracts.RequestPermission()
) { isGranted ->
    if (isGranted) {
        // Permission granted
    }
}

fun requestCameraPermission() {
    when {
        ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
            == PackageManager.PERMISSION_GRANTED -> {
            // Already granted
        }
        else -> {
            permissionLauncher.launch(Manifest.permission.CAMERA)
        }
    }
}

Best Practices

Do:

• Use ViewModel for UI state
• Handle configuration changes
• Request permissions at runtime
• Use Coroutines for async

Don't:

• Block the main thread
• Hardcode strings
• Ignore lifecycle
• Skip null checks

Troubleshooting

Issue	Cause	Solution
ANR	Main thread blocked	Move to background
Memory leak	Context reference	Use lifecycle-aware
Crash on rotation	State not saved	Use ViewModel

References

• Android Developer Docs
• Android Architecture