Android Platform Skill

Quick Start

Activity Lifecycle

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

Fragment Usage

class UserFragment : Fragment() {
    private val viewModel: UserViewModel by viewModels()
    
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        viewModel.user.observe(viewLifecycleOwner) { user ->
            updateUI(user)
        }
    }
}

Key Concepts

Lifecycle Callbacks

• onCreate(): Initial setup
• onStart(): Become visible
• onResume(): Gain focus
• onPause(): Lose focus
• onStop(): Hidden
• onDestroy(): Final cleanup

Fragment Lifecycle

Similar to Activity but with:

• onAttach(): Attached to activity
• onDetach(): Detached
• Fragment manager for transactions

Intent System

// Explicit
startActivity(Intent(this, DetailActivity::class.java))

// Implicit
startActivity(Intent(Intent.ACTION_VIEW, Uri.parse("https://example.com")))

Services

• Started: startService()
• Bound: bindService()
• Foreground: Visible notification

Best Practices

✅ Handle lifecycle properly ✅ Use ViewModel for state ✅ Unregister listeners ✅ Test configuration changes ✅ Respect process lifecycle

Resources

• Activity Lifecycle
• Fragment Guide
• Service Documentation