IF Notes

00_CODE_SYNTAX_NOTES

14 min read

📋 Catatan Syntax & Code Snippet untuk Ujian IF3210

File ini berisi semua contoh kode, method, dan syntax penting dari PPT 9-15. Cocok untuk soal “apa yang terjadi di snippet ini?” atau “syntax yang benar/salah”.

🟢 BAB 9: Activity & Fragment Lifecycle

Activity Lifecycle Callbacks (Urutan WAJIB HAFAL)

Activity launched → onCreate() → onStart() → onResume() → [RUNNING]
                                                            ↓
                                          onPause() ← [kehilangan fokus]
                                          onStop()  ← [tidak visible]
                                          onDestroy() ← [hancur]

Kembali dari onStop: onRestart() → onStart() → onResume()

Fragment Lifecycle (Bedanya dari Activity!)

onAttach() → onCreate() → onCreateView() → onViewCreated()
→ onStart() → onResume() → [AKTIF]
→ onPause() → onStop() → onDestroyView() → onDestroy() → onDetach()

Poin Penting: Fragment punya onAttach(), onCreateView(), onViewCreated(), onDestroyView(), onDetach() yang Activity TIDAK punya.

Simpan State saat Config Change (Rotasi Layar)

// SIMPAN
override fun onSaveInstanceState(outState: Bundle) {
    outState.putString("KEY", value)
    super.onSaveInstanceState(outState)
}
 
// RESTORE - di onCreate
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    val restoredValue = savedInstanceState?.getString("KEY")
}

Fragment juga bisa restore di: onCreate(), onCreateView(), onViewCreated().

LifecycleObserver Pattern

class MyObserver : LifecycleObserver {
    @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
    fun connectListener() { ... }
}
 
// Tambah observer ke lifecycle owner:
myLifecycleOwner.getLifecycle().addObserver(MyObserver())

Keyword: LifecycleOwner = punya lifecycle (Fragment, AppCompatActivity). LifecycleObserver = yang mengawasi.

💾 BAB 10: Room Database & Coroutines

Entity (Representasi Tabel)

@Entity(tableName = "colors")
data class Color(
    @PrimaryKey(autoGenerate = true) val _id: Int,
    @ColumnInfo(name = "hex_color") val hex: String,
    val name: String
)

⚠️ Perhatikan: @ColumnInfo(name = "hex_color") mengubah nama kolom di DB.

DAO (Data Access Object)

@Dao
interface ColorDao {
    @Query("SELECT * FROM colors")
    suspend fun getAll(): Array<Color>
 
    @Query("SELECT * FROM colors WHERE name = :name")
    suspend fun getColorByName(name: String): LiveData<Color>
 
    @Insert
    suspend fun insert(vararg color: Color)
 
    @Update
    suspend fun update(color: Color)
 
    @Delete
    suspend fun delete(color: Color)
}

⚠️ Perhatikan: :name di Query merujuk ke parameter fungsi. vararg = bisa masukkan banyak argumen.

Database Singleton Pattern (SERING KELUAR DI SOAL)

@Database(entities = [Color::class], version = 1)
abstract class ColorDatabase : RoomDatabase() {
    abstract fun colorDao(): ColorDao
 
    companion object {
        @Volatile
        private var INSTANCE: ColorDatabase? = null
 
        fun getInstance(context: Context): ColorDatabase {
            return INSTANCE ?: synchronized(this) {
                INSTANCE ?: Room.databaseBuilder(
                    context.applicationContext,
                    ColorDatabase::class.java, "color_database"
                )
                .fallbackToDestructiveMigration()
                .build()
                .also { INSTANCE = it }
            }
        }
    }
}

⚠️ Yang harus kamu tahu:

  • @Volatile → perubahan INSTANCE langsung visible ke semua thread
  • synchronized(this) → cuma 1 thread yang boleh bikin DB
  • ?: ... ?: ... → Double-check locking pattern
  • .also { INSTANCE = it } → simpan instance yang baru dibuat
  • fallbackToDestructiveMigration() → hapus semua data lama kalau versi DB naik

Pakai DAO

val colorDao = ColorDatabase.getInstance(application).colorDao()
val newColor = Color(hex = "#6200EE", name = "purple")
colorDao.insert(newColor)

Coroutine Dispatchers (WAJIB TAHU)

DispatcherDeskripsiContoh
Dispatchers.MainUI & task ringanUpdate LiveData, panggil suspend function
Dispatchers.IONetwork & diskDatabase, file IO, Retrofit call
Dispatchers.DefaultCPU intensiveParsing JSON, sorting besar

withContext (Pindah Dispatcher)

suspend fun get(url: String) {
    // Mulai di Dispatchers.Main
    withContext(Dispatchers.IO) {
        // Pindah ke Dispatchers.IO
        // Lakukan network request
    }
    // Kembali ke Dispatchers.Main
}

CoroutineScope (launch vs async)

// launch - kalau TIDAK butuh hasil balik
viewModelScope.launch {
    fetchDocs()
}
 
// async - kalau BUTUH hasil balik
val result = viewModelScope.async {
    fetchData()
}.await()

ViewModel + Coroutine

class ColorViewModel(val dao: ColorDao, application: Application)
    : AndroidViewModel(application) {
 
    fun save(color: Color) {
        viewModelScope.launch {
            colorDao.insert(color)
        }
    }
}

viewModelScope otomatis cancel kalau ViewModel cleared.

Testing Room Database

@RunWith(AndroidJUnit4::class)
class DatabaseTest {
    private lateinit val colorDao: ColorDao
    private lateinit val db: ColorDatabase
 
    @Before
    fun createDb() {
        val context = ApplicationProvider.getApplicationContext()
        db = Room.inMemoryDatabaseBuilder(context, ColorDatabase::class.java)
            .allowMainThreadQueries()
            .build()
        colorDao = db.colorDao()
    }
 
    @After
    fun closeDb() = db.close()
 
    @Test
    fun insertAndRetrieve() {
        colorDao.insert(red, green, blue)
        val colors = colorDao.getAll()
        assert(colors.size == 3)
    }
}

Keyword: inMemoryDatabaseBuilder = DB cuma di RAM, hilang setelah test selesai.

🛠️ BAB 11: Services, Broadcast, Notification, Content Provider

Broadcast - Jenis

sendBroadcast()           → Asynchronous, semua receiver dapat
sendOrderedBroadcast()    → Synchronous, satu per satu
LocalBroadcastManager.sendBroadcast() → Hanya dalam app sendiri (aman!)

Register BroadcastReceiver (Dynamic)

// Register di onCreate
val filter = IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION)
receiver = NetworkReceiver()
this.registerReceiver(receiver, filter)
 
// Unregister di onDestroy
this.unregisterReceiver(receiver)

⚠️ WAJIB unregister! Kalau tidak → memory leak.

BroadcastReceiver Implementation

class NetworkReceiver : BroadcastReceiver() {
    override fun onReceive(context: Context, intent: Intent) {
        // Punya waktu HANYA 5 DETIK untuk eksekusi!
        val conn = context.getSystemService(Context.CONNECTIVITY_SERVICE)
                    as ConnectivityManager
        val networkInfo: NetworkInfo? = conn.activeNetworkInfo
        // ... proses network status
    }
}

⚠️ onReceive() punya batas waktu 5 DETIK, lalu receiver DIHANCURKAN.

Service Types (Method yang dipanggil)

JenisMulai denganBerhenti dengan
StartedstartService()stopSelf() atau stopService()
BoundbindService()Otomatis saat semua client unbind
IntentServicestartService()Otomatis setelah onHandleIntent() selesai

Service berjalan di MAIN THREAD by default (kecuali IntentService).

Notification Builder

// Java-style dari PPT (mungkin keluar di soal!)
mNotifyManager = getSystemService(NOTIFICATION_SERVICE) as NotificationManager
 
mNotifyBuilder = NotificationCompat.Builder(this)
    .setContentTitle("You've been notified!")
    .setContentText("This is your notification text.")
    .setSmallIcon(R.drawable.ic_android_black_24dp)
 
val myNotification = mNotifyBuilder.build()
mNotifyManager.notify(NOTIFICATION_ID, myNotification)

Keyword: PendingIntent = memberi app lain hak menjalankan Intent atas namamu (untuk notif tap action).

Content Provider - Arsitektur

Activity/Adapter → ContentResolver → ContentProvider → Data (SQLite)
  • ContentResolver mengembalikan data sebagai Cursor (baris + kolom)
  • Content Provider butuh permission di Manifest
  • Tanpa permission eksplisit = semua app bisa baca/tulis (bahaya!)

🌐 BAB 12: Connectivity & Retrofit

Permission di Manifest (WAJIB)

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

⚠️ INTERNET = Normal permission (auto-granted). Tapi network operation di main thread → NetworkOnMainThreadException!

Permission Types

LevelGrantedPrompt?Contoh
NormalInstall timeTidakINTERNET, BLUETOOTH, VIBRATE
SignatureInstall timeTidakN/A
DangerousRuntimeYaCAMERA, CALL_PHONE, GET_ACCOUNTS

Retrofit Interface Definition

interface UserService {
    @GET("/users/{id}")
    suspend fun getUser(@Path("id") id: String): User
}

Retrofit + Repository Pattern

class UserRepository constructor(private val userService: UserService) {
    suspend fun getUserById(id: String): User {
        return userService.getUser(id)
    }
}
 
// Setup Retrofit
var retrofit = Retrofit.Builder()
    .baseUrl("https://...")
    .build()
 
var userRepository = UserRepository(retrofit.create(UserService::class.java))
var john = userRepository.getUserById("john")

Moshi + Retrofit (JSON Parsing)

private val moshi = Moshi.Builder()
    .add(KotlinJsonAdapterFactory())
    .build()
 
val retrofit = Retrofit.Builder()
    .addConverterFactory(MoshiConverterFactory.create(moshi))
    .baseUrl(BASE_URL)
    .build()
 
object API {
    val retrofitService: SimpleService by lazy {
        retrofit.create(SimpleService::class.java)
    }
}

by lazy = instance baru dibuat saat pertama kali diakses.

ViewModel + Retrofit + LiveData

class MainViewModel(savedStateHandle: SavedStateHandle,
    userRepository: UserRepository) : ViewModel() {
 
    private val userId: String = savedStateHandle["uid"]
        ?: throw IllegalArgumentException("Missing user ID")
 
    private val _user = MutableLiveData<User>()
    val user = _user as LiveData<User>
 
    init {
        viewModelScope.launch {
            try {
                val user = userRepository.getUserById(userId)
                _user.value = user
            } catch (error: Exception) {
                // show error message to user
            }
        }
    }
}

Check Network Connection

fun isOnline(): Boolean {
    val connMgr = getSystemService(Context.CONNECTIVITY_SERVICE)
                    as ConnectivityManager
    val networkInfo: NetworkInfo? = connMgr.activeNetworkInfo
    return networkInfo?.isConnected == true
}

Network Callback (Modern API)

connectivityManager.registerDefaultNetworkCallback(object :
    ConnectivityManager.NetworkCallback() {
 
    override fun onAvailable(network: Network) { ... }
    override fun onLost(network: Network) { ... }
    override fun onCapabilitiesChanged(
        network: Network,
        networkCapabilities: NetworkCapabilities) { ... }
})

Optimizing Network Usage

(getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager).apply {
    if (isActiveNetworkMetered) {
        when (restrictBackgroundStatus) {
            RESTRICT_BACKGROUND_STATUS_ENABLED -> { /* blocked */ }
            RESTRICT_BACKGROUND_STATUS_WHITELISTED -> { /* allowed */ }
            RESTRICT_BACKGROUND_STATUS_DISABLED -> { /* no restriction */ }
        }
    }
}

🐦 BAB 13: Dart & Flutter Syntax

Variabel & Tipe Data

String firstName = 'John';    // Eksplisit
var lastName = 'Smith';        // Tipe diinfer
int age = 20;
double height = 5.9;
bool isMarried = false;
 
// String interpolation
print('Name is $firstName $lastName');
print('Age is ${age + 1}');  // Gunakan {} untuk expression

final vs const (SERING KELUAR)

final date = DateTime.now();   // ✅ OK, dihitung saat runtime
const date = DateTime.now();   // ❌ Error! const harus compile-time
 
const pi = 3.14;              // ✅ OK
final gravity;                 // ❌ Error! final harus diinisialisasi
final gravity = Gravity();     // ✅ OK
gravity.setForce(...);         // ✅ OK, object-nya masih mutable!

⚠️ final = referensi-nya fixed, tapi isi objeknya masih bisa berubah! ⚠️ const = semuanya fixed + canonicalized (1 copy di memory).

const Canonicalization

const point1 = ImmutablePoint(2, 3);
const point2 = ImmutablePoint(2, 3);
print(identical(point1, point2));  // true → SATU OBJEK di memory
 
final point3 = ImmutablePoint(2, 3);
final point4 = ImmutablePoint(2, 3);
print(identical(point3, point4));  // false → DUA OBJEK berbeda

Null Safety (Dart 3.0)

int a = 100;     // Non-nullable, WAJIB ada nilai
int b;           // ❌ Compile-time error!
int? c;          // ✅ Nullable, boleh null
late int d;      // ✅ Non-nullable tapi diinisialisasi nanti
print(d);        // ❌ Runtime error: belum diinisialisasi!
d = 3;
print(d);        // ✅ OK

Null-aware Operators (WAJIB HAFAL)

String? str;
 
print(str.length);      // ❌ Compile-time error
print(str?.length);     // ✅ Print null jika str null (safe call)
print(str ?? 'Default'); // ✅ Print 'Default' jika str null (elvis)
str ??= 'Default';      // ✅ Assign 'Default' HANYA jika str null
int length = str!.length; // ⚠️ Paksa non-null (crash jika null!)

Object vs dynamic

Object obj = 'Hello';
print(obj.length);          // ❌ Compile-time error (Object gak punya .length)
print((obj as String).length); // ✅ OK, cast dulu
 
dynamic dyn = 'Hello';
print(dyn.length);          // ✅ OK (bypass compile-time check)
print(dyn.isEven);          // ❌ Runtime error! String gak punya isEven

Type Checking & Conversion

// Type check
if (obj is String) { ... }
if (obj is! int) { ... }
print(obj.runtimeType);
 
// Conversion
int one = int.parse('1');         // String → int
String oneStr = one.toString();   // int → String
pi.toInt();                       // double → int
String str = obj as String;       // Parent → child type

Functions: Parameters & Default Values

// Optional positional parameters
void sayMessage(String message, [String? author]) {
    print("$message -- ${author ?? 'Anonymous'}");
}
 
// Named parameters & default values
void setDimensions({int width = 10, int height = 10}) {
    print("Width: $width, Height: $height");
}
 
void main() {
    sayMessage('Hello, Dart!');
    setDimensions(height: 20, width: 30);  // Urutan bebas!
}

Arrow Functions

// Normal
int add(int a, int b) { return a + b; }
 
// Arrow (HANYA untuk 1 expression yang return value)
int add(int a, int b) => a + b;

⚠️ Jangan pakai arrow kalau fungsi tidak return apa-apa!

Higher-Order Functions & Anonymous Functions

// Function sebagai parameter
void printOPResult(int a, int b, Function(int, int) op) {
    var result = op(a, b);
    print('Result: $result');
}
 
// Anonymous function & forEach
myList.forEach((e) { print(e); });
var myList2 = myList.map((e) => e * 2).toList();

Closures

Function makeAdder(int base) {
    return (int i) => base + i;  // Captures 'base'
}
 
var addFrom2 = makeAdder(2);
print(addFrom2(10));  // 12

⚠️ Dart: Closure di loop AMAN (tiap iterasi punya copy sendiri). JavaScript: TIDAK aman (bad closure).

Classes & Constructors

class Person {
    String name;
    int age;
 
    // Constructor
    Person({required this.name, required this.age});
 
    // Named constructor
    Person.fromMap(Map<String, dynamic> data)
        : name = data['name'],
          age = data['age'];
 
    void displayInfo() {
        print('Name: $name, Age: $age');
    }
}

Inheritance

class Student extends Person {
    String university;
 
    Student({
        required super.name,
        required super.age,
        required this.university
    });
 
    @override
    void displayInfo() {
        super.displayInfo();
        print('University: $university');
    }
}
 
// Type check
Person alice = Student(...);
assert(alice is Person);    // true
assert(alice is Student);   // true
assert(alice is! Employee); // true
var studentAlice = alice as Student;  // Downcast

Abstract Class (Dart gak punya keyword interface)

abstract class GameCharacter {
    String name;
    GameCharacter(this.name);
    void performAbility(); // Harus di-implement oleh subclass
}

Mixin (Multiple Inheritance)

mixin Logger {
    void log(String message) { /* persist message */ }
}
 
class OrderProcessor extends Processor with Logger, ... {
    void createOrder(String details) {
        log('Order created: $details');  // Method dari mixin!
    }
}

Extension Methods

extension EmailValidator on String {
    bool get isValidEmail {
        return RegExp(r'^[a-zA-Z0-9.]+@[a-zA-Z0-9]+\.[a-zA-Z]+')
            .hasMatch(this);
    }
}
 
var email = '[email protected]';
if (email.isValidEmail) { ... }  // Pakai langsung pada String!

Enums & Switch Expression

enum Status { loading, success, error }
Status status = .loading; // Shorthand Dart 3
 
// Switch EXPRESSION (mengembalikan value)
var token = switch (char) {
    '+' || '-' || '*' || '/' => 'Operator',
    ',' || ';' => 'Punctuation',
    _ => throw FormatException('Invalid character'),
};

Spread, if, for in Collection Literals

bool includeOddNumbers = true;
var numbers = [1, 2, 3, 4, 5];
var evenNumbers = [2, 4];
var combinedList = [
    if (includeOddNumbers) ...numbers.where((n) => n.isOdd),
    for (var n in evenNumbers) n,
];
// Result: [1, 3, 5, 2, 4]

StatefulWidget Pattern (HAFAL!)

class CounterWidget extends StatefulWidget {
    const CounterWidget({super.key});
 
    @override
    _CounterWidgetState createState() => _CounterWidgetState();
}
 
class _CounterWidgetState extends State<CounterWidget> {
    int _counter = 0;
 
    void _incrementCounter() {
        setState(() {    // ← Ini yang trigger rebuild!
            _counter++;
        });
    }
 
    @override
    Widget build(BuildContext context) {
        return Text('Counter: $_counter');
    }
}

⚠️ Tanpa setState(), UI TIDAK akan update walaupun variabel berubah!

Dart Coding Conventions (bisa keluar di soal pilihan ganda)

ApaFormatContoh
Variable/functionlowerCamelCasemyVariable, getUserName()
Class/extensionUpperCamelCaseMyClass, EmailValidator
Packagesnake_casemy_package
PrivateLeading __age, _helper()
Global variableLeading kkColorScheme
StringSingle-quoted'hello' (kecuali ada single quote di dalamnya)

🔒 BAB 14: Mobile Security

Android Manifest Permission

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.android.app.myapp">
    <uses-permission android:name="android.permission.RECEIVE_SMS" />
    ...
</manifest>

OWASP Top 10 Mobile 2024 (HAFAL URUTAN)

  1. M1: Improper Credential Usage
  2. M2: Inadequate Supply Chain Security
  3. M3: Insecure Authentication/Authorization
  4. M4: Insufficient Input/Output Validation
  5. M5: Insecure Communication
  6. M6: Inadequate Privacy Controls
  7. M7: Insufficient Binary Protections
  8. M8: Security Misconfiguration
  9. M9: Insecure Data Storage
  10. M10: Insufficient Cryptography

Security Best Practices Summary

  • Encrypt: AES 256-bit, simpan key di KeyStore
  • Communication: HTTPS, Certificate Pinning, HMAC
  • Storage: Internal app-specific storage, EncryptedSharedPreferences
  • Permission: Minta minimal, runtime kalau dangerous, jelaskan ke user
  • Code: Input validation, hindari dynamic code loading, disable IPC by default
  • Identifier: Jangan pakai IMEI → gunakan user-resettable ID

🚀 BAB 15: Jetpack Compose

Basic Composable

@Composable
fun Greeting(name: String) {
    Text(text = "Hello $name!")
}
 
// Dalam Activity:
class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            MyAppTheme {
                Surface(color = MaterialTheme.colors.background) {
                    Greeting("Android")
                }
            }
        }
    }
}

Modifier Chaining (URUTAN PENTING!)

val shape = RoundedCornerShape(8.dp)
Text(
    text = "Text 1",
    modifier = Modifier.fillMaxWidth()
        .padding(16.dp)        // Padding LUAR
        .border(2.dp, color, shape)
        .padding(1.dp)
        .background(color, shape)
        .clickable(onClick = { })
        .padding(16.dp)        // Padding DALAM
)

⚠️ padding sebelum background = space di LUAR background. Setelah = space di DALAM.

Layouts: Column, Row, Box

Box(modifier = Modifier.fillMaxWidth()) {
    Column(modifier = Modifier.padding(16.dp).fillMaxWidth()) {
        Text("Column Text 1")
        Text("Column Text 2")
        Row(
            modifier = Modifier.fillMaxWidth(),
            horizontalArrangement = Arrangement.SpaceEvenly
        ) {
            Text(text = "Row Text 1")
            Text(text = "Row Text 2")
        }
    }
    Text("Stack Text", modifier = Modifier
        .align(Alignment.TopEnd)
        .padding(end = 16.dp, top = 16.dp)
    )
}
  • Column = vertikal (atas-bawah)
  • Row = horizontal (kiri-kanan)
  • Box = stack/tumpuk (elemen terakhir di atas)

State Management (PALING PENTING)

// State yang survive recomposition
var nameState by remember { mutableStateOf("") }
 
TextField(
    value = nameState,
    label = { Text("Name") },
    onValueChange = { s: String -> nameState = s }
)

rememberSaveable (Survive rotation)

var state by rememberSaveable {
    mutableStateOf("Compose!!!")
}

Observable State in Class

class Score(team: String, score: Int) {
    var team by mutableStateOf(team)
    var score by mutableStateOf(score)
}
 
// Perubahan langsung trigger recomposition!
score.score += 1

LiveData → Compose

@Composable
fun UserScreen(usersLiveData: LiveData<List<UserBinding>>) {
    val users by usersLiveData.observeAsState()
    // users sekarang bisa dipakai langsung
}

Alternatives: Flow.collectAsState(), Observable.subscribeAsState()

ViewModel + Compose (Full Pattern)

@Composable
fun UserScreen(viewModel: UsersViewModel = viewModel()) {
    val users by viewModel.allUsers.observeAsState()
    Column(modifier = Modifier.fillMaxSize()) {
        UserList(
            users = users ?: emptyList(),
            onDeleteUser = { user -> viewModel.deleteUser(user) }
        )
    }
}

LazyColumn (RecyclerView replacement)

@Composable
fun UserListScreen(users: List<User>) {
    LazyColumn(modifier = Modifier.fillMaxSize()) {
        item {
            Text("Header", Modifier.fillMaxWidth().padding(8.dp))
        }
        items(users) { user ->
            Text("${user.name} - ${user.age}", Modifier.fillMaxWidth().padding(8.dp))
        }
    }
}

Variant: itemsIndexed(users) { index, user -> ... } untuk akses index.

Scaffold (App Structure)

Scaffold(
    topBar = {
        TopAppBar(
            title = { Text("Compose") },
            actions = {
                IconButton(onClick = {}) {
                    Icon(Icons.Default.Search, "Search")
                }
            }
        )
    },
    floatingActionButton = {
        FloatingActionButton(onClick = { }) {
            Icon(Icons.Filled.Add, "Add")
        }
    },
    bottomBar = { ... }
) { /* content */ }

Side Effects

// LaunchedEffect: Jalankan coroutine saat composable pertama kali muncul
LaunchedEffect(someKey) {
    val s = withContext(Dispatchers.IO) {
        delay(5_000)
        "Hello Compose!"
    }
    welcomeMsg.value = s
}
 
// DisposableEffect: Cleanup saat composable dihancurkan
DisposableEffect(someKey) {
    // setup listener
    onDispose {
        // Cleanup!
    }
}
 
// rememberCoroutineScope: Launch dari callback
val scope = rememberCoroutineScope()
Button(onClick = {
    scope.launch {
        // do async work
    }
})

Interop: Compose dalam Fragment

class MyFragment : Fragment() {
    override fun onCreateView(...): View? {
        return ComposeView(requireContext()).apply {
            setContent {
                AppTheme { YourComposable() }
            }
        }
    }
}

Interop: Old View dalam Compose

@Composable
fun MyCalendar(onDateUpdate: (Date) -> Unit) {
    AndroidView(
        factory = { context: Context ->
            LayoutInflater.from(context)
                .inflate(R.layout.my_layout, null, false)
        },
        update = { view ->
            // Update view saat recomposition
        }
    )
}

Compose Resource Access

stringResource(R.string.your_string)
dimensionResource(R.dimen.padding_small)
colorResource(R.color.blue)

🎯 Quick Reference: “Apa yang Salah dengan Snippet Ini?”

❌ Network di Main Thread

fun loadData() {
    val data = URL("https://...").readText()  // CRASH! NetworkOnMainThreadException
}

Fix: Wrap dalam viewModelScope.launch { withContext(Dispatchers.IO) { ... } }

❌ Room query tanpa suspend

@Query("SELECT * FROM colors")
fun getAll(): List<Color>  // ⚠️ Kalau dipanggil dari Main Thread → CRASH!

Fix: Tambahkan suspend → suspend fun getAll(): List<Color>

❌ Dart: Modifikasi const

const list = [1, 2, 3];
list.add(4);  // ❌ Runtime Error! const = immutable

❌ Flutter: Update state tanpa setState

void _increment() {
    _counter++;  // Variabel berubah, tapi UI TIDAK update
}

Fix: Wrap dalam setState(() { _counter++; })

❌ Compose: State tanpa remember

@Composable
fun Counter() {
    var count = mutableStateOf(0)  // ❌ Reset setiap recomposition!
    Button(onClick = { count.value++ }) { Text("${count.value}") }
}

Fix: var count by remember { mutableStateOf(0) }

Graph View

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