Animation

Animation làm cho ứng dụng trở nên sống động và tăng trải nghiệm người dùng. Compose cung cấp nhiều APIs mạnh mẽ để tạo animations một cách dễ dàng.

1. animate*AsState - Animation đơn giản nhất

Cách sử dụng

Thay đổi giá trị state → Compose tự động animate:

@Composable
fun ExpandingBox() {
    var expanded by remember { mutableStateOf(false) }

    // Tự động animate khi expanded thay đổi
    val size by animateDpAsState(
        targetValue = if (expanded) 200.dp else 100.dp,
        label = "size"
    )

    Box(
        modifier = Modifier
            .size(size)
            .background(Color.Blue)
            .clickable { expanded = !expanded }
    )
}

Các variants

// Animate Dp
val size by animateDpAsState(targetValue = if (big) 200.dp else 100.dp)

// Animate Color
val color by animateColorAsState(targetValue = if (selected) Color.Red else Color.Gray)

// Animate Float
val alpha by animateFloatAsState(targetValue = if (visible) 1f else 0f)

// Animate Int
val count by animateIntAsState(targetValue = targetCount)

// Animate Offset
val offset by animateOffsetAsState(targetValue = Offset(x, y))

Custom AnimationSpec

val size by animateDpAsState(
    targetValue = if (expanded) 200.dp else 100.dp,
    animationSpec = spring(
        dampingRatio = Spring.DampingRatioMediumBouncy,
        stiffness = Spring.StiffnessLow
    ),
    label = "size"
)

val color by animateColorAsState(
    targetValue = targetColor,
    animationSpec = tween(durationMillis = 500, easing = LinearEasing),
    label = "color"
)

---

2. AnimatedVisibility - Hiển thị/ẩn với animation

Cơ bản

@Composable
fun ToastMessage(visible: Boolean, message: String) {
    AnimatedVisibility(visible = visible) {
        Card(modifier = Modifier.padding(16.dp)) {
            Text(message, modifier = Modifier.padding(16.dp))
        }
    }
}

Custom Enter/Exit Transitions

@Composable
fun SlideInContent(visible: Boolean) {
    AnimatedVisibility(
        visible = visible,
        enter = fadeIn(animationSpec = tween(300)) +
                slideInVertically(initialOffsetY = { -it }),
        exit = fadeOut(animationSpec = tween(300)) +
               slideOutVertically(targetOffsetY = { -it })
    ) {
        Card {
            Text("Sliding Content")
        }
    }
}

Các EnterTransition

Transition	Mô tả
fadeIn()	Fade từ transparent
slideInHorizontally()	Slide từ trái/phải
slideInVertically()	Slide từ trên/dưới
scaleIn()	Scale từ nhỏ
expandIn()	Expand từ một góc
expandHorizontally()	Expand theo chiều ngang
expandVertically()	Expand theo chiều dọc

Animate children riêng biệt

@Composable
fun AnimateChildren(visible: Boolean) {
    AnimatedVisibility(
        visible = visible,
        enter = fadeIn(),
        exit = fadeOut()
    ) {
        Column {
            Text(
                "Title",
                modifier = Modifier.animateEnterExit(
                    enter = slideInVertically { -it },
                    exit = slideOutVertically { -it }
                )
            )
            Text(
                "Subtitle",
                modifier = Modifier.animateEnterExit(
                    enter = slideInVertically { it },
                    exit = slideOutVertically { it }
                )
            )
        }
    }
}

---

3. AnimatedContent - Chuyển đổi nội dung

Cơ bản

@Composable
fun CounterAnimation(count: Int) {
    AnimatedContent(
        targetState = count,
        label = "counter"
    ) { targetCount ->
        Text(
            text = "$targetCount",
            style = MaterialTheme.typography.displayLarge
        )
    }
}

Custom Transition

@Composable
fun TabContent(selectedTab: Int) {
    AnimatedContent(
        targetState = selectedTab,
        transitionSpec = {
            if (targetState > initialState) {
                // Slide left khi chuyển sang tab bên phải
                slideInHorizontally { it } + fadeIn() togetherWith
                slideOutHorizontally { -it } + fadeOut()
            } else {
                // Slide right khi chuyển sang tab bên trái
                slideInHorizontally { -it } + fadeIn() togetherWith
                slideOutHorizontally { it } + fadeOut()
            }.using(SizeTransform(clip = false))
        },
        label = "tab"
    ) { tab ->
        when (tab) {
            0 -> HomeTab()
            1 -> SearchTab()
            2 -> ProfileTab()
        }
    }
}

---

4. Crossfade - Fade chuyển đổi

@Composable
fun LoadingState(isLoading: Boolean) {
    Crossfade(
        targetState = isLoading,
        animationSpec = tween(500),
        label = "loading"
    ) { loading ->
        if (loading) {
            CircularProgressIndicator()
        } else {
            Text("Content loaded!")
        }
    }
}

---

5. updateTransition - Animation phức tạp

Khi bạn cần animate nhiều properties cùng lúc:

enum class ButtonState { Idle, Pressed }

@Composable
fun AnimatedButton() {
    var buttonState by remember { mutableStateOf(ButtonState.Idle) }

    val transition = updateTransition(targetState = buttonState, label = "button")

    val scale by transition.animateFloat(label = "scale") { state ->
        when (state) {
            ButtonState.Idle -> 1f
            ButtonState.Pressed -> 0.95f
        }
    }

    val backgroundColor by transition.animateColor(label = "background") { state ->
        when (state) {
            ButtonState.Idle -> Color.Blue
            ButtonState.Pressed -> Color.DarkGray
        }
    }

    val borderWidth by transition.animateDp(label = "border") { state ->
        when (state) {
            ButtonState.Idle -> 0.dp
            ButtonState.Pressed -> 2.dp
        }
    }

    Box(
        modifier = Modifier
            .scale(scale)
            .background(backgroundColor, RoundedCornerShape(8.dp))
            .border(borderWidth, Color.White, RoundedCornerShape(8.dp))
            .padding(16.dp)
            .pointerInput(Unit) {
                detectTapGestures(
                    onPress = {
                        buttonState = ButtonState.Pressed
                        tryAwaitRelease()
                        buttonState = ButtonState.Idle
                    }
                )
            }
    ) {
        Text("Press Me", color = Color.White)
    }
}

---

6. rememberInfiniteTransition - Animation vô hạn

@Composable
fun PulsingDot() {
    val infiniteTransition = rememberInfiniteTransition(label = "pulse")

    val scale by infiniteTransition.animateFloat(
        initialValue = 1f,
        targetValue = 1.5f,
        animationSpec = infiniteRepeatable(
            animation = tween(1000),
            repeatMode = RepeatMode.Reverse
        ),
        label = "scale"
    )

    val alpha by infiniteTransition.animateFloat(
        initialValue = 1f,
        targetValue = 0.3f,
        animationSpec = infiniteRepeatable(
            animation = tween(1000),
            repeatMode = RepeatMode.Reverse
        ),
        label = "alpha"
    )

    Box(
        modifier = Modifier
            .size(50.dp)
            .scale(scale)
            .alpha(alpha)
            .background(Color.Red, CircleShape)
    )
}

Loading Shimmer Effect

@Composable
fun ShimmerEffect() {
    val transition = rememberInfiniteTransition(label = "shimmer")

    val translateX by transition.animateFloat(
        initialValue = -300f,
        targetValue = 300f,
        animationSpec = infiniteRepeatable(
            animation = tween(1000, easing = LinearEasing)
        ),
        label = "shimmer"
    )

    Box(
        modifier = Modifier
            .fillMaxWidth()
            .height(100.dp)
            .background(
                brush = Brush.horizontalGradient(
                    colors = listOf(
                        Color.LightGray,
                        Color.White,
                        Color.LightGray
                    ),
                    startX = translateX,
                    endX = translateX + 200f
                )
            )
    )
}

---

7. Animatable - Low-level Control

Khi cần kiểm soát animation hoàn toàn:

@Composable
fun DraggableCard() {
    val offsetX = remember { Animatable(0f) }

    Box(
        modifier = Modifier
            .offset { IntOffset(offsetX.value.roundToInt(), 0) }
            .pointerInput(Unit) {
                detectHorizontalDragGestures(
                    onDragEnd = {
                        // Spring back to original position
                        launch {
                            offsetX.animateTo(
                                targetValue = 0f,
                                animationSpec = spring(stiffness = Spring.StiffnessLow)
                            )
                        }
                    }
                ) { _, dragAmount ->
                    launch {
                        offsetX.snapTo(offsetX.value + dragAmount)
                    }
                }
            }
            .size(100.dp)
            .background(Color.Blue, RoundedCornerShape(8.dp))
    )
}

Animate to/SnapTo/Stop

val animatable = remember { Animatable(0f) }

// Animate với animation spec
animatable.animateTo(100f, animationSpec = tween(500))

// Jump trực tiếp đến giá trị
animatable.snapTo(100f)

// Dừng animation
animatable.stop()

// Animate với velocity (như fling)
animatable.animateDecay(initialVelocity = 1000f, animationSpec = exponentialDecay())

---

8. AnimationSpec Types

tween - Easing-based

tween<Float>(
    durationMillis = 300,
    delayMillis = 50,
    easing = FastOutSlowInEasing
)

spring - Physics-based

spring<Float>(
    dampingRatio = Spring.DampingRatioMediumBouncy,
    stiffness = Spring.StiffnessLow
)

keyframes - Multi-step

keyframes<Float> {
    durationMillis = 1000
    0f at 0 with LinearEasing
    0.5f at 200 with FastOutLinearInEasing
    1f at 1000
}

repeatable / infiniteRepeatable

repeatable<Float>(
    iterations = 3,
    animation = tween(500),
    repeatMode = RepeatMode.Reverse
)

infiniteRepeatable<Float>(
    animation = tween(500),
    repeatMode = RepeatMode.Restart
)

---

9. Gesture-based Animation

@Composable
fun SwipeableCard() {
    var offset by remember { mutableStateOf(0f) }
    var dismissed by remember { mutableStateOf(false) }

    val animatedOffset by animateFloatAsState(
        targetValue = if (dismissed) 1000f else offset,
        animationSpec = spring(stiffness = Spring.StiffnessLow),
        finishedListener = {
            if (dismissed) {
                // Handle dismiss
            }
        },
        label = "swipe"
    )

    Box(
        modifier = Modifier
            .offset { IntOffset(animatedOffset.roundToInt(), 0) }
            .draggable(
                orientation = Orientation.Horizontal,
                state = rememberDraggableState { delta ->
                    offset += delta
                },
                onDragStopped = { velocity ->
                    if (abs(offset) > 200 || abs(velocity) > 1000) {
                        dismissed = true
                    } else {
                        offset = 0f
                    }
                }
            )
            .size(200.dp)
            .background(Color.Blue, RoundedCornerShape(16.dp))
    )
}

---

10. Navigation Animation

@Composable
fun AnimatedNavHost() {
    val navController = rememberNavController()

    NavHost(
        navController = navController,
        startDestination = "home"
    ) {
        composable(
            route = "home",
            enterTransition = { fadeIn(tween(300)) },
            exitTransition = { fadeOut(tween(300)) }
        ) {
            HomeScreen()
        }

        composable(
            route = "detail",
            enterTransition = {
                slideInHorizontally(initialOffsetX = { it }) + fadeIn()
            },
            exitTransition = {
                slideOutHorizontally(targetOffsetX = { -it }) + fadeOut()
            },
            popEnterTransition = {
                slideInHorizontally(initialOffsetX = { -it }) + fadeIn()
            },
            popExitTransition = {
                slideOutHorizontally(targetOffsetX = { it }) + fadeOut()
            }
        ) {
            DetailScreen()
        }
    }
}

---

📝 Tóm tắt

API	Mục đích
animate*AsState	Animation đơn giản
AnimatedVisibility	Hiện/ẩn với animation
AnimatedContent	Chuyển đổi nội dung
Crossfade	Fade transition
updateTransition	Animation phức tạp nhiều properties
rememberInfiniteTransition	Animation vô hạn
Animatable	Low-level control

Chọn API nào?

Cần animate gì?
├── Một giá trị đơn lẻ → animate*AsState
├── Visibility → AnimatedVisibility
├── Content switch → AnimatedContent hoặc Crossfade
├── Nhiều properties cùng lúc → updateTransition
├── Infinite loop → rememberInfiniteTransition
└── Full control → Animatable