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[DEPRECATED, use AnimatedContent instead] Jetpack Compose tool for screen transitions
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enum class ComposableTransitionState { | |
VISIBLE, ENTERING, EXITING, | |
} | |
@Composable | |
fun <Key, State> ComposableSwitcher( | |
key: Key, | |
state: State, | |
snapOnInitialComposition: Boolean = true, | |
content: @Composable (Key, State, Transition<ComposableTransitionState>) -> Unit, | |
) { | |
val items: MutableList<TransitionItem<Key, State>> = remember { | |
mutableStateListOf<TransitionItem<Key, State>>().apply { | |
if (snapOnInitialComposition) { | |
this += TransitionItem( | |
key = key, | |
state = state, | |
content = { children -> | |
val transition = updateTransition(VISIBLE) | |
children(transition) | |
} | |
) | |
} | |
} | |
} | |
val currentKey = remember { | |
mutableStateOf(if (snapOnInitialComposition) key else Any()) | |
} | |
if (key != currentKey.value) { | |
currentKey.value = key | |
val keysAndStates = items.map { it.key to it.state }.toMutableList() | |
val currentKeyIndex = keysAndStates.indexOfFirst { (it, _) -> it == key } | |
if (currentKeyIndex == -1) { | |
keysAndStates += key to state | |
} else { | |
keysAndStates[currentKeyIndex] = key to state | |
} | |
items.clear() | |
keysAndStates.mapTo(items) { (itemKey, itemState) -> | |
TransitionItem(key = itemKey, state = itemState, content = @Composable { children -> | |
val isVisible = itemKey == key | |
val transitionState = remember { | |
MutableTransitionState(when (isVisible) { | |
true -> ENTERING | |
false -> VISIBLE | |
}) | |
} | |
transitionState.targetState = when (isVisible) { | |
true -> VISIBLE | |
false -> EXITING | |
} | |
val transition = updateTransition(transitionState) | |
if (!isVisible && transitionState.currentState == transitionState.targetState) { | |
items.removeAll { it.key == itemKey } | |
} | |
children(transition) | |
}) | |
} | |
} else { | |
// Updating current key's state if it changed. Don't want to update every time since it triggers recomposition | |
items.indexOfFirst { it.key == key }.takeIf { it >= 0 }?.let { indexOfKey -> | |
val newState = items[indexOfKey].copy(state = state) | |
if (items[indexOfKey] != newState) { | |
items[indexOfKey] = newState | |
} | |
} | |
} | |
Box { | |
items.forEach { (itemKey, itemState, content) -> | |
key(itemKey) { | |
content { transition -> | |
content(itemKey, itemState, transition) | |
} | |
} | |
} | |
} | |
} | |
private data class TransitionItem<Key, State>( | |
val key: Key, | |
val state: State, | |
val content: @Composable (children: @Composable (Transition<ComposableTransitionState>) -> Unit) -> Unit, | |
) |
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@Preview | |
@Composable | |
fun ComposableSwitcherPreview() { | |
val screens = remember { | |
listOf( | |
"Screen A", | |
"Screen B", | |
"Screen C", | |
) | |
} | |
var screenIndex by remember { mutableStateOf(0) } | |
var slideLeft by remember { mutableStateOf(true) } | |
fun navigateNextScreen() { | |
screenIndex = (screenIndex + 1).coerceIn(0, screens.lastIndex) | |
slideLeft = true | |
} | |
fun navigatePreviousScreen() { | |
screenIndex = (screenIndex - 1).coerceIn(0, screens.lastIndex) | |
slideLeft = false | |
} | |
ComposableSwitcher( | |
key = screenIndex, | |
state = screens[screenIndex], | |
) { _, screenData, transition -> | |
val offset by transition.animateFloat(transitionSpec = { tween(durationMillis = 2000) }) { state -> | |
when (state) { | |
VISIBLE -> 0.0f | |
ENTERING -> if (slideLeft) 1.0f else -1.0f | |
EXITING -> if (slideLeft) -1.0f else 1.0f | |
} | |
} | |
BoxWithConstraints { | |
val width = maxWidth | |
Box { | |
Box( | |
modifier = Modifier | |
.fillMaxSize() | |
.offset(x = width * offset) | |
) { | |
Text(text = screenData, modifier = Modifier.align(Alignment.Center)) | |
} | |
IconButton(modifier = Modifier.align(Alignment.CenterStart), onClick = ::navigatePreviousScreen) { | |
Icon(imageVector = Icons.Default.ArrowBack, contentDescription = null) | |
} | |
IconButton(modifier = Modifier.align(Alignment.CenterEnd), onClick = ::navigateNextScreen) { | |
Icon(imageVector = Icons.Default.ArrowForward, contentDescription = null) | |
} | |
} | |
} | |
} | |
} |
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