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Jetpack Compose simple number picker
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@Composable | |
fun NumberPicker( | |
state: MutableState<Int>, | |
modifier: Modifier = Modifier, | |
range: IntRange? = null, | |
textStyle: TextStyle = LocalTextStyle.current, | |
onStateChanged: (Int) -> Unit = {}, | |
) { | |
val coroutineScope = rememberCoroutineScope() | |
val numbersColumnHeight = 36.dp | |
val halvedNumbersColumnHeight = numbersColumnHeight / 2 | |
val halvedNumbersColumnHeightPx = with(LocalDensity.current) { halvedNumbersColumnHeight.toPx() } | |
fun animatedStateValue(offset: Float): Int = state.value - (offset / halvedNumbersColumnHeightPx).toInt() | |
val animatedOffset = remember { Animatable(0f) }.apply { | |
if (range != null) { | |
val offsetRange = remember(state.value, range) { | |
val value = state.value | |
val first = -(range.last - value) * halvedNumbersColumnHeightPx | |
val last = -(range.first - value) * halvedNumbersColumnHeightPx | |
first..last | |
} | |
updateBounds(offsetRange.start, offsetRange.endInclusive) | |
} | |
} | |
val coercedAnimatedOffset = animatedOffset.value % halvedNumbersColumnHeightPx | |
val animatedStateValue = animatedStateValue(animatedOffset.value) | |
Column( | |
modifier = modifier | |
.wrapContentSize() | |
.draggable( | |
orientation = Orientation.Vertical, | |
state = rememberDraggableState { deltaY -> | |
coroutineScope.launch { | |
animatedOffset.snapTo(animatedOffset.value + deltaY) | |
} | |
}, | |
onDragStopped = { velocity -> | |
coroutineScope.launch { | |
val endValue = animatedOffset.fling( | |
initialVelocity = velocity, | |
animationSpec = exponentialDecay(frictionMultiplier = 20f), | |
adjustTarget = { target -> | |
val coercedTarget = target % halvedNumbersColumnHeightPx | |
val coercedAnchors = listOf(-halvedNumbersColumnHeightPx, 0f, halvedNumbersColumnHeightPx) | |
val coercedPoint = coercedAnchors.minByOrNull { abs(it - coercedTarget) }!! | |
val base = halvedNumbersColumnHeightPx * (target / halvedNumbersColumnHeightPx).toInt() | |
coercedPoint + base | |
} | |
).endState.value | |
state.value = animatedStateValue(endValue) | |
onStateChanged(state.value) | |
animatedOffset.snapTo(0f) | |
} | |
} | |
) | |
) { | |
val spacing = 4.dp | |
val arrowColor = MaterialTheme.colors.onSecondary.copy(alpha = ContentAlpha.disabled) | |
Arrow(direction = ArrowDirection.UP, tint = arrowColor) | |
Spacer(modifier = Modifier.height(spacing)) | |
Box( | |
modifier = Modifier | |
.align(Alignment.CenterHorizontally) | |
.offset { IntOffset(x = 0, y = coercedAnimatedOffset.roundToInt()) } | |
) { | |
val baseLabelModifier = Modifier.align(Alignment.Center) | |
ProvideTextStyle(textStyle) { | |
Label( | |
text = (animatedStateValue - 1).toString(), | |
modifier = baseLabelModifier | |
.offset(y = -halvedNumbersColumnHeight) | |
.alpha(coercedAnimatedOffset / halvedNumbersColumnHeightPx) | |
) | |
Label( | |
text = animatedStateValue.toString(), | |
modifier = baseLabelModifier | |
.alpha(1 - abs(coercedAnimatedOffset) / halvedNumbersColumnHeightPx) | |
) | |
Label( | |
text = (animatedStateValue + 1).toString(), | |
modifier = baseLabelModifier | |
.offset(y = halvedNumbersColumnHeight) | |
.alpha(-coercedAnimatedOffset / halvedNumbersColumnHeightPx) | |
) | |
} | |
} | |
Spacer(modifier = Modifier.height(spacing)) | |
Arrow(direction = ArrowDirection.DOWN, tint = arrowColor) | |
} | |
} | |
@Composable | |
private fun Label(text: String, modifier: Modifier) { | |
Text( | |
text = text, | |
modifier = modifier.pointerInput(Unit) { | |
detectTapGestures(onLongPress = { | |
// FIXME: Empty to disable text selection | |
}) | |
} | |
) | |
} | |
private suspend fun Animatable<Float, AnimationVector1D>.fling( | |
initialVelocity: Float, | |
animationSpec: DecayAnimationSpec<Float>, | |
adjustTarget: ((Float) -> Float)?, | |
block: (Animatable<Float, AnimationVector1D>.() -> Unit)? = null, | |
): AnimationResult<Float, AnimationVector1D> { | |
val targetValue = animationSpec.calculateTargetValue(value, initialVelocity) | |
val adjustedTarget = adjustTarget?.invoke(targetValue) | |
return if (adjustedTarget != null) { | |
animateTo( | |
targetValue = adjustedTarget, | |
initialVelocity = initialVelocity, | |
block = block | |
) | |
} else { | |
animateDecay( | |
initialVelocity = initialVelocity, | |
animationSpec = animationSpec, | |
block = block, | |
) | |
} | |
} |
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@Preview | |
@Composable | |
fun PreviewNumberPicker() { | |
Box(modifier = Modifier.fillMaxSize()) { | |
NumberPicker( | |
state = remember { mutableStateOf(9) }, | |
range = 0..10, | |
modifier = Modifier.align(Alignment.Center) | |
) | |
} | |
} |
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There is a generic version here with wrapSelectorWheel parameter