Support fling for nested scroll on TimetableGrid. #1273
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,6 +1,8 @@ | ||
| package io.github.droidkaigi.confsched2023.sessions.section | ||
|
|
||
| import androidx.compose.animation.core.Animatable | ||
| import androidx.compose.animation.core.AnimationState | ||
| import androidx.compose.animation.core.animateDecay | ||
| import androidx.compose.animation.core.exponentialDecay | ||
| import androidx.compose.foundation.ExperimentalFoundationApi | ||
| import androidx.compose.foundation.focusGroup | ||
|
|
@@ -35,14 +37,18 @@ import androidx.compose.ui.Modifier | |
| import androidx.compose.ui.draw.clipToBounds | ||
| import androidx.compose.ui.draw.drawBehind | ||
| import androidx.compose.ui.geometry.Offset | ||
| import androidx.compose.ui.input.nestedscroll.NestedScrollConnection | ||
| import androidx.compose.ui.input.nestedscroll.NestedScrollDispatcher | ||
| import androidx.compose.ui.input.nestedscroll.NestedScrollSource | ||
| import androidx.compose.ui.input.nestedscroll.nestedScroll | ||
| import androidx.compose.ui.input.pointer.PointerInputChange | ||
| import androidx.compose.ui.input.pointer.PointerInputScope | ||
| import androidx.compose.ui.input.pointer.pointerInput | ||
| import androidx.compose.ui.input.pointer.positionChange | ||
| import androidx.compose.ui.input.pointer.util.VelocityTracker | ||
| import androidx.compose.ui.layout.Placeable | ||
| import androidx.compose.ui.layout.onGloballyPositioned | ||
| import androidx.compose.ui.layout.positionInRoot | ||
| import androidx.compose.ui.platform.LocalDensity | ||
| import androidx.compose.ui.platform.LocalLayoutDirection | ||
| import androidx.compose.ui.semantics.ScrollAxisRange | ||
|
|
@@ -84,14 +90,12 @@ data class TimetableGridUiState(val timetable: Timetable) | |
| @Composable | ||
| fun TimetableGrid( | ||
| uiState: TimetableGridUiState, | ||
| onTimetableItemClick: (TimetableItem) -> Unit, | ||
| modifier: Modifier = Modifier, | ||
| contentPadding: PaddingValues = PaddingValues(), | ||
| ) { | ||
| TimetableGrid( | ||
| timetable = uiState.timetable, | ||
| onTimetableItemClick = onTimetableItemClick, | ||
| modifier = modifier, | ||
| contentPadding = contentPadding, | ||
|
|
@@ -101,7 +105,6 @@ fun TimetableGrid( | |
| @Composable | ||
| fun TimetableGrid( | ||
| timetable: Timetable, | ||
| onTimetableItemClick: (TimetableItem) -> Unit, | ||
| modifier: Modifier = Modifier, | ||
| contentPadding: PaddingValues = PaddingValues(), | ||
|
|
@@ -133,7 +136,6 @@ fun TimetableGrid( | |
| TimetableGrid( | ||
| timetable = timetable, | ||
| timetableState = timetableGridState, | ||
| modifier = modifier, | ||
| contentPadding = PaddingValues( | ||
| top = 16.dp + contentPadding.calculateTopPadding(), | ||
|
|
@@ -157,7 +159,6 @@ fun TimetableGrid( | |
| fun TimetableGrid( | ||
| timetable: Timetable, | ||
| timetableState: TimetableState, | ||
| modifier: Modifier = Modifier, | ||
| contentPadding: PaddingValues = PaddingValues(), | ||
| content: @Composable (TimetableItem, Int) -> Unit, | ||
|
|
@@ -186,10 +187,14 @@ fun TimetableGrid( | |
| content(timetableItemWithFavorite.timetableItem, itemHeightPx) | ||
| } | ||
|
|
||
| val nestedScrollConnection = remember { object : NestedScrollConnection {} } | ||
| val nestedScrollDispatcher = remember { NestedScrollDispatcher() } | ||
|
|
||
| LazyLayout( | ||
| modifier = modifier | ||
| .focusGroup() | ||
| .clipToBounds() | ||
| .nestedScroll(nestedScrollConnection, nestedScrollDispatcher) | ||
| .drawBehind { | ||
| timetableScreen.timeHorizontalLines.value.forEach { | ||
| drawLine( | ||
|
|
@@ -225,8 +230,14 @@ fun TimetableGrid( | |
| } | ||
| }, | ||
| ) | ||
| .onGloballyPositioned { coordinates -> | ||
| timetableState.screenScrollState.componentPositionInRoot = coordinates.positionInRoot() | ||
| } | ||
| .pointerInput(Unit) { | ||
| detectDragGestures( | ||
| onDragStart = { | ||
| scrollState.resetTracking() | ||
| }, | ||
| onDrag = { change, dragAmount -> | ||
| if (timetableScreen.enableHorizontalScroll(dragAmount.x)) { | ||
| if (change.positionChange() != Offset.Zero) change.consume() | ||
|
|
@@ -245,7 +256,7 @@ fun TimetableGrid( | |
| }, | ||
| onDragEnd = { | ||
| coroutineScope.launch { | ||
| scrollState.flingIfPossible(nestedScrollDispatcher) | ||
| } | ||
| }, | ||
| ) | ||
|
|
@@ -322,7 +333,6 @@ fun TimetableGrid( | |
| fun TimetablePreview() { | ||
| TimetableGrid( | ||
| timetable = Timetable.fake(), | ||
| onTimetableItemClick = {}, | ||
| modifier = Modifier.fillMaxSize(), | ||
| ) | ||
|
|
@@ -480,6 +490,8 @@ class ScreenScrollState( | |
| private val velocityTracker = VelocityTracker() | ||
| private val _scrollX = Animatable(initialScrollX) | ||
| private val _scrollY = Animatable(initialScrollY) | ||
| var componentPositionInRoot = Offset.Zero | ||
| private var cancelFling = false | ||
|
|
||
| val scrollX: Float | ||
| get() = _scrollX.value | ||
|
|
@@ -497,9 +509,11 @@ class ScreenScrollState( | |
| timeMillis: Long, | ||
| position: Offset, | ||
| ) { | ||
| cancelFling = true | ||
| if (scrollX.isNaN().not() && scrollY.isNaN().not()) { | ||
| coroutineScope { | ||
| val positionInRoot = position + componentPositionInRoot | ||
| velocityTracker.addPosition(timeMillis = timeMillis, position = positionInRoot) | ||
| launch { | ||
| _scrollX.snapTo(scrollX) | ||
| } | ||
|
|
@@ -510,19 +524,46 @@ class ScreenScrollState( | |
| } | ||
| } | ||
|
|
||
| suspend fun flingIfPossible(nestedScrollDispatcher: NestedScrollDispatcher) = coroutineScope { | ||
| cancelFling = false | ||
| val velocity = velocityTracker.calculateVelocity() | ||
| launch { | ||
| _scrollX.animateDecay( | ||
| velocity.x / 2f, | ||
| exponentialDecay(), | ||
| ) | ||
| } | ||
|
|
||
| var lastValue = 0f | ||
| AnimationState( | ||
| initialValue = 0f, | ||
| initialVelocity = velocity.y, | ||
| ).animateDecay( | ||
| exponentialDecay(), | ||
| ) { | ||
| launch { | ||
| val delta = Offset(0f, value - lastValue) | ||
| lastValue = value | ||
| val preConsumed = nestedScrollDispatcher.dispatchPreScroll( | ||
| available = delta, | ||
| source = NestedScrollSource.Fling, | ||
| ) | ||
|
|
||
| val weAvailable = delta - preConsumed | ||
| val previousY = _scrollY.value | ||
| _scrollY.snapTo(_scrollY.value + weAvailable.y) | ||
| val weConsumed = Offset(0f, _scrollY.value - previousY) | ||
|
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||
| nestedScrollDispatcher.dispatchPostScroll( | ||
| consumed = preConsumed + weConsumed, | ||
| available = weAvailable - weConsumed, | ||
| source = NestedScrollSource.Fling, | ||
| ) | ||
|
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||
| if (cancelFling) { | ||
| [email protected]() | ||
| } | ||
| } | ||
| } | ||
| } | ||
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||
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|
@@ -672,6 +713,9 @@ private class TimetableScreen( | |
| position: Offset, | ||
| nestedScrollDispatcher: NestedScrollDispatcher, | ||
| ) { | ||
| // If the position does not change, VelocityTracker malfunctions. Therefore return here. | ||
| if (dragAmount == Offset.Zero) return | ||
|
There was a problem hiding this comment. Wow! I did not know that! 😮 |
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| val parentConsumed = nestedScrollDispatcher.dispatchPreScroll( | ||
| available = dragAmount, | ||
| source = NestedScrollSource.Drag, | ||
|
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||
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It's so good! 👍