| /* |
| * Copyright 2019 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package androidx.ui.core.demos.gestures |
| |
| import androidx.compose.Composable |
| import androidx.compose.state |
| import androidx.ui.core.Constraints |
| import androidx.ui.core.Direction |
| import androidx.ui.core.Layout |
| import androidx.ui.core.Modifier |
| import androidx.ui.core.clipToBounds |
| import androidx.ui.core.gesture.doubleTapGestureFilter |
| import androidx.ui.core.gesture.ScrollCallback |
| import androidx.ui.core.gesture.longPressGestureFilter |
| import androidx.ui.core.gesture.pressIndicatorGestureFilter |
| import androidx.ui.core.gesture.tapGestureFilter |
| import androidx.ui.core.gesture.scrollGestureFilter |
| import androidx.ui.core.gesture.scrollorientationlocking.Orientation |
| import androidx.compose.foundation.Border |
| import androidx.compose.foundation.Box |
| import androidx.compose.foundation.Text |
| import androidx.compose.foundation.background |
| import androidx.compose.foundation.drawBorder |
| import androidx.ui.geometry.Offset |
| import androidx.ui.graphics.Color |
| import androidx.compose.foundation.layout.Column |
| import androidx.compose.foundation.layout.fillMaxWidth |
| import androidx.compose.foundation.layout.preferredHeight |
| import androidx.ui.unit.Dp |
| import androidx.ui.unit.dp |
| import kotlin.math.roundToInt |
| |
| /** |
| * Demonstration for how multiple DragGestureDetectors interact. |
| */ |
| @Composable |
| fun NestedScrollingDemo() { |
| Column { |
| Text("Demonstrates nested scrolling.") |
| Text("There are 3 fake vertical scrollers inside another vertical scroller. Try " + |
| "scrolling with 1 or many fingers.") |
| Scrollable { |
| RepeatingColumn(repetitions = 3) { |
| Box(Modifier.preferredHeight(398.dp), padding = 72.dp) { |
| // Inner composable that scrolls |
| Scrollable { |
| RepeatingColumn(repetitions = 5) { |
| // Composable that indicates it is being pressed |
| Pressable( |
| height = 72.dp |
| ) |
| } |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| /** |
| * A very simple ScrollView like implementation that allows for vertical scrolling. |
| */ |
| @Composable |
| private fun Scrollable(children: @Composable () -> Unit) { |
| val offset = state { 0f } |
| val maxOffset = state { 0f } |
| |
| val scrollObserver = object : ScrollCallback { |
| override fun onScroll(scrollDistance: Float): Float { |
| val resultingOffset = offset.value + scrollDistance |
| val dyToConsume = |
| when { |
| resultingOffset > 0f -> { |
| 0f - offset.value |
| } |
| resultingOffset < maxOffset.value -> { |
| maxOffset.value - offset.value |
| } |
| else -> { |
| scrollDistance |
| } |
| } |
| offset.value += dyToConsume |
| return dyToConsume |
| } |
| } |
| |
| val canDrag = { direction: Direction -> |
| when (direction) { |
| Direction.UP -> true |
| Direction.DOWN -> true |
| else -> false |
| } |
| } |
| |
| Layout( |
| children = children, |
| modifier = Modifier |
| .scrollGestureFilter(scrollObserver, Orientation.Vertical, canDrag) |
| .clipToBounds(), |
| measureBlock = { measurables, constraints -> |
| val placeable = |
| measurables.first() |
| .measure(constraints.copy(minHeight = 0, maxHeight = Constraints.Infinity)) |
| |
| maxOffset.value = (constraints.maxHeight - placeable.height).toFloat() |
| |
| layout(constraints.maxWidth, constraints.maxHeight) { |
| placeable.place(0, offset.value.roundToInt()) |
| } |
| }) |
| } |
| |
| /** |
| * A very simple Button like implementation that visually indicates when it is being pressed. |
| */ |
| @Composable |
| private fun Pressable( |
| height: Dp |
| ) { |
| |
| val pressedColor = PressedColor |
| val defaultColor = DefaultBackgroundColor |
| |
| val color = state { defaultColor } |
| val showPressed = state { false } |
| |
| val onPress: (Offset) -> Unit = { |
| showPressed.value = true |
| } |
| |
| val onRelease = { |
| showPressed.value = false |
| } |
| |
| val onTap: (Offset) -> Unit = { |
| color.value = color.value.next() |
| } |
| |
| val onDoubleTap: (Offset) -> Unit = { |
| color.value = color.value.prev() |
| } |
| |
| val onLongPress = { _: Offset -> |
| color.value = defaultColor |
| showPressed.value = false |
| } |
| |
| val gestureDetectors = |
| Modifier |
| .pressIndicatorGestureFilter(onPress, onRelease, onRelease) |
| .tapGestureFilter(onTap) |
| .doubleTapGestureFilter(onDoubleTap) |
| .longPressGestureFilter(onLongPress) |
| |
| val layout = Modifier.fillMaxWidth().preferredHeight(height) |
| |
| val pressOverlay = |
| if (showPressed.value) Modifier.background(color = pressedColor) else Modifier |
| Box(gestureDetectors.plus(layout).background(color = color.value).plus(pressOverlay)) |
| } |
| |
| /** |
| * A simple composable that repeats its children as a vertical list of divided items [repetitions] |
| * times. |
| */ |
| @Composable |
| private fun RepeatingColumn(repetitions: Int, row: @Composable () -> Unit) { |
| Column(Modifier.drawBorder(border = Border(2.dp, BorderColor))) { |
| for (i in 1..repetitions) { |
| row() |
| if (i != repetitions) { |
| Box( |
| Modifier.fillMaxWidth().preferredHeight(1.dp), |
| backgroundColor = Color(0f, 0f, 0f, .12f) |
| ) |
| } |
| } |
| } |
| } |