| /* |
| * 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.compose.animation.demos |
| |
| import android.util.Log |
| import androidx.compose.animation.core.SpringSpec |
| import androidx.compose.animation.core.fling |
| import androidx.compose.Composable |
| import androidx.compose.state |
| import androidx.compose.animation.animatedFloat |
| import androidx.ui.core.Modifier |
| import androidx.ui.core.gesture.DragObserver |
| import androidx.ui.core.gesture.rawDragGestureFilter |
| import androidx.compose.foundation.Canvas |
| import androidx.compose.foundation.Text |
| import androidx.compose.ui.geometry.Offset |
| import androidx.compose.ui.geometry.Size |
| import androidx.compose.ui.graphics.Color |
| import androidx.compose.ui.graphics.drawscope.DrawScope |
| import androidx.compose.foundation.layout.Column |
| import androidx.compose.foundation.layout.fillMaxHeight |
| import androidx.compose.foundation.layout.fillMaxWidth |
| import androidx.compose.foundation.layout.padding |
| import androidx.compose.foundation.layout.preferredHeight |
| import androidx.ui.unit.dp |
| import androidx.ui.unit.sp |
| import kotlin.math.roundToInt |
| |
| @Composable |
| fun SpringBackScrollingDemo() { |
| Column(Modifier.fillMaxHeight()) { |
| Text( |
| "<== Scroll horizontally ==>", |
| fontSize = 20.sp, |
| modifier = Modifier.padding(40.dp) |
| ) |
| val animScroll = animatedFloat(0f) |
| val itemWidth = state { 0f } |
| val isFlinging = state { false } |
| val gesture = Modifier.rawDragGestureFilter(dragObserver = object : DragObserver { |
| override fun onDrag(dragDistance: Offset): Offset { |
| animScroll.snapTo(animScroll.targetValue + dragDistance.x) |
| return dragDistance |
| } |
| |
| override fun onStop(velocity: Offset) { |
| isFlinging.value = true |
| animScroll.fling(velocity.x, onEnd = { _, _, _ -> |
| isFlinging.value = false |
| }) |
| } |
| }) |
| Canvas(gesture.fillMaxWidth().preferredHeight(400.dp)) { |
| itemWidth.value = size.width / 2f |
| if (isFlinging.value) { |
| // Figure out what position to spring back to |
| val target = animScroll.targetValue |
| var rem = target % itemWidth.value |
| if (animScroll.velocity < 0) { |
| if (rem > 0) { |
| rem -= itemWidth.value |
| } |
| } else { |
| if (rem < 0) { |
| rem += itemWidth.value |
| } |
| } |
| val springBackTarget = target - rem |
| |
| // Spring back as soon as the target position is crossed. |
| if ((animScroll.velocity > 0 && animScroll.value > springBackTarget) || |
| (animScroll.velocity < 0 && animScroll.value < springBackTarget) |
| ) { |
| animScroll.animateTo( |
| springBackTarget, |
| SpringSpec(dampingRatio = 0.8f, stiffness = 200f) |
| ) |
| } |
| } |
| if (DEBUG) { |
| Log.w( |
| "Anim", "Spring back scrolling, redrawing with new" + |
| " scroll value: ${animScroll.value}" |
| ) |
| } |
| drawRects(animScroll.value) |
| } |
| } |
| } |
| |
| private fun DrawScope.drawRects(animScroll: Float) { |
| val width = size.width / 2f |
| val scroll = animScroll + width / 2 |
| var startingPos = scroll % width |
| if (startingPos > 0) { |
| startingPos -= width |
| } |
| var startingColorIndex = ((scroll - startingPos) / width).roundToInt().rem(colors.size) |
| if (startingColorIndex < 0) { |
| startingColorIndex += colors.size |
| } |
| |
| val rectSize = Size(width - 20.0f, size.height) |
| |
| drawRect( |
| colors[startingColorIndex], |
| topLeft = Offset(startingPos + 10, 0f), |
| size = rectSize |
| ) |
| |
| drawRect( |
| colors[(startingColorIndex + colors.size - 1) % colors.size], |
| topLeft = Offset(startingPos + width + 10, 0f), |
| size = rectSize |
| ) |
| |
| drawRect( |
| colors[(startingColorIndex + colors.size - 2) % colors.size], |
| topLeft = Offset(startingPos + width * 2 + 10, 0.0f), |
| size = rectSize |
| ) |
| } |
| |
| private val colors = listOf( |
| Color(0xFFdaf8e3), |
| Color(0xFF97ebdb), |
| Color(0xFF00c2c7), |
| Color(0xFF0086ad), |
| Color(0xFF005582), |
| Color(0xFF0086ad), |
| Color(0xFF00c2c7), |
| Color(0xFF97ebdb) |
| ) |