| /* |
| * 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.Animatable |
| import androidx.compose.animation.core.SpringSpec |
| import androidx.compose.animation.core.calculateTargetValue |
| import androidx.compose.animation.core.exponentialDecay |
| import androidx.compose.foundation.Canvas |
| import androidx.compose.foundation.gestures.draggable |
| import androidx.compose.foundation.layout.Column |
| import androidx.compose.foundation.layout.fillMaxWidth |
| import androidx.compose.foundation.layout.padding |
| import androidx.compose.foundation.layout.preferredHeight |
| import androidx.compose.material.Text |
| import androidx.compose.runtime.Composable |
| import androidx.compose.runtime.mutableStateOf |
| import androidx.compose.runtime.remember |
| import androidx.compose.runtime.rememberCoroutineScope |
| import androidx.compose.ui.Modifier |
| import androidx.compose.ui.geometry.Offset |
| import androidx.compose.ui.geometry.Size |
| import androidx.compose.ui.gesture.scrollorientationlocking.Orientation |
| import androidx.compose.ui.graphics.Color |
| import androidx.compose.ui.graphics.drawscope.DrawScope |
| import androidx.compose.ui.unit.dp |
| import androidx.compose.ui.unit.sp |
| import kotlinx.coroutines.launch |
| import kotlin.math.roundToInt |
| |
| const val DEBUG = false |
| |
| @Composable |
| fun FancyScrollingDemo() { |
| Column { |
| Text( |
| "<== Scroll horizontally ==>", |
| fontSize = 20.sp, |
| modifier = Modifier.padding(40.dp) |
| ) |
| val animScroll = remember { Animatable(0f) } |
| val itemWidth = remember { mutableStateOf(0f) } |
| val scope = rememberCoroutineScope() |
| val modifier = Modifier.draggable( |
| orientation = Orientation.Horizontal, |
| onDrag = { delta: Float -> |
| // Snap to new drag position |
| animScroll.snapTo(animScroll.value + delta) |
| }, |
| |
| onDragStopped = { velocity: Float -> |
| |
| // Uses default decay animation to calculate where the fling will settle, |
| // and adjust that position as needed. The target animation will be used for |
| // animating to the adjusted target. |
| scope.launch { |
| val decay = exponentialDecay<Float>() |
| val target = decay.calculateTargetValue(animScroll.value, velocity) |
| // Adjust the target position to center align the item |
| var rem = target % itemWidth.value |
| if (rem < 0) { |
| rem += itemWidth.value |
| } |
| animScroll.animateTo( |
| targetValue = target - rem, |
| initialVelocity = velocity, |
| animationSpec = SpringSpec(dampingRatio = 2.0f, stiffness = 100f) |
| ) |
| } |
| } |
| ) |
| |
| Canvas(modifier.fillMaxWidth().preferredHeight(400.dp)) { |
| val width = size.width / 2f |
| val scroll = animScroll.value + width / 2 |
| itemWidth.value = width |
| if (DEBUG) { |
| Log.w( |
| "Anim", |
| "Drawing items with updated" + |
| " Scroll: ${animScroll.value}" |
| ) |
| } |
| drawItems(scroll, width, size.height) |
| } |
| } |
| } |
| |
| private fun DrawScope.drawItems( |
| scrollPosition: Float, |
| width: Float, |
| height: Float |
| ) { |
| var startingPos = scrollPosition % width |
| if (startingPos > 0) { |
| startingPos -= width |
| } |
| var startingColorIndex = |
| ((scrollPosition - startingPos) / width).roundToInt().rem(pastelColors.size) |
| if (startingColorIndex < 0) { |
| startingColorIndex += pastelColors.size |
| } |
| |
| val size = Size(width - 20, height) |
| drawRect( |
| pastelColors[startingColorIndex], |
| topLeft = Offset(startingPos + 10, 0f), |
| size = size |
| ) |
| |
| drawRect( |
| pastelColors[(startingColorIndex + pastelColors.size - 1) % pastelColors.size], |
| topLeft = Offset(startingPos + width + 10, 0.0f), |
| size = size |
| ) |
| |
| drawRect( |
| pastelColors[(startingColorIndex + pastelColors.size - 2) % pastelColors.size], |
| topLeft = Offset(startingPos + width * 2 + 10, 0.0f), |
| size = size |
| ) |
| } |
| |
| private val colors = listOf( |
| Color(0xFFffd9d9), |
| Color(0xFFffa3a3), |
| Color(0xFFff7373), |
| Color(0xFFff3b3b), |
| Color(0xFFce0000), |
| Color(0xFFff3b3b), |
| Color(0xFFff7373), |
| Color(0xFFffa3a3) |
| ) |
