xref: /compose/animation/animation-core/samples/src/main/java/androidx/compose/animation/core/samples/AnimatableSamples.kt

/*
 * Copyright 2020 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.core.samples

import androidx.annotation.Sampled
import androidx.compose.animation.core.Animatable
import androidx.compose.animation.core.AnimationEndReason
import androidx.compose.animation.core.AnimationVector2D
import androidx.compose.animation.core.DeferredTargetAnimation
import androidx.compose.animation.core.ExperimentalAnimatableApi
import androidx.compose.animation.core.Spring
import androidx.compose.animation.core.VectorConverter
import androidx.compose.animation.core.calculateTargetValue
import androidx.compose.animation.core.exponentialDecay
import androidx.compose.animation.core.spring
import androidx.compose.animation.core.tween
import androidx.compose.animation.splineBasedDecay
import androidx.compose.foundation.background
import androidx.compose.foundation.clickable
import androidx.compose.foundation.gestures.awaitFirstDown
import androidx.compose.foundation.gestures.verticalDrag
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.fillMaxHeight
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.offset
import androidx.compose.foundation.layout.size
import androidx.compose.foundation.layout.width
import androidx.compose.foundation.shape.CircleShape
import androidx.compose.material.Text
import androidx.compose.runtime.Composable
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.rememberCoroutineScope
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.composed
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.geometry.Size
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.graphics.graphicsLayer
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.approachLayout
import androidx.compose.ui.unit.Constraints
import androidx.compose.ui.unit.IntOffset
import androidx.compose.ui.unit.IntSize
import androidx.compose.ui.unit.dp
import kotlin.math.roundToInt
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.coroutineScope
import kotlinx.coroutines.launch

@Sampled
@Composable
fun AnimatableAnimateToGenericsType() {
    // Creates an `Animatable` to animate Offset and `remember` it.
    val animatedOffset = remember { Animatable(Offset(0f, 0f), Offset.VectorConverter) }

    Box(
        Modifier.fillMaxSize().background(Color(0xffb99aff)).pointerInput(Unit) {
            coroutineScope {
                while (true) {
                    val offset = awaitPointerEventScope { awaitFirstDown().position }
                    // Launch a new coroutine for animation so the touch detection thread is not
                    // blocked.
                    launch {
                        // Animates to the pressed position, with the given animation spec.
                        animatedOffset.animateTo(
                            offset,
                            animationSpec = spring(stiffness = Spring.StiffnessLow)
                        )
                    }
                }
            }
        }
    ) {
        Text("Tap anywhere", Modifier.align(Alignment.Center))
        Box(
            Modifier.offset {
                    // Use the animated offset as the offset of the Box.
                    IntOffset(
                        animatedOffset.value.x.roundToInt(),
                        animatedOffset.value.y.roundToInt()
                    )
                }
                .size(40.dp)
                .background(Color(0xff3c1361), CircleShape)
        )
    }
}

@Sampled
fun AnimatableDecayAndAnimateToSample() {
    /**
     * In this example, we create a swipe-to-dismiss modifier that dismisses the child via a
     * vertical swipe-up.
     */
    fun Modifier.swipeToDismiss(): Modifier = composed {
        // Creates a Float type `Animatable` and `remember`s it
        val animatedOffsetY = remember { Animatable(0f) }
        this.pointerInput(Unit) {
                coroutineScope {
                    while (true) {
                        val pointerId = awaitPointerEventScope { awaitFirstDown().id }
                        val velocityTracker = VelocityTracker()
                        awaitPointerEventScope {
                            verticalDrag(pointerId) {
                                // Snaps the value by the amount of finger movement
                                launch {
                                    animatedOffsetY.snapTo(
                                        animatedOffsetY.value + it.positionChange().y
                                    )
                                }
                                velocityTracker.addPosition(it.uptimeMillis, it.position)
                            }
                        }
                        // At this point, drag has finished. Now we obtain the velocity at the end
                        // of
                        // the drag, and animate the offset with it as the starting velocity.
                        val velocity = velocityTracker.calculateVelocity().y

                        // The goal for the animation below is to animate the dismissal if the fling
                        // velocity is high enough. Otherwise, spring back.
                        launch {
                            // Checks where the animation will end using decay
                            val decay = splineBasedDecay<Float>(this@pointerInput)

                            // If the animation can naturally end outside of visual bounds, we will
                            // animate with decay.
                            if (
                                decay.calculateTargetValue(animatedOffsetY.value, velocity) <
                                    -size.height
                            ) {
                                // (Optionally) updates lower bounds. This stops the animation as
                                // soon
                                // as bounds are reached.
                                animatedOffsetY.updateBounds(lowerBound = -size.height.toFloat())
                                // Animate with the decay animation spec using the fling velocity
                                animatedOffsetY.animateDecay(velocity, decay)
                            } else {
                                // Not enough velocity to be dismissed, spring back to 0f
                                animatedOffsetY.animateTo(0f, initialVelocity = velocity)
                            }
                        }
                    }
                }
            }
            .offset { IntOffset(0, animatedOffsetY.value.roundToInt()) }
    }
}

@Sampled
fun AnimatableAnimationResultSample() {
    suspend fun CoroutineScope.animateBouncingOffBounds(
        animatable: Animatable<Offset, *>,
        flingVelocity: Offset,
        parentSize: Size
    ) {
        launch {
            var startVelocity = flingVelocity
            // Set bounds for the animation, so that when it reaches bounds it will stop
            // immediately. We can then inspect the returned `AnimationResult` and decide whether
            // we should start another animation.
            animatable.updateBounds(Offset(0f, 0f), Offset(parentSize.width, parentSize.height))
            do {
                val result = animatable.animateDecay(startVelocity, exponentialDecay())
                // Copy out the end velocity of the previous animation.
                startVelocity = result.endState.velocity

                // Negate the velocity for the dimension that hits the bounds, to create a
                // bouncing off the bounds effect.
                with(animatable) {
                    if (value.x == upperBound?.x || value.x == lowerBound?.x) {
                        // x dimension hits bounds
                        startVelocity = startVelocity.copy(x = -startVelocity.x)
                    }
                    if (value.y == upperBound?.y || value.y == lowerBound?.y) {
                        // y dimension hits bounds
                        startVelocity = startVelocity.copy(y = -startVelocity.y)
                    }
                }
                // Repeat the animation until the animation ends for reasons other than hitting
                // bounds, e.g. if `stop()` is called, or preempted by another animation.
            } while (result.endReason == AnimationEndReason.BoundReached)
        }
    }
}

@Sampled
fun AnimatableFadeIn() {
    fun Modifier.fadeIn(): Modifier = composed {
        // Creates an `Animatable` and remembers it.
        val alphaAnimation = remember { Animatable(0f) }
        // Launches a coroutine for the animation when entering the composition.
        // Uses `alphaAnimation` as the subject so the job in `LaunchedEffect` will run only when
        // `alphaAnimation` is created, which happens one time when the modifier enters
        // composition.
        LaunchedEffect(alphaAnimation) {
            // Animates to 1f from 0f for the fade-in, and uses a 500ms tween animation.
            alphaAnimation.animateTo(
                targetValue = 1f,
                // Default animationSpec uses [spring] animation, here we overwrite the default.
                animationSpec = tween(500)
            )
        }
        this.graphicsLayer(alpha = alphaAnimation.value)
    }
}

@OptIn(ExperimentalAnimatableApi::class)
@Sampled
@Composable
fun DeferredTargetAnimationSample() {
    // Creates a custom modifier that animates the constraints and measures child with the
    // animated constraints. This modifier is built on top of `Modifier.approachLayout` to approach
    // th destination size determined by the lookahead pass. A resize animation will be kicked off
    // whenever the lookahead size changes, to animate children from current size to destination
    // size. Fixed constraints created based on the animation value will be used to measure
    // child, so the child layout gradually changes its animated constraints until the approach
    // completes.
    fun Modifier.animateConstraints(
        sizeAnimation: DeferredTargetAnimation<IntSize, AnimationVector2D>,
        coroutineScope: CoroutineScope
    ) =
        this.approachLayout(
            isMeasurementApproachInProgress = { lookaheadSize ->
                // Update the target of the size animation.
                sizeAnimation.updateTarget(lookaheadSize, coroutineScope)
                // Return true if the size animation has pending target change or is currently
                // running.
                !sizeAnimation.isIdle
            }
        ) { measurable, _ ->
            // In the measurement approach, the goal is to gradually reach the destination size
            // (i.e. lookahead size). To achieve that, we use an animation to track the current
            // size, and animate to the destination size whenever it changes. Once the animation
            // finishes, the approach is complete.

            // First, update the target of the animation, and read the current animated size.
            val (width, height) = sizeAnimation.updateTarget(lookaheadSize, coroutineScope)
            // Then create fixed size constraints using the animated size
            val animatedConstraints = Constraints.fixed(width, height)
            // Measure child with animated constraints.
            val placeable = measurable.measure(animatedConstraints)
            layout(placeable.width, placeable.height) { placeable.place(0, 0) }
        }

    var fullWidth by remember { mutableStateOf(false) }

    // Creates a size animation with a target unknown at the time of instantiation.
    val sizeAnimation = remember { DeferredTargetAnimation(IntSize.VectorConverter) }
    val coroutineScope = rememberCoroutineScope()
    Row(
        (if (fullWidth) Modifier.fillMaxWidth() else Modifier.width(100.dp))
            .height(200.dp)
            // Use the custom modifier created above to animate the constraints passed
            // to the child, and therefore resize children in an animation.
            .animateConstraints(sizeAnimation, coroutineScope)
            .clickable { fullWidth = !fullWidth }
    ) {
        Box(
            Modifier.weight(1f).fillMaxHeight().background(Color(0xffff6f69)),
        )
        Box(Modifier.weight(2f).fillMaxHeight().background(Color(0xffffcc5c)))
    }
}