1 /*
<lambda>null2 * Copyright (C) 2024 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package com.android.compose.animation.scene
18
19 import androidx.activity.BackEventCompat
20 import androidx.activity.compose.PredictiveBackHandler
21 import androidx.compose.animation.core.snap
22 import androidx.compose.foundation.gestures.Orientation
23 import androidx.compose.runtime.Composable
24 import com.android.compose.animation.scene.UserActionResult.ChangeScene
25 import com.android.compose.animation.scene.UserActionResult.HideOverlay
26 import com.android.compose.animation.scene.UserActionResult.ReplaceByOverlay
27 import com.android.compose.animation.scene.UserActionResult.ShowOverlay
28 import com.android.compose.animation.scene.transition.animateProgress
29 import kotlinx.coroutines.flow.Flow
30 import kotlinx.coroutines.flow.first
31 import kotlinx.coroutines.flow.map
32
33 @Composable
34 internal fun PredictiveBackHandler(
35 layoutImpl: SceneTransitionLayoutImpl,
36 result: UserActionResult?,
37 ) {
38 PredictiveBackHandler(enabled = result != null) { events: Flow<BackEventCompat> ->
39 if (result == null) {
40 // Note: We have to collect progress otherwise PredictiveBackHandler will throw.
41 events.first()
42 return@PredictiveBackHandler
43 }
44
45 val animation =
46 createSwipeAnimation(
47 layoutImpl,
48 if (result.transitionKey != null) {
49 result
50 } else {
51 result.copy(transitionKey = TransitionKey.PredictiveBack)
52 },
53 isUpOrLeft = false,
54 // Note that the orientation does not matter here given that it's only used to
55 // compute the distance. In our case the distance is always 1f.
56 orientation = Orientation.Horizontal,
57 distance = 1f,
58 )
59
60 animateProgress(
61 state = layoutImpl.state,
62 animation = animation,
63 progress = events.map { it.progress },
64
65 // Use the transformationSpec.progressSpec. We will lazily access it later once the
66 // transition has been started, because at this point the transformation spec of the
67 // transition is not computed yet.
68 commitSpec = null,
69
70 // The predictive back APIs will automatically animate the progress for us in this case
71 // so there is no need to animate it.
72 cancelSpec = snap(),
73 animationScope = layoutImpl.animationScope,
74 )
75 }
76 }
77
copynull78 private fun UserActionResult.copy(
79 transitionKey: TransitionKey? = this.transitionKey
80 ): UserActionResult {
81 return when (this) {
82 is ChangeScene -> copy(transitionKey = transitionKey)
83 is ShowOverlay -> copy(transitionKey = transitionKey)
84 is HideOverlay -> copy(transitionKey = transitionKey)
85 is ReplaceByOverlay -> copy(transitionKey = transitionKey)
86 }
87 }
88