1 /*
<lambda>null2 * Copyright 2020 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 androidx.paging
18
19 import androidx.paging.LoadState.NotLoading
20 import kotlin.jvm.JvmName
21 import kotlin.jvm.JvmSuppressWildcards
22 import kotlinx.coroutines.FlowPreview
23 import kotlinx.coroutines.flow.Flow
24 import kotlinx.coroutines.flow.debounce
25 import kotlinx.coroutines.flow.filter
26 import kotlinx.coroutines.flow.firstOrNull
27
28 /**
29 * Collection of pagination [LoadState]s for both a [PagingSource], and [RemoteMediator].
30 *
31 * Note: The [LoadType] [REFRESH][LoadType.REFRESH] always has [LoadState.endOfPaginationReached]
32 * set to `false`.
33 */
34 public class CombinedLoadStates(
35 /**
36 * Convenience for combined behavior of [REFRESH][LoadType.REFRESH] [LoadState], which generally
37 * defers to [mediator] if it exists, but if previously was [LoadState.Loading], awaits for both
38 * [source] and [mediator] to become [LoadState.NotLoading] to ensure the remote load was
39 * applied.
40 *
41 * For use cases that require reacting to [LoadState] of [source] and [mediator] specifically,
42 * e.g., showing cached data when network loads via [mediator] fail, [LoadStates] exposed via
43 * [source] and [mediator] should be used directly.
44 */
45 public val refresh: LoadState,
46 /**
47 * Convenience for combined behavior of [PREPEND][LoadType.REFRESH] [LoadState], which generally
48 * defers to [mediator] if it exists, but if previously was [LoadState.Loading], awaits for both
49 * [source] and [mediator] to become [LoadState.NotLoading] to ensure the remote load was
50 * applied.
51 *
52 * For use cases that require reacting to [LoadState] of [source] and [mediator] specifically,
53 * e.g., showing cached data when network loads via [mediator] fail, [LoadStates] exposed via
54 * [source] and [mediator] should be used directly.
55 */
56 public val prepend: LoadState,
57 /**
58 * Convenience for combined behavior of [APPEND][LoadType.REFRESH] [LoadState], which generally
59 * defers to [mediator] if it exists, but if previously was [LoadState.Loading], awaits for both
60 * [source] and [mediator] to become [LoadState.NotLoading] to ensure the remote load was
61 * applied.
62 *
63 * For use cases that require reacting to [LoadState] of [source] and [mediator] specifically,
64 * e.g., showing cached data when network loads via [mediator] fail, [LoadStates] exposed via
65 * [source] and [mediator] should be used directly.
66 */
67 public val append: LoadState,
68 /** [LoadStates] corresponding to loads from a [PagingSource]. */
69 public val source: LoadStates,
70
71 /**
72 * [LoadStates] corresponding to loads from a [RemoteMediator], or `null` if [RemoteMediator]
73 * not present.
74 */
75 public val mediator: LoadStates? = null,
76 ) {
77
78 override fun equals(other: Any?): Boolean {
79 if (this === other) return true
80 if (other == null || this::class != other::class) return false
81
82 other as CombinedLoadStates
83
84 if (refresh != other.refresh) return false
85 if (prepend != other.prepend) return false
86 if (append != other.append) return false
87 if (source != other.source) return false
88 if (mediator != other.mediator) return false
89
90 return true
91 }
92
93 override fun hashCode(): Int {
94 var result = refresh.hashCode()
95 result = 31 * result + prepend.hashCode()
96 result = 31 * result + append.hashCode()
97 result = 31 * result + source.hashCode()
98 result = 31 * result + (mediator?.hashCode() ?: 0)
99 return result
100 }
101
102 override fun toString(): String {
103 return "CombinedLoadStates(refresh=$refresh, prepend=$prepend, append=$append, " +
104 "source=$source, mediator=$mediator)"
105 }
106
107 internal fun forEach(op: (LoadType, Boolean, LoadState) -> Unit) {
108 source.forEach { type, state -> op(type, false, state) }
109 mediator?.forEach { type, state -> op(type, true, state) }
110 }
111
112 /** Returns true when [source] and [mediator] is in [NotLoading] for all [LoadType] */
113 public val isIdle = source.isIdle && mediator?.isIdle ?: true
114
115 /**
116 * Returns true if either [source] or [mediator] has a [LoadType] that is in [LoadState.Error]
117 */
118 @get:JvmName("hasError") public val hasError = source.hasError || mediator?.hasError ?: false
119 }
120
121 /**
122 * Function to wait on a Flow<CombinedLoadStates> until a load has completed.
123 *
124 * It collects on the Flow<CombinedLoadStates> and suspends until it collects and returns the
125 * firstOrNull [CombinedLoadStates] where all [LoadStates] have settled into a non-loading state
126 * i.e. [LoadState.NotLoading] or [LoadState.Error].
127 *
128 * A use case could be scrolling to a position after refresh has completed:
129 * ```
130 * override fun onCreate(savedInstanceState: Bundle?) {
131 * ...
132 * refreshButton.setOnClickListener {
133 * pagingAdapter.refresh()
134 * lifecycleScope.launch {
135 * // wait for refresh to complete
136 * pagingAdapter.loadStateFlow.awaitNotLoading()
137 * // do work after refresh
138 * recyclerView.scrollToPosition(position)
139 * }
140 * }
141 * }
142 * ```
143 */
144 @OptIn(FlowPreview::class)
awaitNotLoadingnull145 public suspend fun Flow<CombinedLoadStates>.awaitNotLoading():
146 @JvmSuppressWildcards CombinedLoadStates? {
147
148 return debounce(1).filter { it.isIdle || it.hasError }.firstOrNull()
149 }
150