1 /*
2 * Copyright 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 package com.android.photopicker.core
17
18 import androidx.compose.runtime.Composable
19 import androidx.compose.runtime.CompositionLocalProvider
20 import androidx.compose.runtime.getValue
21 import androidx.compose.ui.platform.LocalSavedStateRegistryOwner
22 import androidx.hilt.navigation.compose.hiltViewModel
23 import androidx.lifecycle.ViewModel
24 import androidx.lifecycle.compose.LocalLifecycleOwner
25 import androidx.lifecycle.viewmodel.compose.LocalViewModelStoreOwner
26 import androidx.lifecycle.viewmodel.compose.viewModel
27 import com.android.photopicker.core.configuration.LocalPhotopickerConfiguration
28 import com.android.photopicker.core.configuration.PhotopickerRuntimeEnv
29 import com.android.photopicker.core.embedded.LocalEmbeddedLifecycle
30
31 /**
32 * A composable function that obtains the requested [ViewModel] based on the current
33 * [PhotopickerRuntimeEnv]. This will re-use existing view models in the current [ViewModelStore]'s
34 * context, or create a new view model if the correct type cannot be found.
35 *
36 * This should be used in place of all other view model constructors, both [hiltViewModel] and
37 * [viewModel] as well as directly calling a ViewModel's public constructor. This ensures the
38 * created view model is properly re-used, and it is cleared when the ViewModelStore is cleared.
39 *
40 * @param <VM> the type of the viewModel to obtain
41 * @return the current instance of the view model, or a newly created view model if none existed in
42 * the [ViewModelStore]
43 */
44 @Composable
obtainViewModelnull45 inline fun <reified VM : ViewModel> obtainViewModel(): VM {
46 val configuration = LocalPhotopickerConfiguration.current
47 var viewModel: VM =
48 when (configuration.runtimeEnv) {
49 // When the current runtime is embedded, override the current ViewModelStore to use
50 // the [LocalEmbeddedLifecycle]'s store, and rely on the [EmbeddedViewModelFactory]
51 // to create and inject view models.
52 PhotopickerRuntimeEnv.EMBEDDED -> {
53 val embeddedLifecycle = LocalEmbeddedLifecycle.current
54 checkNotNull(embeddedLifecycle) {
55 "Cannot obtain view models in embedded runtime when" +
56 " LocalEmbeddedLifecycle is not set."
57 }
58 var embeddedViewModel: VM? = null
59 CompositionLocalProvider(
60 LocalViewModelStoreOwner provides embeddedLifecycle,
61 LocalLifecycleOwner provides embeddedLifecycle,
62 LocalSavedStateRegistryOwner provides embeddedLifecycle,
63 ) {
64 embeddedViewModel =
65 viewModel(
66 embeddedLifecycle,
67 factory = embeddedLifecycle.defaultViewModelProviderFactory
68 )
69 }
70 // This should never actually be null, as the [EmbeddedViewModelFactory] will throw
71 // an error rather than return a null value, but we need to de-null the type before
72 // returning it to the calling composable.
73 checkNotNull(embeddedViewModel) {
74 "Unable to obtain viewmodel from embedded factory: ${VM::class.simpleName}"
75 }
76 }
77 // When the current run time is activity, rely on the standard hiltViewModel injection,
78 // which scopes the view model to the navigation graph's current backstack entry.
79 PhotopickerRuntimeEnv.ACTIVITY -> hiltViewModel()
80 }
81 return viewModel
82 }
83