ViewModelProvider.kt
/*
* Copyright 2017 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.lifecycle
import androidx.annotation.MainThread
import kotlin.reflect.KClass
/**
* Returns an existing ViewModel or creates a new one in the scope (usually, a fragment or
* an activity), associated with this `ViewModelProvider`.
*
* @see ViewModelProvider.get(Class)
*/
@MainThread
public inline fun <reified VM : ViewModel> ViewModelProvider.get(): VM = get(VM::class.java)
/**
* An implementation of [Lazy] used by [androidx.fragment.app.Fragment.viewModels] and
* [androidx.activity.ComponentActivity.viewmodels].
*
* [storeProducer] is a lambda that will be called during initialization, [VM] will be created
* in the scope of returned [ViewModelStore].
*
* [factoryProducer] is a lambda that will be called during initialization,
* returned [ViewModelProvider.Factory] will be used for creation of [VM]
*/
public class ViewModelLazy<VM : ViewModel> (
private val viewModelClass: KClass<VM>,
private val storeProducer: () -> ViewModelStore,
private val factoryProducer: () -> ViewModelProvider.Factory
) : Lazy<VM> {
private var cached: VM? = null
override val value: VM
get() {
val viewModel = cached
return if (viewModel == null) {
val factory = factoryProducer()
val store = storeProducer()
ViewModelProvider(store, factory).get(viewModelClass.java).also {
cached = it
}
} else {
viewModel
}
}
override fun isInitialized(): Boolean = cached != null
}