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/*
* Copyright (C) 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 com.android.permissioncontroller.permission.data
import androidx.lifecycle.SavedStateHandle
/**
* LiveData that loads wrapped value once. Once the wrapped data becomes non-stale it holds onto the
* value forever.
*
* This even extends over live-cycle events as the data is stored in the {@link SaveStateHandle}.
* This means that the data has to be writable to {@link SavedStateHandle} though, i.e. Serialzable,
* Parcelable, list, set, map, or a literal
*/
class LoadAndFreezeLifeData<T>(
private val state: SavedStateHandle,
private val key: String,
private val wrapped: SmartUpdateMediatorLiveData<T>
) : SmartUpdateMediatorLiveData<T>() {
init {
if (state.get<T>(key) == null) {
addSource(wrapped) { v ->
if (wrapped.isInitialized) {
value = v
if (!wrapped.isStale) {
state.set(key, v)
removeSource(wrapped)
}
}
}
} else {
value = state[key]
}
}
override fun onUpdate() {
// do nothing
}
}
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