LiveDataAdapter.kt
/*
* Copyright 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 androidx.compose.runtime.livedata
import androidx.compose.runtime.Composable
import androidx.compose.runtime.DisposableEffect
import androidx.compose.runtime.State
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.platform.LocalLifecycleOwner
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.LifecycleOwner
import androidx.lifecycle.LiveData
import androidx.lifecycle.Observer
/**
* Starts observing this [LiveData] and represents its values via [State]. Every time there would
* be new value posted into the [LiveData] the returned [State] will be updated causing
* recomposition of every [State.value] usage.
*
* The inner observer will automatically be removed when this composable disposes or the current
* [LifecycleOwner] moves to the [Lifecycle.State.DESTROYED] state.
*
* @sample androidx.compose.runtime.livedata.samples.LiveDataSample
*/
@Composable
fun <T> LiveData<T>.observeAsState(): State<T?> = observeAsState(value)
/**
* Starts observing this [LiveData] and represents its values via [State]. Every time there would
* be new value posted into the [LiveData] the returned [State] will be updated causing
* recomposition of every [State.value] usage.
*
* The inner observer will automatically be removed when this composable disposes or the current
* [LifecycleOwner] moves to the [Lifecycle.State.DESTROYED] state.
*
* @sample androidx.compose.runtime.livedata.samples.LiveDataWithInitialSample
*/
@Composable
fun <R, T : R> LiveData<T>.observeAsState(initial: R): State<R> {
val lifecycleOwner = LocalLifecycleOwner.current
val state = remember { mutableStateOf(initial) }
DisposableEffect(this, lifecycleOwner) {
val observer = Observer<T> { state.value = it }
observe(lifecycleOwner, observer)
onDispose { removeObserver(observer) }
}
return state
}