LazyAnimatedValue.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.material
import androidx.compose.animation.core.AnimatedValue
import androidx.compose.animation.core.AnimationVector
// TODO: b/171041025 replace if/when similar functionality is added to the AnimatedValue APIs
/**
* A lazy wrapper around [AnimatedValue] that delays creating the [AnimatedValue] until the
* initial value / target is known. This is similar to [androidx.compose.animation.animate], but
* can be used outside of a Composable function.
*
* @property factory lazily invoked factory to create an [AnimatedValue] for the given target
*/
internal class LazyAnimatedValue<T, V : AnimationVector>(
private val factory: (target: T) -> AnimatedValue<T, V>
) {
private var animatedValue: AnimatedValue<T, V>? = null
/**
* @return a new [AnimatedValue] with an initial value equal to [targetValue], or the
* existing [AnimatedValue] if it has already been created.
*/
fun animatedValueForTarget(targetValue: T): AnimatedValue<T, V> {
return animatedValue ?: factory(targetValue).also { animatedValue = it }
}
}