TransitionHandler.kt
/*
* Copyright (C) 2022 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.constraintlayout.compose
import androidx.compose.runtime.ExperimentalComposeApi
import androidx.compose.runtime.monotonicFrameClock
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.unit.Velocity
import kotlin.coroutines.coroutineContext
/**
* Helper class that handles the interactions between Compose and
* [androidx.constraintlayout.core.state.Transition].
*/
@OptIn(ExperimentalComposeApi::class)
@PublishedApi
internal class TransitionHandler(
private val motionMeasurer: MotionMeasurer,
private val motionProgress: MotionProgress
) {
private val transition: androidx.constraintlayout.core.state.Transition
get() = motionMeasurer.transition
/**
* The [motionProgress] is updated based on the [Offset] from a single drag event.
*/
suspend fun updateProgressOnDrag(dragAmount: Offset) {
val progressDelta = transition.dragToProgress(
motionProgress.progress,
motionMeasurer.layoutCurrentWidth,
motionMeasurer.layoutCurrentHeight,
dragAmount.x,
dragAmount.y
)
var newProgress = motionProgress.progress + progressDelta
newProgress = newProgress.coerceIn(0f, 1f)
motionProgress.updateProgress(newProgress)
}
/**
* Called when a swipe event ends, sets up the underlying Transition with the [velocity] of the
* swipe at the next frame..
*/
suspend fun onTouchUp(velocity: Velocity) {
coroutineContext.monotonicFrameClock.withFrameNanos { timeNanos ->
transition.setTouchUp(motionProgress.progress, timeNanos, velocity.x, velocity.y)
}
}
/**
* Call to update the [motionProgress] after a swipe has ended and as long as there are no other
* touch gestures.
*/
suspend fun updateProgressWhileTouchUp() {
val newProgress = coroutineContext.monotonicFrameClock.withFrameNanos { timeNanos ->
transition.getTouchUpProgress(timeNanos)
}
motionProgress.updateProgress(newProgress)
}
/**
* Returns true if the progress is still expected to be updated by [updateProgressWhileTouchUp].
*/
fun pendingProgressWhileTouchUp(): Boolean {
return transition.isTouchNotDone(motionProgress.progress)
}
}