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AnimatingFabContent.kt
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AnimatingFabContent.kt
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/*
* 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
*
* https://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.example.compose.jetchat.components
import androidx.compose.animation.core.FastOutSlowInEasing
import androidx.compose.animation.core.LinearEasing
import androidx.compose.animation.core.animateFloat
import androidx.compose.animation.core.tween
import androidx.compose.animation.core.updateTransition
import androidx.compose.foundation.layout.Box
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.alpha
import androidx.compose.ui.layout.Layout
import androidx.compose.ui.util.lerp
import kotlin.math.roundToInt
/**
* A layout that shows an icon and a text element used as the content for a FAB that extends with
* an animation.
*/
@Composable
fun AnimatingFabContent(
icon: @Composable () -> Unit,
text: @Composable () -> Unit,
modifier: Modifier = Modifier,
extended: Boolean = true
) {
val currentState = if (extended) ExpandableFabStates.Extended else ExpandableFabStates.Collapsed
val transition = updateTransition(currentState)
val textOpacity by transition.animateFloat(
transitionSpec = {
if (targetState == ExpandableFabStates.Collapsed) {
tween(
easing = LinearEasing,
durationMillis = (transitionDuration / 12f * 5).roundToInt() // 5 / 12 frames
)
} else {
tween(
easing = LinearEasing,
delayMillis = (transitionDuration / 3f).roundToInt(), // 4 / 12 frames
durationMillis = (transitionDuration / 12f * 5).roundToInt() // 5 / 12 frames
)
}
}
) { progress ->
if (progress == ExpandableFabStates.Collapsed) {
0f
} else {
1f
}
}
val fabWidthFactor by transition.animateFloat(
transitionSpec = {
if (targetState == ExpandableFabStates.Collapsed) {
tween(
easing = FastOutSlowInEasing,
durationMillis = transitionDuration
)
} else {
tween(
easing = FastOutSlowInEasing,
durationMillis = transitionDuration
)
}
}
) { progress ->
if (progress == ExpandableFabStates.Collapsed) {
0f
} else {
1f
}
}
// Using functions instead of Floats here can improve performance, preventing recompositions.
IconAndTextRow(
icon,
text,
{ textOpacity },
{ fabWidthFactor },
modifier = modifier
)
}
@Composable
private fun IconAndTextRow(
icon: @Composable () -> Unit,
text: @Composable () -> Unit,
opacityProgress: () -> Float, // Functions instead of Floats, to slightly improve performance
widthProgress: () -> Float,
modifier: Modifier
) {
Layout(
modifier = modifier,
content = {
icon()
Box(modifier = Modifier.alpha(opacityProgress())) {
text()
}
}
) { measurables, constraints ->
val iconPlaceable = measurables[0].measure(constraints)
val textPlaceable = measurables[1].measure(constraints)
val height = constraints.maxHeight
// FAB has an aspect ratio of 1 so the initial width is the height
val initialWidth = height.toFloat()
// Use it to get the padding
val iconPadding = (initialWidth - iconPlaceable.width) / 2f
// The full width will be : padding + icon + padding + text + padding
val expandedWidth = iconPlaceable.width + textPlaceable.width + iconPadding * 3
// Apply the animation factor to go from initialWidth to fullWidth
val width = lerp(initialWidth, expandedWidth, widthProgress())
layout(width.roundToInt(), height) {
iconPlaceable.place(
iconPadding.roundToInt(),
constraints.maxHeight / 2 - iconPlaceable.height / 2
)
textPlaceable.place(
(iconPlaceable.width + iconPadding * 2).roundToInt(),
constraints.maxHeight / 2 - textPlaceable.height / 2
)
}
}
}
private enum class ExpandableFabStates { Collapsed, Extended }
private const val transitionDuration = 200