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159
app/src/main/java/dev/chungjungsoo/gptmobile/util/PinnedExitUntilCollapsedScrollBehavior.kt
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,159 @@ | ||
| package dev.chungjungsoo.gptmobile.util | ||
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|
||
| import androidx.compose.animation.core.AnimationSpec | ||
| import androidx.compose.animation.core.AnimationState | ||
| import androidx.compose.animation.core.DecayAnimationSpec | ||
| import androidx.compose.animation.core.Spring | ||
| import androidx.compose.animation.core.animateDecay | ||
| import androidx.compose.animation.core.animateTo | ||
| import androidx.compose.animation.core.spring | ||
| import androidx.compose.animation.rememberSplineBasedDecay | ||
| import androidx.compose.material3.ExperimentalMaterial3Api | ||
| import androidx.compose.material3.TopAppBarScrollBehavior | ||
| import androidx.compose.material3.TopAppBarState | ||
| import androidx.compose.material3.rememberTopAppBarState | ||
| import androidx.compose.runtime.Composable | ||
| import androidx.compose.ui.geometry.Offset | ||
| import androidx.compose.ui.input.nestedscroll.NestedScrollConnection | ||
| import androidx.compose.ui.input.nestedscroll.NestedScrollSource | ||
| import androidx.compose.ui.unit.Velocity | ||
| import kotlin.math.abs | ||
|
|
||
| /** | ||
| * Special thanks to @BenjyTec: https://stackoverflow.com/a/78538564/8606428 | ||
| */ | ||
| @ExperimentalMaterial3Api | ||
| @Composable | ||
| fun pinnedExitUntilCollapsedScrollBehavior( | ||
| state: TopAppBarState = rememberTopAppBarState(), | ||
| canScroll: () -> Boolean = { true }, | ||
| snapAnimationSpec: AnimationSpec<Float>? = spring(stiffness = Spring.StiffnessMediumLow), | ||
| flingAnimationSpec: DecayAnimationSpec<Float>? = rememberSplineBasedDecay() | ||
| ): TopAppBarScrollBehavior = | ||
| PinnedExitUntilCollapsedScrollBehavior( | ||
| state = state, | ||
| snapAnimationSpec = snapAnimationSpec, | ||
| flingAnimationSpec = flingAnimationSpec, | ||
| canScroll = canScroll | ||
| ) | ||
|
|
||
| @OptIn(ExperimentalMaterial3Api::class) | ||
| private class PinnedExitUntilCollapsedScrollBehavior( | ||
| override val state: TopAppBarState, | ||
| override val snapAnimationSpec: AnimationSpec<Float>?, | ||
| override val flingAnimationSpec: DecayAnimationSpec<Float>?, | ||
| val canScroll: () -> Boolean = { true } | ||
| ) : TopAppBarScrollBehavior { | ||
| override val isPinned: Boolean = true | ||
| override var nestedScrollConnection = | ||
| object : NestedScrollConnection { | ||
| override fun onPreScroll(available: Offset, source: NestedScrollSource): Offset { | ||
| // Don't intercept if scrolling down. | ||
| if (!canScroll() || available.y > 0f) return Offset.Zero | ||
|
|
||
| val prevHeightOffset = state.heightOffset | ||
| state.heightOffset = state.heightOffset + available.y | ||
| return if (prevHeightOffset != state.heightOffset) { | ||
| // We're in the middle of top app bar collapse or expand. | ||
| // Consume only the scroll on the Y axis. | ||
| available.copy(x = 0f) | ||
| } else { | ||
| Offset.Zero | ||
| } | ||
| } | ||
|
|
||
| override fun onPostScroll( | ||
| consumed: Offset, | ||
| available: Offset, | ||
| source: NestedScrollSource | ||
| ): Offset { | ||
| if (!canScroll()) return Offset.Zero | ||
| state.contentOffset += consumed.y | ||
|
|
||
| if (available.y < 0f || consumed.y < 0f) { | ||
| // When scrolling up, just update the state's height offset. | ||
| val oldHeightOffset = state.heightOffset | ||
| state.heightOffset = state.heightOffset + consumed.y | ||
| return Offset(0f, state.heightOffset - oldHeightOffset) | ||
| } | ||
|
|
||
| if (consumed.y == 0f && available.y > 0) { | ||
| // Reset the total content offset to zero when scrolling all the way down. This | ||
| // will eliminate some float precision inaccuracies. | ||
| state.contentOffset = 0f | ||
| } | ||
|
|
||
| if (available.y > 0f) { | ||
| // Adjust the height offset in case the consumed delta Y is less than what was | ||
| // recorded as available delta Y in the pre-scroll. | ||
| val oldHeightOffset = state.heightOffset | ||
| state.heightOffset = state.heightOffset + available.y | ||
| return Offset(0f, state.heightOffset - oldHeightOffset) | ||
| } | ||
| return Offset.Zero | ||
| } | ||
|
|
||
| override suspend fun onPostFling(consumed: Velocity, available: Velocity): Velocity { | ||
| val superConsumed = super.onPostFling(consumed, available) | ||
| return superConsumed + settleAppBar( | ||
| state, | ||
| available.y, | ||
| flingAnimationSpec, | ||
| snapAnimationSpec | ||
| ) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| @OptIn(ExperimentalMaterial3Api::class) | ||
| private suspend fun settleAppBar( | ||
| state: TopAppBarState, | ||
| velocity: Float, | ||
| flingAnimationSpec: DecayAnimationSpec<Float>?, | ||
| snapAnimationSpec: AnimationSpec<Float>? | ||
| ): Velocity { | ||
| // Check if the app bar is completely collapsed/expanded. If so, no need to settle the app bar, | ||
| // and just return Zero Velocity. | ||
| // Note that we don't check for 0f due to float precision with the collapsedFraction | ||
| // calculation. | ||
| if (state.collapsedFraction < 0.01f || state.collapsedFraction == 1f) { | ||
| return Velocity.Zero | ||
| } | ||
| var remainingVelocity = velocity | ||
| // In case there is an initial velocity that was left after a previous user fling, animate to | ||
| // continue the motion to expand or collapse the app bar. | ||
| if (flingAnimationSpec != null && abs(velocity) > 1f) { | ||
| var lastValue = 0f | ||
| AnimationState( | ||
| initialValue = 0f, | ||
| initialVelocity = velocity | ||
| ) | ||
| .animateDecay(flingAnimationSpec) { | ||
| val delta = value - lastValue | ||
| val initialHeightOffset = state.heightOffset | ||
| state.heightOffset = initialHeightOffset + delta | ||
| val consumed = abs(initialHeightOffset - state.heightOffset) | ||
| lastValue = value | ||
| remainingVelocity = this.velocity | ||
| // avoid rounding errors and stop if anything is unconsumed | ||
| if (abs(delta - consumed) > 0.5f) this.cancelAnimation() | ||
| } | ||
| } | ||
| // Snap if animation specs were provided. | ||
| if (snapAnimationSpec != null) { | ||
| if (state.heightOffset < 0 && | ||
| state.heightOffset > state.heightOffsetLimit | ||
| ) { | ||
| AnimationState(initialValue = state.heightOffset).animateTo( | ||
| if (state.collapsedFraction < 0.5f) { | ||
| 0f | ||
| } else { | ||
| state.heightOffsetLimit | ||
| }, | ||
| animationSpec = snapAnimationSpec | ||
| ) { state.heightOffset = value } | ||
| } | ||
| } | ||
|
|
||
| return Velocity(0f, remainingVelocity) | ||
| } |