Handle scroll cancellation exception (#696)

* Catch scroll cancellation exception * Fix demo
JetBrains · Jul 20, 2023 · 41556ad · 41556ad
1 parent 0fdc2a1
commit 41556ad
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Showing 2 changed files with 46 additions and 33 deletions.
diff --git a/...dation/src/commonMain/kotlin/androidx/compose/foundation/gestures/MouseWheelScrollable.kt b/...dation/src/commonMain/kotlin/androidx/compose/foundation/gestures/MouseWheelScrollable.kt
@@ -33,6 +33,7 @@ import androidx.compose.ui.util.fastAny
 import androidx.compose.ui.util.fastForEach
 import kotlin.math.abs
 import kotlin.math.roundToInt
+import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.channels.Channel
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
@@ -146,11 +147,14 @@ private class AnimatedMouseWheelScrollNode(
             while (isActive) {
                 val event = channel.receive()
                 isAnimationRunning = true
-                scrollingLogic.animatedDispatchScroll(event, speed = 1f * density) {
-                    // Sum delta from all pending events to avoid multiple animation restarts.
-                    channel.sumOrNull()
+                try {
+                    scrollingLogic.animatedDispatchScroll(event, speed = 1f * density) {
+                        // Sum delta from all pending events to avoid multiple animation restarts.
+                        channel.sumOrNull()
+                    }
+                } finally {
+                    isAnimationRunning = false
                 }
-                isAnimationRunning = false
             }
         }
     }
@@ -229,38 +233,42 @@ private class AnimatedMouseWheelScrollNode(
         if (target.isLowScrollingDelta()) {
             return
         }
-        scrollableState.scroll {
-            var requiredAnimation = true
-            var lastValue = 0f
-            val anim = AnimationState(0f)
-            while (requiredAnimation) {
-                requiredAnimation = false
-                val durationMillis = (abs(target - anim.value) / speed)
-                    .roundToInt()
-                    .coerceAtMost(maxDurationMillis)
-                anim.animateTo(
-                    target,
-                    animationSpec = tween(
-                        durationMillis = durationMillis,
-                        easing = LinearEasing
-                    ),
-                    sequentialAnimation = true
-                ) {
-                    val delta = value - lastValue
-                    if (!delta.isLowScrollingDelta()) {
-                        val consumedDelta = scrollBy(delta)
-                        if (!(delta - consumedDelta).isLowScrollingDelta()) {
+        var requiredAnimation = true
+        var lastValue = 0f
+        val anim = AnimationState(0f)
+        while (requiredAnimation) {
+            requiredAnimation = false
+            val durationMillis = (abs(target - anim.value) / speed)
+                .roundToInt()
+                .coerceAtMost(maxDurationMillis)
+            try {
+                scrollableState.scroll {
+                    anim.animateTo(
+                        target,
+                        animationSpec = tween(
+                            durationMillis = durationMillis,
+                            easing = LinearEasing
+                        ),
+                        sequentialAnimation = true
+                    ) {
+                        val delta = value - lastValue
+                        if (!delta.isLowScrollingDelta()) {
+                            val consumedDelta = scrollBy(delta)
+                            if (!(delta - consumedDelta).isLowScrollingDelta()) {
+                                cancelAnimation()
+                                return@animateTo
+                            }
+                            lastValue += delta
+                        }
+                        tryReceiveNext()?.let {
+                            target += it
+                            requiredAnimation = !(target - lastValue).isLowScrollingDelta()
                             cancelAnimation()
-                            return@animateTo
                         }
-                        lastValue += delta
-                    }
-                    tryReceiveNext()?.let {
-                        target += it
-                        requiredAnimation = !(target - lastValue).isLowScrollingDelta()
-                        cancelAnimation()
                     }
                 }
+            } catch (ignore: CancellationException) {
+                requiredAnimation = true
             }
         }
     }

diff --git a/compose/mpp/demo/src/commonMain/kotlin/androidx/compose/mpp/demo/LazyLayouts.kt b/compose/mpp/demo/src/commonMain/kotlin/androidx/compose/mpp/demo/LazyLayouts.kt
@@ -37,6 +37,7 @@ import androidx.compose.ui.platform.LocalLayoutDirection
 import androidx.compose.ui.unit.LayoutDirection
 import androidx.compose.ui.unit.dp
 import kotlin.random.Random
+import kotlinx.coroutines.CancellationException
 
 val LazyLayouts = Screen.Selection(
     "LazyLayouts",
@@ -52,7 +53,11 @@ private fun ExampleLazyColumn() {
     LaunchedEffect(Unit) {
         while (true) {
             withFrameMillis { }
-            state.scrollBy(2f)
+            try {
+                state.scrollBy(2f)
+            } catch (ignore: CancellationException) {
+                // Ignore cancelling by manual input
+            }
         }
     }
     LazyColumn(Modifier.fillMaxSize(), state = state) {