“未应用待处理的组合”异常是什么意思，如何避免？答案

【问题标题】：What does "pending composition has not been applied" exception mean and how can it be avoided?“未应用待处理的组合”异常是什么意思，如何避免？
【发布时间】：2022-04-15 04:32:58
【问题描述】：

我有一个工作的应用程序，但有时，由于我不知道的原因，应用程序崩溃并显示以下消息：

java.lang.IllegalStateException：未应用待处理的组合

我在任何地方都找不到有关此异常发生的信息，我也不明白如何避免它。

编辑#1：经过一番研究和测试，我发现在BottomNavigation中快速切换选项卡时会抛出这个异常（选项卡包含LazyColumn）

【问题讨论】：

如果没有minimal reproducible example，很难为您提供帮助。我在互联网上没有找到太多，但首先我会检查像LazyColumn 这样的懒惰视图 - 尝试将它们滚动很多。如果这没有帮助，请尝试逐一注释掉应用程序的某些部分以对其进行本地化。这可能是 Compose 的错误，但要修复它，维护人员需要有一个样本来重现它。
@PhilipDukhov 感谢您的建议，我会尽力寻找原因，我会尽快补充问题
@PhilipDukhov 我补充了这个问题，但我不知道我应该提供哪个代码（我应该这样做）
如果您有代码可以定期复现，我建议您filing an issue 包括示例项目和设备型号/Android 版本。我能够找到一种similar issue，但例外情况不同，所以我认为它不相关。
@PhilipDukhov 知道了，谢谢帮助！

标签： android android-jetpack-compose illegalstateexception

【解决方案1】：

由于我没有足够的声誉来写评论，所以我会在这里写。也许对你有帮助

我今天遇到了同样的错误。如果我开始调试并且我将大量日志记录行放入我的代码中，以了解究竟是什么导致了这个问题。我弄清楚了对我来说是什么导致了这个错误。我的代码中存在引发异常（数组索引越界）的实际问题，但似乎某处重组捕获了这个实际错误并引发了更一般的错误。

简化我的代码看起来像这样

val items = myViewModel.items.collectAsState().value
val focusRequesters = myViewModel.focusRequesters.collectAsState().value
LazyColumn() {
    items(items = items) { item ->
        // When I added new item then I got error in this line, 
        // because I forgot to add new focusRequester when I was adding new item. 
        // so it was actually array index out of bounds error
        val focusRequester = focusRequesters[item.position]
        ...
        // Code to show item
    }
    item {
         AddItemButton(myViewModel)
    }
}

它在日志中显示给我的实际错误是这个通用错误。

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.courtesy.test, PID: 27394
    java.lang.IllegalStateException: pending composition has not been applied
        at androidx.compose.runtime.CompositionImpl.drainPendingModificationsForCompositionLocked(Composition.kt:530)
        at androidx.compose.runtime.CompositionImpl.composeContent(Composition.kt:567)
        at androidx.compose.runtime.Recomposer.composeInitial$runtime_release(Recomposer.kt:811)
        at androidx.compose.runtime.ComposerImpl$CompositionContextImpl.composeInitial$runtime_release(Composer.kt:3583)
        at androidx.compose.runtime.CompositionImpl.setContent(Composition.kt:503)
        at androidx.compose.ui.layout.LayoutNodeSubcompositionsState.subcomposeInto(SubcomposeLayout.kt:408)
        at androidx.compose.ui.layout.LayoutNodeSubcompositionsState.subcompose(SubcomposeLayout.kt:383)
        at androidx.compose.ui.layout.LayoutNodeSubcompositionsState.subcompose(SubcomposeLayout.kt:374)
        at androidx.compose.ui.layout.LayoutNodeSubcompositionsState.subcompose(SubcomposeLayout.kt:363)
        at androidx.compose.ui.layout.LayoutNodeSubcompositionsState$Scope.subcompose(SubcomposeLayout.kt:648)
        at androidx.compose.material.ScaffoldKt$ScaffoldLayout$1$1$1.invoke(Scaffold.kt:316)
        at androidx.compose.material.ScaffoldKt$ScaffoldLayout$1$1$1.invoke(Scaffold.kt:243)
        at androidx.compose.ui.layout.MeasureScope$layout$1.placeChildren(MeasureScope.kt:68)
        at androidx.compose.ui.layout.LayoutNodeSubcompositionsState$createMeasurePolicy$1$measure$1.placeChildren(SubcomposeLayout.kt:527)
        at androidx.compose.ui.node.LayoutNode$layoutChildren$1.invoke(LayoutNode.kt:980)
        at androidx.compose.ui.node.LayoutNode$layoutChildren$1.invoke(LayoutNode.kt:965)
        at androidx.compose.runtime.snapshots.Snapshot$Companion.observe(Snapshot.kt:2063)
        at androidx.compose.runtime.snapshots.SnapshotStateObserver.observeReads(SnapshotStateObserver.kt:112)
        at androidx.compose.ui.node.OwnerSnapshotObserver.observeReads$ui_release(OwnerSnapshotObserver.kt:78)
        at androidx.compose.ui.node.OwnerSnapshotObserver.observeLayoutSnapshotReads$ui_release(OwnerSnapshotObserver.kt:52)
        at androidx.compose.ui.node.LayoutNode.layoutChildren$ui_release(LayoutNode.kt:965)
        at androidx.compose.ui.node.LayoutNode.onNodePlaced$ui_release(LayoutNode.kt:950)
        at androidx.compose.ui.node.InnerPlaceable.placeAt-f8xVGno(InnerPlaceable.kt:78)
        at androidx.compose.ui.layout.Placeable.access$placeAt-f8xVGno(Placeable.kt:31)
        at androidx.compose.ui.layout.Placeable$PlacementScope.place-70tqf50(Placeable.kt:370)
        at androidx.compose.ui.node.OuterMeasurablePlaceable.placeOuterWrapper-f8xVGno(OuterMeasurablePlaceable.kt:158)
        at androidx.compose.ui.node.OuterMeasurablePlaceable.access$placeOuterWrapper-f8xVGno(OuterMeasurablePlaceable.kt:28)
        at androidx.compose.ui.node.OuterMeasurablePlaceable$placeAt$1.invoke(OuterMeasurablePlaceable.kt:146)
        at androidx.compose.ui.node.OuterMeasurablePlaceable$placeAt$1.invoke(OuterMeasurablePlaceable.kt:145)
        at androidx.compose.runtime.snapshots.Snapshot$Companion.observe(Snapshot.kt:2063)
        at androidx.compose.runtime.snapshots.SnapshotStateObserver.observeReads(SnapshotStateObserver.kt:112)
        at androidx.compose.ui.node.OwnerSnapshotObserver.observeReads$ui_release(OwnerSnapshotObserver.kt:78)
        at androidx.compose.ui.node.OwnerSnapshotObserver.observeLayoutModifierSnapshotReads$ui_release(OwnerSnapshotObserver.kt:59)
        at androidx.compose.ui.node.OuterMeasurablePlaceable.placeAt-f8xVGno(OuterMeasurablePlaceable.kt:145)
        at androidx.compose.ui.node.OuterMeasurablePlaceable.replace(OuterMeasurablePlaceable.kt:170)
        at androidx.compose.ui.node.LayoutNode.replace$ui_release(LayoutNode.kt:838)
        at androidx.compose.ui.node.MeasureAndLayoutDelegate.remeasureAndRelayoutIfNeeded(MeasureAndLayoutDelegate.kt:262)
        at androidx.compose.ui.node.MeasureAndLayoutDelegate.access$remeasureAndRelayoutIfNeeded(MeasureAndLayoutDelegate.kt:36)
        at androidx.compose.ui.node.MeasureAndLayoutDelegate.measureAndLayout(MeasureAndLayoutDelegate.kt:201)
E/AndroidRuntime:     at androidx.compose.ui.platform.AndroidComposeView.onMeasure(AndroidComposeView.android.kt:773)
        at android.view.View.measure(View.java:25466)
        at androidx.compose.ui.platform.AbstractComposeView.internalOnMeasure$ui_release(ComposeView.android.kt:298)
        at androidx.compose.ui.platform.AbstractComposeView.onMeasure(ComposeView.android.kt:285)
        at android.view.View.measure(View.java:25466)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6957)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
        at androidx.appcompat.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:145)
        at android.view.View.measure(View.java:25466)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6957)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1552)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:842)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:721)
        at android.view.View.measure(View.java:25466)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6957)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
        at android.view.View.measure(View.java:25466)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6957)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1552)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:842)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:721)
        at android.view.View.measure(View.java:25466)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6957)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
        at com.android.internal.policy.DecorView.onMeasure(DecorView.java:747)
        at android.view.View.measure(View.java:25466)
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:3397)
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:2228)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2486)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1952)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:8171)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:972)
        at android.view.Choreographer.doCallbacks(Choreographer.java:796)
        at android.view.Choreographer.doFrame(Choreographer.java:731)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:957)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

所以至少对我来说，当重组过程中发生实际错误时会引发此错误。当然，如果它能显示实际错误而不是这个一般错误，那就太好了。

【讨论】：