lazyLayout(lazyColumn) 中的listOf(listOf(string)) 撰写

Question

目前只有外部List会触发重组。当内部列表中的字符串也被更改/添加时，如何触发重组？

private var data by mutableStateOf<List<List<StringObject>>>(
    // Initialize with some sample data (20 rows, 10 columns)
    List(20) { outerIndex ->
        List(10) { innerIndex ->
            val value = "Value ${outerIndex * 10 + innerIndex + 1}"
            val imageUrl = if (innerIndex % 2 == 0)
                "https://example.com/image${innerIndex + 1}.jpg"
            else
                null
            StringObject(value, imageUrl)
        } as List<StringObject>
    }
)

我尝试更换这个

mutableStateOf<List<List<StringObject>>>

这样：

mutableStateOf<List<MutableList<StringObject>>>

但这会使应用程序因并发修改而崩溃。我是 Compose 的新手，老实说，由于所有这些不可变和状态的东西，它很糟糕。新语言应该在内部自行管理这些东西。

java.util.ConcurrentModificationException
  at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:1029)
  at java.util.ArrayList$Itr.next(ArrayList.java:982)
  at com.example.composetablee.MainActivity.addColumn(MainActivity.kt:143)
  at com.example.composetablee.MainActivity.access$addColumn(MainActivity.kt:28)
  at com.example.composetablee.MainActivity$onCreate$1$1$1$1$1$1$1.invoke(MainActivity.kt:51)
  at com.example.composetablee.MainActivity$onCreate$1$1$1$1$1$1$1.invoke(MainActivity.kt:51)
  at androidx.compose.foundation.ClickableKt$clickable$4$gesture$1$1$2.invoke-k-4lQ0M(Clickable.kt:167)
  at androidx.compose.foundation.ClickableKt$clickable$4$gesture$1$1$2.invoke(Clickable.kt:156)
  at androidx.compose.foundation.gestures.TapGestureDetectorKt$detectTapAndPress$2$1.invokeSuspend(TapGestureDetector.kt:255)
  at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
  at kotlinx.coroutines.DispatchedTaskKt.resume(DispatchedTask.kt:178)
  at kotlinx.coroutines.DispatchedTaskKt.dispatch(DispatchedTask.kt:166)
  at kotlinx.coroutines.CancellableContinuationImpl.dispatchResume(CancellableContinuationImpl.kt:397)
  at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl(CancellableContinuationImpl.kt:431)
  at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl$default(CancellableContinuationImpl.kt:420)
  at kotlinx.coroutines.CancellableContinuationImpl.resumeWith(CancellableContinuationImpl.kt:328)
  at androidx.compose.ui.input.pointer.SuspendingPointerInputFilter$PointerEventHandlerCoroutine.offerPointerEvent(SuspendingPointerInputFilter.kt:566)
  at androidx.compose.ui.input.pointer.SuspendingPointerInputFilter.dispatchPointerEvent(SuspendingPointerInputFilter.kt:456)
  at androidx.compose.ui.input.pointer.SuspendingPointerInputFilter.onPointerEvent-H0pRuoY(SuspendingPointerInputFilter.kt:469)
  at androidx.compose.ui.node.BackwardsCompatNode.onPointerEvent-H0pRuoY(BackwardsCompatNode.kt:374)
  at androidx.compose.ui.input.pointer.Node.dispatchMainEventPass(HitPathTracker.kt:314)
  at androidx.compose.ui.input.pointer.Node.dispatchMainEventPass(HitPathTracker.kt:301)
  at androidx.compose.ui.input.pointer.Node.dispatchMainEventPass(HitPathTracker.kt:301)
  at androidx.compose.ui.input.pointer.NodeParent.dispatchMainEventPass(HitPathTracker.kt:183)
  at androidx.compose.ui.input.pointer.HitPathTracker.dispatchChanges(HitPathTracker.kt:102)
  at androidx.compose.ui.input.pointer.PointerInputEventProcessor.process-BIzXfog(PointerInputEventProcessor.kt:98)
  at androidx.compose.ui.platform.AndroidComposeView.sendMotionEvent-8iAsVTc(AndroidComposeView.android.kt:1361)
  at androidx.compose.ui.platform.AndroidComposeView.handleMotionEvent-8iAsVTc(AndroidComposeView.android.kt:1307)
  at androidx.compose.ui.platform.AndroidComposeView.dispatchTouchEvent(AndroidComposeView.android.kt:1246)
  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3324)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2998)
  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3324)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2998)
  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3324)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2998)
  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3324)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2998)
  at com.android.internal.policy.DecorView.superDispatchTouchEvent(DecorView.java:776)
  at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1967)
  at android.app.Activity.dispatchTouchEvent(Activity.java:4522)
  at com.android.internal.policy.DecorView.dispatchTouchEvent(DecorView.java:734)
  at android.view.View.dispatchPointerEvent(View.java:16476)
  at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:8490)

如何处理不可变列表，因为它不允许我在其中添加内容？制作可变副本似乎资源成本高昂，尤其是如果有大量列表数据的话。

Answer 1

如果要创建列表的列表，可以使用以下代码：

val parentList = mutableStateListOf<List<String>>(listOf("A", "B"), listOf("M", "N"), listOf("X", "Y"))

要将新列表添加到

parentList

，请使用

parentList.add(listOf("1", "2"))

要将新元素添加到

parentList

内的列表中，请执行

parentList[2] = parentList[2].plus("Z")  // parentList[2] now contains X, Y, Z

通过这种方法，Jetpack Compose 应该能够正确获取对

parentList

或任何嵌套列表所做的更改。

---

关于

ConcurrentModificationException

，请检查 MainActivity 中的

addColumn

函数。问题就在那里触发。