Two dimensional viewport throws Unexpected null value exception when no child is laid out yet #148255
Description
Steps to reproduce
- Run the example app
Expected results
App should run without any errors.
Actual results
You will get Unexpected null value exception but the app is in working state.
Code sample
Code sample
import 'dart:math' as math;
import 'dart:ui';
import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
theme: ThemeData(useMaterial3: false),
home: Scaffold(
body: SimpleBuilderTableView(
mainAxis: Axis.vertical,
verticalDetails: const ScrollableDetails.vertical(),
horizontalDetails: const ScrollableDetails.horizontal(),
diagonalDragBehavior: DiagonalDragBehavior.none,
clipBehavior: Clip.hardEdge,
delegate: TwoDimensionalChildBuilderDelegate(
maxXIndex: 50,
maxYIndex: 50,
addAutomaticKeepAlives: false,
addRepaintBoundaries: false,
builder: (BuildContext context, ChildVicinity vicinity) {
if (vicinity.xIndex > 10) {
return ColoredBox(
color: vicinity.xIndex.isOdd ? Colors.red : Colors.green,
child: SizedBox.square(dimension: 200),
);
}
return null;
}),
),
),
);
}
}
class SimpleBuilderTableView extends TwoDimensionalScrollView {
const SimpleBuilderTableView({
super.key,
super.primary,
super.mainAxis = Axis.vertical,
super.verticalDetails = const ScrollableDetails.vertical(),
super.horizontalDetails = const ScrollableDetails.horizontal(),
required TwoDimensionalChildBuilderDelegate delegate,
super.cacheExtent,
super.diagonalDragBehavior = DiagonalDragBehavior.none,
super.dragStartBehavior = DragStartBehavior.start,
super.keyboardDismissBehavior = ScrollViewKeyboardDismissBehavior.manual,
super.clipBehavior = Clip.hardEdge,
}) : super(delegate: delegate);
@override
Widget buildViewport(BuildContext context, ViewportOffset verticalOffset,
ViewportOffset horizontalOffset) {
return SimpleBuilderTableViewport(
horizontalOffset: horizontalOffset,
horizontalAxisDirection: horizontalDetails.direction,
verticalOffset: verticalOffset,
verticalAxisDirection: verticalDetails.direction,
mainAxis: mainAxis,
delegate: delegate as TwoDimensionalChildBuilderDelegate,
cacheExtent: cacheExtent,
clipBehavior: clipBehavior,
);
}
}
class SimpleBuilderTableViewport extends TwoDimensionalViewport {
const SimpleBuilderTableViewport({
super.key,
required super.verticalOffset,
required super.verticalAxisDirection,
required super.horizontalOffset,
required super.horizontalAxisDirection,
required TwoDimensionalChildBuilderDelegate delegate,
required super.mainAxis,
super.cacheExtent,
super.clipBehavior = Clip.hardEdge,
}) : super(delegate: delegate);
@override
RenderTwoDimensionalViewport createRenderObject(BuildContext context) {
return RenderSimpleBuilderTableViewport(
horizontalOffset: horizontalOffset,
horizontalAxisDirection: horizontalAxisDirection,
verticalOffset: verticalOffset,
verticalAxisDirection: verticalAxisDirection,
mainAxis: mainAxis,
delegate: delegate as TwoDimensionalChildBuilderDelegate,
childManager: context as TwoDimensionalChildManager,
cacheExtent: cacheExtent,
clipBehavior: clipBehavior,
);
}
@override
void updateRenderObject(
BuildContext context, RenderSimpleBuilderTableViewport renderObject) {
renderObject
..horizontalOffset = horizontalOffset
..horizontalAxisDirection = horizontalAxisDirection
..verticalOffset = verticalOffset
..verticalAxisDirection = verticalAxisDirection
..mainAxis = mainAxis
..delegate = delegate
..cacheExtent = cacheExtent
..clipBehavior = clipBehavior;
}
}
class RenderSimpleBuilderTableViewport extends RenderTwoDimensionalViewport {
RenderSimpleBuilderTableViewport({
required super.horizontalOffset,
required super.horizontalAxisDirection,
required super.verticalOffset,
required super.verticalAxisDirection,
required TwoDimensionalChildBuilderDelegate delegate,
required super.mainAxis,
required super.childManager,
super.cacheExtent,
super.clipBehavior = Clip.hardEdge,
}) : super(delegate: delegate);
RenderBox? testGetChildFor(ChildVicinity vicinity) => getChildFor(vicinity);
@override
void layoutChildSequence() {
// Really simple table implementation for testing.
// Every child is 200x200 square
final double horizontalPixels = horizontalOffset.pixels;
final double verticalPixels = verticalOffset.pixels;
final double viewportWidth = viewportDimension.width + cacheExtent;
final double viewportHeight = viewportDimension.height + cacheExtent;
final TwoDimensionalChildBuilderDelegate builderDelegate =
delegate as TwoDimensionalChildBuilderDelegate;
final int maxRowIndex;
final int maxColumnIndex;
maxRowIndex = builderDelegate.maxYIndex ?? 5;
maxColumnIndex = builderDelegate.maxXIndex ?? 5;
final int leadingColumn = math.max((horizontalPixels / 200).floor(), 0);
final int leadingRow = math.max((verticalPixels / 200).floor(), 0);
final int trailingColumn = math.min(
((horizontalPixels + viewportWidth) / 200).ceil(),
maxColumnIndex,
);
final int trailingRow = math.min(
((verticalPixels + viewportHeight) / 200).ceil(),
maxRowIndex,
);
double xLayoutOffset = (leadingColumn * 200) - horizontalOffset.pixels;
for (int column = leadingColumn; column <= trailingColumn; column++) {
double yLayoutOffset = (leadingRow * 200) - verticalOffset.pixels;
for (int row = leadingRow; row <= trailingRow; row++) {
final ChildVicinity vicinity =
ChildVicinity(xIndex: column, yIndex: row);
final RenderBox? child = buildOrObtainChildFor(vicinity);
child?.layout(constraints.tighten(width: 200.0, height: 200.0));
if (child != null) {
parentDataOf(child).layoutOffset =
Offset(xLayoutOffset, yLayoutOffset);
}
yLayoutOffset += 200;
}
xLayoutOffset += 200;
}
final double verticalExtent = 200 * (maxRowIndex + 1);
verticalOffset.applyContentDimensions(
0.0,
clampDouble(
verticalExtent - viewportDimension.height, 0.0, double.infinity),
);
final double horizontalExtent = 200 * (maxColumnIndex + 1);
horizontalOffset.applyContentDimensions(
0.0,
clampDouble(
horizontalExtent - viewportDimension.width, 0.0, double.infinity),
);
}
}Logs
Logs
══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
The following TypeErrorImpl was thrown during performLayout():
Unexpected null value.
The relevant error-causing widget was:
SimpleBuilderTableViewport
SimpleBuilderTableViewport:file:///lib/main.dart:62:12
When the exception was thrown, this was the stack:
dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 296:3 throw_
dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart 586:18 nullCheck
packages/flutter/src/widgets/two_dimensional_viewport.dart 1321:28 [_reifyChildren]
packages/flutter/src/widgets/two_dimensional_viewport.dart 1260:7 <fn>
packages/flutter/src/rendering/object.dart 2688:51 <fn>
packages/flutter/src/rendering/object.dart 1098:7 [_enableMutationsToDirtySubtrees]
packages/flutter/src/rendering/object.dart 2688:7 invokeLayoutCallback
packages/flutter/src/widgets/two_dimensional_viewport.dart 1250:5 performLayout
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/custom_layout.dart 173:10 layoutChild
packages/flutter/src/material/scaffold.dart 1097:7 performLayout
packages/flutter/src/rendering/custom_layout.dart 237:7 [_callPerformLayout]
packages/flutter/src/rendering/custom_layout.dart 404:5 performLayout
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/proxy_box.dart 1448:11 performLayout
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/layout_helper.dart 61:10 layoutChild
packages/flutter/src/rendering/stack.dart 595:43 [_computeSize]
packages/flutter/src/rendering/stack.dart 622:12 performLayout
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/proxy_box.dart 3728:13 performLayout
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/widgets/overlay.dart 1002:12 layoutChild
packages/flutter/src/widgets/overlay.dart 1311:9 performLayout
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/custom_paint.dart 569:11 performLayout
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/proxy_box.dart 111:21 <fn>
packages/flutter/src/rendering/object.dart 2577:7 layout
packages/flutter/src/rendering/view.dart 281:7 performLayout
packages/flutter/src/rendering/object.dart 2416:7 [_layoutWithoutResize]
packages/flutter/src/rendering/object.dart 1052:17 flushLayout
packages/flutter/src/rendering/object.dart 1065:14 flushLayout
packages/flutter/src/rendering/binding.dart 602:5 drawFrame
packages/flutter/src/widgets/binding.dart 1138:13 drawFrame
packages/flutter/src/rendering/binding.dart 468:5 [_handlePersistentFrameCallback]
packages/flutter/src/scheduler/binding.dart 1392:7 [_invokeFrameCallback]
packages/flutter/src/scheduler/binding.dart 1313:9 handleDrawFrame
packages/flutter/src/scheduler/binding.dart 1035:9 <fn>
dart-sdk/lib/_internal/js_dev_runtime/private/isolate_helper.dart 48:11 internalCallback
The following RenderObject was being processed when the exception was fired: RenderSimpleBuilderTableViewport#c3adc NEEDS-LAYOUT NEEDS-PAINT:
needs compositing
creator: SimpleBuilderTableViewport ← IgnorePointer-[GlobalKey#86c87] ← Semantics ← Listener ←
_GestureSemantics ← RawGestureDetector-[LabeledGlobalKey<RawGestureDetectorState>#a96f5] ←
Listener ← _ScrollableScope ← _ScrollSemantics-[GlobalKey#02c3d] ←
NotificationListener<ScrollMetricsNotification> ←
_HorizontalInnerDimension-[LabeledGlobalKey<ScrollableState>#4de8e] ←
IgnorePointer-[GlobalKey#6a5e6] ← ⋯
parentData: <none> (can use size)
constraints: BoxConstraints(0.0<=w<=1138.0, 0.0<=h<=682.0)
size: Size(1138.0, 682.0)
This RenderObject has no descendants.
════════════════════════════════════════════════════════════════════════════════════════════════════Flutter Doctor output
Doctor output
[✓] Flutter (Channel master, 3.22.0-31.0.pre.23, on macOS 14.4.1 23E224
darwin-arm64, locale en-US)
• Flutter version 3.22.0-31.0.pre.23 on channel master at
/flutter
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision 9abde3e615 (12 hours ago), 2024-05-13 04:47:24 -0400
• Engine revision fab7a74178
• Dart version 3.5.0 (build 3.5.0-147.0.dev)
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[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
• Android SDK at /SDK
• Platform android-34, build-tools 34.0.0
• ANDROID_HOME = /SDK
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Studio.app/Contents/jbr/Contents/Home/bin/java
• Java version OpenJDK Runtime Environment (build
17.0.10+0-17.0.10b1087.21-11572160)
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• Java version OpenJDK Runtime Environment (build
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[✓] Connected device (4 available)
• macOS (desktop) • macos • darwin-arm64
• macOS 14.4.1 23E224 darwin-arm64
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• macOS 14.4.1 23E224 darwin-arm64
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web-javascript • Google Chrome 119.0.6045.123
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