Fix main stocks screen (#8008)

We weren't triggering a relayout when the number of children changed.

Fixes #8001

packages/flutter/lib/src/rendering/sliver_fixed_extent_list.dart

@@ -21,6 +21,7 @@ abstract class RenderSliverFixedExtentBoxAdaptor extends RenderSliverMultiBoxAda
   @override
   void performLayout() {
     assert(childManager.debugAssertChildListLocked());
+    childManager.setDidUnderflow(false);
 
     final double itemExtent = this.itemExtent;
     double indexToScrollOffset(int index) => itemExtent * index;

packages/flutter/lib/src/rendering/sliver_grid.dart

@@ -445,6 +445,8 @@ class RenderSliverGrid extends RenderSliverMultiBoxAdaptor {
   @override
   void performLayout() {
     assert(childManager.debugAssertChildListLocked());
+    childManager.setDidUnderflow(false);
+
     final double scrollOffset = constraints.scrollOffset;
     assert(scrollOffset >= 0.0);
     final double remainingPaintExtent = constraints.remainingPaintExtent;

packages/flutter/lib/src/rendering/sliver_list.dart

@@ -17,6 +17,8 @@ class RenderSliverList extends RenderSliverMultiBoxAdaptor {
   @override
   void performLayout() {
     assert(childManager.debugAssertChildListLocked());
+    childManager.setDidUnderflow(false);
+
     double scrollOffset = constraints.scrollOffset;
     assert(scrollOffset >= 0.0);
     double remainingPaintExtent = constraints.remainingPaintExtent;

packages/flutter/lib/src/rendering/sliver_multi_box_adaptor.dart

@@ -75,6 +75,8 @@ abstract class RenderSliverBoxChildManager {
   /// the child list after this function returns.
   void didAdoptChild(RenderBox child);
 
+  void setDidUnderflow(bool value);
+
   /// In debug mode, asserts that this manager is not expecting any
   /// modifications to the [RenderSliverMultiBoxAdaptor]'s child list.
   ///
@@ -174,6 +176,7 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
         firstChildParentData.layoutOffset = scrollOffset;
         result = true;
       } else {
+        childManager.setDidUnderflow(true);
         result = false;
       }
     });
@@ -206,6 +209,7 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
       firstChild.layout(childConstraints, parentUsesSize: parentUsesSize);
       return firstChild;
     }
+    childManager.setDidUnderflow(true);
     return null;
   }
 
@@ -238,6 +242,7 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
       child.layout(childConstraints, parentUsesSize: parentUsesSize);
       return child;
     }
+    childManager.setDidUnderflow(true);
     return null;
   }
 

packages/flutter/lib/src/widgets/overscroll_indicator.dart

@@ -108,6 +108,8 @@ class _GlowingOverscrollIndicatorState extends State<GlowingOverscrollIndicator>
   }
 
   bool _handleScrollNotification(ScrollNotification2 notification) {
+    if (notification.depth != 0)
+      return false;
     if (notification is OverscrollNotification) {
       _GlowController controller;
       if (notification.overscroll < 0.0) {

packages/flutter/lib/src/widgets/sliver.dart

@@ -258,7 +258,7 @@ class SliverMultiBoxAdaptorElement extends RenderObjectElement implements Render
       performRebuild();
   }
 
-  Map<int, Element> _childElements = new SplayTreeMap<int, Element>();
+  SplayTreeMap<int, Element> _childElements = new SplayTreeMap<int, Element>();
   Map<int, Widget> _childWidgets = new HashMap<int, Widget>();
   RenderBox _currentBeforeChild;
 
@@ -269,14 +269,18 @@ class SliverMultiBoxAdaptorElement extends RenderObjectElement implements Render
     _currentBeforeChild = null;
     assert(_currentlyUpdatingChildIndex == null);
     try {
-      // The "toList()" below is to get a copy of the array so that we can
-      // mutate _childElements within the loop. Basically we just update all the
-      // same indexes as we had before. If any of them mutate the tree, then
-      // this will also trigger a layout and so forth. (We won't call the
-      // delegate's build function multiple times, though, because we cache the
-      // delegate's results until the next time we need to rebuild the whole
-      // block widget.)
-      for (int index in _childElements.keys.toList()) {
+      int firstIndex = _childElements.firstKey();
+      int lastIndex = _childElements.lastKey();
+      if (_childElements.isEmpty) {
+        firstIndex = 0;
+        lastIndex = 0;
+      } else if (_didUnderflow) {
+        lastIndex += 1;
+      }
+      // We won't call the delegate's build function multiple times, because we
+      // cache the delegate's results until the next time we need to rebuild the
+      // whole widget.
+      for (int index = firstIndex; index <= lastIndex; ++index) {
         _currentlyUpdatingChildIndex = index;
         Element newChild = updateChild(_childElements[index], _build(index), index);
         if (newChild != null) {
@@ -397,6 +401,13 @@ class SliverMultiBoxAdaptorElement extends RenderObjectElement implements Render
     childParentData.index = _currentlyUpdatingChildIndex;
   }
 
+  bool _didUnderflow = false;
+
+  @override
+  void setDidUnderflow(bool value) {
+    _didUnderflow = value;
+  }
+
   @override
   void insertChildRenderObject(@checked RenderObject child, int slot) {
     assert(slot != null);

packages/flutter/test/rendering/slivers_block_test.dart

@@ -59,6 +59,9 @@ class TestRenderSliverBoxChildManager extends RenderSliverBoxChildManager {
     final SliverMultiBoxAdaptorParentData childParentData = child.parentData;
     childParentData.index = _currentlyUpdatingChildIndex;
   }
+
+  @override
+  void setDidUnderflow(bool value) { }
 }
 
 void main() {

packages/flutter/test/widgets/list_test.dart

@@ -89,4 +89,55 @@ void main() {
     expect(log, equals(<int>[4, 5, 6, 7]));
     log.clear();
   });
+
+  testWidgets('ListView can build out of underflow', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      new ListView(
+        itemExtent: 100.0,
+      ),
+    );
+
+    expect(find.text('0'), findsNothing);
+    expect(find.text('1'), findsNothing);
+    expect(find.text('2'), findsNothing);
+    expect(find.text('3'), findsNothing);
+    expect(find.text('4'), findsNothing);
+    expect(find.text('5'), findsNothing);
+
+    await tester.pumpWidget(
+      new ListView(
+        itemExtent: 100.0,
+        children: new List<Widget>.generate(2, (int i) {
+          return new Container(
+            child: new Text('$i'),
+          );
+        }),
+      ),
+    );
+
+    expect(find.text('0'), findsOneWidget);
+    expect(find.text('1'), findsOneWidget);
+    expect(find.text('2'), findsNothing);
+    expect(find.text('3'), findsNothing);
+    expect(find.text('4'), findsNothing);
+    expect(find.text('5'), findsNothing);
+
+    await tester.pumpWidget(
+      new ListView(
+        itemExtent: 100.0,
+        children: new List<Widget>.generate(5, (int i) {
+          return new Container(
+            child: new Text('$i'),
+          );
+        }),
+      ),
+    );
+
+    expect(find.text('0'), findsOneWidget);
+    expect(find.text('1'), findsOneWidget);
+    expect(find.text('2'), findsOneWidget);
+    expect(find.text('3'), findsOneWidget);
+    expect(find.text('4'), findsOneWidget);
+    expect(find.text('5'), findsNothing);
+  });
 }

packages/flutter/test/widgets/overscroll_indicator_test.dart

@@ -197,6 +197,29 @@ void main() {
     expect(painter, doesNotOverscroll);
   });
 
+  testWidgets('Nested overscrolls do not throw exceptions', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      new PageView(
+        children: <Widget>[
+          new ListView(
+            children: <Widget>[
+              new Container(
+                width: 2000.0,
+                height: 2000.0,
+                decoration: new BoxDecoration(
+                  backgroundColor: const Color(0xFF00FF00),
+                ),
+              ),
+            ],
+          ),
+        ],
+      ),
+    );
+
+    await tester.scrollAt(const Point(100.0, 100.0), const Offset(0.0, 2000.0));
+    await tester.pumpUntilNoTransientCallbacks();
+  });
+
   testWidgets('Changing settings', (WidgetTester tester) async {
     RenderObject painter;