Fixed issue where PaginatedDataTable would not fill the width of its containing Card (#48531)

packages/flutter/lib/src/material/paginated_data_table.dart

@@ -426,6 +426,8 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
     ]);
 
     // CARD
+    return LayoutBuilder(
+      builder: (BuildContext context, BoxConstraints constraints) {
         return Card(
           semanticContainer: false,
           child: Column(
@@ -460,6 +462,8 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
               SingleChildScrollView(
                 scrollDirection: Axis.horizontal,
                 dragStartBehavior: widget.dragStartBehavior,
+                child: ConstrainedBox(
+                  constraints: BoxConstraints(minWidth: constraints.minWidth),
                   child: DataTable(
                     key: _tableKey,
                     columns: widget.columns,
@@ -470,10 +474,10 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
                     headingRowHeight: widget.headingRowHeight,
                     horizontalMargin: widget.horizontalMargin,
                     columnSpacing: widget.columnSpacing,
-              showCheckboxColumn: widget.showCheckboxColumn,
                     rows: _getRows(_firstRowIndex, widget.rowsPerPage),
                   ),
                 ),
+              ),
               DefaultTextStyle(
                 style: footerTextStyle,
                 child: IconTheme.merge(
@@ -481,6 +485,7 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
                     opacity: 0.54
                   ),
                   child: Container(
+                    // TODO(bkonyi): this won't handle text zoom correctly, https://github.com/flutter/flutter/issues/48522
                     height: 56.0,
                     child: SingleChildScrollView(
                       dragStartBehavior: widget.dragStartBehavior,
@@ -496,5 +501,7 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
             ],
           ),
         );
+      },
+    );
   }
 }

packages/flutter/test/material/paginated_data_table_test.dart

@@ -50,6 +50,9 @@ class TestDataSource extends DataTableSource {
 }
 
 void main() {
+  final TestWidgetsFlutterBinding binding =
+      TestWidgetsFlutterBinding.ensureInitialized() as TestWidgetsFlutterBinding;
+
   testWidgets('PaginatedDataTable paging', (WidgetTester tester) async {
     final TestDataSource source = TestDataSource();
 
@@ -382,6 +385,16 @@ void main() {
     const double _defaultColumnSpacing = 56.0;
     const double _customHorizontalMargin = 10.0;
     const double _customColumnSpacing = 15.0;
+
+    const double _width = 400;
+    const double _height = 400;
+
+    final Size originalSize = binding.renderView.size;
+
+    // Ensure the containing Card is small enough that we don't expand too
+    // much, resulting in our custom margin being ignored.
+    await binding.setSurfaceSize(const Size(_width, _height));
+
     final TestDataSource source = TestDataSource(
       onSelectChanged: (bool value) {},
     );
@@ -527,6 +540,9 @@ void main() {
       tester.getRect(padding).right - tester.getRect(cellContent).right,
       _customHorizontalMargin,
     );
+
+    // Reset the surface size.
+    await binding.setSurfaceSize(originalSize);
   });
 
   testWidgets('PaginatedDataTable custom horizontal padding - no checkbox', (WidgetTester tester) async {
@@ -651,4 +667,63 @@ void main() {
       _customHorizontalMargin,
     );
   });
+
+  testWidgets('PaginatedDataTable table fills Card width', (WidgetTester tester) async {
+    final TestDataSource source = TestDataSource();
+
+    // Note: 800 is wide enough to ensure that all of the columns fit in the
+    // Card. The DataTable can be larger than its containing Card, but this test
+    // is only concerned with ensuring the DataTable is at least as wide as the
+    // Card.
+    const double _originalWidth = 800;
+    const double _expandedWidth = 1600;
+    const double _height = 400;
+
+    final Size originalSize = binding.renderView.size;
+
+    Widget buildWidget() => MaterialApp(
+      home: PaginatedDataTable(
+        header: const Text('Test table'),
+        source: source,
+        rowsPerPage: 2,
+        availableRowsPerPage: const <int>[
+          2, 4, 8, 16,
+        ],
+        onRowsPerPageChanged: (int rowsPerPage) {},
+        onPageChanged: (int rowIndex) {},
+        columns: const <DataColumn>[
+          DataColumn(label: Text('Name')),
+          DataColumn(label: Text('Calories'), numeric: true),
+          DataColumn(label: Text('Generation')),
+        ],
+      ),
+    );
+
+    await binding.setSurfaceSize(const Size(_originalWidth, _height));
+    await tester.pumpWidget(buildWidget());
+
+    // Widths should be equal before we resize...
+    expect(
+      tester.renderObject<RenderBox>(find.byType(DataTable).first).size.width,
+      moreOrLessEquals(
+        tester.renderObject<RenderBox>(find.byType(Card).first).size.width)
+    );
+
+    await binding.setSurfaceSize(const Size(_expandedWidth, _height));
+    await tester.pumpWidget(buildWidget());
+
+    final double cardWidth = tester.renderObject<RenderBox>(find.byType(Card).first).size.width;
+
+    // ... and should still be equal after the resize.
+    expect(
+      tester.renderObject<RenderBox>(find.byType(DataTable).first).size.width,
+      moreOrLessEquals(cardWidth)
+    );
+
+    // Double check to ensure we actually resized the surface properly.
+    expect(cardWidth, moreOrLessEquals(_expandedWidth));
+
+    // Reset the surface size.
+    await binding.setSurfaceSize(originalSize);
+  });
 }