Header for PaginatedDataTable (#4468)

Also renames ButtonTheme.footer to ButtonTheme.bar.

examples/flutter_gallery/lib/demo/cards_demo.dart

@@ -96,7 +96,7 @@ class TravelDestinationItem extends StatelessWidget {
             ),
             // share, explore buttons
             // TODO(abarth): The theme and the bar should be part of card.
-            new ButtonTheme.footer(
+            new ButtonTheme.bar(
               child: new ButtonBar(
                 alignment: MainAxisAlignment.start,
                 children: <Widget>[

examples/flutter_gallery/lib/demo/data_table_demo.dart

@@ -91,6 +91,8 @@ class DesertDataSource extends DataTableSource {
     notifyListeners();
   }
 
+  int _selectedCount = 0;
+
   @override
   DataRow getRow(int index) {
     assert(index >= 0);
@@ -101,8 +103,12 @@ class DesertDataSource extends DataTableSource {
       index: index,
       selected: desert.selected,
       onSelectChanged: (bool value) {
-        desert.selected = value;
-        notifyListeners();
+        if (desert.selected != value) {
+          _selectedCount += value ? 1 : -1;
+          assert(_selectedCount >= 0);
+          desert.selected = value;
+          notifyListeners();
+        }
       },
       cells: <DataCell>[
         new DataCell(new Text('${desert.name}')),
@@ -122,6 +128,16 @@ class DesertDataSource extends DataTableSource {
 
   @override
   bool get isRowCountApproximate => false;
+
+  @override
+  int get selectedRowCount => _selectedCount;
+
+  void _selectAll(bool checked) {
+    for (Desert desert in _deserts)
+      desert.selected = checked;
+    _selectedCount = checked ? _deserts.length : 0;
+    notifyListeners();
+  }
 }
 
 class DataTableDemo extends StatefulWidget {
@@ -135,10 +151,10 @@ class _DataTableDemoState extends State<DataTableDemo> {
   int _rowsPerPage = PaginatedDataTable.defaultRowsPerPage;
   int _sortColumnIndex;
   bool _sortAscending = true;
-  DesertDataSource _deserts = new DesertDataSource();
+  DesertDataSource _desertsDataSource = new DesertDataSource();
 
   void _sort/*<T>*/(Comparable<dynamic/*=T*/> getField(Desert d), int columnIndex, bool ascending) {
-    _deserts._sort/*<T>*/(getField, ascending);
+    _desertsDataSource._sort/*<T>*/(getField, ascending);
     setState(() {
       _sortColumnIndex = columnIndex;
       _sortAscending = ascending;
@@ -153,10 +169,12 @@ class _DataTableDemoState extends State<DataTableDemo> {
         padding: const EdgeInsets.all(20.0),
         children: <Widget>[
           new PaginatedDataTable(
+            header: new Text('Nutrition'),
             rowsPerPage: _rowsPerPage,
             onRowsPerPageChanged: (int value) { setState(() { _rowsPerPage = value; }); },
             sortColumnIndex: _sortColumnIndex,
             sortAscending: _sortAscending,
+            onSelectAll: _desertsDataSource._selectAll,
             columns: <DataColumn>[
               new DataColumn(
                 label: new Text('Dessert (100g serving)'),
@@ -200,7 +218,7 @@ class _DataTableDemoState extends State<DataTableDemo> {
                 onSort: (int columnIndex, bool ascending) => _sort/*<num>*/((Desert d) => d.iron, columnIndex, ascending)
               ),
             ],
-            source: _deserts
+            source: _desertsDataSource
           )
         ]
       )

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

@@ -50,15 +50,21 @@ class ButtonTheme extends InheritedWidget {
     Widget child
   }) : super(key: key, child: child);
 
-  /// Creates a button theme that is appropriate for footer buttons.
+  /// Creates a button theme that is appropriate for button bars, as used in
+  /// dialog footers and in the headers of data tables.
   ///
   /// This theme is denser, with a smaller [minWidth] and [padding], than the
   /// default theme. Also, this theme uses [ButtonTextTheme.accent] rather than
   /// [ButtonTextTheme.normal].
   ///
+  /// For best effect, the label of the button at the edge of the container
+  /// should have text that ends up wider than 64.0 pixels. This ensures that
+  /// the alignment of the text matches the alignment of the edge of the
+  /// container.
+  ///
   /// For example, buttons at the bottom of [Dialog] or [Card] widgets use this
   /// button theme.
-  const ButtonTheme.footer({
+  const ButtonTheme.bar({
     Key key,
     this.textTheme: ButtonTextTheme.accent,
     this.minWidth: 64.0,

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

@@ -51,7 +51,7 @@ class ButtonBar extends StatelessWidget {
       ),
       child: new Row(
         mainAxisAlignment: alignment,
-        children: children.map((Widget child) {
+        children: children.map/*<Widget>*/((Widget child) {
           return new Padding(
             padding: new EdgeInsets.symmetric(horizontal: paddingUnit),
             child: child

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

@@ -54,4 +54,9 @@ abstract class DataTableSource extends ChangeNotifier {
   /// then later the exact number becomes available, then call
   /// [notifyListeners].
   bool get isRowCountApproximate;
+
+  /// Called to obtain the number of rows that are currently selected.
+  ///
+  /// If the selected row count changes, call [notifyListeners].
+  int get selectedRowCount;
 }
\ No newline at end of file

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

@@ -96,7 +96,7 @@ class Dialog extends StatelessWidget {
     }
 
     if (actions != null) {
-      dialogBody.add(new ButtonTheme.footer(
+      dialogBody.add(new ButtonTheme.bar(
         child: new ButtonBar(
           alignment: MainAxisAlignment.end,
           children: actions

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

@@ -4,9 +4,12 @@
 
 import 'dart:math' as math;
 
+import 'package:meta/meta.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/rendering.dart';
 
+import 'button.dart';
+import 'button_bar.dart';
 import 'card.dart';
 import 'data_table.dart';
 import 'data_table_source.dart';
@@ -23,6 +26,9 @@ import 'theme.dart';
 class PaginatedDataTable extends StatefulWidget {
   /// Creates a widget describing a paginated [DataTable] on a [Card].
   ///
+  /// The [header] should give the card's header, typically a [Text] widget. It
+  /// must not be null.
+  ///
   /// The [columns] argument must be a list of as many [DataColumn] objects as
   /// the table is to have columns, ignoring the leading checkbox column if any.
   /// The [columns] argument must have a length greater than zero and cannot be
@@ -43,10 +49,12 @@ class PaginatedDataTable extends StatefulWidget {
   /// widget unless the data table really is to now show entirely different
   /// data from a new source.
   ///
-  /// The [rowsPerPage] and [availableRowsPerPage] must not be null (though they
-  /// both have defaults, so don't have to be specified).
+  /// The [rowsPerPage] and [availableRowsPerPage] must not be null (they
+  /// both have defaults, though, so don't have to be specified).
   PaginatedDataTable({
     Key key,
+    @required this.header,
+    this.actions,
     this.columns,
     this.sortColumnIndex,
     this.sortAscending: true,
@@ -56,8 +64,9 @@ class PaginatedDataTable extends StatefulWidget {
     this.rowsPerPage: defaultRowsPerPage,
     this.availableRowsPerPage: const <int>[defaultRowsPerPage, defaultRowsPerPage * 2, defaultRowsPerPage * 5, defaultRowsPerPage * 10],
     this.onRowsPerPageChanged,
-    this.source
+    @required this.source
   }) : super(key: key) {
+    assert(header != null);
     assert(columns != null);
     assert(columns.length > 0);
     assert(sortColumnIndex == null || (sortColumnIndex >= 0 && sortColumnIndex < columns.length));
@@ -69,6 +78,24 @@ class PaginatedDataTable extends StatefulWidget {
     assert(source != null);
   }
 
+  /// The table card's header.
+  ///
+  /// This is typically a [Text] widget, but can also be a [ButtonBar] with
+  /// [FlatButton]s. Suitable defaults are automatically provided for the font,
+  /// button color, button padding, and so forth.
+  ///
+  /// If items in the table are selectable, then, when the selection is not
+  /// empty, the header is replaced by a count of the selected items.
+  final Widget header;
+
+  /// Icon buttons to show at the top right of the table.
+  ///
+  /// Typically, the exact actions included in this list will vary based on
+  /// whether any rows are selected or not.
+  ///
+  /// These should be size 24.0 with default padding (8.0).
+  final List<Widget> actions;
+
   /// The configuration and labels for the columns in the table.
   final List<DataColumn> columns;
 
@@ -142,6 +169,7 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
   int _firstRowIndex;
   int _rowCount;
   bool _rowCountApproximate;
+  int _selectedRowCount;
   final Map<int, DataRow> _rows = <int, DataRow>{};
 
   @override
@@ -172,6 +200,7 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
     setState(() {
       _rowCount = config.source.rowCount;
       _rowCountApproximate = config.source.isRowCountApproximate;
+      _selectedRowCount = config.source.selectedRowCount;
       _rows.clear();
     });
   }
@@ -237,7 +266,42 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
 
   @override
   Widget build(BuildContext context) {
-    final TextStyle textStyle = Theme.of(context).textTheme.caption;
+    // TODO(ianh): This whole build function doesn't handle RTL yet.
+    ThemeData themeData = Theme.of(context);
+    // HEADER
+    final List<Widget> headerWidgets = <Widget>[];
+    double leftPadding = 24.0;
+    if (_selectedRowCount == 0) {
+      headerWidgets.add(new Flexible(child: config.header));
+      if (config.header is ButtonBar) {
+        // We adjust the padding when a button bar is present, because the
+        // ButtonBar introduces 2 pixels of outside padding, plus 2 pixels
+        // around each button on each side, and the button itself will have 8
+        // pixels internally on each side, yet we want the left edge of the
+        // inside of the button to line up with the 24.0 left inset.
+        // TODO(ianh): Better magic. See https://github.com/flutter/flutter/issues/4460
+        leftPadding = 12.0;
+      }
+    } else if (_selectedRowCount == 1) {
+      // TODO(ianh): Real l10n.
+      headerWidgets.add(new Flexible(child: new Text('1 item selected')));
+    } else {
+      headerWidgets.add(new Flexible(child: new Text('$_selectedRowCount items selected')));
+    }
+    if (config.actions != null) {
+      headerWidgets.addAll(
+        config.actions.map/*<Widget>*/((Widget widget) {
+          return new Padding(
+            // 8.0 is the default padding of an icon button
+            padding: new EdgeInsets.only(left: 24.0 - 8.0 * 2.0),
+            child: widget
+          );
+        }).toList()
+      );
+    }
+
+    // FOOTER
+    final TextStyle footerTextStyle = themeData.textTheme.caption;
     final List<Widget> footerWidgets = <Widget>[];
     if (config.onRowsPerPageChanged != null) {
       List<Widget> availableRowsPerPage = config.availableRowsPerPage
@@ -256,7 +320,7 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
             items: availableRowsPerPage,
             value: config.rowsPerPage,
             onChanged: config.onRowsPerPageChanged,
-            style: textStyle,
+            style: footerTextStyle,
             iconSize: 24.0
           )
         ),
@@ -285,21 +349,39 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
       ),
       new Container(width: 14.0),
     ]);
+
+    // CARD
     return new Card(
-      // TODO(ianh): data table card headers
-      /*
-         - title, top left
-            - 20px Roboto Regular, black87
-         - persistent actions, top left
-         - header when there's a selection
-            - accent 50?
-            - show number of selected items
-            - different actions
-         - actions, top right
-            - 24px icons, black54
-      */
       child: new BlockBody(
         children: <Widget>[
+          new DefaultTextStyle(
+            // These typographic styles aren't quite the regular ones. We pick the closest ones from the regular
+            // list and then tweak them appropriately.
+            // See https://www.google.com/design/spec/components/data-tables.html#data-tables-tables-within-cards
+            style: _selectedRowCount > 0 ? themeData.textTheme.subhead.copyWith(color: themeData.accentColor)
+                                         : themeData.textTheme.title.copyWith(fontWeight: FontWeight.w400),
+            child: new IconTheme(
+              data: new IconThemeData(
+                opacity: 0.54
+              ),
+              child: new ButtonTheme.bar(
+                child: new Container(
+                  height: 64.0,
+                  padding: new EdgeInsets.fromLTRB(leftPadding, 0.0, 14.0, 0.0),
+                  // TODO(ianh): This decoration will prevent ink splashes from being visible.
+                  // Instead, we should have a widget that prints the decoration on the material.
+                  // See https://github.com/flutter/flutter/issues/3782
+                  decoration: _selectedRowCount > 0 ? new BoxDecoration(
+                    backgroundColor: themeData.secondaryHeaderColor
+                  ) : null,
+                  child: new Row(
+                    mainAxisAlignment: MainAxisAlignment.end,
+                    children: headerWidgets
+                  )
+                )
+              )
+            )
+          ),
           new ScrollableViewport(
             scrollDirection: Axis.horizontal,
             child: new DataTable(
@@ -312,7 +394,7 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
             )
           ),
           new DefaultTextStyle(
-            style: textStyle,
+            style: footerTextStyle,
             child: new IconTheme(
               data: new IconThemeData(
                 opacity: 0.54

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

@@ -67,6 +67,7 @@ class ThemeData {
     Color unselectedWidgetColor,
     Color disabledColor,
     Color buttonColor,
+    Color secondaryHeaderColor,
     Color textSelectionColor,
     Color textSelectionHandleColor,
     Color backgroundColor,
@@ -93,6 +94,7 @@ class ThemeData {
     unselectedWidgetColor ??= isDark ? Colors.white70 : Colors.black54;
     disabledColor ??= isDark ? Colors.white30 : Colors.black26;
     buttonColor ??= isDark ? primarySwatch[600] : Colors.grey[300];
+    secondaryHeaderColor ??= primarySwatch[50]; // TODO(ianh): dark theme support (https://github.com/flutter/flutter/issues/3370)
     textSelectionColor ??= isDark ? accentColor : primarySwatch[200];
     textSelectionHandleColor ??= isDark ? Colors.tealAccent[400] : primarySwatch[300];
     backgroundColor ??= isDark ? Colors.grey[700] : primarySwatch[200];
@@ -117,6 +119,7 @@ class ThemeData {
       unselectedWidgetColor: unselectedWidgetColor,
       disabledColor: disabledColor,
       buttonColor: buttonColor,
+      secondaryHeaderColor: secondaryHeaderColor,
       textSelectionColor: textSelectionColor,
       textSelectionHandleColor: textSelectionHandleColor,
       backgroundColor: backgroundColor,
@@ -150,6 +153,7 @@ class ThemeData {
     this.unselectedWidgetColor,
     this.disabledColor,
     this.buttonColor,
+    this.secondaryHeaderColor,
     this.textSelectionColor,
     this.textSelectionHandleColor,
     this.backgroundColor,
@@ -174,6 +178,7 @@ class ThemeData {
     assert(unselectedWidgetColor != null);
     assert(disabledColor != null);
     assert(buttonColor != null);
+    assert(secondaryHeaderColor != null);
     assert(textSelectionColor != null);
     assert(textSelectionHandleColor != null);
     assert(disabledColor != null);
@@ -257,6 +262,12 @@ class ThemeData {
   /// The default color of the [Material] used in [RaisedButton]s.
   final Color buttonColor;
 
+  /// The color of the header of a [PaginatedDataTable] when there are selected rows.
+  // According to the spec for data tables:
+  // https://material.google.com/components/data-tables.html#data-tables-tables-within-cards
+  // ...this should be the "50-value of secondary app color".
+  final Color secondaryHeaderColor;
+
   /// The color of text selections in text fields, such as [Input].
   final Color textSelectionColor;
 
@@ -301,6 +312,7 @@ class ThemeData {
       unselectedWidgetColor: Color.lerp(begin.unselectedWidgetColor, end.unselectedWidgetColor, t),
       disabledColor: Color.lerp(begin.disabledColor, end.disabledColor, t),
       buttonColor: Color.lerp(begin.buttonColor, end.buttonColor, t),
+      secondaryHeaderColor: Color.lerp(begin.secondaryHeaderColor, end.secondaryHeaderColor, t),
       textSelectionColor: Color.lerp(begin.textSelectionColor, end.textSelectionColor, t),
       textSelectionHandleColor: Color.lerp(begin.textSelectionHandleColor, end.textSelectionHandleColor, t),
       backgroundColor: Color.lerp(begin.backgroundColor, end.backgroundColor, t),
@@ -332,6 +344,7 @@ class ThemeData {
            (otherData.unselectedWidgetColor == unselectedWidgetColor) &&
            (otherData.disabledColor == disabledColor) &&
            (otherData.buttonColor == buttonColor) &&
+           (otherData.secondaryHeaderColor == secondaryHeaderColor) &&
            (otherData.textSelectionColor == textSelectionColor) &&
            (otherData.textSelectionHandleColor == textSelectionHandleColor) &&
            (otherData.backgroundColor == backgroundColor) &&
@@ -360,12 +373,13 @@ class ThemeData {
       unselectedWidgetColor,
       disabledColor,
       buttonColor,
+      secondaryHeaderColor,
       textSelectionColor,
       textSelectionHandleColor,
       backgroundColor,
       accentColor,
+      accentColorBrightness,
       hashValues( // Too many values.
-        accentColorBrightness,
         indicatorColor,
         hintColor,
         errorColor,