Add support for custom semantics actions to Android and iOS. (#18882)

examples/flutter_gallery/lib/demo/material/leave_behind_demo.dart

@@ -5,6 +5,7 @@
 import 'package:collection/collection.dart' show lowerBound;
 
 import 'package:flutter/material.dart';
+import 'package:flutter/semantics.dart';
 
 enum LeaveBehindDemoAction {
   reset,
@@ -85,52 +86,55 @@ class LeaveBehindDemoState extends State<LeaveBehindDemo> {
     });
   }
 
-  Widget buildItem(LeaveBehindItem item) {
-    final ThemeData theme = Theme.of(context);
-    return new Dismissible(
-      key: new ObjectKey(item),
-      direction: _dismissDirection,
-      onDismissed: (DismissDirection direction) {
+  void _handleArchive(LeaveBehindItem item) {
     setState(() {
       leaveBehindItems.remove(item);
     });
-        final String action = (direction == DismissDirection.endToStart) ? 'archived' : 'deleted';
     _scaffoldKey.currentState.showSnackBar(new SnackBar(
-          content: new Text('You $action item ${item.index}'),
+      content: new Text('You archived item ${item.index}'),
       action: new SnackBarAction(
         label: 'UNDO',
         onPressed: () { handleUndo(item); }
       )
     ));
-      },
-      background: new Container(
-        color: theme.primaryColor,
-        child: const ListTile(
-          leading: const Icon(Icons.delete, color: Colors.white, size: 36.0)
-        )
-      ),
-      secondaryBackground: new Container(
-        color: theme.primaryColor,
-        child: const ListTile(
-          trailing: const Icon(Icons.archive, color: Colors.white, size: 36.0)
-        )
-      ),
-      child: new Container(
-        decoration: new BoxDecoration(
-          color: theme.canvasColor,
-          border: new Border(bottom: new BorderSide(color: theme.dividerColor))
-        ),
-        child: new ListTile(
-          title: new Text(item.name),
-          subtitle: new Text('${item.subject}\n${item.body}'),
-          isThreeLine: true
-        )
+  }
+
+  void _handleDelete(LeaveBehindItem item) {
+    setState(() {
+      leaveBehindItems.remove(item);
+    });
+    _scaffoldKey.currentState.showSnackBar(new SnackBar(
+      content: new Text('You deleted item ${item.index}'),
+      action: new SnackBarAction(
+        label: 'UNDO',
+        onPressed: () { handleUndo(item); }
       )
-    );
+    ));
   }
 
   @override
   Widget build(BuildContext context) {
+    Widget body;
+    if (leaveBehindItems.isEmpty) {
+      body = new Center(
+        child: new RaisedButton(
+          onPressed: () => handleDemoAction(LeaveBehindDemoAction.reset),
+          child: const Text('Reset the list'),
+        ),
+      );
+    } else {
+      body = new ListView(
+        children: leaveBehindItems.map((LeaveBehindItem item) {
+          return new _LeaveBehindListItem(
+            item: item,
+            onArchive: _handleArchive,
+            onDelete: _handleDelete,
+            dismissDirection: _dismissDirection,
+          );
+        }).toList()
+      );
+    }
+
     return new Scaffold(
       key: _scaffoldKey,
       appBar: new AppBar(
@@ -163,15 +167,73 @@ class LeaveBehindDemoState extends State<LeaveBehindDemo> {
           )
         ]
       ),
-      body: leaveBehindItems.isEmpty
-          ? new Center(
-              child: new RaisedButton(
-                onPressed: () => handleDemoAction(LeaveBehindDemoAction.reset),
-                child: const Text('Reset the list'),
+      body: body,
+    );
+  }
+}
+
+class _LeaveBehindListItem extends StatelessWidget {
+  const _LeaveBehindListItem({
+    Key key,
+    @required this.item,
+    @required this.onArchive,
+    @required this.onDelete,
+    @required this.dismissDirection,
+  }) : super(key: key);
+
+  final LeaveBehindItem item;
+  final DismissDirection dismissDirection;
+  final void Function(LeaveBehindItem) onArchive;
+  final void Function(LeaveBehindItem) onDelete;
+
+  void _handleArchive() {
+    onArchive(item);
+  }
+
+  void _handleDelete() {
+    onDelete(item);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final ThemeData theme = Theme.of(context);
+    return new Semantics(
+      customSemanticsActions: <CustomSemanticsAction, VoidCallback>{
+        const CustomSemanticsAction(label: 'Archive'): _handleArchive,
+        const CustomSemanticsAction(label: 'Delete'): _handleDelete,
+      },
+      child: new Dismissible(
+        key: new ObjectKey(item),
+        direction: dismissDirection,
+        onDismissed: (DismissDirection direction) {
+          if (direction == DismissDirection.endToStart)
+            _handleArchive();
+          else
+            _handleDelete();
+        },
+        background: new Container(
+          color: theme.primaryColor,
+          child: const ListTile(
+            leading: const Icon(Icons.delete, color: Colors.white, size: 36.0)
+          )
         ),
+        secondaryBackground: new Container(
+          color: theme.primaryColor,
+          child: const ListTile(
+            trailing: const Icon(Icons.archive, color: Colors.white, size: 36.0)
           )
-          : new ListView(
-             children: leaveBehindItems.map(buildItem).toList()
+        ),
+        child: new Container(
+          decoration: new BoxDecoration(
+            color: theme.canvasColor,
+            border: new Border(bottom: new BorderSide(color: theme.dividerColor))
+          ),
+          child: new ListTile(
+            title: new Text(item.name),
+            subtitle: new Text('${item.subject}\n${item.body}'),
+            isThreeLine: true
+          ),
+        ),
       ),
     );
   }

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

@@ -3159,6 +3159,7 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
     SetSelectionHandler onSetSelection,
     VoidCallback onDidGainAccessibilityFocus,
     VoidCallback onDidLoseAccessibilityFocus,
+    Map<CustomSemanticsAction, VoidCallback> customSemanticsActions,
   }) : assert(container != null),
        _container = container,
        _explicitChildNodes = explicitChildNodes,
@@ -3197,6 +3198,7 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
        _onSetSelection = onSetSelection,
        _onDidGainAccessibilityFocus = onDidGainAccessibilityFocus,
        _onDidLoseAccessibilityFocus = onDidLoseAccessibilityFocus,
+       _customSemanticsActions = customSemanticsActions,
        super(child);
 
   /// If 'container' is true, this [RenderObject] will introduce a new
@@ -3779,6 +3781,24 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
       markNeedsSemanticsUpdate();
   }
 
+  /// The handlers and supported [CustomSemanticsAction]s for this node.
+  /// 
+  /// These handlers are called whenever the user performs the associated
+  /// custom accessibility action from a special platform menu. Providing any
+  /// custom actions here also adds [SemanticsAction.customAction] to the node.
+  /// 
+  /// See also:
+  /// 
+  ///   * [CustomSemanticsAction], for an explaination of custom actions.
+  Map<CustomSemanticsAction, VoidCallback> get customSemanticsActions => _customSemanticsActions;
+  Map<CustomSemanticsAction, VoidCallback> _customSemanticsActions;
+  set customSemanticsActions(Map<CustomSemanticsAction, VoidCallback> value) {
+    if (_customSemanticsActions == value)
+      return;
+    _customSemanticsActions = value;
+    markNeedsSemanticsUpdate();
+  }
+
   @override
   void describeSemanticsConfiguration(SemanticsConfiguration config) {
     super.describeSemanticsConfiguration(config);
@@ -3860,6 +3880,8 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
       config.onDidGainAccessibilityFocus = _performDidGainAccessibilityFocus;
     if (onDidLoseAccessibilityFocus != null)
       config.onDidLoseAccessibilityFocus = _performDidLoseAccessibilityFocus;
+    if (customSemanticsActions != null)
+      config.customSemanticsActions = _customSemanticsActions;
   }
 
   void _performTap() {

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

@@ -5089,6 +5089,7 @@ class Semantics extends SingleChildRenderObjectWidget {
     SetSelectionHandler onSetSelection,
     VoidCallback onDidGainAccessibilityFocus,
     VoidCallback onDidLoseAccessibilityFocus,
+    Map<CustomSemanticsAction, VoidCallback> customSemanticsActions,
   }) : this.fromProperties(
     key: key,
     child: child,
@@ -5129,6 +5130,7 @@ class Semantics extends SingleChildRenderObjectWidget {
       onMoveCursorBackwardByCharacter: onMoveCursorBackwardByCharacter,
       onDidGainAccessibilityFocus: onDidGainAccessibilityFocus,
       onDidLoseAccessibilityFocus: onDidLoseAccessibilityFocus,
+      customSemanticsActions: customSemanticsActions,
     onSetSelection: onSetSelection,),
   );
 
@@ -5216,6 +5218,7 @@ class Semantics extends SingleChildRenderObjectWidget {
       onSetSelection: properties.onSetSelection,
       onDidGainAccessibilityFocus: properties.onDidGainAccessibilityFocus,
       onDidLoseAccessibilityFocus: properties.onDidLoseAccessibilityFocus,
+      customSemanticsActions: properties.customSemanticsActions,
     );
   }
 
@@ -5270,7 +5273,8 @@ class Semantics extends SingleChildRenderObjectWidget {
       ..onMoveCursorBackwardByCharacter = properties.onMoveCursorForwardByCharacter
       ..onSetSelection = properties.onSetSelection
       ..onDidGainAccessibilityFocus = properties.onDidGainAccessibilityFocus
-      ..onDidLoseAccessibilityFocus = properties.onDidLoseAccessibilityFocus;
+      ..onDidLoseAccessibilityFocus = properties.onDidLoseAccessibilityFocus
+      ..customSemanticsActions = properties.customSemanticsActions;
   }
 
   @override

packages/flutter/test/semantics/custom_semantics_action_test.dart

+import 'package:test/test.dart';
+import 'package:flutter/semantics.dart';
+
+void main() {
+  group(CustomSemanticsAction, () {
+
+    test('is provided a canonical id based on the label', () {
+      final CustomSemanticsAction action1 = new CustomSemanticsAction(label: _nonconst('test'));
+      final CustomSemanticsAction action2 = new CustomSemanticsAction(label: _nonconst('test'));
+      final CustomSemanticsAction action3 = new CustomSemanticsAction(label: _nonconst('not test'));
+      final int id1 = CustomSemanticsAction.getIdentifier(action1);
+      final int id2 = CustomSemanticsAction.getIdentifier(action2);
+      final int id3 = CustomSemanticsAction.getIdentifier(action3);
+
+      expect(id1, id2);
+      expect(id2, isNot(id3));
+      expect(CustomSemanticsAction.getAction(id1), action1);
+      expect(CustomSemanticsAction.getAction(id2), action1);
+      expect(CustomSemanticsAction.getAction(id3), action3);
+    });
+
+  });
+}
+
+T _nonconst<T>(T value) => value;

packages/flutter/test/semantics/semantics_test.dart

@@ -337,6 +337,7 @@ void main() {
       '   mergeAllDescendantsIntoThisNode: false\n'
       '   Rect.fromLTRB(0.0, 0.0, 0.0, 0.0)\n'
       '   actions: []\n'
+      '   customActions: []\n'
       '   flags: []\n'
       '   invisible\n'
       '   isHidden: false\n'
@@ -404,8 +405,49 @@ void main() {
     );
   });
 
+  test('Custom actions debug properties', () {
+    final SemanticsConfiguration configuration = new SemanticsConfiguration();
+    const CustomSemanticsAction action1 = const CustomSemanticsAction(label: 'action1');
+    const CustomSemanticsAction action2 = const CustomSemanticsAction(label: 'action2');
+    const CustomSemanticsAction action3 = const CustomSemanticsAction(label: 'action3');
+    configuration.customSemanticsActions = <CustomSemanticsAction, VoidCallback>{
+      action1: () {},
+      action2: () {},
+      action3: () {},
+    };
+    final SemanticsNode actionNode = new SemanticsNode();
+    actionNode.updateWith(config: configuration);
+
+    expect(
+      actionNode.toStringDeep(minLevel: DiagnosticLevel.hidden),
+      'SemanticsNode#1\n'
+      '   STALE\n'
+      '   owner: null\n'
+      '   isMergedIntoParent: false\n'
+      '   mergeAllDescendantsIntoThisNode: false\n'
+      '   Rect.fromLTRB(0.0, 0.0, 0.0, 0.0)\n'
+      '   actions: customAction\n'
+      '   customActions: action1, action2, action3\n'
+      '   flags: []\n'
+      '   invisible\n'
+      '   isHidden: false\n'
+      '   label: ""\n'
+      '   value: ""\n'
+      '   increasedValue: ""\n'
+      '   decreasedValue: ""\n'
+      '   hint: ""\n'
+      '   textDirection: null\n'
+      '   sortKey: null\n'
+      '   scrollExtentMin: null\n'
+      '   scrollPosition: null\n'
+      '   scrollExtentMax: null\n'
+    );
+
+  });
+
   test('SemanticsConfiguration getter/setter', () {
     final SemanticsConfiguration config = new SemanticsConfiguration();
+    const CustomSemanticsAction customAction = const CustomSemanticsAction(label: 'test');
 
     expect(config.isSemanticBoundary, isFalse);
     expect(config.isButton, isFalse);
@@ -428,6 +470,7 @@ void main() {
     expect(config.onMoveCursorForwardByCharacter, isNull);
     expect(config.onMoveCursorBackwardByCharacter, isNull);
     expect(config.onTap, isNull);
+    expect(config.customSemanticsActions[customAction], isNull);
 
     config.isSemanticBoundary = true;
     config.isButton = true;
@@ -450,6 +493,7 @@ void main() {
     final MoveCursorHandler onMoveCursorForwardByCharacter = (bool _) { };
     final MoveCursorHandler onMoveCursorBackwardByCharacter = (bool _) { };
     final VoidCallback onTap = () { };
+    final VoidCallback onCustomAction = () {};
 
     config.onShowOnScreen = onShowOnScreen;
     config.onScrollDown = onScrollDown;
@@ -462,6 +506,7 @@ void main() {
     config.onMoveCursorForwardByCharacter = onMoveCursorForwardByCharacter;
     config.onMoveCursorBackwardByCharacter = onMoveCursorBackwardByCharacter;
     config.onTap = onTap;
+    config.customSemanticsActions[customAction] = onCustomAction;
 
     expect(config.isSemanticBoundary, isTrue);
     expect(config.isButton, isTrue);
@@ -484,6 +529,7 @@ void main() {
     expect(config.onMoveCursorForwardByCharacter, same(onMoveCursorForwardByCharacter));
     expect(config.onMoveCursorBackwardByCharacter, same(onMoveCursorBackwardByCharacter));
     expect(config.onTap, same(onTap));
+    expect(config.customSemanticsActions[customAction], same(onCustomAction));
   });
 }