用户输入与无障碍功能

dart

return Listener(
  onPointerSignal: (event) {
    if (event is PointerScrollEvent) print(event.scrollDelta.dy);
  },
  child: ListView(),
);

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dart

class _BasicActionDetectorState extends State<BasicActionDetector> {
  bool _hasFocus = false;
  @override
  Widget build(BuildContext context) {
    return FocusableActionDetector(
      onFocusChange: (value) => setState(() => _hasFocus = value),
      actions: <Type, Action<Intent>>{
        ActivateIntent: CallbackAction<Intent>(
          onInvoke: (intent) {
            print('Enter or Space was pressed!');
            return null;
          },
        ),
      },
      child: Stack(
        clipBehavior: Clip.none,
        children: [
          const FlutterLogo(size: 100),
          // Position focus in the negative margin for a cool effect
          if (_hasFocus)
            Positioned(
              left: -4,
              top: -4,
              bottom: -4,
              right: -4,
              child: _roundedBorder(),
            ),
        ],
      ),
    );
  }
}

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dart

return Column(
  children: [
    FocusTraversalGroup(child: MyFormWithMultipleColumnsAndRows()),
    SubmitButton(),
  ],
);

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dart

  @override
  Widget build(BuildContext context) {
    return Focus(
      onKeyEvent: (node, event) {
        if (event is KeyDownEvent) {
          print(event.logicalKey);
        }
        return KeyEventResult.ignored;
      },
      child: ConstrainedBox(
        constraints: const BoxConstraints(maxWidth: 400),
        child: const TextField(
          decoration: InputDecoration(border: OutlineInputBorder()),
        ),
      ),
    );
  }
}

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dart

// Define a class for each type of shortcut action you want
class CreateNewItemIntent extends Intent {
  const CreateNewItemIntent();
}
​
Widget build(BuildContext context) {
  return Shortcuts(
    // Bind intents to key combinations
    shortcuts: const <ShortcutActivator, Intent>{
      SingleActivator(LogicalKeyboardKey.keyN, control: true):
          CreateNewItemIntent(),
    },
    child: Actions(
      // Bind intents to an actual method in your code
      actions: <Type, Action<Intent>>{
        CreateNewItemIntent: CallbackAction<CreateNewItemIntent>(
          onInvoke: (intent) => _createNewItem(),
        ),
      },
      // Your sub-tree must be wrapped in a focusNode, so it can take focus.
      child: Focus(autofocus: true, child: Container()),
    ),
  );
}

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dart

@override
void initState() {
  super.initState();
  HardwareKeyboard.instance.addHandler(_handleKey);
}
​
@override
void dispose() {
  HardwareKeyboard.instance.removeHandler(_handleKey);
  super.dispose();
}

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dart

static bool isKeyDown(Set<LogicalKeyboardKey> keys) {
  return keys
      .intersection(HardwareKeyboard.instance.logicalKeysPressed)
      .isNotEmpty;
}

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dart

bool _handleKey(KeyEvent event) {
  bool isShiftDown = isKeyDown({
    LogicalKeyboardKey.shiftLeft,
    LogicalKeyboardKey.shiftRight,
  });
​
  if (isShiftDown && event.logicalKey == LogicalKeyboardKey.keyN) {
    _createNewItem();
    return true;
  }
​
  return false;
}

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dart

// Show hand cursor
return MouseRegion(
  cursor: SystemMouseCursors.click,
  // Request focus when clicked
  child: GestureDetector(
    onTap: () {
      Focus.of(context).requestFocus();
      _submit();
    },
    child: Logo(showBorder: hasFocus),
  ),
);

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dart

return MouseRegion(
  onEnter: (_) => setState(() => _isMouseOver = true),
  onExit: (_) => setState(() => _isMouseOver = false),
  onHover: (e) => print(e.localPosition),
  child: Container(
    height: 500,
    color: _isMouseOver ? Colors.blue : Colors.black,
  ),
);

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dart

double densityAmt = touchMode ? 0.0 : -1.0;
VisualDensity density = VisualDensity(
  horizontal: densityAmt,
  vertical: densityAmt,
);
return MaterialApp(
  theme: ThemeData(visualDensity: density),
  home: MainAppScaffold(),
  debugShowCheckedModeBanner: false,
);

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dart

VisualDensity density = Theme.of(context).visualDensity;

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