处理用户输入

int count = 0;

@override
Widget build(BuildContext context) {
  return ElevatedButton(
    style: ElevatedButton.styleFrom(
      textStyle: const TextStyle(fontSize: 20),
    ),
    onPressed: () {
      setState(() {
        count += 1;
      });
    },
    child: const Text('Enabled'),
  );
}

@override
Widget build(BuildContext context) {
  return const SelectableText('''
Two households, both alike in dignity,
In fair Verona, where we lay our scene,
From ancient grudge break to new mutiny,
Where civil blood makes civil hands unclean.
From forth the fatal loins of these two foes''');
}

@override
Widget build(BuildContext context) {
  return RichText(
    text: TextSpan(
      text: 'Hello ',
      style: DefaultTextStyle.of(context).style,
      children: const <TextSpan>[
        TextSpan(text: 'bold', style: TextStyle(fontWeight: FontWeight.bold)),
        TextSpan(text: ' world!'),
      ],
    ),
  );
}

final TextEditingController _controller = TextEditingController();

@override
Widget build(BuildContext context) {
  return TextField(
    controller: _controller,
    decoration: const InputDecoration(
      border: OutlineInputBorder(),
      labelText: 'Mascot Name',
    ),
  );
}

enum Calendar { day, week, month, year }

// StatefulWidget...
Calendar calendarView = Calendar.day;

@override
Widget build(BuildContext context) {
  return SegmentedButton<Calendar>(
    segments: const <ButtonSegment<Calendar>>[
      ButtonSegment<Calendar>(
          value: Calendar.day,
          label: Text('Day'),
          icon: Icon(Icons.calendar_view_day)),
      ButtonSegment<Calendar>(
          value: Calendar.week,
          label: Text('Week'),
          icon: Icon(Icons.calendar_view_week)),
      ButtonSegment<Calendar>(
          value: Calendar.month,
          label: Text('Month'),
          icon: Icon(Icons.calendar_view_month)),
      ButtonSegment<Calendar>(
          value: Calendar.year,
          label: Text('Year'),
          icon: Icon(Icons.calendar_today)),
    ],
    selected: <Calendar>{calendarView},
    onSelectionChanged: (Set<Calendar> newSelection) {
      setState(() {
        Suggested change
        // By default there is only a single segment that can be
        // selected at one time, so its value is always the first
        // By default, only a single segment can be
        // selected at one time, so its value is always the first
        calendarView = newSelection.first;
      });
    },
  );
}

@override
Widget build(BuildContext context) {
  return const SizedBox(
    width: 500,
    child: Wrap(
      alignment: WrapAlignment.center,
      spacing: 8,
      runSpacing: 4,
      children: [
        Chip(
          avatar: CircleAvatar(
              backgroundImage: AssetImage('assets/images/dash_chef.png')),
          label: Text('Chef Dash'),
        ),
        Chip(
          avatar: CircleAvatar(
              backgroundImage:
                  AssetImage('assets/images/dash_firefighter.png')),
          label: Text('Firefighter Dash'),
        ),
        Chip(
          avatar: CircleAvatar(
              backgroundImage: AssetImage('assets/images/dash_musician.png')),
          label: Text('Musician Dash'),
        ),
        Chip(
          avatar: CircleAvatar(
              backgroundImage: AssetImage('assets/images/dash_artist.png')),
          label: Text('Artist Dash'),
        ),
      ],
    ),
  );
}

enum ColorLabel {
  blue('Blue', Colors.blue),
  pink('Pink', Colors.pink),
  green('Green', Colors.green),
  yellow('Orange', Colors.orange),
  grey('Grey', Colors.grey);

  const ColorLabel(this.label, this.color);
  final String label;
  final Color color;
}

// StatefulWidget...
@override
Widget build(BuildContext context) {
  return DropdownMenu<ColorLabel>(
    initialSelection: ColorLabel.green,
    controller: colorController,
    // requestFocusOnTap is enabled/disabled by platforms when it is null.
    // On mobile platforms, this is false by default. Setting this to true will
    // trigger focus request on the text field and virtual keyboard will appear
    // afterward. On desktop platforms however, this defaults to true.
    requestFocusOnTap: true,
    label: const Text('Color'),
    onSelected: (ColorLabel? color) {
      setState(() {
        selectedColor = color;
      });
    },
    dropdownMenuEntries: ColorLabel.values
      .map<DropdownMenuEntry<ColorLabel>>(
          (ColorLabel color) {
            return DropdownMenuEntry<ColorLabel>(
              value: color,
              label: color.label,
              enabled: color.label != 'Grey',
              style: MenuItemButton.styleFrom(
                foregroundColor: color.color,
              ),
            );
      }).toList(),
  );
}

double _currentVolume = 1;

@override
Widget build(BuildContext context) {
  return Slider(
    value: _currentVolume,
    max: 5,
    divisions: 5,
    label: _currentVolume.toString(),
    onChanged: (double value) {
      setState(() {
        _currentVolume = value;
      });
    },
  );
}

bool isChecked = false;

@override
Widget build(BuildContext context) {
  return Checkbox(
    checkColor: Colors.white,
    value: isChecked,
    onChanged: (bool? value) {
      setState(() {
        isChecked = value!;
      });
    },
  );
}

bool light = true;

@override
Widget build(BuildContext context) {
  return Switch(
    // This bool value toggles the switch.
    value: light,
    activeColor: Colors.red,
    onChanged: (bool value) {
      // This is called when the user toggles the switch.
      setState(() {
        light = value;
      });
    },
  );
}

enum Character { musician, chef, firefighter, artist }

class RadioExample extends StatefulWidget {
  const RadioExample({super.key});

  @override
  State<RadioExample> createState() => _RadioExampleState();
}

class _RadioExampleState extends State<RadioExample> {
  Character? _character = Character.musician;

  void setCharacter(Character? value) {
    setState(() {
      _character = value;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      children: <Widget>[
        ListTile(
          title: const Text('Musician'),
          leading: Radio<Character>(
            value: Character.musician,
            groupValue: _character,
            onChanged: setCharacter,
          ),
        ),
        ListTile(
          title: const Text('Chef'),
          leading: Radio<Character>(
            value: Character.chef,
            groupValue: _character,
            onChanged: setCharacter,
          ),
        ),
        ListTile(
          title: const Text('Firefighter'),
          leading: Radio<Character>(
            value: Character.firefighter,
            groupValue: _character,
            onChanged: setCharacter,
          ),
        ),
        ListTile(
          title: const Text('Artist'),
          leading: Radio<Character>(
            value: Character.artist,
            groupValue: _character,
            onChanged: setCharacter,
          ),
        ),
      ],
    );
  }
}

double timeDilation = 1.0;
bool _lights = false;

@override
Widget build(BuildContext context) {
  return Column(
    children: [
      CheckboxListTile(
        title: const Text('Animate Slowly'),
        value: timeDilation != 1.0,
        onChanged: (bool? value) {
          setState(() {
            timeDilation = value! ? 10.0 : 1.0;
          });
        },
        secondary: const Icon(Icons.hourglass_empty),
      ),
      SwitchListTile(
        title: const Text('Lights'),
        value: _lights,
        onChanged: (bool value) {
          setState(() {
            _lights = value;
          });
        },
        secondary: const Icon(Icons.lightbulb_outline),
      ),
    ],
  );
}

DateTime? selectedDate;

@override
Widget build(BuildContext context) {
  var date = selectedDate;

  return Column(children: [
    Text(
      date == null
          ? "You haven't picked a date yet."
          : DateFormat('MM-dd-yyyy').format(date),
    ),
    ElevatedButton.icon(
      icon: const Icon(Icons.calendar_today),
      onPressed: () async {
        var pickedDate = await showDatePicker(
          context: context,
          initialEntryMode: DatePickerEntryMode.calendarOnly,
          initialDate: DateTime.now(),
          firstDate: DateTime(2019),
          lastDate: DateTime(2050),
        );

        setState(() {
          selectedDate = pickedDate;
        });
      },
      label: const Text('Pick a date'),
    )
  ]);
}

TimeOfDay? selectedTime;

@override
Widget build(BuildContext context) {
  var time = selectedTime;

  return Column(children: [
    Text(
      time == null ? "You haven't picked a time yet." : time.format(context),
    ),
    ElevatedButton.icon(
      icon: const Icon(Icons.calendar_today),
      onPressed: () async {
        var pickedTime = await showTimePicker(
          context: context,
          initialEntryMode: TimePickerEntryMode.dial,
          initialTime: TimeOfDay.now(),
        );

        setState(() {
          selectedTime = pickedTime;
        });
      },
      label: const Text('Pick a time'),
    )
  ]);
}

List<int> items = List<int>.generate(100, (int index) => index);

@override
Widget build(BuildContext context) {
  return ListView.builder(
    itemCount: items.length,
    padding: const EdgeInsets.symmetric(vertical: 16),
    itemBuilder: (BuildContext context, int index) {
      return Dismissible(
        background: Container(
          color: Colors.green,
        ),
        key: ValueKey<int>(items[index]),
        onDismissed: (DismissDirection direction) {
          setState(() {
            items.removeAt(index);
          });
        },
        child: ListTile(
          title: Text(
            'Item ${items[index]}',
          ),
        ),
      );
    },
  );
}