linkage_picker

A cupertino-picker-style linkage picker widget. Provided [DatePicker] implement and you can extend [LinkagePickerWidget] to achieve what you want in more scene easily.

DatePicker

DatePicker is a pre-archive linkage picker

DatePicker(
  start: DateTime(2000, today.month, today.day),
  end: DateTime(2050, today.month, today.day),
  date: date,
)

You can use showAsBottomSheet to show DatePicker as BottomSheet-Style

DatePicker(
  ...
).showAsBottomSheet(context)

Or wrap it anywhere just like this

ValueListenableBuilder<bool>(
  valueListenable: showPicker,
  builder: (context, value, _) {
    return value
        ? Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              DatePicker(
                ...,
                onControllerCreated: (controller) {
                  this.controller = controller;
                },
              ),
              TextButton(
                onPressed: () {
                  showPicker.value = false;
                  final result = controller.result;
                  if (result != null) {
                    content.value = DateFormat('yyyy-MM-dd').format(result);
                  }
                },
                child: const Text('Confirm')),
            ],
          )
        : const SizedBox.shrink();
  })

CustomPicker

You can extend LinkagePickerWidget to develop your own linkage picker

class CustomPicker extends LinkagePickerWidget<CustomData, String> {
  CustomPicker()
      : super(
          maxLevel: LinkagePickerLevel.second,
          dataBuilder: (level, parent) {
            return switch (level) {
              LinkagePickerLevel.first => LinkagePickerData<CustomData>[...],
              LinkagePickerLevel.second => LinkagePickerData<CustomData>[...],
              _ => throw UnimplementedError(),
            };
          },
          equalizer: (level, value1, value2) {
            return switch (level) {
              _ => (value1 as CustomData).equals(value2 as CustomData),
            };
          },
          resultConverter: (selection) {
            final getResultString(selection.first, selection.last);
          },
          conflictResolver: (level, previous, currents) {
            return switch (level) {
              LinkagePickerLevel.first => null,
              LinkagePickerLevel.second =>
                (previous as CustomData).copyWith(...),
              _ => throw UnimplementedError(),
            };
          },
          initialValue: <CustomData>[...],
          pickerStyle: LinkagePickerStyle(
            itemBuilder: (level, data, selected) {
              switch (level) {
                case LinkagePickerLevel.first:
                  return buildFirstPickerItem(data, selected);
                case LinkagePickerLevel.second:
                  return buildSecondPickerItem(data, selected);
                default:
                  throw UnimplementedError();
              }
            },
          ),
        );
}

LinkagePickerWidget<T,R>

• T: The type of the data source value
• R: The type of the result
• maxLevel: The maximum level of the picker
• dataBuilder: Return the datasource from current level and parent data.
• equalizer: Tell Widget whether two value are equal in current level.
• resultConverter: Convert the result to the type you want
• conflictResolver: Convert picker selected result to navigation result.
• initialValue: The initial value of picker
• pickerStyle: Customize the style of the picker
• onControllerCreated: Callback when controller created

LinkagePickerStyle

• diameterRatio: Same as [CupertinoPicker.diameterRatio]
• itemExtent: Same as [CupertinoPicker.itemExtent]
• backgroundColor: Same as [CupertinoPicker.backgroundColor]
• offAxisFraction: Same as [CupertinoPicker.offAxisFraction]
• squeeze: Same as [CupertinoPicker.squeeze]
• useMagnifier: Same as [CupertinoPicker.useMagnifier]
• magnification: Same as [CupertinoPicker.magnification]
• selectionOverlay: Same as [CupertinoPicker.selectionOverlay]
• heightRatio: The ratio of the height of the picker to the height of the item
• itemBuilder: Customize the item of the picker