cake_wallet/lib/src/widgets/picker.dart

import 'dart:ui';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:cake_wallet/src/widgets/alert_background.dart';
import 'package:cake_wallet/src/widgets/cake_scrollbar.dart';
import 'package:cake_wallet/src/widgets/alert_close_button.dart';
import 'package:cake_wallet/palette.dart';

class Picker<Item extends Object> extends StatefulWidget {
  Picker({
    @required this.selectedAtIndex,
    @required this.items,
    @required this.title,
    @required this.onItemSelected,
    this.displayItem,
    this.images,
    this.description,
    this.mainAxisAlignment = MainAxisAlignment.start,
  });

  final int selectedAtIndex;
  final List<Item> items;
  final List<Image> images;
  final String title;
  final String description;
  final Function(Item) onItemSelected;
  final MainAxisAlignment mainAxisAlignment;
  final String Function(Item) displayItem;

  @override
  PickerState createState() => PickerState<Item>(items, images, onItemSelected);
}

class PickerState<Item> extends State<Picker> {
  PickerState(this.items, this.images, this.onItemSelected);

  final Function(Item) onItemSelected;
  final List<Item> items;
  final List<Image> images;

  final closeButton = Image.asset(
    'assets/images/close.png',
    color: Palette.darkBlueCraiola,
  );
  ScrollController controller = ScrollController();

  final double backgroundHeight = 193;
  final double thumbHeight = 72;
  double fromTop = 0;

  @override
  Widget build(BuildContext context) {
    controller.addListener(() {
      fromTop = controller.hasClients
          ? (controller.offset /
              controller.position.maxScrollExtent *
              (backgroundHeight - thumbHeight))
          : 0;
      setState(() {});
    });

    final isShowScrollThumb = items != null ? items.length > 3 : false;

    return AlertBackground(
        child: Stack(
      alignment: Alignment.center,
      children: <Widget>[
        Column(
          mainAxisSize: MainAxisSize.min,
          children: <Widget>[
            Container(
              padding: EdgeInsets.only(left: 24, right: 24),
              child: Text(
                widget.title,
                textAlign: TextAlign.center,
                style: TextStyle(
                    fontSize: 18,
                    fontFamily: 'Lato',
                    fontWeight: FontWeight.bold,
                    decoration: TextDecoration.none,
                    color: Colors.white),
              ),
            ),
            Padding(
              padding: EdgeInsets.only(left: 24, right: 24, top: 24),
              child: GestureDetector(
                onTap: () => null,
                child: ClipRRect(
                  borderRadius: BorderRadius.all(Radius.circular(14)),
                  child: Container(
                      height: 233,
                      color: Theme.of(context).accentTextTheme.title.color,
                      child: Stack(
                        alignment: Alignment.center,
                        children: <Widget>[
                          ListView.separated(
                            padding: EdgeInsets.all(0),
                            controller: controller,
                            separatorBuilder: (context, index) => Divider(
                              color: Theme.of(context)
                                  .accentTextTheme
                                  .title
                                  .backgroundColor,
                              height: 1,
                            ),
                            itemCount: items == null ? 0 : items.length,
                            itemBuilder: (context, index) {
                              final item = items[index];
                              final image =
                                  images != null ? images[index] : null;
                              final isItemSelected =
                                  index == widget.selectedAtIndex;

                              final color = isItemSelected
                                  ? Theme.of(context).textTheme.body2.color
                                  : Theme.of(context)
                                      .accentTextTheme
                                      .title
                                      .color;
                              final textColor = isItemSelected
                                  ? Palette.blueCraiola
                                  : Theme.of(context)
                                      .primaryTextTheme
                                      .title
                                      .color;

                              return GestureDetector(
                                onTap: () {
                                  if (onItemSelected == null) {
                                    return;
                                  }
                                  Navigator.of(context).pop();
                                  onItemSelected(item);
                                },
                                child: Container(
                                  height: 77,
                                  padding: EdgeInsets.only(left: 24, right: 24),
                                  color: color,
                                  child: Row(
                                    mainAxisSize: MainAxisSize.max,
                                    mainAxisAlignment: widget.mainAxisAlignment,
                                    crossAxisAlignment:
                                        CrossAxisAlignment.center,
                                    children: <Widget>[
                                      image ?? Offstage(),
                                      Padding(
                                        padding: EdgeInsets.only(
                                            left: image != null ? 12 : 0),
                                        child: Text(
                                          widget.displayItem?.call(item) ??
                                              item.toString(),
                                          style: TextStyle(
                                            fontSize: 18,
                                            fontFamily: 'Lato',
                                            fontWeight: FontWeight.w600,
                                            color: textColor,
                                            decoration: TextDecoration.none,
                                          ),
                                        ),
                                      )
                                    ],
                                  ),
                                ),
                              );
                            },
                          ),
                          ((widget.description != null) &&
                                  (widget.description.isNotEmpty))
                              ? Positioned(
                                  bottom: 24,
                                  left: 24,
                                  right: 24,
                                  child: Text(
                                    widget.description,
                                    textAlign: TextAlign.center,
                                    style: TextStyle(
                                        fontSize: 12,
                                        fontWeight: FontWeight.w500,
                                        fontFamily: 'Lato',
                                        decoration: TextDecoration.none,
                                        color: Theme.of(context)
                                            .primaryTextTheme
                                            .title
                                            .color),
                                  ))
                              : Offstage(),
                          isShowScrollThumb
                              ? CakeScrollbar(
                                  backgroundHeight: backgroundHeight,
                                  thumbHeight: thumbHeight,
                                  fromTop: fromTop)
                              : Offstage(),
                        ],
                      )),
                ),
              ),
            )
          ],
        ),
        AlertCloseButton(image: closeButton)
      ],
    ));
  }
}