tangheem/lib/widgets/auto_scroll_view/scroll_id.dart

import 'package:flutter/material.dart';

class ScrollToId {
  final ScrollController scrollController;
  List<ScrollContentWithKey> scrollContentsList = [];
  Axis scrollDirection;

  ScrollToId({this.scrollController});

  String idPosition() {
    double sumSize = 0;
    for (ScrollContentWithKey scrollContents in scrollContentsList) {
      if (scrollDirection == Axis.vertical) {
        sumSize += scrollContents.key.currentContext.size.height;
      } else {
        sumSize += scrollContents.key.currentContext.size.width;
      }

      if (scrollController.offset < sumSize) {
        return scrollContents.id;
      }
    }
    return null;
  }

  Future<void> animateTo(String id, {@required Duration duration, @required Curve curve}) async {
    Function _function = (double offset) {
      scrollController.animateTo(offset, duration: duration, curve: curve);
    };
    _scroll(id: id, scrollFunction: _function);
  }

  Future<void> jumpTo(String id) async {
    Function _function = (double offset) {
      scrollController.jumpTo(offset);
    };
    _scroll(id: id, scrollFunction: _function);
  }

  Future<void> animateToNext({@required Duration duration, @required Curve curve}) async {
    Function _function = (double offset) {
      scrollController.animateTo(offset, duration: duration, curve: curve);
    };
    _scroll(id: _getNextId(number: 1), scrollFunction: _function);
  }

  Future<void> jumpToNext() async {
    Function _function = (double offset) {
      scrollController.jumpTo(offset);
    };
    _scroll(id: _getNextId(number: 1), scrollFunction: _function);
  }

  Future<void> animateToBefore({@required Duration duration, @required Curve curve}) async {
    Function _function = (double offset) {
      scrollController.animateTo(offset, duration: duration, curve: curve);
    };
    _scroll(id: _getNextId(number: -1), scrollFunction: _function);
  }

  Future<void> jumpToBefore() async {
    Function _function = (double offset) {
      scrollController.jumpTo(offset);
    };
    _scroll(id: _getNextId(number: -1), scrollFunction: _function);
  }

  String _getNextId({int number}) {
    double sumSize = 0;
    for (int i = 0; i < scrollContentsList.length; i++) {
      if (scrollDirection == Axis.vertical) {
        sumSize += scrollContentsList[i].key.currentContext.size.height;
      } else {
        sumSize += scrollContentsList[i].key.currentContext.size.width;
      }

      if (scrollController.offset < sumSize) {
        if (number == 1 && i == scrollContentsList.length - 1) return null;
        if (number == -1 && i == 0) return null;

        return scrollContentsList[i + number].id;
      }
    }
    return null;
  }

  void _scroll({String id, Function scrollFunction}) {
    double sumSize = 0;

    for (ScrollContentWithKey scrollContents in scrollContentsList) {
      if (scrollContents.id == id) {
        try {
          if (sumSize < scrollController.position.maxScrollExtent) {
            scrollFunction(sumSize);
            break;
          } else {
            scrollFunction(scrollController.position.maxScrollExtent);
            break;
          }
        } catch (e) {
          print('$e');
          break;
        }
      } else {
        try {
          if (scrollDirection == Axis.vertical) {
            sumSize += scrollContents.key.currentContext.size.height;
          } else {
            sumSize += scrollContents.key.currentContext.size.width;
          }
        } catch (e) {
          print('$e');
        }
      }
    }
  }
}

class ScrollContent {
  final String id;
  final Widget child;

  ScrollContent({@required this.id, @required this.child});
}

class ScrollContentWithKey {
  final Widget child;
  final String id;
  final GlobalKey key;

  ScrollContentWithKey({this.child, this.key, this.id});

  factory ScrollContentWithKey.fromWithout(ScrollContent scrollContent) {
    return ScrollContentWithKey(child: scrollContent.child, id: scrollContent.id, key: GlobalKey());
  }
}