A Flutter grid view which supports waterfall flow layout

waterfall_flow

a flutter grid view easy to build waterfall flow layout quickly.

use

• add library to your pubspec.yaml

dependencies:
  waterfall_flow: any

• import library in dart file

  import 'package:waterfall_flow/waterfall_flow.dart';
  

easy to use

you can define waterfall flow layout within sliverwaterfallflowdelegate.

            waterfallflow.builder(
              //cacheextent: 0.0,
              padding: edgeinsets.all(5.0),
              griddelegate: sliverwaterfallflowdelegate(
                  crossaxiscount: 2,
                  crossaxisspacing: 5.0,
                  mainaxisspacing: 5.0,
                  /// follow max child trailing layout offset and layout with full cross axis extend
                  /// last child as loadmore item/no more item in [gridview] and [waterfallflow]
                  /// with full cross axis extend
                  //  lastchildlayouttype.fullcrossaxisextend,

                  /// as foot at trailing and layout with full cross axis extend
                  /// show no more item at trailing when children are not full of viewport
                  /// if children is full of viewport, it's the same as fullcrossaxisextend
                  //  lastchildlayouttype.foot,
                  lastchildlayouttypebuilder: (index) => index == _list.length
                      ? lastchildlayouttype.foot
                      : lastchildlayouttype.none,
                  ),

collectgarbage

track the indexes are collect, you can collect garbage at that monment(for example image cache)

more detail

        waterfallflow.builder(
            griddelegate: sliverwaterfallflowdelegate(
                collectgarbage: (list<int> garbages) {
                  ///collectgarbage
                  garbages.foreach((index) {
                    final provider = extendednetworkimageprovider(
                      _list[index].imageurl,
                    );
                    provider.evict();
                  });
                },
              ),

viewportbuilder

track the indexes go into the viewport, it’s not include cache extent.

        waterfallflow.builder(
            griddelegate: sliverwaterfallflowdelegate(
                viewportbuilder: (int firstindex, int lastindex) {
                print("viewport : [$firstindex,$lastindex]");
                }),

lastchildlayouttypebuilder

build lastchild as special child in the case that it is loadmore/no more item.

        enum lastchildlayouttype {
        /// as default child
        none,

        /// follow max child trailing layout offset and layout with full cross axis extend
        /// last child as loadmore item/no more item in [extendedgridview] and [waterfallflow]
        /// with full cross axis extend
        fullcrossaxisextend,

        /// as foot at trailing and layout with full cross axis extend
        /// show no more item at trailing when children are not full of viewport
        /// if children is full of viewport, it's the same as fullcrossaxisextend
        foot,
        }

      waterfallflow.builder(
        griddelegate: sliverwaterfallflowdelegate(
            lastchildlayouttypebuilder: (index) => index == length
                ? lastchildlayouttype.foot
                : lastchildlayouttype.none,
            ),

closetotrailing

when reverse property of list is true, layout is as following.
it likes chat list, and new session will insert to zero index.
but it’s not right when items are not full of viewport.

     trailing
-----------------
|               |
|               |
|     item2     |
|     item1     |
|     item0     |
-----------------
     leading

to solve it, you could set closetotrailing to true, layout is as following.
support [extendedgridview],[extendedlist],[waterfallflow].
and it also works when reverse is flase, layout will close to trailing.

     trailing
-----------------
|     item2     |
|     item1     |
|     item0     |
|               |
|               |
-----------------
     leading

      waterfallflow.builder(
        reverse: true,
        griddelegate: sliverwaterfallflowdelegate(closetotrailing: true),