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waterfall_flow

A Flutter grid view easy to build waterfall flow layout quickly.

Web demo for WaterfallFlow

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• waterfall_flow
  • Use
  • Easy to use
  • CollectGarbage
  • ViewportBuilder
  • LastChildLayoutTypeBuilder
  • CloseToTrailing

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.

• SliverWaterfallFlowDelegateWithFixedCrossAxisCount

parameter	description	default
crossAxisCount	The number of children in the cross axis.	required

• SliverWaterfallFlowDelegateWithMaxCrossAxisExtent

parameter	description	default
maxCrossAxisExtent	The maximum extent of tiles in the cross axis.	required

• SliverWaterfallFlowDelegate

parameter	description	default
mainAxisSpacing	The number of logical pixels between each child along the main axis.	0.0
crossAxisSpacing	The number of logical pixels between each child along the cross axis.	0.0
collectGarbage	Call when collect garbage, return indexs to collect	-
lastChildLayoutTypeBuilder	The builder to get layout type of last child ,Notice: it should only for last child	-
viewportBuilder	The builder to get indexs in viewport	-
closeToTrailing	Whether make layout close to trailing	false

            WaterfallFlow.builder(
              //cacheExtent: 0.0,
              padding: EdgeInsets.all(5.0),
              gridDelegate: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
                  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: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
                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: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
                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: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
            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: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(closeToTrailing: true),