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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,187 @@ | ||
| part of '../loader.dart'; | ||
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| enum LoaderType { loading, error, empty } | ||
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| mixin AutoLoadMoreMixin<T> on Model { | ||
| @protected | ||
| final List<T> _data = []; | ||
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| bool _more = true; | ||
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| ///has more comments | ||
| bool get hasMore => _more; | ||
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| int _offset = 0; | ||
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| CancelableOperation _autoLoadOperation; | ||
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| @protected | ||
| Future<Result<List<T>>> loadData(int offset); | ||
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| int get offset => _offset; | ||
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| dynamic error; | ||
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| List get items { | ||
| final items = List.from(_data); | ||
| if (error != null) { | ||
| items.add(LoaderType.error); | ||
| return items; | ||
| } | ||
| if (_autoLoadOperation != null) { | ||
| items.add(LoaderType.loading); | ||
| return items; | ||
| } | ||
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| if (items.isEmpty) { | ||
| return const [LoaderType.empty]; | ||
| } | ||
| return items; | ||
| } | ||
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| int get size => items.length; | ||
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| /// | ||
| /// load more items | ||
| /// | ||
| /// [notification] use notification to check is need load more items | ||
| /// | ||
| void loadMore({ScrollEndNotification notification}) { | ||
| if (error != null) { | ||
| return; | ||
| } | ||
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| if (notification != null && | ||
| (!_more || | ||
| notification.metrics.extentAfter > 500 || | ||
| _autoLoadOperation != null)) { | ||
| return; | ||
| } | ||
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| final offset = this.offset; | ||
| _autoLoadOperation = | ||
| CancelableOperation<Result<List<T>>>.fromFuture(loadData(offset)) | ||
| ..value.then((r) { | ||
| if (r == null || r.isError) { | ||
| error = r == null ? "result is null" : r.asError.error.toString(); | ||
| } else { | ||
| final result = LoadMoreResult._from(r.asValue); | ||
| _more = result.hasMore; | ||
| _offset += result.loaded; | ||
| _data.addAll(result.value); | ||
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| onDataLoaded(offset, result); | ||
| } | ||
| }).whenComplete(() { | ||
| notifyListeners(); | ||
| _autoLoadOperation = null; | ||
| }); | ||
| notifyListeners(); | ||
| } | ||
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| @protected | ||
| void onDataLoaded(int offset, LoadMoreResult result) {} | ||
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| ///create builder for [ListView] | ||
| IndexedWidgetBuilder createBuilder(List data, | ||
| {IndexedWidgetBuilder builder}) { | ||
| return (context, index) { | ||
| final widget = buildItem(context, data, index) ?? | ||
| (builder == null ? null : builder(context, index)); | ||
| assert(widget != null, 'can not build ${data[index]}'); | ||
| return widget; | ||
| }; | ||
| } | ||
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| IndexedWidgetBuilder obtainBuilder() { | ||
| return (context, index) { | ||
| return buildItem(context, items, index); | ||
| }; | ||
| } | ||
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| ///build item for position [index] | ||
| /// | ||
| /// return null if you do not care this position | ||
| /// | ||
| @protected | ||
| Widget buildItem(BuildContext context, List list, int index) { | ||
| if (list[index] == LoaderType.loading) { | ||
| return buildLoadingItem(context, list.length == 1); | ||
| } else if (list[index] == LoaderType.error) { | ||
| return buildErrorItem(context, list.length == 1); | ||
| } else if (list[index] == LoaderType.empty) { | ||
| return buildEmptyWidget(context); | ||
| } | ||
| return null; | ||
| } | ||
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| @protected | ||
| Widget buildLoadingItem(BuildContext context, bool empty) { | ||
| return SimpleLoading(height: empty ? 200 : 50); | ||
| } | ||
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| @protected | ||
| Widget buildErrorItem(BuildContext context, bool isEmpty) { | ||
| final retry = () { | ||
| error = null; | ||
| loadMore(); | ||
| }; | ||
| if (isEmpty) { | ||
| return SimpleFailed( | ||
| retry: retry, | ||
| message: error.toString(), | ||
| ); | ||
| } else { | ||
| return Container( | ||
| height: 56, | ||
| child: Center( | ||
| child: RaisedButton( | ||
| onPressed: retry, | ||
| child: Text("加载失败！点击重试"), | ||
| textColor: Theme.of(context).primaryTextTheme.body1.color, | ||
| color: Theme.of(context).errorColor, | ||
| ), | ||
| ), | ||
| ); | ||
| } | ||
| } | ||
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| @protected | ||
| Widget buildEmptyWidget(BuildContext context) { | ||
| return Container( | ||
| constraints: BoxConstraints(minHeight: 200), | ||
| child: Center(child: Text('暂无数据...')), | ||
| ); | ||
| } | ||
| } | ||
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| class LoadMoreResult<T> extends ValueResult<List<T>> { | ||
| ///已加载的数据条目 | ||
| final int loaded; | ||
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| final bool hasMore; | ||
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| final dynamic payload; | ||
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| LoadMoreResult(List<T> value, {int loaded, this.hasMore = true, this.payload}) | ||
| : assert(value != null), | ||
| this.loaded = loaded ?? value.length, | ||
| super(value); | ||
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| factory LoadMoreResult._from(ValueResult<List<T>> result) { | ||
| if (result is LoadMoreResult) { | ||
| return result; | ||
| } | ||
| return LoadMoreResult(result.value); | ||
| } | ||
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| ///utils method for result mapping | ||
| static Result<R> map<T, R>(Result<T> result, R Function(T source) map) { | ||
| if (result.isError) return result.asError; | ||
| return Result.value(map(result.asValue.value)); | ||
| } | ||
| } | ||
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| ///delegate to load more item | ||
| ///[offset] loaded data length | ||
| typedef LoadMoreDelegate<T> = Future<Result<List<T>>> Function(int offset); |
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