viewAsset method

@override Future<void> viewAsset(BuildContext context, int? index, AssetEntity currentAsset)

Determine how to browse assets in the viewer. 定义如何在查看器中浏览资源

Implementation

@override
Future<void> viewAsset(
  BuildContext context,
  int? index,
  AssetEntity currentAsset,
) async {
  final p = context.read<DefaultAssetPickerProvider>();
  // - When we reached the maximum select count and the asset is not selected,
  //   do nothing.
  // - When the special type is WeChat Moment, pictures and videos cannot
  //   be selected at the same time. Video select should be banned if any
  //   pictures are selected.
  if ((!p.selectedAssets.contains(currentAsset) && p.selectedMaximumAssets) ||
      (isWeChatMoment &&
          currentAsset.type == AssetType.video &&
          p.selectedAssets.isNotEmpty)) {
    return;
  }
  final revert = effectiveShouldRevertGrid(context);
  // ignore: no_leading_underscores_for_local_identifiers
  final int _debugFlow; // Only for debug process.
  final List<AssetEntity> current;
  final List<AssetEntity>? selected;
  final int effectiveIndex;
  if (isWeChatMoment) {
    if (currentAsset.type == AssetType.video) {
      current = <AssetEntity>[currentAsset];
      selected = null;
      effectiveIndex = 0;
      _debugFlow = 10;
    } else {
      final List<AssetEntity> list;
      if (index == null) {
        list = p.selectedAssets.reversed.toList(growable: false);
      } else {
        list = p.currentAssets;
      }
      current = list.where((e) => e.type == AssetType.image).toList();
      selected = p.selectedAssets;
      final i = current.indexOf(currentAsset);
      effectiveIndex = revert ? current.length - i - 1 : i;
      _debugFlow = switch ((index == null, revert)) {
        (true, true) => 21,
        (true, false) => 20,
        (false, true) => 31,
        (false, false) => 30,
      };
    }
  } else {
    selected = p.selectedAssets;
    final List<AssetEntity> list;
    if (index == null) {
      if (revert) {
        list = p.selectedAssets.reversed.toList(growable: false);
      } else {
        list = p.selectedAssets;
      }
      effectiveIndex = selected.indexOf(currentAsset);
      current = list;
    } else {
      current = p.currentAssets;
      effectiveIndex = revert ? current.length - index - 1 : index;
    }
    _debugFlow = switch ((index == null, revert)) {
      (true, true) => 41,
      (true, false) => 40,
      (false, true) => 51,
      (false, false) => 50,
    };
  }
  if (current.isEmpty) {
    throw StateError('Previewing empty assets is not allowed. $_debugFlow');
  }
  final List<AssetEntity>? result = await AssetPickerViewer.pushToViewer(
    context,
    currentIndex: effectiveIndex,
    previewAssets: current,
    themeData: theme,
    previewThumbnailSize: previewThumbnailSize,
    selectPredicate: selectPredicate,
    selectedAssets: selected,
    selectorProvider: p,
    specialPickerType: specialPickerType,
    maxAssets: p.maxAssets,
    shouldReversePreview: revert,
    shouldAutoplayPreview: shouldAutoplayPreview,
  );
  if (result != null) {
    Navigator.maybeOf(context)?.maybePop(result);
  }
}