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Add header support #215

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Add header support #215

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ab3f70f
Add header support
cl3m Jul 4, 2024
de4e9d4
Merge branch 'Dimibe:main' into cl3m-patch-1
cl3m Nov 27, 2024
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24 changes: 17 additions & 7 deletions lib/grouped_list.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -210,6 +210,9 @@ class GroupedListView<T, E> extends StatefulWidget {
/// the scroll position changes drastically.
final double? itemExtent;

/// Widget to be placed at the top of the list.
final Widget? header;

/// Widget to be placed at the bottom of the list.
final Widget? footer;

Expand Down Expand Up @@ -258,6 +261,7 @@ class GroupedListView<T, E> extends StatefulWidget {
this.restorationId,
this.semanticChildCount,
this.itemExtent,
this.header,
this.footer,
}) : assert(itemBuilder != null ||
indexedItemBuilder != null ||
Expand Down Expand Up @@ -326,11 +330,15 @@ class _GroupedListViewState<T, E> extends State<GroupedListView<T, E>> {
/// If the [index] points to an separator and the previous and next items
/// are in different groups, a group header widget is displayed.
Widget itemBuilder(context, index) {
if (widget.footer != null && index == _sortedElements.length * 2) {
if (widget.header != null && index == 0) {
return widget.header!;
}
if (widget.footer != null && index == _itemCount() - 1) {
return widget.footer!;
}
var actualIndex = index ~/ 2;
if (index == hiddenIndex) {
var indexWithoutHeader = index - (widget.header != null ? 1 : 0);
var actualIndex = indexWithoutHeader ~/ 2;
if (indexWithoutHeader == hiddenIndex) {
return Opacity(
opacity: widget.useStickyGroupSeparators ? 0 : 1,
child: _buildGroupSeparator(_sortedElements[actualIndex]),
Expand All @@ -345,7 +353,7 @@ class _GroupedListViewState<T, E> extends State<GroupedListView<T, E>> {
var next = isValidIndex(nextIndex)
? widget.groupBy(_sortedElements[nextIndex])
: null;
if (isSeparator(index)) {
if (isSeparator(indexWithoutHeader)) {
if (prev != curr) {
return _buildGroupSeparator(_sortedElements[actualIndex]);
}
Expand All @@ -372,9 +380,7 @@ class _GroupedListViewState<T, E> extends State<GroupedListView<T, E>> {
restorationId: widget.restorationId,
keyboardDismissBehavior: widget.keyboardDismissBehavior,
semanticChildCount: widget.semanticChildCount,
itemCount: widget.footer == null
? _sortedElements.length * 2
: (_sortedElements.length * 2) + 1,
itemCount: _itemCount(),
addAutomaticKeepAlives: widget.addAutomaticKeepAlives,
addRepaintBoundaries: widget.addRepaintBoundaries,
addSemanticIndexes: widget.addSemanticIndexes,
Expand All @@ -394,6 +400,10 @@ class _GroupedListViewState<T, E> extends State<GroupedListView<T, E>> {
);
}

int _itemCount() {
return _sortedElements.length * 2 + (widget.footer == null ? 0 : 1) + (widget.header == null ? 0 : 1);
}

/// Returns the widget for element positioned at [index]. The widget is
/// retrieved either by [widget.indexedItemBuilder], [widget.itemBuilder]
/// or [widget.interdependentItemBuilder].
Expand Down