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[LazyLoadScrollView] : Add support of onStartOfPage

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Signed-off-by: Sahil Kumar <[email protected]>
This commit is contained in:
Sahil Kumar
2020-12-02 19:30:55 +05:30
parent 390062f1c2
commit 546fdaf487
1 changed files with 33 additions and 16 deletions
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lib/src/lazy_load_scroll_view.dart
+33 -16
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@@ -1,18 +1,18 @@
import 'package:flutter/widgets.dart';
enum LoadingStatus { LOADING, STABLE }
enum _LoadingStatus { LOADING, STABLE }
/// Signature for EndOfPageListeners
typedef EndOfPageListenerCallback = void Function();
/// A widget that wraps a [Widget] and will trigger [onEndOfPage] when it
/// reaches the bottom of the list
/// A widget that wraps a [Widget] and will trigger [onEndOfPage]/[onStartOfPage] when it
/// reaches the bottom/start of the list
class LazyLoadScrollView extends StatefulWidget {
/// The [Widget] that this widget watches for changes on
final Widget child;
/// Called when the [child] reaches the start of the list
final VoidCallback onStartOfPage;
/// Called when the [child] reaches the end of the list
final EndOfPageListenerCallback onEndOfPage;
final VoidCallback onEndOfPage;
/// The offset to take into account when triggering [onEndOfPage] in pixels
final int scrollOffset;
@@ -20,14 +20,15 @@ class LazyLoadScrollView extends StatefulWidget {
/// Used to determine if loading of new data has finished. You should use set this if you aren't using a FutureBuilder or StreamBuilder
final bool isLoading;
/// Initiates a LazyLoadScrollView widget
LazyLoadScrollView({
Key key,
@required this.child,
@required this.onEndOfPage,
this.onStartOfPage,
this.onEndOfPage,
this.isLoading = false,
this.scrollOffset = 100,
}) : assert(onEndOfPage != null),
assert(child != null),
}) : assert(child != null),
super(key: key);
@override
@@ -35,13 +36,13 @@ class LazyLoadScrollView extends StatefulWidget {
}
class _LazyLoadScrollViewState extends State<LazyLoadScrollView> {
LoadingStatus _loadMoreStatus = LoadingStatus.STABLE;
_LoadingStatus _loadMoreStatus = _LoadingStatus.STABLE;
@override
void didUpdateWidget(LazyLoadScrollView oldWidget) {
super.didUpdateWidget(oldWidget);
if (!widget.isLoading) {
_loadMoreStatus = LoadingStatus.STABLE;
_loadMoreStatus = _LoadingStatus.STABLE;
}
}
@@ -59,21 +60,37 @@ class _LazyLoadScrollViewState extends State<LazyLoadScrollView> {
notification.metrics.maxScrollExtent - notification.metrics.pixels <=
widget.scrollOffset) {
if (_loadMoreStatus != null &&
_loadMoreStatus == LoadingStatus.STABLE) {
_loadMoreStatus = LoadingStatus.LOADING;
_loadMoreStatus == _LoadingStatus.STABLE) {
_loadMoreStatus = _LoadingStatus.LOADING;
widget.onEndOfPage();
}
}
if (notification.metrics.minScrollExtent < notification.metrics.pixels &&
notification.metrics.pixels - notification.metrics.minScrollExtent <=
widget.scrollOffset) {
if (_loadMoreStatus != null &&
_loadMoreStatus == _LoadingStatus.STABLE) {
_loadMoreStatus = _LoadingStatus.LOADING;
widget.onStartOfPage();
}
}
return true;
}
if (notification is OverscrollNotification) {
if (notification.overscroll > 0) {
if (_loadMoreStatus != null &&
_loadMoreStatus == LoadingStatus.STABLE) {
_loadMoreStatus = LoadingStatus.LOADING;
_loadMoreStatus == _LoadingStatus.STABLE) {
_loadMoreStatus = _LoadingStatus.LOADING;
widget.onEndOfPage();
}
}
if (notification.overscroll < 0) {
if (_loadMoreStatus != null &&
_loadMoreStatus == _LoadingStatus.STABLE) {
_loadMoreStatus = _LoadingStatus.LOADING;
widget.onStartOfPage();
}
}
return true;
}
return false;