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Description:

sticky infinite list

Sticky Infinite List #

Infinite list with sticky headers.
This package was made in order to make possible
render infinite list in both directions with sticky headers, unlike most
packages in Dart Pub.
Supports various header positioning. Also supports Vertical and
Horizontal scroll list
It highly customizable and doesn't have any third party dependencies or native(Android/iOS) code.
In addition to default usage, this package exposes some classes, that
can be overridden if needed. Also some classes it can be used inside
Scrollable widgets independently from InfiniteList container.
This package uses CustomScrollView to perform scroll with all
benefits for performance that Flutter provides.
Features #

sticky headers within infinite list
multi directional infinite list
customization for sticky header position
horizontal sticky list support
dynamic header build on content scroll
dynamic min offset calculation on content scroll

Flutter before 1.20 #
If you're using Flutter version lower than 1.20 consider using v2.x.x.
Migration guide #
If you using older MAJOR versions, please
visit this migration guide
Property not defined #
If you get similar error message during the build please read this
section first.
Demo #

Getting Started #
Install package and import

import 'package:sticky_infinite_list/sticky_infinite_list.dart';
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Package exposes InfiniteList, InfiniteListItem, StickyListItem,
StickyListItemRenderObject classes
Examples #
Simple example #
To start using Infinite list with sticky headers,
you need to create instance InfiniteList with builder specified.
No need to specify any additional config to make it work

import 'package:sticky_infinite_list/sticky_infinite_list.dart';

class Example extends StatelessWidget {

@override
Widget build(BuildContext context) {
return InfiniteList(
builder: (BuildContext context, int index) {
/// Builder requires [InfiniteList] to be returned
return InfiniteListItem(
/// Header builder
headerBuilder: (BuildContext context) {
return Container(
///...
);
},
/// Content builder
contentBuilder: (BuildContext context) {
return Container(
///...
);
},
);
}
);
}
}
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Or with header overlay content

import 'package:sticky_infinite_list/sticky_infinite_list.dart';

class Example extends StatelessWidget {

@override
Widget build(BuildContext context) {
return InfiniteList(
builder: (BuildContext context, int index) {
/// Builder requires [InfiniteList] to be returned
return InfiniteListItem.overlay(
/// Header builder
headerBuilder: (BuildContext context) {
return Container(
///...
);
},
/// Content builder
contentBuilder: (BuildContext context) {
return Container(
///...
);
},
);
}
);
}
}
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State #
When min offset callback invoked or header builder is invoked
object StickyState is passed as parameter
This object describes current state for sticky header.
class StickyState<I> {
/// Position, that header already passed
///
/// Value can be between 0.0 and 1.0
///
/// If it's `0.0` - sticky in max start position
///
/// `1.0` - max end position
///
/// If [InfiniteListItem.initialHeaderBuild] is true, initial
/// header render will be with position = 0
final double position;

/// Number of pixels, that outside of viewport
///
/// If [InfiniteListItem.initialHeaderBuild] is true, initial
/// header render will be with offset = 0
///
/// For header bottom positions (or right positions for horizontal)
/// offset value also will be amount of pixels that was scrolled away
final double offset;

/// Item index
final I index;

/// If header is in sticky state
///
/// If [InfiniteListItem.minOffsetProvider] is defined,
/// it could be that header builder will be emitted with new state
/// on scroll, but [sticky] will be false, if offset already passed
/// min offset value
///
/// WHen [InfiniteListItem.minOffsetProvider] is called, [sticky]
/// will always be `false`. Since for min offset calculation
/// offset itself not defined yet
final bool sticky;

/// Scroll item height.
///
/// If [InfiniteListItem.initialHeaderBuild] is true, initial
/// header render will be called without this value
final double contentSize;
}
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Extended configuration #
Available configuration
Alongside with minimal config to start using.
InfiniteList allows you to define config for scroll list rendering
InfiniteList(
/// Optional parameter to pass ScrollController instance
controller: ScrollController(),

/// Optional parameter
/// to specify scroll direction
///
/// By default scroll will be rendered with just positive
/// direction `InfiniteListDirection.forward`
///
/// If you need infinite list in both directions use `InfiniteListDirection.multi`
direction: InfiniteListDirection.multi,

/// Negative max child count.
///
/// Will be used only when `direction: InfiniteListDirection.multi`
///
/// If it's not provided, scroll will be infinite in negative direction
negChildCount: 100,

/// Positive max child count
///
/// Specifies number of elements for forward list
///
/// If it's not provided, scroll will be infinite in positive direction
posChildCount: 100,

/// ScrollView anchor value.
anchor: 0.0,

/// ScrollView physics value.
physics: null,

/// Item builder
///
/// Should return `InfiniteListItem`
builder: (BuildContext context, int index) {
return InfiniteListItem(
//...
)
}
)
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InfiniteListItem allows you to specify more options for you customization.
InfiniteListItem(
/// See class description for more info
///
/// Forces initial header render when [headerStateBuilder]
/// is specified.
initialHeaderBuild: false,

/// Simple Header builder
/// that will be called once during List item render
headerBuilder: (BuildContext context) {},

/// Header builder, that will be invoked each time
/// when header should change it's position
///
/// Unlike prev method, it also provides `state` of header
/// position
///
/// This callback has higher priority than [headerBuilder],
/// so if both header builders will be provided,
/// [headerBuilder] will be ignored
headerStateBuilder: (BuildContext context, StickyState<int> state) {},

/// Content builder
contentBuilder: (BuildContext context) {},

/// Min offset invoker
///
/// This callback is called on each header position change,
/// to define when header should be stick to the bottom of
/// content.
///
/// If this method returns `0`,
/// header will be in sticky state until list item
/// will be visible inside view port
///
/// If this method not provided or it returns null, header
/// will be sticky until offset equals to
/// header size
minOffsetProvider: (StickyState<int> state) {},

/// Header alignment against main axis direction
///
/// See [HeaderMainAxisAlignment] for more info
HeaderMainAxisAlignment mainAxisAlignment: HeaderMainAxisAlignment.start,

/// Header alignment against cross axis direction
///
/// See [HeaderCrossAxisAlignment] for more info
HeaderCrossAxisAlignment crossAxisAlignment: HeaderCrossAxisAlignment.start,

/// Header position against scroll axis for relative positioned headers
///
/// Only for relative header positioning
HeaderPositionAxis positionAxis: HeaderPositionAxis.mainAxis,

/// List item padding, see [EdgeInsets] for more info
EdgeInsets padding: const EdgeInsets.all(8.0),

/// Scroll direction
///
/// Can be vertical or horizontal (see [Axis] class)
///
/// This value also affects how bottom or top
/// edge header positioned headers behave
scrollDirection: Axis.vertical,
);
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Demos #
Header alignment demo
Relative positioning

Relative cross axis positioning

Overlay positioning

Horizontal scroll demo

Reverse infinite scroll #
Currently package doesn't support CustomScrollView.reverse option.
But same result can be achieved with defining anchor = 1 and
posChildCount = 0. In that way viewport center will be stick to the
bottom and positive list won't render anything.
Additionally you can specify header alignment to any side.
import 'package:sticky_infinite_list/sticky_infinite_list.dart';

class Example extends StatelessWidget {

@override
Widget build(BuildContext context) {
return InfiniteList(
anchor: 1.0,

direction: InfiniteListDirection.multi,

posChildCount: 0,

builder: (BuildContext context, int index) {
/// Builder requires [InfiniteList] to be returned
return InfiniteListItem(

mainAxisAlignment: HeaderMainAxisAlignment.end,
crossAxisAlignment: HeaderCrossAxisAlignment.start,

/// Header builder
headerBuilder: (BuildContext context) {
return Container(
///...
);
},
/// Content builder
contentBuilder: (BuildContext context) {
return Container(
///...
);
},
);
}
);
}
}
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Demo

For more info take a look at
Example project
Available for override #
In most cases it will be enough to just use InfiniteListItem
But in some cases you may need to add additional functionality to
each item.
Luckily you can extend and override base InfiniteListItem class
/// Generic `I` is index type, by default list item uses `int`

class SomeCustomListItem<I> extends InfiniteListItem<I> {
/// Header alignment against main axis direction
///
/// See [HeaderMainAxisAlignment] for more info
@override
final HeaderMainAxisAlignment mainAxisAlignment = HeaderMainAxisAlignment.start;

/// Header alignment against cross axis direction
///
/// See [HeaderCrossAxisAlignment] for more info
@override
final HeaderCrossAxisAlignment crossAxisAlignment = HeaderCrossAxisAlignment.start;

/// Header position against scroll axis for relative positioned headers
///
/// See [HeaderPositionAxis] for more info
@override
final HeaderPositionAxis positionAxis = HeaderPositionAxis.mainAxis;

/// If header should overlay content or not
@override
final bool overlayContent = false;

/// Let item builder know if it should watch
/// header position changes
///
/// If this value is `true` - it will invoke [buildHeader]
/// each time header position changes
@override
bool get watchStickyState => true;

/// Let item builder know that this class
/// provides header
///
/// If it returns `false` - [buildHeader] will be ignored
/// and never called
@override
bool get hasStickyHeader => true;

/// This methods builds header
///
/// If [watchStickyState] is `true`,
/// it will be invoked on each header position change
/// and `state` option will be provided
///
/// Otherwise it will be called only once on initial render
/// and each header position change won't invoke this method.
///
/// Also in that case `state` will be `null`
@override
Widget buildHeader(BuildContext context, [StickyState<I> state]) {}

/// Content item builder
///
/// This method invoked only once
@override
Widget buildContent(BuildContext context) {}

/// Called during init state (see [Statefull] widget [State.initState])
///
/// For additional information about [Statefull] widget `initState`
/// lifecycle - see Flutter docs
@protected
@mustCallSuper
void initState() {}

/// Called during item dispose (see [Statefull] widget [State.dispose])
///
/// For additional information about [Statefull] widget `dispose`
/// lifecycle - see Flutter docs
@protected
@mustCallSuper
void dispose() {}
}
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Need more override?..
Alongside with list item override, to use inside InfiniteList builder,
you can also use or extend StickyListItem, that exposed by this
package too, independently.
This class uses Stream to inform it's parent about header position changes
Also it requires to be rendered inside Scrollable widget and Viewport,
since it subscribes to scroll event and calculates position
against Viewport coordinates (see StickyListItemRenderObject class
for more information)
For example
Widget build(BuildContext context) {
return SingleChildScrollView(
child: Column(
children: <Widget>[
Container(
height: height,
color: Colors.lightBlueAccent,
child: Placeholder(),
),
StickyListItem<String>(
streamSink: _headerStream.sink, /// stream to update header during scroll
header: Container(
height: _headerHeight,
width: double.infinity,
color: Colors.orange,
child: Center(
child: StreamBuilder<StickyState<String>>(
stream: _headerStream.stream, /// stream to update header during scroll
builder: (_, snapshot) {
if (!snapshot.hasData) {
return Container();
}

final position = (snapshot.data.position * 100).round();

return Text('Positioned relative. Position: $position%');
},
),
),
),
content: Container(
height: height,
color: Colors.blueAccent,
child: Placeholder(),
),
itemIndex: "single-child",
),
StickyListItem<String>.overlay(
streamSink: _headerOverlayStream.sink, /// stream to update header during scroll
header: Container(
height: _headerHeight,
width: double.infinity,
color: Colors.orange,
child: Center(
child: StreamBuilder<StickyState<String>>(
stream: _headerOverlayStream.stream, /// stream to update header during scroll
builder: (_, snapshot) {
if (!snapshot.hasData) {
return Container();
}

final position = (snapshot.data.position * 100).round();

return Text('Positioned overlay. Position: $position%');
},
),
),
),
content: Container(
height: height,
color: Colors.lightBlueAccent,
child: Placeholder(),
),
itemIndex: "single-overlayed-child",
),
Container(
height: height,
color: Colors.cyan,
child: Placeholder(),
),
],
),
);
}
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This code will render single child scroll with 4 widgets. Two middle
items - items with sticky header.
Demo

For more complex example please take a look at "Single Example" page
in Example project
Changelog #
Please see the Changelog page to know what's recently changed.
Bugs/Requests #
If you encounter any problems feel free to open an issue.
If you feel the library is missing a feature,
please raise a ticket on Github and I'll look into it.
Pull request are also welcome.
Known issues #
Currently this package can't work with reverse scroll. For some reason
flutter calculates coordinate for negative list items in a
different way in reverse mode, comparing to regular scroll direction.
But there is an workaround can be used, described
in Reverse infinite scroll
Flutter version related errors #
Named parameter clipBehavior isn't defined error #
If you get this kind of error, most likely you are using Flutter 1.17.
If so, please ensure that you're using 2.x.x version.