list_treeview 0.4.2

A treeview for Flutter. Based on the listview. Infinitely increasing child levels and child nodes.

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ListTreeView

A tree view for Flutter, built on top of ListView. It manages the tree structure of your data and leaves the UI entirely to you.

Features

• Bring your own UI. The widget only manages the tree structure of the data — you design every row yourself in an itemBuilder.
• Efficient. Rows are recycled through ListView's builder, so only visible nodes are built.
• Unlimited depth. Child levels and child nodes can grow infinitely.
• Imperative control. Insert, remove, expand/collapse, and select nodes through a controller.
• Flutter 3.0+ / Dart 3.

Preview

Basic & Expand All	Insert & Remove	Selection	Async Lazy Load

Installation

Run this command:

flutter pub add list_treeview

This adds a line like the following to your package's pubspec.yaml (and runs an implicit flutter pub get):

dependencies:
  list_treeview: ^0.4.0

Then import it in your Dart code:

import 'package:list_treeview/list_treeview.dart';

Quick start

1. Initialize the controller

The controller must be created before the tree view is built — usually in initState.

class _TreePageState extends State<TreePage> {
  late TreeViewController _controller;

  @override
  void initState() {
    super.initState();
    _controller = TreeViewController();
  }
}

2. Define your data model

Your data class must extend NodeData. Beyond that you can add any properties you like. Make your own fields nullable (or give them defaults) so they remain optional.

/// The data bound to each node.
/// You must extend [NodeData]; everything else is up to you.
class TreeNodeData extends NodeData {
  TreeNodeData({this.label, this.color}) : super();

  final String? label;
  final Color? color;
}

3. Provide the data

Build your node hierarchy with addChild and hand the root-level nodes to the controller via treeData. Data can be loaded synchronously or asynchronously.

Future<void> loadData() async {
  // Data may be fetched asynchronously.
  await Future.delayed(const Duration(seconds: 1));

  final colors = TreeNodeData(label: 'Colors');
  colors.addChild(TreeNodeData(
      label: 'rgb(0,139,69)', color: const Color.fromARGB(255, 0, 139, 69)));
  colors.addChild(TreeNodeData(
      label: 'rgb(0,191,255)', color: const Color.fromARGB(255, 0, 191, 255)));

  final shapes = TreeNodeData(label: 'Shapes');
  shapes.addChild(TreeNodeData(label: 'Circle'));
  shapes.addChild(TreeNodeData(label: 'Square'));

  // Set the root-level nodes.
  _controller.treeData([colors, shapes]);

  setState(() {});
}

4. Build the tree

Render the tree with ListTreeView. Inside itemBuilder, cast the NodeData back to your own type and use level to indent each row.

ListTreeView(
  controller: _controller,
  itemBuilder: (BuildContext context, NodeData data) {
    final item = data as TreeNodeData;
    return Padding(
      padding: EdgeInsets.only(left: item.level * 16.0),
      child: ListTile(
        title: Text(item.label ?? ''),
        // Show a chevron only for nodes that have children.
        trailing: item.children.isNotEmpty
            ? Icon(item.isExpand ? Icons.expand_less : Icons.expand_more)
            : null,
      ),
    );
  },
  onTap: (NodeData item) => debugPrint('tapped index ${item.index}'),
  onLongPress: (NodeData item) => _controller.removeItem(item),
);

By default, tapping a row automatically expands or collapses it (toggleNodeOnTap is true). Set toggleNodeOnTap: false to drive expansion yourself with expandOrCollapse.

Operations

Insert

// Insert as the first child of [parent].
_controller.insertAtFront(parent, newNode);

// Append as the last child.
_controller.insertAtRear(parent, newNode);

// Insert at a specific index.
_controller.insertAtIndex(1, parent, newNode);

// Insert several nodes at the front in one call.
_controller.insertAllAtFront(parent, [nodeA, nodeB]);

Pass null as parent to insert at the root level:

_controller.insertAtFront(null, newNode);   // prepend a root node
_controller.insertAtRear(null, newNode);    // append a root node
_controller.insertAtIndex(1, null, newNode); // insert at root index 1

By default a node is inserted only when its parent is expanded. Pass closeCanInsert: true to insert even when the parent is collapsed:

_controller.insertAtFront(parent, newNode, closeCanInsert: true);

Remove

_controller.removeItem(item);

Expand / collapse

/// Toggle the node at a visible [index] (e.g. `item.index`).
_controller.expandOrCollapse(item.index);

/// Expand or collapse the whole tree at once.
_controller.expandAll();
_controller.collapseAll();

/// Query the current state.
final expanded = _controller.isExpanded(item);

Lazy loading note: child controllers are created only when a parent expands, so expandAll() expands every node whose children are already loaded. Nodes that fetch their children asynchronously are skipped until they have been loaded.

Select

/// Select / deselect a single node.
_controller.selectItem(item);

/// Select / deselect a node together with all of its descendants.
_controller.selectAllChild(item);

Read the result via item.isSelected inside your itemBuilder.

API reference

ListTreeView

Property	Type	Default	Description
controller	TreeViewController	required	Manages the tree data and operations.
itemBuilder	Widget Function(BuildContext, NodeData)	required	Builds the widget for each visible node.
onTap	Function(NodeData)?	null	Called when a row is tapped.
onLongPress	Function(NodeData)?	null	Called when a row is long-pressed.
toggleNodeOnTap	bool	true	Auto expand/collapse a node on tap. Set false to control it yourself.
shrinkWrap	bool	false	Forwarded to the underlying ListView.
reverse	bool	false	Forwarded to the underlying ListView.
padding	EdgeInsetsGeometry	EdgeInsets.all(0)	Padding around the list.
removeTop	bool	true	Remove the top MediaQuery padding.
removeBottom	bool	true	Remove the bottom MediaQuery padding.

TreeViewController

Method	Returns	Description
treeData(List? data)	void	Sets the root-level nodes.
insertAtFront(parent, node, {closeCanInsert})	void	Inserts node as the first child of parent. Pass null for root level.
insertAllAtFront(parent, nodes, {closeCanInsert})	void	Inserts multiple nodes at the front. Pass null for root level.
insertAtRear(parent, node, {closeCanInsert})	void	Appends node as the last child. Pass null for root level.
insertAtIndex(index, parent, node, {closeCanInsert})	void	Inserts node at index. Pass null for root level.
removeItem(item)	void	Removes item from the tree.
expandOrCollapse(index)	TreeNode	Toggles the node at the visible index.
expandItem(treeNode) / collapseItem(treeNode)	void	Expands / collapses a node.
expandAll()	void	Expands every (loaded) node in the tree.
collapseAll()	void	Collapses every node in the tree.
isExpanded(item)	bool	Whether item is expanded.
selectItem(item)	void	Toggles the selection of item.
selectAllChild(item)	void	Toggles the selection of item and all descendants.
indexOfItem(item)	int	Visible index of item.
levelOfNode(item)	int	Depth level of item.
parentOfItem(item)	NodeData?	Parent of item (null for root-level nodes).
itemChildrenLength(item)	int	Number of direct children.
numberOfVisibleChild()	int	Total number of currently visible rows.
rebuild()	void	Forces the tree to rebuild.

NodeData

Extend this class for your own model. The tree keeps the following fields up to date, so you can read them inside itemBuilder:

Property	Type	Description
children	List<NodeData>	Direct child nodes. Use addChild() to append.
level	int	Depth of the node (root level is 0). Use for indenting.
index	int	Index among all currently visible nodes.
indexInParent	int	Index within the parent's children.
isExpand	bool	Whether the node is currently expanded.
isSelected	bool	Whether the node is selected.
addChild(NodeData child)	void	Appends a child node.

Example

The example directory is a gallery of focused, runnable demos, each on its own detail page:

• Basic & Expand All — a nested tree with expand-all / collapse-all toolbar actions.
• Insert & Remove — add child nodes from any row and remove subtrees.
• Selection — select a node together with all of its descendants.
• Async Lazy Load — fetch a branch's children on first tap.

Run it with:

cd example
flutter run

License

Released under the MIT License.