Enable long-press handling

lib/src/tree_node.dart

@@ -109,6 +109,14 @@ class _TreeNodeState<T> extends State<TreeNode<T>>
     }
   }
 
+  void _handleLongPress() {
+    TreeView<T>? _treeView = TreeView.of<T>(context);
+    assert(_treeView != null, 'TreeView must exist in context');
+    if (_treeView!.onNodeLongPress != null) {
+      _treeView.onNodeLongPress!(widget.node.key);
+    }
+  }
+
   void _handleDoubleTap() {
     TreeView<T>? _treeView = TreeView.of<T>(context);
     assert(_treeView != null, 'TreeView must exist in context');
@@ -213,17 +221,20 @@ class _TreeNodeState<T> extends State<TreeNode<T>>
     Widget _tappable = _treeView.onNodeDoubleTap != null
         ? InkWell(
             onTap: _handleTap,
+            onLongPress: _handleLongPress,
             onDoubleTap: _handleDoubleTap,
             child: labelContainer,
           )
         : InkWell(
             onTap: _handleTap,
+            onLongPress: _handleLongPress,
             child: labelContainer,
           );
     if (widget.node.isParent) {
       if (_treeView.supportParentDoubleTap && canSelectParent) {
         _tappable = InkWell(
           onTap: canSelectParent ? _handleTap : _handleExpand,
+          onLongPress: _handleLongPress,
           onDoubleTap: () {
             _handleExpand();
             _handleDoubleTap();
@@ -233,12 +244,14 @@ class _TreeNodeState<T> extends State<TreeNode<T>>
       } else if (_treeView.supportParentDoubleTap) {
         _tappable = InkWell(
           onTap: _handleExpand,
+          onLongPress: _handleLongPress,
           onDoubleTap: _handleDoubleTap,
           child: labelContainer,
         );
       } else {
         _tappable = InkWell(
           onTap: canSelectParent ? _handleTap : _handleExpand,
+          onLongPress: _handleLongPress,
           child: labelContainer,
         );
       }

lib/src/tree_view.dart

@@ -38,6 +38,9 @@ class TreeView<T> extends InheritedWidget {
   /// The double tap handler for a node. Passes the node key.
   final Function(String)? onNodeDoubleTap;
 
+  /// The long press handler for a node. Passes the node key.
+  final Function(String)? onNodeLongPress;
+
   /// The expand/collapse handler for a node. Passes the node key and the
   /// expansion state.
   final Function(String, bool)? onExpansionChanged;
@@ -81,6 +84,7 @@ class TreeView<T> extends InheritedWidget {
     required this.controller,
     this.onNodeTap,
     this.onNodeDoubleTap,
+    this.onNodeLongPress,
     this.physics,
     this.onExpansionChanged,
     this.allowParentSelect: false,
@@ -107,6 +111,7 @@ class TreeView<T> extends InheritedWidget {
   bool updateShouldNotify(TreeView oldWidget) {
     return oldWidget.controller.children != this.controller.children ||
         oldWidget.onNodeTap != this.onNodeTap ||
+        oldWidget.onNodeLongPress != this.onNodeLongPress ||
         oldWidget.onExpansionChanged != this.onExpansionChanged ||
         oldWidget.theme != this.theme ||
         oldWidget.supportParentDoubleTap != this.supportParentDoubleTap ||