public static FocusTraversalPolicy of(BuildContext context, bool nullOk = false)
{
D.assert(context != null);
_FocusTraversalGroupMarker inherited = context?.dependOnInheritedWidgetOfExactType <_FocusTraversalGroupMarker>();
D.assert(() => {
if (nullOk)
{
return(true);
}
if (inherited == null)
{
throw new UIWidgetsError(
"Unable to find a FocusTraversalGroup widget in the context.\n" +
"FocusTraversalGroup.of() was called with a context that does not contain a " +
"FocusTraversalGroup.\n" +
"No FocusTraversalGroup ancestor could be found starting from the context that was " +
"passed to FocusTraversalGroup.of(). This can happen because there is not a " +
"WidgetsApp or MaterialApp widget (those widgets introduce a FocusTraversalGroup), " +
"or it can happen if the context comes from a widget above those widgets.\n" +
"The context used was:\n" +
$" {context}"
);
}
return(true);
});
return(inherited?.policy);
}
public _FocusTraversalGroupInfo(
_FocusTraversalGroupMarker marker,
FocusTraversalPolicy defaultPolicy = null,
List <FocusNode> members = null
)
{
groupNode = marker?.focusNode;
policy = marker?.policy ?? defaultPolicy ?? new ReadingOrderTraversalPolicy();
this.members = members ?? new List <FocusNode>();
}
public List <FocusNode> _sortAllDescendants(FocusScopeNode scope)
{
D.assert(scope != null);
_FocusTraversalGroupMarker scopeGroupMarker = _getMarker(scope.context);
FocusTraversalPolicy defaultPolicy = scopeGroupMarker?.policy ?? new ReadingOrderTraversalPolicy();
Dictionary <FocusNode, _FocusTraversalGroupInfo> groups = new Dictionary <FocusNode, _FocusTraversalGroupInfo>();
foreach (FocusNode node in scope.descendants)
{
_FocusTraversalGroupMarker groupMarker = _getMarker(node.context);
FocusNode groupNode = groupMarker?.focusNode;
if (node == groupNode)
{
BuildContext parentContext = FocusTravesalUtils._getAncestor(groupNode.context, count: 2);
_FocusTraversalGroupMarker parentMarker = _getMarker(parentContext);
FocusNode parentNode = parentMarker?.focusNode;
groups[groupNode] = groups.getOrDefault(parentNode) ?? new _FocusTraversalGroupInfo(parentMarker, members: new List <FocusNode>(), defaultPolicy: defaultPolicy);
D.assert(!groups[parentNode].members.Contains(node));
groups[parentNode].members.Add(groupNode);
continue;
}
if (node.canRequestFocus && !node.skipTraversal)
{
groups[groupNode] = groups.getOrDefault(groupNode) ?? new _FocusTraversalGroupInfo(groupMarker, members: new List <FocusNode>(), defaultPolicy: defaultPolicy);
D.assert(!groups[groupNode].members.Contains(node));
groups[groupNode].members.Add(node);
}
}
HashSet <FocusNode> groupKeys = new HashSet <FocusNode>(groups.Keys);
foreach (FocusNode key in groups.Keys)
{
List <FocusNode> sortedMembers = groups.getOrDefault(key).policy.sortDescendants(groups.getOrDefault(key).members).ToList();
groups[key].members.Clear();
groups[key].members.AddRange(sortedMembers);
}
List <FocusNode> sortedDescendants = new List <FocusNode>();
void visitGroups(_FocusTraversalGroupInfo info)
{
foreach (FocusNode node in info.members)
{
if (groupKeys.Contains(node))
{
visitGroups(groups[node]);
}
else
{
sortedDescendants.Add(node);
}
}
}
visitGroups(groups[scopeGroupMarker?.focusNode]);
D.assert(
FocusTravesalUtils.difference(new HashSet <FocusNode>(sortedDescendants), (new HashSet <FocusNode>(scope.traversalDescendants))).isEmpty(),
() => $"sorted descendants contains more nodes than it should: ({FocusTravesalUtils.difference(new HashSet<FocusNode>(sortedDescendants),(new HashSet<FocusNode>(scope.traversalDescendants)))})"
);
D.assert(
FocusTravesalUtils.difference(new HashSet <FocusNode>(scope.traversalDescendants), new HashSet <FocusNode>(sortedDescendants)).isEmpty(),
() => $"sorted descendants are missing some nodes: ({FocusTravesalUtils.difference(new HashSet<FocusNode>(scope.traversalDescendants),new HashSet<FocusNode>(sortedDescendants))})"
);
return(sortedDescendants);
}