isFocused method
Returns true when id matches the current focus.
When searchPath is true, returns true if id is an ancestor of the
currently focused widget.
Implementation
bool isFocused(String id, {bool searchPath = false}) {
if (_focusedId == id) return true;
if (searchPath && _focusedId != null) {
var current = _focusedId;
while (current != null) {
if (current == id) return true;
current = _parents[current];
}
}
return false;
}