How do I get all nodes in a parent in JavaFX?

问题:

In C# I found a method that was pretty sweet that allowed you to get all the descendants and all of THEIR descendants from a specified control.

I'm looking for a similar method for JavaFX.

I saw that the Parent class is what I want to work with since it is the class from which all Node classes that bear children are derived.

This is what I have so far (and I haven't really found anything on google with searches like "JavaFX get all nodes from a scene"):

public static ArrayList<Node> GetAllNodes(Parent root){
    ArrayList<Node> Descendents = new ArrayList<>();
    root.getChildrenUnmodifiable().stream().forEach(N -> {
        if (!Descendents.contains(N)) Descendents.add(N);
        if (N.getClass() == Parent.class) Descendents.addAll(
            GetAllNodes((Parent)N)
        );
    });
}

So how do I tell if N is a parent (or extended from a parent)? Am I doing that right? It doesn't seem to be working... It's grabbing all the nodes from the root (parent) node but not from the nodes with children in them. I feel like this is something that's probably got an answer to it but I'm just asking the question... wrong. How do I go about doing this?

回答1:

public static ArrayList<Node> getAllNodes(Parent root) {
    ArrayList<Node> nodes = new ArrayList<Node>();
    addAllDescendents(root, nodes);
    return nodes;
}

private static void addAllDescendents(Parent parent, ArrayList<Node> nodes) {
    for (Node node : parent.getChildrenUnmodifiable()) {
        nodes.add(node);
        if (node instanceof Parent)
            addAllDescendents((Parent)node, nodes);
    }
}

回答2:

I use this,

public class NodeUtils {

    public static <T extends Pane> List<Node> paneNodes(T parent) {
        return paneNodes(parent, new ArrayList<Node>());
    }

    private static <T extends Pane> List<Node> paneNodes(T parent, List<Node> nodes) {
        for (Node node : parent.getChildren()) {
            if (node instanceof Pane) {
                paneNodes((Pane) node, nodes);
            } else {
                nodes.add(node);
            }
        }

        return nodes;
    }
}

Usage,

List<Node> nodes = NodeUtils.paneNodes(aVBoxOrAnotherContainer);

This source code uses the references of the existing nodes. It does not clone them.

回答3:

I'd like to add to Hans' answer, that you have to check if parent is a SplitPane. Because SplitPanes have an empty list using getUnmodifiableChildren(), you'll have to use getItems() instead. (I do not know if there are other parents that do not provide their children via getUnmodifiableChildren(). SplitPane was the first I found...)

回答4:

Unfortunately this won't get subnodes for most container components. If you try a TabPane as parent, you'll find no children, but you can find tabs in it with getTabs(). The same is with SplitPane and other. So every container will require a specific approach.

You could use node.lookupAll("*"), but it also doesn't look inside.

The solution could be a "Prototype" pattern - creating a meta class with common interface of getChildren() method, which is realized in subclasses - one for each type.

Approach example is given here.

回答5:

This seems to get ALL nodes. (In Kotlin)

fun getAllNodes(root: Parent): ArrayList<Node> {
    var nodes = ArrayList<Node>()
    fun recurseNodes(node: Node) {
        nodes.add(node)
        if(node is Parent)
            for(child in node.childrenUnmodifiable) {
                recurseNodes(child)
            }
    }
    recurseNodes(root)
    return nodes
}

回答6:

This works for me:

public class FXUtil {

    public static final List<Node> getAllChildren(final Parent parent) {
        final List<Node> result = new LinkedList<>();

        if (parent != null) {

            final List<Node> childrenLvl1 = parent.getChildrenUnmodifiable();
            result.addAll(childrenLvl1);

            final List<Node> childrenLvl2 =
                    childrenLvl1.stream()
                                .filter(c -> c instanceof Parent)
                                .map(c -> (Parent) c)
                                .map(FXUtil::getAllChildren)
                                .flatMap(List::stream)
                                .collect(Collectors.toList());
            result.addAll(childrenLvl2);
        }

        return result;
    }

}