creating nested TreeItem in javafx

Question

At the time my TreeItem in TreeTableView looks flat and like this:

    //////////////////row//////////////////////////////
    for (Entry<String, String> entryRow : dc.getSortedfuncAll().entrySet()) {
        root.getChildren().add(new TreeItem<String>(entryRow.getValue()));

    }
    // ////////////////treetable////////////////////////////
    final TreeTableView<String> treeTableView = new TreeTableView<>(root);

• AUF_1086686287581_9999
• AUF_1086686329972_10049
• AUF_1079023138936_6682
• AUF_1087981634453_7022
• AUF_1060589919844_59496
• AUF_1421268568003_1743
• AUF_1422451819445_14260
• AUF_1421268533080_1741
• AUF_1421268719761_1776
• AUF_1421272434570_1781
• AUF_1421268568003_1743

consider having the following relation between them: it is result of TreeMap<String,ArrayList<String>>:

{AUF_1060589919844_59496=[AUF_1086686287581_9999,AUF_1086686329972_10049,AUF_1079023138936_6682],
AUF_1087981634453_7022=[AUF_1421268533080_1741, AUF_1421268568003_1743],
AUF_1421268533080_1741=[AUF_1421268719761_1776], 
AUF_1421272434570_1781=[AUF_1087981634453_7022], 
AUF_1422451819445_14260=[AUF_1421268568003_1743]}

I want to have them hierarchal like this:

• AUF_1060589919844_59496
  • AUF_1079023138936_6682
  • AUF_1086686287581_9999
  • AUF_1086686329972_10049
• AUF_1421272434570_1781
  • AUF_1087981634453_7022
    • AUF_1421268568003_1743
    • AUF_1421268533080_1741
      • AUF_1421268719761_1776
• AUF_1422451819445_14260
  • AUF_1421268568003_1743

where should I try to apply it? (cell Factory?) and can you figure out a method to make the nested relationship?

Answer 1

Here is a solution which assumes that you know and supply as input the initial tree roots before-hand.

The solution works by recursively traversing the data structure to determine the TreeItems to be recorded at each level of the tree hierarchy. The solution assumes that the nodes in the input graph data structure is not cyclical. If there are cycles in the input data, the solution would loop forever.

This solution creates all of the tree item values up front before the tree is displayed rather than determining the tree item values for a given level when the user clicks to expand that level.

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeView;
import javafx.stage.Stage;

import java.util.Arrays;
import java.util.List;
import java.util.TreeMap;
import java.util.stream.Collectors;

public class NestedTree extends Application {
    @Override
    public void start(Stage stage) {
        // create some sample data.
        TreeMap<String, List<String>> data = new TreeMap<>();

        data.put("AUF_1060589919844_59496", Arrays.asList("AUF_1086686287581_9999", "AUF_1086686329972_10049", "AUF_1079023138936_6682"));
        data.put("AUF_1087981634453_7022", Arrays.asList("AUF_1421268533080_1741", "AUF_1421268568003_1743"));
        data.put("AUF_1421268533080_1741", Arrays.asList("AUF_1421268719761_1776"));
        data.put("AUF_1421272434570_1781", Arrays.asList("AUF_1087981634453_7022"));
        data.put("AUF_1422451819445_14260", Arrays.asList("AUF_1421268568003_1743"));

        String[] rootKeys = {
                "AUF_1060589919844_59496",
                "AUF_1421272434570_1781",
                "AUF_1422451819445_14260"
        };

        // create the tree from the data.
        TreeView<String> tree = createTreeView(
                data,
                rootKeys
        );

        // display the tree.
        Scene scene = new Scene(tree);
        stage.setScene(scene);
        stage.show();
    }

    /**
     * Create a TreeView of a set of data
     * given the data and identified roots within the data.
     */
    private TreeView<String> createTreeView(
            TreeMap<String, List<String>> data,
            String[] rootKeys
    ) {
        TreeItem<String> root = new TreeItem<>();
        Arrays.stream(rootKeys).sorted().forEach(
                rootKey ->
                        root.getChildren().add(
                                createTreeItem(data, rootKey)
                        )
        );

        TreeView<String> tree = new TreeView<>();
        tree.setRoot(root);
        tree.setShowRoot(false);

        return tree;
    }

    /**
     * Create a TreeItem for a TreeView from a set of data
     * given the data and an identified root within the data.
     */
    private TreeItem<String> createTreeItem(
            TreeMap<String, List<String>> data,
            String rootKey
    ) {
        TreeItem<String> item = new TreeItem<>();
        item.setValue(rootKey);
        item.setExpanded(true);

        List<String> childData = data.get(rootKey);
        if (childData != null) {
            childData.stream()
                .sorted()
                .map(
                        child -> createTreeItem(data, child)
                )
                .collect(
                        Collectors.toCollection(item::getChildren)
                );
        }

        return item;
    }

    public static void main(String[] args) {
        Application.launch(args);
    }
}