import java.util.ArrayList;
import java.util.Random;

import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeView;
import javafx.stage.Stage;


public class TestTreeView extends Application {
	public static void main(String[] args) {
        launch(args);
    }
     
    @Override
    public void start(Stage primaryStage) {
    	TreeView<String> treeView = new TreeView<>();

        Group g = new Group();
        g.getChildren().addAll(treeView);
        primaryStage.setScene(new Scene(g, 500, 400));
        primaryStage.show();

		TreeItem<String> root = new DynamicTreeItem(0);
		root.setValue("root");
		
		treeView.setRoot(root);
		root.setExpanded(true);
		
    	treeView.getSelectionModel().selectedItemProperty().addListener(new ChangeListener<TreeItem<String>>() {
			@Override
			public void changed(ObservableValue<? extends TreeItem<String>> observable, TreeItem<String> oldVal, TreeItem<String> newVal) {
				System.out.println("Selected: "+newVal + " (oldval:"+oldVal+")");
			}
    		
    	});

    }
}

class DynamicTreeItem extends TreeItem<String> {
    private boolean isFirstTimeChildren = true;
    private boolean isLeaf = false;
    private int depth;
    private static final int MAX_DEPTH=5;
    private Random rand = new Random();

    
    public DynamicTreeItem(int depth) {
    	this.depth = depth;
    	if(depth >= MAX_DEPTH)
    		isLeaf = true;
    }

	@Override
	public boolean isLeaf() {
		return isLeaf;
	}

	@Override
	public ObservableList<TreeItem<String>> getChildren() {
		//dynamically load children first time in
		if (isFirstTimeChildren) {
			isFirstTimeChildren = false;
			super.getChildren().setAll(buildChildren(this));
		}

		return super.getChildren();
	}

	private ObservableList<DynamicTreeItem> buildChildren(DynamicTreeItem itm) {

		//build a random number of nodes
		int items = rand.nextInt(20)+1;
		ArrayList<DynamicTreeItem> list = new ArrayList<>();

		int childdepth = depth+1;
		for(int i=0; i<items; i++) {
			DynamicTreeItem item = new DynamicTreeItem(childdepth);
			item.setValue(childdepth+"/"+i);
			list.add(item);
		}
		
		ObservableList<DynamicTreeItem> children = FXCollections.observableList(list);
		return children;
	}
	
}