public void PathLineHandler(Stage stage){
    final TreeItem<File> treeitem = treeview.getSelectionModel().getSelectedItem();
    if(treeitem.isExpanded()){
        treeitem.setExpanded(false);
    }else {
        EventHandler<ActionEvent> startEvent = new EventHandler<ActionEvent>() {

            public void handle(ActionEvent event) {
                treeitem.setGraphic(new ImageView(waiting));

            }
        };
        EventHandler<ActionEvent> endEvent = new EventHandler<ActionEvent>() {
            public void handle(ActionEvent event) {
                treeitem.setExpanded(true);
                String path = treeitem.getValue().getAbsolutePath();
                root.setText(path);

            }
        };

        Timeline timeline = new Timeline();

        KeyFrame key1 = new KeyFrame(Duration.ZERO);
        KeyFrame key2 = new KeyFrame(Duration.seconds(2), "end", startEvent);
        timeline.getKeyFrames().addAll(key1,key2);
        timeline.setOnFinished(endEvent);
        timeline.playFromStart();
    }
}

package Application;

import java.io.File;

import javafx.animation.KeyFrame;
import javafx.animation.KeyValue;
import javafx.animation.PauseTransition;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.control.TreeCell;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeView;
import javafx.scene.effect.InnerShadow;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.input.KeyEvent;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.scene.paint.Color;
import javafx.stage.Modality;
import javafx.stage.Stage;
import javafx.util.Callback;
import javafx.util.Duration;

//Основное окно
public class FileManager extends Application {

    FileSeeker fseek = new FileSeeker(new File("C:\"));
    TreeView<File> treeview = new TreeView<File>(fseek);
    final Label warn = new Label("Выберите Каталог");
    Label root = new Label("C:\");

    final Image waiting = new Image(getClass().getResourceAsStream("ImagesAndCss/hourglass.png"));
    String iconAdd = FileManager.class.getResource("ImagesAndCss/kde_add_folder_to_archive.png").toExternalForm();

    @Override
    public void start(final Stage primaryStage) throws Exception {

        EventHandler<ActionEvent> addDir = new EventHandler<ActionEvent>() {
            public void handle(ActionEvent event) {
                CodeHandler(primaryStage);
                }
        };
        EventHandler<KeyEvent> addDirf7 = new EventHandler<KeyEvent>() {
            public void handle(KeyEvent event) {
                CodeHandler(primaryStage);
            }
        };
        EventHandler<MouseEvent> pathLine = new EventHandler<MouseEvent>() {
            public void handle(MouseEvent event) {
                PathLineHandler(primaryStage);
            }
        };

        String css = FileManager.class.getResource("ImagesAndCss/Main.css").toExternalForm();
        String icon = FileManager.class.getResource("ImagesAndCss/foldopen16.png").toExternalForm();

        Button addDirectory = new Button("Создать каталог (F7)");
        addDirectory.setGraphic(new ImageView(iconAdd));
        addDirectory.setId("AddDir");
        final BorderPane spane = new BorderPane();
        spane.setStyle("-fx-text-fill: white;-fx-background-color: #24011F;");

        HBox But = new HBox();
        But.setPadding(new Insets(5));

        Scene scene = new Scene(spane, 600, 600);

        scene.getStylesheets().add(css);

        root.setStyle("-fx-text-fill: white;");
        warn.setStyle("-fx-text-fill: yellow;");

        reduceNames(treeview);
        addDirectory.setOnAction(addDir);

        fseek.setExpanded(true);

        But.getChildren().addAll(addDirectory,warn);

        spane.setTop(root);
        spane.setCenter(treeview);
        spane.setBottom(But);

        madeShadow(treeview,50);
        madeShadow(But,2);

        scene.setOnKeyPressed(addDirf7);
        treeview.setOnMouseClicked(pathLine);

        primaryStage.setTitle("Файловый менеджер");
        primaryStage.setScene(scene);
        primaryStage.getIcons().add(new Image(icon));
        primaryStage.show();

    }

    //Код для обработчиков
    //Добавление каталога
    public void CodeHandler(Stage stage){
        try{
            File f = treeview.getSelectionModel().getSelectedItem().getValue();
            if(f == null || !f.isDirectory()){
                warn.setText("Ошибка.Вы выбрали файл, а не Директорию");
            } else {
                warn.setText("Выберите каталог");
            final Stage addDirStage = new AddDirectory(stage,f.getAbsolutePath());
            addDirStage.show();
            }
            }catch(NullPointerException e) {
                warn.setText("Директория не выбрана!");
            }
        }

    //Заморозка и обновление линии
    public void PathLineHandler(Stage stage){
        final TreeItem<File> treeitem = treeview.getSelectionModel().getSelectedItem();
        if(treeitem.isExpanded()){
            treeitem.setExpanded(false);
        }else {
            EventHandler<ActionEvent> startEvent = new EventHandler<ActionEvent>() {

                public void handle(ActionEvent event) {
                    treeitem.setGraphic(new ImageView(waiting));

                }
            };
            EventHandler<ActionEvent> endEvent = new EventHandler<ActionEvent>() {
                public void handle(ActionEvent event) {
                    treeitem.setExpanded(true);
                    String path = treeitem.getValue().getAbsolutePath();
                    root.setText(path);

                }
            };

            Timeline timeline = new Timeline();

            KeyFrame key1 = new KeyFrame(Duration.ZERO);
            KeyFrame key2 = new KeyFrame(Duration.seconds(2), "end", startEvent);
            timeline.getKeyFrames().addAll(key1,key2);
            timeline.setOnFinished(endEvent);
            timeline.playFromStart();
        }
    }

    //Обрезает имена файлов и каталогов,добавляет иконки
    public void reduceNames(TreeView<File> treeview) {
        treeview.setCellFactory(new Callback<TreeView<File>, TreeCell<File>>() {
            public TreeCell<File> call(TreeView<File> tv) {
                return new TreeCell<File>() {
                    @Override
                    protected void updateItem(File item, boolean empty) {
                        super.updateItem(item, empty);
                        setText((empty || item == null) ? "" : item.getName());
                        setGraphic((empty || item == null) ? null : this.getTreeItem().getGraphic());
                    }

                };
            }
        });
    }

    //Дополнительное окно с добавлением каталога
    public class AddDirectory extends Stage {

        public AddDirectory(Stage parent,final String path) {
            initOwner(parent);
            initModality(Modality.WINDOW_MODAL);

            BorderPane bpane = new BorderPane();
            bpane.setStyle("-fx-text-fill: white; -fx-background-color: #24011F; ");

            HBox buts = new HBox(5);
            HBox addField = new HBox();

            addField.setPadding(new Insets(5));
            buts.setPadding(new Insets(5));

            Button add = new Button("Создать");
            Button cancel = new Button("Отмена");

            Label pathl = new Label("Имя Каталога: ");

            add.setStyle("-fx-color: green;");
            cancel.setStyle("-fx-color: red;");
            pathl.setStyle("-fx-text-fill: white");

            final TextField enterpath = new TextField("Новый Каталог");

            enterpath.setMinWidth(400);
            enterpath.setMaxWidth(600);

            buts.getChildren().addAll(add,cancel);
            addField.getChildren().addAll(pathl,enterpath);
            bpane.setBottom(buts);
            bpane.setCenter(addField);

            add.setOnAction(new EventHandler<ActionEvent>() {
                public void handle(ActionEvent event) {
                    File f = new File(path + "\" + enterpath.getText());
                    if(!f.exists()){
                        f.mkdir();
                        close();
                    }

                }
            });


            cancel.setOnAction(new EventHandler<ActionEvent>() {
                public void handle(ActionEvent event) {
                    close();
                }
            });



            Scene scene = new Scene(bpane, 500, 100);
            scene.getOnKeyPressed();

            setResizable(false);
            setScene(scene);
            getIcons().add(new Image(iconAdd));
            setTitle("Добавить каталог");


        }
    }

    //Эффект внутренней тени
    public void madeShadow(Node node, double res){
        InnerShadow insh = new InnerShadow(res, Color.BLACK);
        node.setEffect(insh);
    }

    //Старт
    public static void main(String [] args){
        launch(args);
    }
}

package Application;

import java.io.File;

import javafx.animation.KeyFrame;
import javafx.animation.KeyValue;
import javafx.animation.PauseTransition;
import javafx.animation.Timeline;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Node;
import javafx.scene.control.TreeItem;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.util.Duration;

public class FileSeeker extends TreeItem<File> {

     Image icon = new Image(FileSeeker.class.getResourceAsStream("ImagesAndCss/ico.png"));
     Image open = new Image(FileSeeker.class.getResourceAsStream("ImagesAndCss/foldopen16.png"));
     Image close = new Image(FileSeeker.class.getResourceAsStream("ImagesAndCss/foldclose16.png"));
     Image waiting = new Image(FileSeeker.class.getResourceAsStream("ImagesAndCss/hourglass.png"));

    public FileSeeker(File file) {
        super(file);
    }

    @Override
    public ObservableList<TreeItem<File>> getChildren() {
        if (isFirstChildren) {
            isFirstChildren = false;
            super.getChildren().setAll(buildFoldersAndFiles(this));
        }
        return super.getChildren();
    }

    @Override
    public boolean isLeaf() {
        if (isFirstLeaf) {
            isFirstLeaf = false;
            File f = (File) getValue();
            isLeaf = f.isFile();
        }

        return isLeaf;
    }

    private ObservableList<TreeItem<File>> buildFoldersAndFiles(TreeItem<File> treeItem) {
        File f = treeItem.getValue();
        f.getName();
        if (f != null) {
            File[] files = f.listFiles();
                ObservableList<TreeItem<File>> children = FXCollections
                        .observableArrayList();

                for (File childFile : files) {
                    if(childFile.isDirectory()){
                    final FileSeeker fs = new FileSeeker(childFile);
                    Setter(fs);
                    fs.expandedProperty().addListener(new ChangeListener<Boolean>() {
                        public void changed(ObservableValue<? extends Boolean> observable, Boolean oldValue,
                                Boolean newValue) {

                            Setter(fs);
                        }
                    });
                    children.add(fs);
                    } else {
                        FileSeeker fs = new FileSeeker(childFile);
                        fs.setGraphic(new ImageView(icon));
                        children.add(fs);
                    }
            }
                return children;
        }

        return FXCollections.emptyObservableList();
    }

    public void Setter(FileSeeker fs){
        if (fs.isExpanded()){
            fs.setGraphic(new ImageView(open));
        } else {
            fs.setGraphic(new ImageView(close));
        }
    }

    private boolean isFirstChildren = true;
    private boolean isFirstLeaf = true;
    private boolean isLeaf;
}