JavaFX Expandable ListView

ExpandableListView.java

/**
 * Copyright (C) 2015 uphy.jp
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package expandablelistview;

import javafx.collections.ObservableList;
import javafx.event.EventHandler;
import javafx.scene.control.ListCell;
import javafx.scene.control.ListView;
import javafx.scene.control.TitledPane;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.BorderPane;
import javafx.scene.text.Text;
import javafx.util.Callback;

import java.util.HashSet;
import java.util.Set;


/**
 * @author Yuhi Ishikura
 */
public class ExpandableListView<E> extends ListView<E> {

  private ContentProvider<E> contentProvider = new ContentProvider<E>() {
    @Override
    public String getTitleOf(final E item) {
      return item.toString();
    }

    @Override
    public String getContentOf(final E item) {
      return getTitleOf(item);
    }
  };

  private final Set<E> expandedItems = new HashSet<E>();

  public ExpandableListView() {
    setSelectionModel(null);
    setCellFactory(new Callback<ListView<E>, ListCell<E>>() {
      @Override
      public ListCell<E> call(final ListView<E> param) {
        final TitledPane titledPane = new TitledPane();
        final Text contentArea = new Text();

        titledPane.setAnimated(false);
        titledPane.setCollapsible(true);
        titledPane.setExpanded(false);

        final BorderPane contentAreaWrapper = new BorderPane();
        contentAreaWrapper.setLeft(contentArea);
        titledPane.setContent(contentAreaWrapper);

        titledPane.addEventHandler(MouseEvent.MOUSE_CLICKED, new EventHandler<MouseEvent>() {
          @Override
          public void handle(final MouseEvent event) {
            final boolean expanded = titledPane.isExpanded();
            final E item = (E)titledPane.getUserData();
            if (item == null) {
              return;
            }
            if (expanded) {
              expandedItems.add(item);
            } else {
              expandedItems.remove(item);
            }
          }
        });
        return new ListCell<E>() {
          @Override
          protected void updateItem(final E item, final boolean empty) {
            super.updateItem(item, empty);
            if (empty) {
              titledPane.setText("");
              contentArea.setText("");
              return;
            }
            final boolean expanded = isExpanded(item);
            titledPane.setUserData(item);
            titledPane.setExpanded(expanded);
            titledPane.setText(contentProvider.getTitleOf(item));
            contentArea.setText(contentProvider.getContentOf(item));
            setGraphic(titledPane);
          }
        };
      }
    });
    getStylesheets().add(String.format("/%s/style.css", getClass().getPackage().getName().replaceAll("\\.", "/")));
  }

  public void setContentProvider(final ContentProvider<E> contentProvider) {
    this.contentProvider = contentProvider;
  }

  public void expand(E item) {
    expand(item, true);
  }

  public void collapse(E item) {
    expand(item, false);
  }

  private void expand(E item, boolean expand) {
    if (expand) {
      this.expandedItems.add(item);
    } else {
      this.expandedItems.remove(item);
    }

    ObservableList<E> o = getItems();
    setItems(null);
    setItems(o);
  }

  public boolean isExpanded(E item) {
    return this.expandedItems.contains(item);
  }

  public static interface ContentProvider<E> {

    String getTitleOf(E item);

    String getContentOf(E item);

  }

}

Main.java

/**
 * Copyright (C) 2015 uphy.jp
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package expandablelistview;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;


/**
 * @author Yuhi Ishikura
 */
public class Main extends Application {

  @Override
  public void start(final Stage primaryStage) throws Exception {
    final ExpandableListView<Item> listView = new ExpandableListView<Item>();
    listView.setContentProvider(new ExpandableListView.ContentProvider<Item>() {
      @Override
      public String getTitleOf(final Item item) {
        return item.getTitle();
      }

      @Override
      public String getContentOf(final Item item) {
        return item.getContent();
      }
    });
    for (int i = 0; i < 100000; i++) {
      listView.getItems().add(new Item("title" + i, "content" + i));
    }

    final BorderPane group = new BorderPane();
    group.setCenter(listView);
    final Scene scene = new Scene(group);
    primaryStage.setScene(scene);
    primaryStage.show();
  }

  public static class Item {

    String title;
    String content;

    public Item(String title, String content) {
      this.title = title;
      this.content = content;
    }

    public String getTitle() {
      return title;
    }

    public String getContent() {
      return content;
    }
  }

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

style.css

.list-cell {
    -fx-padding: 0;
    -fx-background-color: white;
}

.titled-pane:focused {
    -fx-text-fill: black;
}

.titled-pane > .title {
    -fx-background-color: -fx-box-border, -fx-inner-border, white;
}

Pretty cool piece of code! I just have one question, have you already implemented a way to get selected children items? Thanks

Thanks my bro!