JavaFX - TreeTableView sortPolicyProperty()

Question

My question is how to create a treetableview(JavaFX8) with my own Comparator.

I have found some examples like JavaFX TableView Sort Policy but they are all TableView not TreeTableView.

Thanks.

Here is my example code :

 import java.util.Comparator;
 import javafx.application.Application;
 import javafx.application.Platform;
 import javafx.beans.property.ReadOnlyObjectWrapper;
 import javafx.beans.property.SimpleStringProperty;
 import javafx.collections.FXCollections;
 import javafx.collections.ObservableList;
 import javafx.geometry.Insets;
 import javafx.scene.Group;
 import javafx.scene.Scene;
 import javafx.scene.control.Label;
 import javafx.scene.control.TreeItem;
 import javafx.scene.control.TreeTableColumn;
 import javafx.scene.control.TreeTableView;
 import javafx.scene.layout.VBox;
 import javafx.scene.text.Font;
 import javafx.stage.Stage;
 import javafx.util.Callback;

public class TableViewSampleWithoutEdit extends Application {
     private TreeTableView<Person> table = new TreeTableView<Person>();
     private ExtraPerson extraPerson = new ExtraPerson("Ninja Village");
     TreeItem root = new TreeItem<>("root");
     private final ObservableList<TreeItem<Person>> data = FXCollections
        .observableArrayList(
                new TreeItem<Person>( new Person("Jacob", "Smith", "jacob.smith@example.com")),
                new TreeItem<Person>( new Person("Isabella", "Johnson","isabella.johnson@example.com")),
                new TreeItem<Person>( new Person("Ethan", "Williams","ethan.williams@example.com")),
                new TreeItem<Person>(  new Person("Emma", "Jones", "emma.jones@example.com")),
                new TreeItem<Person>( new Person("Michael", "Brown", "michael.brown@example.com")),
                new TreeItem<Person>( extraPerson));

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

@Override
public void start(Stage stage) {
    Scene scene = new Scene(new Group());
    stage.setTitle("Table View Sample");
    stage.setWidth(450);
    stage.setHeight(500);

    final Label label = new Label("Address Book");
    label.setFont(new Font("Arial", 20));

    table.setEditable(true);
    Platform.runLater(() -> {
    TreeTableColumn<Person, String> firstNameCol = new TreeTableColumn("First Name");
    firstNameCol.setMinWidth(100);
    firstNameCol.setCellValueFactory(cellData -> {

        if (cellData.getValue().getValue()instanceof Person) {
            return new ReadOnlyObjectWrapper(cellData.getValue().getValue().getFirstName());

        }
        return new ReadOnlyObjectWrapper(cellData.getValue().getValue());
    });
    TreeTableColumn<Person, String> lastNameCol = new TreeTableColumn("Last Name");
    lastNameCol.setMinWidth(100);
    lastNameCol.setCellValueFactory(cellData -> {
        if (cellData.getValue().getValue()instanceof Person) {

            return new ReadOnlyObjectWrapper(cellData.getValue().getValue().getLastName());

        }
        return new ReadOnlyObjectWrapper(cellData.getValue().getValue());
    });       

    /**
     * Adding comparator to extraPerson
     */

    table.sortPolicyProperty().set(
            new Callback<TreeTableView<Person>, Boolean>() {

                @Override
                public Boolean call(final TreeTableView<Person> param) {
                    Comparator<TreeItem<Person>> comparator = new Comparator<TreeItem<Person>>() {
                        @Override
                        public int compare(TreeItem<Person> r1, TreeItem<Person> r2) {
                            if (r1.getValue() == extraPerson) {
                                return 1;
                            } else if (r2.getValue() == extraPerson) {
                                return -1;
                            } else if (param.getComparator() == null) {
                                return 0;
                            } else {System.out.println("c");
                                return param.getComparator()
                                        .compare(r1, r2);
                            }
                        }
                    };
                    ObservableList<TreeItem<Person>> tables = FXCollections.observableArrayList();
                    for (int i = 0; i < table.getExpandedItemCount(); i++) {
                        tables.add(table.getTreeItem(0));
                    }

                    FXCollections.sort(tables,comparator);
                    if (tables.size()>0) {
                        table.getRoot().getChildren().setAll(tables);
                    }

                    return true;
                }

            });
    root.getChildren().setAll(data);
    table.setRoot(root);
    table.getColumns().addAll(firstNameCol, lastNameCol);
    root.setExpanded(true);
    final VBox vbox = new VBox();
    vbox.setSpacing(5);
    vbox.setPadding(new Insets(10, 0, 0, 10));
    vbox.getChildren().addAll(label, table);

    ((Group) scene.getRoot()).getChildren().addAll(vbox);

    stage.setScene(scene);
    stage.show();
}

public static class Person {

    private final SimpleStringProperty firstName;
    private final SimpleStringProperty lastName;
    private final SimpleStringProperty email;

    private Person(String fName, String lName, String email) {
        this.firstName = new SimpleStringProperty(fName);
        this.lastName = new SimpleStringProperty(lName);
        this.email = new SimpleStringProperty(email);
    }

    public String getFirstName() {
        return firstName.get();
    }

    public void setFirstName(String fName) {
        firstName.set(fName);
    }

    public String getLastName() {
        return lastName.get();
    }

    public void setLastName(String fName) {
        lastName.set(fName);
    }

    public String getEmail() {
        return email.get();
    }

    public void setEmail(String fName) {
        email.set(fName);
    }
}

public static class ExtraPerson extends Person {

    private final SimpleStringProperty address;

    private ExtraPerson(String address) {
        super("Itachi", "Uchiha", "leaf@village.ninja");
        this.address = new SimpleStringProperty(address);
    }

    public String getAddress() {
        return address.get();
    }

    public void setAddress(String address) {
        this.address.set(address);
    }

}
}

Answer 1

Just replace this ...

ObservableList<TreeItem<Person>> tables = FXCollections.observableArrayList();
for (int i = 0; i < table.getExpandedItemCount(); i++) {
    tables.add(table.getTreeItem(0));
}

FXCollections.sort(tables,comparator);
if (tables.size()>0) {
    table.getRoot().getChildren().setAll(tables);
}

... with this ...

if(table.getRoot() != null)
    FXCollections.sort(table.getRoot().getChildren(), comparator);

... and it will work (at least for the TreeTableView in your question).

It is exactly the same that in the answer you have mentioned:

You create a Comparator to be used on a collection of objects in your TreeTableView. The only difference that you use this comparator on different lists: in the linked answer it is used to compare table.getItems() and I modified this to be used on table.getRoot().getChildren() (child nodes of the root node).

Notice if you add more than one level1 TreeItem, or you increase the tree-level you have to adapt it, but the workflow is the same.