javafx - sort tableview with drag and drop (rows)

Question

my aim is to sort a tableview with drag and drop. I followed this example: http://docs.oracle.com/javafx/2/fxml_get_started/fxml_tutorial_intermediate.htm

For drag and drop I added the fxml via Scene Builder

<TableView fx:id="tableView" onDragDetected="#dragDetected" onDragDropped="#dragDropped" onDragOver="#dragOver"

and made the controllers

@FXML
    private void dragDetected(MouseEvent event) {
        System.out.println("dragDetected");

        Integer idx;
        idx = tableView.getSelectionModel().getFocusedIndex();
        Dragboard db = tableView.startDragAndDrop(TransferMode.MOVE);
        ClipboardContent content = new ClipboardContent();
        content.putString(idx.toString());
        db.setContent(content);

        System.out.println(idx);
//        System.out.println(event.getPickResult());
        event.consume();
    }

    @FXML
    private void dragOver(DragEvent event) {
        event.acceptTransferModes(TransferMode.COPY_OR_MOVE);
        event.consume();
    }

    @FXML
    private void dragDropped(DragEvent event) {
        System.out.println("dragDropped");

        System.out.println(event.getTarget());
        System.out.println(event.getPickResult());
    }

but at drag dropped I cant get the row of the place where I dropped the object. All I get is the cell Information. Text[text="Smith", x=0.0, y=0.0, ...

How do I get this work? Maybe Class TableRow<T> could help, but I do not understand how to use it proberly.

Answer 1

As you suspected, the answer is to use a TableRow. You do this by setting a row factory on your table, which is used to create the table rows as they are needed. You can create them and set the drag handlers on them before returning them.

So, remove the onDragDetected, onDragDropped etc attributes from the FXML, and in the initialize method in the controller set the drag handlers on the row.

Here is a complete example, using the usual example from the Oracle tutorials. I didn't use FXML in this example (I just created the table view directly in the Java class), but you can just move all the table view configuration to the initialize method.

import java.util.function.Function;

import javafx.application.Application;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.beans.value.ObservableValue;
import javafx.scene.Scene;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableRow;
import javafx.scene.control.TableView;
import javafx.scene.input.ClipboardContent;
import javafx.scene.input.DataFormat;
import javafx.scene.input.Dragboard;
import javafx.scene.input.TransferMode;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;

public class TableViewDragRows extends Application {

    private static final DataFormat SERIALIZED_MIME_TYPE = new DataFormat("application/x-java-serialized-object");

    @Override
    public void start(Stage primaryStage) {
        TableView<Person> tableView = new TableView<>();
        tableView.getColumns().add(createCol("First Name", Person::firstNameProperty, 150));
        tableView.getColumns().add(createCol("Last Name", Person::lastNameProperty, 150));
        tableView.getColumns().add(createCol("Email", Person::emailProperty, 200));

        tableView.getItems().addAll(
            new Person("Jacob", "Smith", "jacob.smith@example.com"),
            new Person("Isabella", "Johnson", "isabella.johnson@example.com"),
            new Person("Ethan", "Williams", "ethan.williams@example.com"),
            new Person("Emma", "Jones", "emma.jones@example.com"),
            new Person("Michael", "Brown", "michael.brown@example.com")
        );

        tableView.setRowFactory(tv -> {
            TableRow<Person> row = new TableRow<>();

            row.setOnDragDetected(event -> {
                if (! row.isEmpty()) {
                    Integer index = row.getIndex();
                    Dragboard db = row.startDragAndDrop(TransferMode.MOVE);
                    db.setDragView(row.snapshot(null, null));
                    ClipboardContent cc = new ClipboardContent();
                    cc.put(SERIALIZED_MIME_TYPE, index);
                    db.setContent(cc);
                    event.consume();
                }
            });

            row.setOnDragOver(event -> {
                Dragboard db = event.getDragboard();
                if (db.hasContent(SERIALIZED_MIME_TYPE)) {
                    if (row.getIndex() != ((Integer)db.getContent(SERIALIZED_MIME_TYPE)).intValue()) {
                        event.acceptTransferModes(TransferMode.COPY_OR_MOVE);
                        event.consume();
                    }
                }
            });

            row.setOnDragDropped(event -> {
                Dragboard db = event.getDragboard();
                if (db.hasContent(SERIALIZED_MIME_TYPE)) {
                    int draggedIndex = (Integer) db.getContent(SERIALIZED_MIME_TYPE);
                    Person draggedPerson = tableView.getItems().remove(draggedIndex);

                    int dropIndex ; 

                    if (row.isEmpty()) {
                        dropIndex = tableView.getItems().size() ;
                    } else {
                        dropIndex = row.getIndex();
                    }

                    tableView.getItems().add(dropIndex, draggedPerson);

                    event.setDropCompleted(true);
                    tableView.getSelectionModel().select(dropIndex);
                    event.consume();
                }
            });

            return row ;
        });


        Scene scene = new Scene(new BorderPane(tableView), 600, 400);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    private TableColumn<Person, String> createCol(String title, 
            Function<Person, ObservableValue<String>> mapper, double size) {

        TableColumn<Person, String> col = new TableColumn<>(title);
        col.setCellValueFactory(cellData -> mapper.apply(cellData.getValue()));
        col.setPrefWidth(size);

        return col ;
    }


   public class Person {
        private final StringProperty firstName = new SimpleStringProperty(this, "firstName");
        private final StringProperty lastName = new SimpleStringProperty(this, "lastName");
        private final StringProperty email = new SimpleStringProperty(this, "email");

        public Person(String firstName, String lastName, String email) {
            this.firstName.set(firstName);
            this.lastName.set(lastName);
            this.email.set(email);
        }

        public final StringProperty firstNameProperty() {
            return this.firstName;
        }

        public final String getFirstName() {
            return this.firstNameProperty().get();
        }

        public final void setFirstName(final String firstName) {
            this.firstNameProperty().set(firstName);
        }

        public final StringProperty lastNameProperty() {
            return this.lastName;
        }

        public final String getLastName() {
            return this.lastNameProperty().get();
        }

        public final void setLastName(final String lastName) {
            this.lastNameProperty().set(lastName);
        }

        public final StringProperty emailProperty() {
            return this.email;
        }

        public final String getEmail() {
            return this.emailProperty().get();
        }

        public final void setEmail(final String email) {
            this.emailProperty().set(email);
        }

    }

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