Home » Java » Desktop Java » Properties Extractor: Best way to get the ListView instantly updating its elements

About Jens Deters

Jens Deters is a Senior Software Developer working in the domain of Aviation Authorities. His main objectives are RIA and Desktop Applications also he loves to play with IoT related stuff.

Properties Extractor: Best way to get the ListView instantly updating its elements

This post is about how to deal with JavaFX ListViews and TableViews and how these controls are getting informed about changed content of the contained elements. I wonder why I didn’t find anything about the following pattern in the relevant books as this is a really crucial mechanism. Many posts out there suggest to force triggering a ChangeEvent getting a ListView to refresh by calling:

list.remove(POJO);
list.add(index,POJO);

after each commited change! Brrr!

 

But there is a much better way:

Enable your list to report changes on the element by providing an properties extractor.

The Demo App

I have created a small demo app to play with for giving it a try. Basically two TableViews and one ListView all sharing the same data. To change properties of the elements one TableView is editable:

PropertiesExtractor-Demo1

The DataModel

The compulsive PersonBean folling the JavaFX Bean Pattern/Convention

public class PersonBean {

    private StringProperty firstName;
    private StringProperty lastName;
    private ObjectProperty<LocalDate> birthday;
    private ObjectBinding<Long> age;

    public PersonBean() {
    }

    public PersonBean(String firstName, String lastName, LocalDate birthday) {
        setFirstName(firstName);
        setLastName(lastName);
        setBirthday(birthday);
    }

    public final StringProperty firstNameProperty() {
        if (firstName == null) {
            firstName = new SimpleStringProperty();
        }
        return firstName;
    }

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

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

    public final StringProperty lastNameProperty() {
        if (lastName == null) {
            lastName = new SimpleStringProperty();
        }
        return lastName;
    }

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

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

    public final ObjectProperty<LocalDate> birthdayProperty() {
        if (birthday == null) {
            birthday = new SimpleObjectProperty<>();
        }
        return birthday;
    }

    public final LocalDate getBirthday() {
        return birthdayProperty().get();
    }

    public final void setBirthday(final java.time.LocalDate birthday) {
        birthdayProperty().set(birthday);

    }

    public String stringValue() {
        return String.format("%s %s %s", getFirstName(), getLastName(), getBirthday().format(DateTimeFormatter.ISO_LOCAL_DATE));
    }

    public final ObjectBinding<Long> ageBinding() {
        if (age == null) {
            age = new ObjectBinding<Long>() {
                {
                    bind(birthdayProperty());
                }

                @Override
                protected Long computeValue() {
                    if (getBirthday() == null) {
                        return null;
                    }
                    return getBirthday().until(LocalDate.now(), ChronoUnit.YEARS);
                }
            };
        }
        return age;
    }

    public static Callback<PersonBean, Observable[]> extractor() {
        return (PersonBean p) -> new Observable[]{p.lastNameProperty(), p.firstNameProperty(), p.birthdayProperty(), p.ageBinding()};
    }
}

DataModel containing a List of randomly created PersonBeans:

public class DataModel {

    private ObservableList<PersonBean> personFXBeans;

    public DataModel() {
        init();
    }

    private void init() {
        personFXBeans = DataSource.getRandomPersonBeansList(100);
    }

    public ObservableList<PersonBean> getPersonFXBeans() {
        return personFXBeans;
    }
}

As you may know to assign a DataModel e.g. to a TableView or a ListView in JavaFX you just have to use the setItems(ObvervableList) method.

@FXML
public void onFillWithDemoDataFXBeans() {
  readOnlyListView.setItems(model.getPersonFXBeans());
  readOnlyTableView.setItems(model.getPersonFXBeans());
  editableTableView.setItems(model.getPersonFXBeans());
}

Now getting a TableView informed about property changes of contained elements is already done you for by the binding either in two ways: via a PropertyValueFactory and by more or less direct property binding:

readOnlyFirstNameColumn.setCellValueFactory(new PropertyValueFactory<>("firstName"));
readOnlyLastNameColumn.setCellValueFactory(new PropertyValueFactory<>("lastName"));
readOnlyBirthdayColumn.setCellValueFactory(new PropertyValueFactory<>("birthday"));
readOnlyAgeColumn.setCellValueFactory(i -> i.getValue().ageBinding());

editableFirstNameColumn.setCellValueFactory(i -> i.getValue().firstNameProperty());
editableLastNameColumn.setCellValueFactory(i -> i.getValue().lastNameProperty());
editableBirthdayColumn.setCellValueFactory(i -> i.getValue().birthdayProperty());
ageColumn.setCellValueFactory(i -> i.getValue().ageBinding());

But the ListView basically only observes the list and not the properties of each element of that list.

When using a ObservableList created by FXCollections.observableArrayList() the ListView will only refresh on ListChange Events like remove() an add() of elements. Therefore:

list.remove(POJO);
list.add(index,POJO);

after each commited change.

But there is a much better way:

Enable your list to report changes on the element by providing an properties extractor. You don’t have to care about refreshing then!

ObservableList persons = FXCollections.observableArrayList(PersonBean.extractor());

See DataSource.getRandomPersonBeansList(int length):

public static ObservableList<PersonBean> getRandomPersonBeansList(int length) {
        ObservableList<PersonBean> persons = FXCollections.observableArrayList(PersonBean.extractor());
        for (int i = 0; i < length; i++) {
            persons.add(new PersonBean(getRandomName(), getRandomLastname(), getRandomLocalDate()));
        }
        return persons;
    }

This Extrator is basically a Callback containing an array of Obvervables which are then observed by the Obervablelist (more precicely: ObservableListWrapper):

My PersonBean already provides it’s extrator callback:

public static Callback<PersonBean, Observable[]> extractor() {
   return (PersonBean p) -> new Observable[]{p.lastNameProperty(), p.firstNameProperty(), p.birthdayProperty(), p.ageBinding()};
}

Following this pattern all controls are updated instantly after applying the change.

Edit data…

PropertiesExtractor-Demo3

and commit:

PropertiesExtractor-Demo4

THE CODE PLEASE!

You can find the complete code at my BitBucket Repo.

Do you want to know how to develop your skillset to become a Java Rockstar?

Subscribe to our newsletter to start Rocking right now!

To get you started we give you our best selling eBooks for FREE!

 

1. JPA Mini Book

2. JVM Troubleshooting Guide

3. JUnit Tutorial for Unit Testing

4. Java Annotations Tutorial

5. Java Interview Questions

6. Spring Interview Questions

7. Android UI Design

 

and many more ....

 

Receive Java & Developer job alerts in your Area

I have read and agree to the terms & conditions

 

Subscribe
Notify of
guest

This site uses Akismet to reduce spam. Learn how your comment data is processed.

0 Comments
Inline Feedbacks
View all comments