JavaFX Tutorial - JavaFX Collections

Collections in JavaFX are defined by the javafx.collections package, which consists of the following interfaces and classes:

Interfaces

interface	Description
ObservableList	A list that allows us to track changes
ListChangeListener	An interface that receives notifications of changes
ObservableMap	A map that allows us to track changes
MapChangeListener	An interface that receives notifications of changes from an ObservableMap

Classes

Class	Description
FXCollections	A utility class maps to java.util.Collections
ListChangeListener.Change	Represents a change made to an ObservableList
MapChangeListener.Change	Represents a change made to an ObservableMap

Example

The following code shows how to use ObservableList, ObservableMap, and FXCollections.

import java.util.ArrayList;
import java.util.List;
//from w ww .j a v a 2  s .  c o m
import javafx.collections.FXCollections;
import javafx.collections.ListChangeListener;
import javafx.collections.ObservableList;

public class Main {

  public static void main(String[] args) {
    List<String> list = new ArrayList<String>();

    ObservableList<String> observableList = FXCollections.observableList(list);
    observableList.addListener(new ListChangeListener() {
      @Override
      public void onChanged(ListChangeListener.Change change) {
        System.out.println("change!");
      }
    });
    observableList.add("item one");
    list.add("item two");
    System.out.println("Size: " + observableList.size());

  }
}

The code above generates the following result.

Example 2

The following code shows how to listen for changes on an ObservableMap.

import java.util.HashMap;
import java.util.Map;
/*from   www  .  j a  v a  2  s . co  m*/
import javafx.collections.FXCollections;
import javafx.collections.MapChangeListener;
import javafx.collections.ObservableMap;

public class Main {

  public static void main(String[] args) {
    Map<String, String> map = new HashMap<String, String>();
    ObservableMap<String, String> observableMap = FXCollections
        .observableMap(map);
    observableMap.addListener(new MapChangeListener() {
      @Override
      public void onChanged(MapChangeListener.Change change) {
        System.out.println("change! ");
      }
    });
    observableMap.put("key 1", "value 1");
    map.put("key 2", "value 2");

  }
}

The code above generates the following result.

Example 3

The following code shows how to find out what has been changed.

import java.util.ArrayList;
import java.util.List;
//w w w .ja  va2 s. c o m
import javafx.collections.FXCollections;
import javafx.collections.ListChangeListener;
import javafx.collections.ObservableList;

public class Main {

  public static void main(String[] args) {
    List<String> list = new ArrayList<String>();

    ObservableList<String> observableList = FXCollections.observableList(list);
    observableList.addListener(new ListChangeListener() {
      
      @Override
      public void onChanged(ListChangeListener.Change change) {
          System.out.println("Detected a change! ");
          while (change.next()) {
              System.out.println("Was added? " + change.wasAdded());
              System.out.println("Was removed? " + change.wasRemoved());
              System.out.println("Was replaced? " + change.wasReplaced());
              System.out.println("Was permutated? " + change.wasPermutated());
              }
          }
      });
    observableList.add("item one");
    list.add("item two");
    System.out.println("Size: " + observableList.size());

  }
}

The code above generates the following result.