Edit multiple elements in ObservableList and only fire change listeners after last change

问题

I have an ObservableList that doesn't only trigger the registered ListChangeListeners when elements are added or removed, but also when specific Observable attributes within these elements are changed, e.g. a list of persons and when a person's adress changes, the ListChangeListeners fire. How can I edit the adress of multiple people and have the Listeners only fire once for all changes together?

回答1:

ObservableList does not provide this functionality by default. If you extend ModifiableObservableList though, you could make it's beginChange() and endChange() functionality accessible to external code.

You need to be careful though that this class is used correctly. If you do not do the same number of beginChange and endChange calls, the listener may not receive any updates at all.

The following code does not contain any implementation regarding update changes. I'll leave this up to you. You'll need to use nextUpdate between calls of beginChange and endChange. You may need to add additional functionality to the doXyz methods to add listeners, if you want that the extractor functionality.

public class BulkEditObservableList<T> extends ModifiableObservableListBase<T> {

    private final List<T> backingList;

    public BulkEditObservableList(List<T> backingList) {
        if (backingList == null) {
            throw new IllegalArgumentException();
        }
        this.backingList = backingList;
    }

    public BulkEditObservableList() {
        this(new ArrayList<>());
    }

    @Override
    public T get(int index) {
        return backingList.get(index);
    }

    @Override
    public int size() {
        return backingList.size();
    }

    @Override
    protected void doAdd(int index, T element) {
        backingList.add(index, element);

    }

    @Override
    protected T doSet(int index, T element) {
        return backingList.set(index, element);
    }

    @Override
    protected T doRemove(int index) {
        return backingList.remove(index);
    }

    public void beginBulkChange() {
        beginChange();
    }

    public void endBulkChange() {
        endChange();
    }

}

Usage example

BulkEditObservableList<Integer> intList = new BulkEditObservableList<>();
intList.addListener((Observable o) -> System.out.println(o));
intList.add(1);

intList.beginBulkChange();
intList.add(2);
intList.add(3);
intList.add(0, 0);
System.out.println("after multi add");
intList.endBulkChange();

Output

[1]
after multi add
[0, 1, 2, 3]

来源：https://stackoverflow.com/questions/59324227/edit-multiple-elements-in-observablelist-and-only-fire-change-listeners-after-la

标签

java

javafx

observable