Javafx: Reduce events of checkable Listbox - javafx

Question

I have a generic Javafx Listbox with checkable items (up to 20 items).
When I (de-)select an item, a property change is released to update other parts of the program.
It works all fine so far.
But I have additionally 2 buttons to (de-)select all items at once.
Also this working as expected, but I get an event for each item, which means that up to 20 property change events are fired, when one would be enough.
It is not a performance problem, not much is done on the events, but it is bad style.
Can anybody suggest a better solution?
public class FilterBox extends AnchorPane {
ListView<Item> listFilter;
Button buttonAll;
Button buttonNone;
public FilterBox() {
init();
place();
action();
getChildren().addAll(listFilter, buttonAll, buttonNone);
handleChange();
}
private void init() {
listFilter = new ListView<>();
buttonAll = new Button("All");
buttonNone = new Button("None");
}
private void place() {
setTopAnchor(listFilter, 0d);
setBottomAnchor(listFilter, 40d);
setLeftAnchor(listFilter, 0d);
setRightAnchor(listFilter, 0d);
setBottomAnchor(buttonAll, 5d);
setLeftAnchor(buttonAll, 0d);
buttonAll.setPrefWidth(75d);
setBottomAnchor(buttonNone, 5d);
setRightAnchor(buttonNone, 0d);
buttonNone.setPrefWidth(75d);
}
private void action() {
listFilter.setCellFactory(CheckBoxListCell.forListView((Item item) -> item.selectedProperty()));
buttonAll.setOnAction((t) -> {
changeAll(true);
});
buttonNone.setOnAction((t) -> {
changeAll(false);
});
}
private void changeAll(Boolean state) {
for (Item i : listFilter.getItems()) {
i.setSelected(state);
}
}
private void setListener(Item item) {
item.selectedProperty().addListener((o, ov, nv) -> {
Trigger.setNewFilterEvent();
});
}
private void handleChange() {
HashSet<String> list = InputData.getSportList();
for (String s : list) {
Item item = new Item(s, true);
listFilter.getItems().add(item);
setListener(item);
}
}
public static class Item {
private final StringProperty name = new SimpleStringProperty();
private final BooleanProperty selected = new SimpleBooleanProperty();
public Item(String name, boolean on) {
setName(name);
setSelected(on);
}
public final StringProperty nameProperty() {
return this.name;
}
public final String getName() {
return this.nameProperty().get();
}
public final void setName(final String name) {
this.nameProperty().set(name);
}
public final BooleanProperty selectedProperty() {
return this.selected;
}
public final boolean isSelected() {
return this.selectedProperty().get();
}
public final void setSelected(final boolean sel) {
this.selectedProperty().set(sel);
}
#Override
public String toString() {
return getName();
}
}
}

Answer 1

Assuming Trigger.setNewFilterEvent() is what you want called only once when the "select all" or the "deselect all" actions are fired, then you can use a boolean flag for this.
public class FilterBox {
private boolean ignoreIndividualChanges;
// other fields omitted for brevity
private void changeAll(boolean state) {
ignoreIndividualChanges = true;
try {
for (Item i : listFilter.getItems()) {
i.setSelected(state);
}
Trigger.setNewFilterEvent(); // fire one event
} finally {
ignoreIndividualChanges = false;
}
}
private void setListener(Item item) {
item.selectedProperty().addListener((obs, ov, nv) -> {
if (!ignoreIndividualChanges) {
Trigger.fireNewFilterEvent();
}
});
}
// other methods omitted for brevity
}
Also, note I changed the parameter type for changeAll from Boolean to boolean. There's no reason to use the reference type here, so you should stick with the primitive type.