javafx: How to bind disable button with dynamic created checkboxes? - javafx

Question

I want to bind the disable of a button with dynamically created checkboxes. The Button should be enabled if a checkbox is selected.
This is my code
public class DietTabPageController {
#FXML
private FlowPane parent;
#FXML
private Button okButton;
private ObservableList<CheckBox> checkBoxes=FXCollections.observableArrayList();
#FXML
private void initialize() {
ObservableList<Diet> diets = DietDAO.getDiets();
diets.forEach(diet -> checkBoxes.add(new CheckBox(diet.getName())));
//checkboxes added in parent Flowpane
parent.getChildren().addAll(checkBoxes);
}
}
Any suggestions? Thanks

Answer 1

You can use JavaFX's really nice Bindings-class!
Try this:
okButton.disableProperty().bind(
Bindings.createBooleanBinding(
()->!checkBoxes.stream().anyMatch(CheckBox::isSelected),
checkBoxes.stream().map(x->x.selectedProperty()).toArray(Observable[]::new)
)
);
This creates a new Binding, which will listen on every checkbox and then call the given function to calculate the value of your property.
Additional reading here: Bindings
Regarding your comment:
I don't know how much you can edit your Diet class, but if you can, there is a very simple way to display your checkboxes and add the button-binding. Take a look at the following sample:
ListView<Diet> dietsView = new ListView<>(diets);
dietsView.setCellFactory(CheckBoxListCell.forListView(diet ->
diet.selectedProperty()));
btn.disableProperty().bind(
Bindings.createBooleanBinding(
() -> !diets.stream().anyMatch(diet->diet.isSelected()),
diets.stream().map(x->x.selectedProperty())
.toArray(Observable[]::new)
)
);
add this to Diet class:
private final BooleanProperty selected = new SimpleBooleanProperty();
public final BooleanProperty selectedProperty() {
return this.selected;
}
public final boolean isSelected() {
return this.selectedProperty().get();
}
public final void setSelected(final boolean on) {
this.selectedProperty().set(on);
}

Answer 2

You need to add listeners to all the selected properties of the CheckBoxes. Every time one of the property changes, modify the Button's disable property, if necessary. BTW: Making checkBoxes observable doesn't seem necessary:
private List<CheckBox> checkBoxes;
#FXML
private void initialize() {
ObservableList<Diet> diets = DietDAO.getDiets();
checkBoxes = new ArrayList<>(diets.size());
ChangeListener<Boolean> listener = (o, oldValue, newValue) -> {
if (newValue) {
// activate button since at least one CheckBox is selected
okButton.setDisable(false);
} else {
// disable button, if the last CheckBox was unselected
for (CheckBox cb : checkBoxes) {
if (cb.isSelected()) {
return; // don't do anything, if there still is a selected CheckBox
}
}
okButton.setDisable(true);
}
};
for (Diet diet : diets) {
CheckBox cb = new CheckBox(diet.getName());
cb.selectedProperty().addListener(listener);
checkBoxes.add(cb);
}
//checkboxes added in parent Flowpane
parent.getChildren().addAll(checkBoxes);
}