CODEWITHSUNDEEP
javajavafx
AnotherNewbplusplus
AnotherNewbplusplus

Reputation: 215

Multiple Boolean Binding in JavaFX

I am attempting to bind a checkbox to multiple checkbox as seen below:

private void bindPanelToPackages(CheckBox panel, CheckBox ...pkg){

    BooleanProperty panelBinding = null;
    BooleanBinding binder = null;

    for(CheckBox p: pkg){
        if(panelBinding == null){
            panelBinding = p.selectedProperty();
        }
        else{
            binder = panelBinding.and(p.selectedProperty());
        }
    }

    if(binder != null){
        panel.selectedProperty().bind(binder);
    }
    else if(panelBinding != null){
        panel.selectedProperty().bindBidirectional(panelBinding);
    }
}

What I want is to allow bidirectional group bindings when 'pkg' has more than one item. That way when I select my packages, the 'panel' will automatically be selected or if I select 'panel', all the 'pkg' will be selected/deselected. I got stuck at :

panel.selectedProperty().bind(binder);

and got

"JavaFX Application Thread" java.lang.RuntimeException: CheckBox.selected : A bound value cannot be set.

since I did a one directional binding for 'binder'. Is there a way I can perform something equivalent to this?:

panel.selectedProperty().bindBidirectional(binder);

I can't seem to find it in the docs or I'm not looking at the right places. Thanks!

Upvotes: 3

Views: 10416

Answers (1)

James_D
James_D

Reputation: 209684

The condition "all check boxes are selected" can only be expressed as a BooleanBinding, not as a BooleanProperty. Basically, the issue is that making that condition false is not clearly defined: there are many ways to do it (i.e. make any non-empty subset of all the checkboxes unselected). Hence you cannot use bidirectional bindings: you have to use listeners on each of the two conditions.

Here is one implementation:

// must keep a reference to the Binding to prevent premature
// garbage collection:

BooleanBinding allSelected ;

private void bindPanelToPackages(CheckBox pane, CheckBox... packages) {

    // BooleanBinding that is true if and only if all check boxes in packages are selected:
    allSelected = Bindings.createBooleanBinding(() -> 
        // compute value of binding:
        Stream.of(packages).allMatch(CheckBox::isSelected), 
        // array of thing to observe to recompute binding - this gives the array
        // of all the check boxes' selectedProperty()s.
        Stream.of(packages).map(CheckBox::selectedProperty).toArray(Observable[]::new));

    // update pane's selected property if binding defined above changes
    allSelected.addListener((obs, wereAllSelected, areAllNowSelected) -> 
        pane.setSelected(areAllNowSelected));

    // use an action listener to listen for a direct action on pane, and update all checkboxes
    // in packages if this happens:
    pane.setOnAction(e -> 
        Stream.of(packages).forEach(box -> box.setSelected(pane.isSelected())));

}

and a SSCCE:

import java.util.stream.IntStream;
import java.util.stream.Stream;

import javafx.application.Application;
import javafx.beans.Observable;
import javafx.beans.binding.Bindings;
import javafx.beans.binding.BooleanBinding;
import javafx.scene.Scene;
import javafx.scene.control.CheckBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class MultipleCheckBoxSelection extends Application {

    private BooleanBinding allSelected ;

    @Override
    public void start(Stage primaryStage) {
        CheckBox selectAll = new CheckBox("Select all");
        int numBoxes = 5 ;
        CheckBox[] boxes = IntStream
                .rangeClosed(1,  numBoxes)
                .mapToObj(i -> new CheckBox("Item "+i))
                .toArray(CheckBox[]::new);

        bindPanelToPackages(selectAll, boxes);


        VBox root = new VBox(10, selectAll);
        root.setStyle("-fx-padding: 15;");
        Stream.of(boxes).forEach(box -> box.setStyle("-fx-padding: 0 0 0 10;"));
        Stream.of(boxes).forEach(root.getChildren()::add);
        Scene scene = new Scene(root, 250, 400);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    private void bindPanelToPackages(CheckBox pane, CheckBox... packages) {

        // BooleanBinding that is true if and only if all check boxes in packages are selected:
        allSelected = Bindings.createBooleanBinding(() -> 
            // compute value of binding:
            Stream.of(packages).allMatch(CheckBox::isSelected), 
            // array of thing to observe to recompute binding - this gives the array
            // of all the check boxes' selectedProperty()s.
            Stream.of(packages).map(CheckBox::selectedProperty).toArray(Observable[]::new));

        // update pane's selected property if binding defined above changes
        allSelected.addListener((obs, wereAllSelected, areAllNowSelected) -> 
            pane.setSelected(areAllNowSelected));

        // use an action listener to listen for a direct action on pane, and update all checkboxes
        // in packages if this happens:
        pane.setOnAction(e -> 
            Stream.of(packages).forEach(box -> box.setSelected(pane.isSelected())));

    }

    public static void main(String[] args) {
        launch(args);
    }
}

Upvotes: 8

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