JavaFX ComboBox binding to value

[Jeff Dickson]

I have a combo box which it's values are bi-directionally bound to values in the ViewModel.
I think I am close but can't get the value of this.accountRisk set to one of the selectable values.  
The bolded code below is what is not working.  Any simplifications to this code would also be appreciated.  

// ClientController->Init
    public ComboBox<String> accountRisk
    def account = this.viewModel.getClient().accountProperty().get()
    accountRisk.itemsProperty().bindBidirectional(account.accountRisks())
    accountRisk.selectionModelProperty().bindBidirectional(account.accountRisk())

// ViewModel
   private final ObjectProperty<ObservableList<String>> accountRisks
   private final ObjectProperty<SingleSelectionModel<String>> accountRisk
   this.accountRisks = new SimpleObjectProperty<>()
   ObservableList<String> risks = FXCollections.observableArrayList("3%", "5%", "7%", "10%")
   this.accountRisks.set(risks)
   this.accountRisk = new SimpleObjectProperty<SingleSelectionModel<String>>()
   this.accountRisk.set(risks.get(2))  // need syntax which sets a SimpleObjectProperty<SingleSelectionModel<String>>

Thanks

[Lou Hamers]

Could you post a more complete example (something that can be copy/pasted that compiles is most helpful)?

Alternatively, what's the error or what isn't working?


To take a guess looking at this pseudocode, it looks like you're trying to set a String on a property that expects a SingleSelectionModel.

accountRisk.get().select(risks.get(2));

This should set the value on your model.

Also I would avoid bidirectional bindings if you don't really need them (one directional is just bind()).

[Lou Hamers]

Oh, you'd have to set a value for accountRisk first though. Otherwise you'll just get an NPE (NullPointerException) from the get(), obviously.

[Jeff Dickson]

Here is a runnable simplified example.  I know that risks.get(2) is an incorrect assignment.  I put it there to show what is desired, but I think it made it more confusing.

The bidirectional binding of the list of values is working correctly, but I also wanted a binding for the selected value.  

If "accountRisk.selectionModelProperty()..." is uncommented, it seems to be competing with the user selected value.  

I just wanted the binding to set the initial value and then allow the user to change it which then bidirectionally sets the selected value back in the ViewModel.

Sorry for the confusion, it was late on Sunday when I gave up trying to make this work.
 

package com.ex.javafx.binding;

import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.property.ObjectProperty;
import javafx.beans.property.SimpleObjectProperty;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;


public class ComboBoxBinding extends Application {
    public static void main(String[] args) {
        launch(args);
    }

    ComboBox<String> accountRisk = new ComboBox<>();
    Button exit_btn = new Button("Exit");


    @Override
    public void start(Stage stage) {
        stage.setTitle("ComboBox Binding Ex");

        ViewModel vm = new ViewModel();

        accountRisk.itemsProperty().bindBidirectional(vm.accountRisks());
        //accountRisk.selectionModelProperty().bindBidirectional(vm.accountRisk());

        exit_btn.setOnAction(e -> Platform.exit());

        HBox box = new HBox(5, accountRisk, exit_btn);
        BorderPane root = new BorderPane();
        root.setCenter(box);

        Scene scene = new Scene(root, 200, 200);
        stage.setScene(scene);
        stage.show();

    }

    public static class ViewModel {
        private final ObjectProperty<ObservableList<String>> accountRisks;
        private final ObjectProperty<SingleSelectionModel<String>> accountRisk;
        ViewModel() {
            this.accountRisks = new SimpleObjectProperty<>();
            ObservableList<String> risks = FXCollections.observableArrayList("3%", "5%", "7%", "10%");
            this.accountRisks.set(risks);
            this.accountRisk = new SimpleObjectProperty<>();
            // this.accountRisk.set(risks.get(2)); // Initialize with one of the available risks
        }

        ObjectProperty<ObservableList<String>> accountRisks() { return accountRisks; };
        ObjectProperty<SingleSelectionModel<String>> accountRisk() { return accountRisk; }
    }

}

[Lou Hamers]

There's some other things we could discuss here but this does it - I did rename one of your accountRisks to accountRisksModel.
I think maybe you were confusing those two items?

import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.property.ObjectProperty;
import javafx.beans.property.SimpleObjectProperty;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ComboBox;
import javafx.scene.control.SingleSelectionModel;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;

public class ComboBoxBinding extends Application {
    
    public static void main(String[] args) {
        launch(args);
    }
    
    ComboBox<String> accountRisk = new ComboBox<>();
    Button exit_btn = new Button("Exit");
    
    @Override
    public void start(Stage stage) {
        stage.setTitle("ComboBox Binding Ex");
        
        ViewModel vm = new ViewModel(accountRisk.getSelectionModel());
        
        accountRisk.itemsProperty().bindBidirectional(vm.accountRisks());
        //accountRisk.selectionModelProperty().bindBidirectional(vm.accountRisk());
        
        exit_btn.setOnAction(e -> Platform.exit());
        
        HBox box = new HBox(5, accountRisk, exit_btn);
        BorderPane root = new BorderPane();
        root.setCenter(box);
        
        Scene scene = new Scene(root, 200, 200);
        stage.setScene(scene);
        stage.show();
        
    }
    
    public static class ViewModel {
        
        private final ObjectProperty<ObservableList<String>> accountRisks;
        private final ObjectProperty<SingleSelectionModel<String>> accountRiskModel;
        
        ViewModel(SingleSelectionModel<String> selectionModel) {
            this.accountRisks = new SimpleObjectProperty<>();
            ObservableList<String> risks = FXCollections.observableArrayList("3%", "5%", "7%", "10%");
            this.accountRisks.set(risks);
            this.accountRiskModel = new SimpleObjectProperty<>(selectionModel);
            accountRiskModel.get().select("%3");
            // this.accountRisk.set(risks.get(2)); // Initialize with one of the available risks
        }
        
        ObjectProperty<ObservableList<String>> accountRisks() {
            return accountRisks;
        }
        
        ;
        
        ObjectProperty<SingleSelectionModel<String>> accountRisk() {
            return accountRiskModel;
        }
    }
    
}

[Lou Hamers]

Normally I'd add a little more info and cleanup but I'm exhausted tonight. Hopefully this will get you going again anyway.

You could also use select(risks.get(2)) like you were trying to use before.

[Jeff Dickson]

Thank you Lou.  

I can't pass the ComboBox's selection model into the view model, so I am trying to set it via a method in the view model.
The view model is injected into all the controllers using DI and is created two levels up.

In the process of renaming a bunch of stuff and incorporating the change into my project, I have created a circular reference or an incorrect order of initialization.

Time to wrap it up for the night, it has been a very long day.

I will work on it again tomorrow night.

Thanks again for the key bit of information.

[Jeff Dickson]

My last problem seems to be related to the groovy compiler.  Groovy was happy with the syntax while the Java compiler was not.  See code comments below.

public class ComboBoxFixedBinding extends Application {

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

    ComboBox<String> accountRiskComboBox = new ComboBox<>();
    Button exit_btn = new Button("Exit");

    @Override
    public void start(Stage stage) {
        stage.setTitle("ComboBox Binding Ex");

        ViewModel vm = new ViewModel(accountRiskComboBox.getSelectionModel());

        accountRiskComboBox.itemsProperty().bindBidirectional(vm.accountRisks());

        exit_btn.setOnAction(e -> Platform.exit());

        HBox box = new HBox(5, accountRiskComboBox, exit_btn);
        BorderPane root = new BorderPane();
        root.setCenter(box);

        Scene scene = new Scene(root, 200, 200);
        stage.setScene(scene);
        stage.show();

    }

    public static class ViewModel {

        private final ObservableList<String> risks;
        private final ObjectProperty<ObservableList<String>> accountRisksProperty;

        ViewModel(SingleSelectionModel<String> selectionModel) {
            this.risks = FXCollections.observableArrayList("3%", "5%", "7%", "10%");

            // Groovy and Java like this syntax
//            this.accountRisksProperty = new SimpleObjectProperty<>();
//            this.accountRisksProperty.set(risks);

            // Groovy is happy with this while Java is not.
            this.accountRisksProperty = new SimpleObjectProperty<ObservableList<String>>().set(risks);

            ObjectProperty<SingleSelectionModel<String>> accountRiskModel = new SimpleObjectProperty<>(selectionModel);
            accountRiskModel.get().select("3%");
        }

        ObjectProperty<ObservableList<String>> accountRisks() {
            return accountRisksProperty;
        }
        
    }

}

[Lou Hamers]

>// Groovy is happy with this while Java is not.

I can't speak too much on Groovy - not sure what black magic it's doing there.

But in Java World calling set() on SimpleObjectProperty returns void, so it needs to be two lines. It's more readable that way, anyway, IMO.