Some bidirectional binding not works

Question

Hello!
Maybe I do something wrong, but bidirectional binding in thic simple code not works properly.
package simple;
import javafx.application.Application;
import javafx.scene.GroupBuilder;
import javafx.scene.Scene;
import javafx.scene.SceneBuilder;
import javafx.scene.control.CheckBox;
import javafx.scene.control.CheckBoxBuilder;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
public class BiDiBug extends Application {
  CheckBox checkBoxResizable;
  public static void main(String[] args) {
    Application.launch(args);
  @Override
  public void start(Stage stage) {
     stage.setResizable(true);
    Scene scene  = SceneBuilder.create()
      .width(200)
      .height(100)
      .fill(Color.TRANSPARENT)
      .root(
        GroupBuilder.create()
             .children(
                checkBoxResizable = CheckBoxBuilder.create()
                  .selected(stage.isResizable())
                  .text("Is Stage resizable")
                  .build()
              .build()
       .build();
    checkBoxResizable.selectedProperty()
            .bindBidirectional(stage.resizableProperty());
    // This code not works too:
    //stage.resizableProperty()
    //          .bindBidirectional(checkBoxResizable.selectedProperty());
    stage.setScene(scene);
    stage.show();
}Is it bug or feature?

Answer 1

The binding seems to work, in the sense that stage.resizable gets updated accordingly. Try adding the following:
    stage.resizableProperty().addListener(new ChangeListener<Boolean>() {
      @Override
      public void changed(ObservableValue<? extends Boolean> observable,
          Boolean oldValue, Boolean newValue) {
        System.out.printf("stage.resizable changed from %s to %s%n", oldValue, newValue);
    });and you'll see that the resizable property does indeed change when you check/uncheck the checkbox.
On my setup (Mac OSX 10.7.5), under JavaFX 2.2.7, JDK 1.7.0_17, I observe the same behavior as you: the resize behavior of the stage does not correspond to the value of its property. The [url http://docs.oracle.com/javafx/2/api/javafx/stage/Stage.html#resizableProperty]Javadocs for stage.resizable do say "This is a hint which allows the implementation to optionally make the Stage resizable by the user." So in fairness, there is no guarantee given that changing this value will have the desired effect.
Interestingly, under JavaFX 8, JDK 1.8.0 (early access, b80), your code works. However, the Javadocs for the stage.resizableProperty() in JavaFX 8 additionally state
>
Warning: Since 8.0 the property cannot be bound and will throw RuntimeException on an attempt to do so. This is because the setting of resizable is asynchronous on some systems or generally might be set by the system / window manager.
so while bindBidirectional(...) seems to work, bind(...) does indeed throw a RuntimeException.
Given all that, I would not try to bind to the resizable property at all. If you only need unidirectional binding, Shakir's solution above will work. If you genuinely need bidirectional binding (for example, if the stage's resizable property might be changed elsewhere in the application, and you need the checkbox to update accordingly), you can "do it by hand":
    checkBoxResizable.selectedProperty().addListener(new ChangeListener<Boolean>() {
      @Override
      public void changed(ObservableValue<? extends Boolean> obs,
          Boolean oldValue, Boolean newValue) {
        if (stage.isResizable() != newValue.booleanValue()) {
          stage.setResizable(newValue);
    stage.resizableProperty().addListener(new ChangeListener<Boolean>() {
      @Override
      public void changed(ObservableValue<? extends Boolean> obs,
          Boolean oldValue, Boolean newValue) {
        if (checkBoxResizable.isSelected() != newValue.booleanValue()) {
          checkBoxResizable.setSelected(newValue);
    }); which seems to work in all versions (again, on my system).