Problem with extending SimpleStringProperty

Question

I am just trying to extend a SimpleStringProperty in OpenJFX 11.0.1 to add some extra functionality. But ist seems not so easy, I experienced strange behavior of my extended Property and I don't know why. I think it should work.

My in this sample code simplified SimpleStringProperty extension contains another readonly string property which should be updated every time the the user types into a bound TextField. In this case remove all not allowed characters and convert the prefix. (I know this is not perfect but short enough to show)

After starting the sample code you will get a window with a rows of Controls. Typing in a String like "001 (242) 555666" the label should show the normalized phone number like "+1242555666".

The initial conversion works correcty.
I never get any exceptions.
The conversion is called when I type in new digits.

But if you play around with typing and deleting after a few seconds the set() method of my property isn't longer triggered by the bidirectional binding to the TextField.

To simplify the example I didn't use a TextFormatter. If I use one the problem doesn't change.

Can anyone help me figure out the problem?

Windows and OS X show the same behavior with OpenJFX 11 and OpenJFX 11.0.1

I tried the same code with JDK 1.8 and there it works fine.

package testproperty;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.stage.Stage;
import javafx.beans.property.ReadOnlyStringProperty;
import javafx.beans.property.ReadOnlyStringWrapper;
import javafx.beans.property.SimpleStringProperty;
import javafx.geometry.Insets;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;


public class TestProperty extends Application {

    // attempt to create an own property
    public class myPhoneNumberProperty extends SimpleStringProperty {

        private final ReadOnlyStringWrapper normalizedNumber = new ReadOnlyStringWrapper("");
        public ReadOnlyStringProperty normalizedNumberProperty() { return normalizedNumber.getReadOnlyProperty(); }
        public String getNormalizedNumber() { return normalizedNumber.get(); }

        public myPhoneNumberProperty() {
            super();
        }

        public myPhoneNumberProperty(String s) {
            super(s);
            calculate();
        }

        @Override
        public void set(String s) {
            super.set(s);
            calculate();
        }

        private void calculate() {
            // some calculations (only for test purposes)
            String original = this.get();
            String result = original.replaceAll("[^0123456789]","");
            if (result.startsWith("00")) result = result.replaceFirst("00", "+");
            if (original.startsWith("+")) result = "+".concat(result);
            normalizedNumber.set(result);
        }
    }


    @Override
    public void start(Stage primaryStage) {

        // create my property
        myPhoneNumberProperty phoneNumberA = new myPhoneNumberProperty("+34 952 111 222");

        // set up grid pane
        GridPane grid = new GridPane();
        grid.setPadding(new Insets(5,5,5,5));
        grid.setVgap(20);
        grid.setHgap(20);

        // set up the row
        Label labelA = new Label("Enter phone number");
        TextField textFieldA = new TextField();
        textFieldA.textProperty().bindBidirectional(phoneNumberA);
        Label labelB = new Label("Normalized number");
        Label labelN = new Label();
        labelN.textProperty().bind(phoneNumberA.normalizedNumberProperty());
        grid.addRow(0, labelA, textFieldA, labelB, labelN);

        // complete scene
        Scene scene = new Scene(grid, 1000, 100);
        primaryStage.setTitle("PhoneNumberProperty TestProg");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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

}

score 1 · Answer 1 · answered Jan 04 '19 at 08:05

1

Your phoneNumberA property object is being garbage collected. To fix this you must keep a strong reference to the object. One option is to make it an instance field.

JavaFX implements bindings using weak listeners/references. Bidirectional bindings have no strong references to the other property. This is different from unidirectional bindings where a reference to the observable value must be kept in order to unbind from it later.

answered Jan 04 '19 at 08:05

Slaw

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Hi, thanks for your answer. I see the problem: in Java 9 the switched over to G1 GC Garbage Collector instead of Parallel GC. Because changing Garbage Collector is not a good option I need a way to prevent my Object from being garbage collected. I would like to do this automatically and self-contained if something is bound to my internal property. Any idea? – A. Rohmann Jan 06 '19 at 08:02
As I mentioned you must keep a strong reference to the object. If using your test code as an example the simple option is to make `phoneNumberA` an instance field rather than a local variable. Local variables fall out of scope once the method returns. In contrast, the JavaFX runtime keeps a strong reference to the `Application` instance so it won't be eligible for GC until the JavaFX runtime exits. _Side note: In Java, the convention is class names use `CamelCase`—it should be `MyPhoneNumberProperty`_. – Slaw Jan 06 '19 at 09:18

Problem with extending SimpleStringProperty

1 Answers1