为什么JavaBean适配器不更新JavaFX属性？

问题描述

我是JavaFX的新手，需要GUI（使用JavaFX属性）和旧的Java代码（不使用JavaFX属性）之间的双向绑定。我尝试使用JavaBean适配器，如下面的简单示例所示：

I'm new to JavaFX and need a bidirectional binding between a GUI (using JavaFX properties) and my old Java code (not using JavaFX properties). I tried using a JavaBean adapter as the following simple example shows:

import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;

import javafx.beans.property.DoubleProperty;
import javafx.beans.property.SimpleDoubleProperty;
import javafx.beans.property.adapter.JavaBeanDoubleProperty;
import javafx.beans.property.adapter.JavaBeanDoublePropertyBuilder;

public class App
{
    public static void main(String[] args) throws NoSuchMethodException
    {
        Pojo pojo = new Pojo();
        FXModel model = new FXModel();

        JavaBeanDoubleProperty adapter = JavaBeanDoublePropertyBuilder
                .create().bean(pojo).name("value").build();

        model.valueProperty().bindBidirectional(adapter);

        System.out.println("Adapter before: " + adapter.get());
        System.out.println("Model before: " + model.getValue());
        System.out.println("Bean before: " + pojo.getValue());

        pojo.setValue(123d);

        System.out.println();
        System.out.println("Adapter after: " + adapter.get());
        System.out.println("Model after: " + model.getValue());
        System.out.println("Bean after: " + pojo.getValue());
    }

    public static class Pojo
    {
        private double value;

        public double getValue()
        {
            return value;
        }

        public void setValue(double value)
        {
            this.value = value;
        }
    }

    public static class FXModel
    {
        private final DoubleProperty value = new SimpleDoubleProperty();

        public double getValue()
        {
            return value.get();
        }

        public void setValue(double value)
        {
            this.value.set(value);
        }

        public DoubleProperty valueProperty()
        {
            return value;
        }
    }
}

生成的输出是

适配器之后： 123.0模型之后：0.0 Bean之后：123.0

Adapter after: 123.0 Model after: 0.0 Bean after: 123.0

因此，通过将普通Java对象设置为新值，将通知JavaBeanDoubleProperty关于更改，但JavaFX属性不是，虽然它绑定到适配器。为什么？

So, by setting the "normal" Java object to a new value the JavaBeanDoubleProperty is informed about the change, but the JavaFX property is not, although it is bound to the adapter. Why?

即使向Pojo添加PropertyChangeSupport，如上所述，

Even by adding a PropertyChangeSupport to Pojo as described here,

public static class Pojo
    {
        private double value;
        private PropertyChangeSupport pcs;

        public Pojo()
        {
            pcs = new PropertyChangeSupport(this);
        }

        public double getValue()
        {
            return value;
        }

        public void setValue(double value)
        {
            final double oldValue = this.value;
            this.value = value;
            pcs.firePropertyChange("name", oldValue, value);
        }

        public void addPropertyChangeListener(
                final PropertyChangeListener listener)
        {
            pcs.addPropertyChangeListener(listener);
        }
    },

它不起作用。 （不幸的是，使用也没有用。）

it does not work. (Unfortunately, a second trial using BeanPathAdapter also did not work.)

推荐答案

你刚刚在 Pojo中做了一个单据。 setValue（double value）。此方法为属性name触发PropertyChangeEvent。它应该是价值。
只需将其更改为

You just made a slip in Pojo.setValue(double value). This method fires a PropertyChangeEvent for the property "name". It supposed to be "value".Just change it to

public void setValue(double value)
{
    final double oldValue = this.value;
    this.value = value;
    pcs.firePropertyChange("value", oldValue, value);
}

它会起作用。

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