考虑以下型号,苹果
public class Apple {
private StringProperty appleName = new SimpleStringProperty("Apple");
public String getAppleName() {
return appleName.get();
}
public StringProperty appleNameProperty() {
return appleName;
}
public void setAppleName(String appleName) {
this.appleName.set(appleName);
}
}
和篮子
public class Basket {
private Apple apple = new Apple();
public Apple getApple() {
return apple;
}
public void setApple(Apple apple) {
this.apple = apple;
}
}
篮子里有一个苹果。现在我正在尝试绑定一个简单的字符串属性,如下所示。
public class Food{
public static void main(String[] args) {
StringProperty localApple = new SimpleStringProperty("lGreenApple");
Basket basket = new Basket();
Apple rGreenApple = new Apple();
rGreenApple.setAppleName("rGreenApple");
basket.setApple(rGreenApple);
Bindings.bindBidirectional(localApple, rGreenApple.appleNameProperty());
rGreenApple.appleNameProperty().set("rGreenApple 2");
System.out.println(localApple.getValue()); //rGreenApple 2
Apple redApple = new Apple();
redApple.setAppleName("rRedApple");
basket.setApple(redApple);
redApple.appleNameProperty().set("rRedApple 2");
System.out.println(localApple.getValue());//Still rGreenApple 2
}
}
在绑定后尝试检索值时,localApple
对象仍然引用rGreenApple
。获得红苹果的干净方法是什么?
你需要
两样东西:
- 使
apple
属性Basket
成为 JavaFX 可观察属性,而不是常规的 JavaBean 样式属性。 - 将本地字符串属性绑定到"属性的属性",即
Basket
的apple
财产的appleName
属性。
第一部分很简单:
public class Basket {
private final ObjectProperty<Apple> apple = new SimpleObjectProperty<>();
public ObjectProperty<Apple> appleProperty() {
return apple ;
}
public final Apple getApple() {
return appleProperty().get();
}
public final void setApple(Apple apple) {
appleProperty().set(apple);
}
}
对于第二部分,最干净的方法是使用 EasyBind 框架:
public class Food{
public static void main(String[] args) {
Basket basket = new Basket();
Apple rGreenApple = new Apple();
rGreenApple.setAppleName("rGreenApple");
basket.setApple(rGreenApple);
Property<String> localApple = EasyBind.monadic(basket.appleProperty())
.selectProperty(Apple::appleNameProperty);
rGreenApple.appleNameProperty().set("rGreenApple 2");
System.out.println(localApple.getValue()); //rGreenApple 2
Apple redApple = new Apple();
redApple.setAppleName("rRedApple");
basket.setApple(redApple);
System.out.println(localApple.getValue());// rRedApple
redApple.appleNameProperty().set("rRedApple 2");
System.out.println(localApple.getValue());// rRedApple 2
}
}
如果没有 EasyBind,您必须手动管理中间侦听器。像这样:
StringProperty localApple = new SimpleStringProperty();
localApple.bindBidirectional(basket.getApple().appleNameProperty());
basket.appleProperty().addListener((obs, oldApple, newApple) -> {
if (oldApple != null) {
localApple.unbindBidirectional(oldApple.appleNameProperty());
}
if (newApple == null) {
localApple.set("");
} else {
localApple.bindBidirectional(newApple.appleNameProperty());
}
});