我在一个较大规模的应用程序中遇到了这个问题，其中一些自定义绑定在源属性值更改时没有被更新。
我设法编写了一个简单的类来复制此问题，但我真的不明白为什么会发生这种情况。以下是一个快速测试，可复制该问题：
import javafx.beans.binding.BooleanBinding;
import javafx.beans.binding.ObjectBinding;
import javafx.beans.property.BooleanProperty;
import javafx.beans.property.ObjectProperty;
import javafx.beans.property.SimpleBooleanProperty;
import javafx.beans.property.SimpleObjectProperty;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
public class TestingBindingsFx {
private final ObjectProperty<MyEvent> objectProperty = new SimpleObjectProperty<MyEvent>(this, "objectProperty");
private final BooleanProperty booleanProperty = new SimpleBooleanProperty(this, "booleanProperty");
private ObjectBinding<MyEvent> bindingObj;
private BooleanBinding bindingBool;
public TestingBindingsFx(ObjectProperty<String> selection) {
setupBindings(selection);
}
private void setupBindings(ObjectProperty<String> selection) {
bindingObj = createObjectBinding(selection);
bindingBool = createBooleanBinding(selection);
objectProperty.bind(bindingObj);
booleanProperty.bind(bindingBool);
}
private static ObjectBinding<MyEvent> createObjectBinding(ObjectProperty<String> selection) {
return new ObjectBinding<MyEvent>() {
{
super.bind(selection);
}
@Override
protected MyEvent computeValue() {
System.out.println("createObjectBinding called");
MyEvent ve = selection.get() == null ? MyEvent.EVENT1
: MyEvent.EVENT2;
return ve;
}
};
}
private static BooleanBinding createBooleanBinding(ObjectProperty<String> selection) {
return new BooleanBinding() {
{
super.bind(selection);
}
@Override
protected boolean computeValue() {
System.out.println("createBooleanBinding called");
return selection.get() == null ? true : false;
}
};
}
public static void main(String[] args) {
ObjClass objclass = new ObjClass();
System.out.println("Instantiating TestingBindingsFx...");
TestingBindingsFx fx = new TestingBindingsFx(objclass.selection);
objclass.selection.addListener(new ChangeListener<String>() {
@Override
public void changed(ObservableValue<? extends String> observable, String oldValue, String newValue) {
System.out.println("changed " + oldValue + "->" + newValue);
}
});
System.out.println("Changing selection property values...");
objclass.selection.set("Test 1");
objclass.selection.set("Test 2");
}
enum MyEvent {
EVENT1,
EVENT2;
}
static class ObjClass {
public final ObjectProperty<String> selection = new SimpleObjectProperty<String>(this, "selection");
}
}
运行后，我看到：
Instantiating TestingBindingsFx... createObjectBinding called createBooleanBinding called Changing selection property values... changed null->Test 1 changed Test 1->Test 2
当我期望看到像这样的东西时：
Instantiating TestingBindingsFx...
createObjectBinding called
createBooleanBinding called
Changing selection property values...
changed null->Test 1
createObjectBinding called
createBooleanBinding called
changed Test 1->Test 2
createObjectBinding called
createBooleanBinding called
ChangeListener已经按照预期工作（只是为了验证目的而放置在那里），每当我更改选择属性的值时，它都会被调用。但是自定义绑定在第一次后永远不会更新，查看代码后我无法理解原因。起初我认为这可能与弱引用有关，但我甚至将绑定对象转换为类级变量，仍然没有变化。
我感觉我可能错过了一些关键的东西, 但是在看了两个小时的代码之后，我就是找不到原因。
在我的实际应用程序中，更奇怪的是，其中一个自定义绑定实际上运行良好。