JavaFX：修改ObjectProperty关联对象属性时如何触发ListView更新

问题背景 #

现有MyObject和MyOtherObject类结构如下（简化为成员变量）：

public class MyObject {
    public StringProperty name = new SimpleStringProperty("");
    public ObjectProperty<MyOtherObject> myOtherObject = new SimpleObjectProperty<>();
    
    @Override
    public String toString() {
        return name + " " + (myOtherObject.get() == null ? "?" : myOtherObject.get().text );
    }
    
    public static Callback<MyObject, Observable[]> extractor() {
        return myObject -> new Observable[] { myObject.name, myObject.myOtherObject };
    }
}

public class MyOtherObject {
    public StringProperty text = new SimpleStringProperty("");
}

将MyObject实例放入ListView时，已通过extractor让列表感知对象属性变化：

ListView<MyObject> myListView = new ListView<>(FXCollections.observableArrayList(MyObject.extractor()));

修改MyObject的name或替换myOtherObject实例时，ListView能正常更新，但直接修改MyOtherObject的text属性时，列表无响应——因为extractor仅监听myOtherObject的引用变化，无法感知其内部属性变更。

优雅解决方案 #

方案1：改进Extractor监听嵌套属性

利用Bindings.selectString自动监听嵌套属性，当myOtherObject实例替换或其text属性变更时，都会触发列表更新：

public static Callback<MyObject, Observable[]> extractor() {
    return myObject -> {
        // 自动处理myOtherObject为null的情况，切换实例时自动更新监听目标
        ObservableValue<String> nestedText = Bindings.selectString(myObject.myOtherObject, "text");
        return new Observable[]{myObject.name, nestedText};
    };
}

方案2：在MyObject内部监听嵌套属性，触发变更通知

通过一个辅助属性触发变更通知，同时处理myOtherObject替换时的监听器清理，避免内存泄漏：

public class MyObject {
    public StringProperty name = new SimpleStringProperty("");
    public ObjectProperty<MyOtherObject> myOtherObject = new SimpleObjectProperty<>();
    // 辅助属性，用于触发嵌套属性变更的通知
    private final ObjectProperty<Void> nestedChangeTrigger = new SimpleObjectProperty<>();

    public MyObject() {
        myOtherObject.addListener((obs, oldObj, newObj) -> {
            // 移除旧对象的监听器
            if (oldObj != null) {
                oldObj.text.removeListener(textChangeListener);
            }
            // 添加新对象的监听器
            if (newObj != null) {
                newObj.text.addListener(textChangeListener);
            }
            // 触发变更通知
            nestedChangeTrigger.set(null);
        });
    }

    private final ChangeListener<String> textChangeListener = (obs, oldText, newText) -> {
        nestedChangeTrigger.set(null);
    };

    @Override
    public String toString() {
        return name.get() + " " + (myOtherObject.get() == null ? "?" : myOtherObject.get().text.get());
    }

    public static Callback<MyObject, Observable[]> extractor() {
        return myObject -> new Observable[]{myObject.name, myObject.myOtherObject, myObject.nestedChangeTrigger};
    }
}

方案3：自定义ListCell直接绑定嵌套属性

将更新逻辑下移到ListCell，通过StringBinding直接监听所有关联属性，无需依赖extractor的全局监听：

ListView<MyObject> myListView = new ListView<>(FXCollections.observableArrayList(MyObject.extractor()));
myListView.setCellFactory(param -> new ListCell<>() {
    @Override
    protected void updateItem(MyObject item, boolean empty) {
        super.updateItem(item, empty);
        if (empty || item == null) {
            setText(null);
            textProperty().unbind(); // 解绑避免内存泄漏
        } else {
            // 绑定文本到name和myOtherObject的text属性
            StringBinding textBinding = Bindings.createStringBinding(
                () -> item.name.get() + " " + (item.myOtherObject.get() == null ? "?" : item.myOtherObject.get().text.get()),
                item.name, 
                item.myOtherObject, 
                item.myOtherObject.isNotNull().flatMap(obj -> obj.text)
            );
            textProperty().bind(textBinding);
        }
    }
});

内容的提问来源于stack exchange，提问作者Michael