Java ListChangeListener WasUpdated（）不起作用 [英] Java ListChangeListener WasUpdated() doesn't work

问题描述

我想在observableList中修改一个名为EventShowable的对象时触发一些代码。
这是我的代码。

  mainApp.getCalendars（）。get（i）.getListEvents（）。addListener（ new ListChangeListener< EventShowable>（）{
 @Override 
 public void onChanged（ListChangeListener.Change<？extends EventShowable> c）{
 while（c.next（））{
 if（c.wasUpdated（））{
 //这不起作用。
 //执行更新
 
} 
 if（c.wasAdded（）） {
 //执行某事} 
  

wasAdded（）执行得很好但不是wasUpdate（ ）。
如何在修改EventShowable时获得有用的东西？谢谢

PS：在JavaDoc中：
public boolean wasUpdated（）
表示getFrom（）（包括）与getTo（）独占之间的元素已更改。 Th is是唯一可选的事件类型，并且可能不会被所有ObservableLists触发。
https://docs.oracle.com/javase/8/javafx/api/javafx/collections/ListChangeListener.Change.html#wasUpdated-- extractor 。

你还没有给出足够的细节来给出完整的答案，但如果你的 EventShowable 定义了诸如

  public class EventShowable {
 public IntegerProperty xProperty（）{...} 
 public StringProperty yProperty（）{。 ..} 
 // ... 
} 
  

然后创建一个触发更新的列表e当 x 或 y 更改时，通风口

  ObservableList< EventShowable> listEvents = 
 FXCollections.observableArrayList（eventShowable  - > 
 new Observable [] {eventShowable.xProperty（），eventShowable.yProperty（）}）; 
  

I want to trigger some code when a object called EventShowable have been modified in an observableList. Here is my code.

                mainApp.getCalendars().get(i).getListEvents().addListener(new ListChangeListener<EventShowable>() {
                @Override
                public void onChanged(ListChangeListener.Change<? extends EventShowable> c) {
                    while (c.next()) {
                        if (c.wasUpdated()) {
                          //this doesn't work.
                          //perform updated

                        }
                        if (c.wasAdded()){
                            //perform something }

The wasAdded() perform well but not the wasUpdate(). How to get something that works when a EventShowable have been modified ? Thanks

P.S : in the JavaDoc : public boolean wasUpdated() Indicates that the elements between getFrom() (inclusive) to getTo() exclusive has changed. This is the only optional event type and may not be fired by all ObservableLists. https://docs.oracle.com/javase/8/javafx/api/javafx/collections/ListChangeListener.Change.html#wasUpdated--

解决方案

Create your list using an extractor.

You haven't really given enough detail to give a complete answer, but if your EventShowable defines properties such as

public class EventShowable {
    public IntegerProperty xProperty() { ... }
    public StringProperty yProperty() { ... }
    // ...
}

then to create a list that fires update events when x or y change you do

ObservableList<EventShowable> listEvents = 
    FXCollections.observableArrayList(eventShowable ->
        new Observable[] { eventShowable.xProperty(), eventShowable.yProperty() });

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