从addListener中的ListView中删除项

Question

我对下面的Java程序有问题。我在Ubuntu系统上使用带有JDK-1.8u25的JavaFX。我想显示一个ListView，并从列表中删除突出显示的条目。我创建了一个列表，并将其与一个可观察列表配对，以通知侦听器事件。然而，通过删除下面的“orderOvList.remove（i，i 1）”项来更改列表似乎会生成另一个侦听器事件。所以，我似乎在侦听器代码的主体中递归。我想过将list元素从nor有序列表中移动，"orderList.remove（i）"，但之后ListView没有更新。

有人有什么想法吗？

下面的代码在我运行后崩溃。

堆栈跟踪：

0
0
Exception in thread "JavaFX Application Thread" java.lang.UnsupportedOperationException
    at java.util.Collections$UnmodifiableCollection.add(Collections.java:1055)
    at javafx.collections.ListChangeBuilder.nextRemove(ListChangeBuilder.java:204)
    at javafx.collections.ObservableListBase.nextRemove(ObservableListBase.java:150)
    at javafx.collections.ModifiableObservableListBase.remove(ModifiableObservableListBase.java:181)
    at com.sun.javafx.collections.ObservableListWrapper.remove(ObservableListWrapper.java:165)
    at TestListView.lambda$start$0(TestListView.java:32)
    at TestListView$$Lambda$82/921981528.invalidated(Unknown Source)
    at com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:137)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
    at javafx.beans.property.ReadOnlyObjectWrapper$ReadOnlyPropertyImpl.fireValueChangedEvent(ReadOnlyObjectWrapper.java:176)
    at javafx.beans.property.ReadOnlyObjectWrapper.fireValueChangedEvent(ReadOnlyObjectWrapper.java:142)
    at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:112)
    at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:145)
    at javafx.scene.control.SelectionModel.setSelectedItem(SelectionModel.java:102)
    at javafx.scene.control.ListView$ListViewBitSetSelectionModel$1.onChanged(ListView.java:1245)
    at javafx.collections.WeakListChangeListener.onChanged(WeakListChangeListener.java:88)
    at com.sun.javafx.collections.ListListenerHelper$Generic.fireValueChangedEvent(ListListenerHelper.java:329)
    at com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(ListListenerHelper.java:73)
    at javafx.collections.ObservableListBase.fireChange(ObservableListBase.java:233)
    at javafx.collections.ListChangeBuilder.commit(ListChangeBuilder.java:482)
    at javafx.collections.ListChangeBuilder.endChange(ListChangeBuilder.java:541)
    at javafx.collections.ObservableListBase.endChange(ObservableListBase.java:205)
    at com.sun.javafx.collections.ObservableListWrapper.remove(ObservableListWrapper.java:167)
    at TestListView.lambda$start$0(TestListView.java:32)
    at TestListView$$Lambda$82/921981528.invalidated(Unknown Source)
    at com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:137)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
    at javafx.beans.property.ReadOnlyObjectWrapper$ReadOnlyPropertyImpl.fireValueChangedEvent(ReadOnlyObjectWrapper.java:176)
    at javafx.beans.property.ReadOnlyObjectWrapper.fireValueChangedEvent(ReadOnlyObjectWrapper.java:142)
    at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:112)
    at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:145)
    at javafx.scene.control.SelectionModel.setSelectedItem(SelectionModel.java:102)
    at javafx.scene.control.MultipleSelectionModelBase.lambda$new$34(MultipleSelectionModelBase.java:67)
    at javafx.scene.control.MultipleSelectionModelBase$$Lambda$75/1274395902.invalidated(Unknown Source)
    at com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:137)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
    at javafx.beans.property.ReadOnlyIntegerWrapper$ReadOnlyPropertyImpl.fireValueChangedEvent(ReadOnlyIntegerWrapper.java:176)
    at javafx.beans.property.ReadOnlyIntegerWrapper.fireValueChangedEvent(ReadOnlyIntegerWrapper.java:142)
    at javafx.beans.property.IntegerPropertyBase.markInvalid(IntegerPropertyBase.java:113)

    at javafx.beans.property.IntegerPropertyBase.set(IntegerPropertyBase.java:146)
    at javafx.scene.control.SelectionModel.setSelectedIndex(SelectionModel.java:68)
    at javafx.scene.control.MultipleSelectionModelBase.select(MultipleSelectionModelBase.java:357)
    at javafx.scene.control.ListView.lambda$new$156(ListView.java:374)
    at javafx.scene.control.ListView$$Lambda$74/963851926.invalidated(Unknown Source)
    at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:349)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
    at javafx.beans.property.ReadOnlyBooleanPropertyBase.fireValueChangedEvent(ReadOnlyBooleanPropertyBase.java:72)
    at javafx.scene.Node$FocusedProperty.notifyListeners(Node.java:7526)
    at javafx.scene.Scene$13.invalidated(Scene.java:2046)
    at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:111)
    at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:145)
    at javafx.scene.Scene$KeyHandler.setFocusOwner(Scene.java:3891)
    at javafx.scene.Scene$KeyHandler.requestFocus(Scene.java:3938)
    at javafx.scene.Scene$KeyHandler.access$1900(Scene.java:3877)
    at javafx.scene.Scene.requestFocus(Scene.java:2010)
    at javafx.scene.Node.requestFocus(Node.java:7687)
    at com.sun.javafx.scene.traversal.TopMostTraversalEngine.focusAndNotify(TopMostTraversalEngine.java:92)
    at com.sun.javafx.scene.traversal.TopMostTraversalEngine.traverseToFirst(TopMostTraversalEngine.java:110)
    at javafx.scene.Scene.focusInitial(Scene.java:1980)
    at javafx.scene.Scene.access$3200(Scene.java:144)
    at javafx.scene.Scene$ScenePulseListener.focusCleanup(Scene.java:2330)
    at javafx.scene.Scene$ScenePulseListener.pulse(Scene.java:2351)
    at com.sun.javafx.tk.Toolkit.lambda$runPulse$28(Toolkit.java:314)
    at com.sun.javafx.tk.Toolkit$$Lambda$154/326451107.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.Toolkit.runPulse(Toolkit.java:313)
    at com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:340)
    at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:451)
    at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:431)
    at com.sun.javafx.tk.quantum.QuantumToolkit.lambda$runToolkit$363(QuantumToolkit.java:298)
    at com.sun.javafx.tk.quantum.QuantumToolkit$$Lambda$46/1868350875.run(Unknown Source)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
    at com.sun.glass.ui.gtk.GtkApplication.lambda$null$45(GtkApplication.java:126)
    at com.sun.glass.ui.gtk.GtkApplication$$Lambda$42/584634336.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:745)

示例代码：

import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Scene;
import javafx.scene.control.ListView;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

import java.util.ArrayList;
import java.util.List;

public class TestListView extends Application {
  @Override
  public void start (Stage stage) {
    List<String> orderList = new ArrayList<String> ();
    ObservableList<String> orderOvList =
      FXCollections.observableList (orderList);
    ListView<String> order = new ListView<String> (orderOvList);

    orderOvList.add ("abc");
    orderOvList.add ("def");
    orderOvList.add ("ghi");
    orderOvList.add ("jkl");

    VBox orderBoxPane = new VBox (6);
    order.getSelectionModel().selectedItemProperty().addListener (
      ov -> {
        int i = order.getSelectionModel ().getSelectedIndex ();

        if (orderOvList.size () >= 0) {
          System.out.println (i);
          orderOvList.remove (i, i + 1);
        }
      });
    orderBoxPane.getChildren ().add (order);

    Scene scene = new Scene (orderBoxPane);
    stage.setTitle ("TestListView");
    stage.setScene (scene);
    stage.show ();
  }
}

Answer 1

一旦用户选择删除所选项目，想要编写代码似乎是一种奇怪的用户体验。我不太确定是什么导致了您看到的异常，但您在侦听器中执行的代码确实会更改所选的值，从而在选择模型上引发新的更改事件。（我本以为是StackOverflowException而不是UnsupportedOperationException。我猜对选择模型中所选项目列表的“嵌套”更改会导致尝试更改不可修改的列表。）

如果这真的是您想要的行为，我会更多地从鼠标按下动作的角度来考虑——当用户单击该项时，将其从列表中删除。您可以通过创建单元格工厂并在所创建的单元格中注册鼠标侦听器来完成此操作：

order.setCellFactory(lv -> {
    ListCell<String> cell = new ListCell<String>() {
        @Override
        public void updateItem(String item, boolean empty) {
            super.updateItem(item, empty);
            setText(item);
        }
    };
    cell.setOnMouseClicked(event -> {
        String item = cell.getItem();
        if (item != null) {
            orderOvList.remove(item);

            // ensure nothing selected after removal:
            order.getSelectionModel().clearSelection();
        }
    });
    return cell ;
});