通过其 changeListener 修改 ObservableList 抛出 UnsupportedOperationException

Question

我正在制作一个简单的 tic-tac-toe GUI-based 游戏。为此，我使用了一个 2D ObservableList，其中填充了 Figures 枚举器。每一步我都会将所选单元格的值更改为 X 或 O，然后我检查是否有人赢了或者游戏是否以平局结束。如果是这样，我用空白重新填充列表。至少它应该是这样工作的。我遇到了标题中描述的问题。这个问题在任何情况下都不会发生，我不明白这里发生了什么，也没有在 Google 上找到它。这是我的代码的简化版本：（感谢帮助）

public class Example{
    enum Figures { NONE, X, O }
    static ObservableList<ObservableList<Figures>> list = FXCollections.observableArrayList();

    public static void main(String... args) {
        for (int i = 0; i < 3; i++) {
            ObservableList<Figures> subList = FXCollections.observableArrayList();
            list.add(subList);

            subList.addListener((ListChangeListener<Figures>) change -> {
                while (change.next()) {
                    Figures figure = subList.get(change.getFrom());
                    if (figure == Figures.NONE) {
                        //show Blank space
                    } else {
                        if (figure == Figures.X) {
                            //show X
                        }
                        if (figure == Figures.O) {
                            //show O
                        }

                        checkState();
                    }
                }
            });
            for (int j = 0; j < 3; j++) {
                subList.add(Figures.NONE);
            }
        }

        //it is a graphical game but here is what I do by clicking buttons to get the exception
        list.get(2).set(0, Figures.X);
        list.get(1).set(0, Figures.O);
        list.get(1).set(1, Figures.X);
        list.get(0).set(1, Figures.O);
        list.get(0).set(2, Figures.X);
    }

    private static void checkState() {
        //checking state and if win or draw
            restartGame();
    }

    private static void restartGame() {
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                list.get(i).set(j, Figures.NONE);
            }
        }
    }
}

和输出

Exception in thread "JavaFX Application Thread" java.lang.UnsupportedOperationException
at java.util.Collections$UnmodifiableList.add(Collections.java:1314)
at javafx.collections.ListChangeBuilder.nextRemove(ListChangeBuilder.java:208)
at javafx.collections.ListChangeBuilder.nextSet(ListChangeBuilder.java:453)
at javafx.collections.ObservableListBase.nextSet(ObservableListBase.java:115)
at javafx.collections.ModifiableObservableListBase.set(ModifiableObservableListBase.java:162)
at Main.restartGame(Main.java:239)
at Main.lambda$gameScene(Main.java:79)
at com.sun.javafx.collections.ListListenerHelper$SingleChange.fireValueChangedEvent(ListListenerHelper.java:164)
at com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(ListListenerHelper.java:73)
at javafx.collections.ObservableListBase.fireChange(ObservableListBase.java:233)
at javafx.collections.ListChangeBuilder.commit(ListChangeBuilder.java:482)
at javafx.collections.ListChangeBuilder.endChange(ListChangeBuilder.java:541)
at javafx.collections.ObservableListBase.endChange(ObservableListBase.java:205)
at javafx.collections.ModifiableObservableListBase.set(ModifiableObservableListBase.java:163)
at Main.gameScene(Main.java:170)
at Main.start(Main.java:27)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication11(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait4(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null2(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater3(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null7(WinApplication.java:177)
at java.lang.Thread.run(Thread.java:748)
Exception in thread "JavaFX Application Thread" java.lang.UnsupportedOperationException
at java.util.Collections$UnmodifiableList.add(Collections.java:1314)
at javafx.collections.ListChangeBuilder.nextRemove(ListChangeBuilder.java:208)
at javafx.collections.ListChangeBuilder.nextSet(ListChangeBuilder.java:453)
at javafx.collections.ObservableListBase.nextSet(ObservableListBase.java:115)
at javafx.collections.ModifiableObservableListBase.set(ModifiableObservableListBase.java:162)
at Main.restartGame(Main.java:239)
at Main.lambda$gameScene(Main.java:79)
at com.sun.javafx.collections.ListListenerHelper$SingleChange.fireValueChangedEvent(ListListenerHelper.java:164)
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 javafx.collections.ModifiableObservableListBase.set(ModifiableObservableListBase.java:163)
at Main.gameScene(Main.java:171)
at Main.start(Main.java:27)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication11(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait4(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null2(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater3(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null7(WinApplication.java:177)
at java.lang.Thread.run(Thread.java:748)

Answer 1

问题是 ListChangeListener 中的 checkState() 函数。根据 ListChangeListener

处的 javadoc

Warning: This class directly accesses the source list to acquire information about the > changes. This effectively makes the Change object invalid when another change occurs on the list. For this reason it is not safe to use this class on a different thread. It also means the source list cannot be modified inside the listener since that would invalidate this Change object for all subsequent listeners.

通过其 changeListener 修改 ObservableList 抛出 UnsupportedOperationException

Modifing ObservableList through its changeListener throws UnsupportedOperationException

java

javafx

observablelist

unsupportedoperation