侦听器中的JavaFX ObservableList remove元素引发异常 [英] JavaFX ObservableList remove element in listener throws exception
问题描述
当我将侦听器附加到可观察列表时,在该侦听器中,我尝试删除某些元素,在某些情况下它会通过,在某些情况下会崩溃.
When I attach listener to observable list and in that listener I try to remove some element, in some cases it passes and in some cases it crashes.
场景: 项目已从列表中删除.它会触发侦听器,然后在该侦听器中尝试删除其他项.
Scenario: Item is removed from a list. It triggers listener, and in that listener I try to delete another item.
- 如果我在侦听器中尝试删除的元素不仅仅与最初删除的元素相邻,那么它可以正常工作.
- 如果我在侦听器中尝试删除刚开始删除的NEXT元素,则会因UnsupportedOperationException崩溃!
- If in listener I try to remove element that is not just next to initially removed, it works OK.
- If in listener I try to remove element that is JUST NEXT to initially removed, it crashes with UnsupportedOperationException!!!
有人有类似的问题吗?您有任何提示,建议或解决方法吗?
Did anybody had similar problem? Do you have any tips, suggestions or workaround?
我知道您可以同时删除两个项目,但是问题是在侦听器中,我需要检测哪些项目也需要删除,因此我要在其中删除我.
I know that you can delete both at the same time, but problem is that in listener I need to detect which items I need to remove also so I delete i there.
这是ObservableList中的错误吗?
Is this a bug in ObservableList?
我希望它总是可以正常工作,或者至少总是崩溃.
I would expect that it always work, or at least to always crash.
这是代码示例:
import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ListChangeListener;
import javafx.collections.ObservableList;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
public class ListRemoveFromListener extends Application {
boolean changing = false;
@Override
public void start(Stage primaryStage) throws Exception {
VBox vbox = new VBox();
Button buttonSuccess = new Button("remove success");
buttonSuccess.setOnAction(e -> {
removeSuccess();
});
Button buttonBreak = new Button("Remove breaks");
buttonBreak.setOnAction(e -> {
removeBreaks();
});
vbox.getChildren().addAll(buttonSuccess, buttonBreak);
Scene scene = new Scene(vbox);
primaryStage.setScene(scene);
primaryStage.show();
}
/**
* If we try in listener to remove element just next to one that was
* initially removed, exception is thrown.
*/
private void removeBreaks() {
ObservableList<String> list = FXCollections.observableArrayList();
list.add("first");
list.add("second");
list.add("third");
list.add("fourth");
list.add("fifth");
list.add("sixth");
list.addListener(new ListChangeListener<String>() {
@Override
public void onChanged(Change<? extends String> c) {
list.remove("second");
}
});
list.remove("third");
}
/**
* If we try in listener to remove element that is not just next to initially
* removed element, element is removed and all works O.
*/
private void removeSuccess() {
ObservableList<String> list = FXCollections.observableArrayList();
list.add("first");
list.add("second");
list.add("third");
list.add("fourth");
list.add("fifth");
list.add("sixth");
list.addListener(new ListChangeListener<String>() {
@Override
public void onChanged(Change<? extends String> c) {
list.remove("fifth");
}
});
list.remove("third");
}
public static void main(String[] args) {
launch(args);
}
}
推荐答案
ListChangeListener.Change 文档状态:
无法在侦听器内部修改源列表
您可以使用 Platform.runLater 调用以计划在将来的某个时间执行的其他更改:
You can work around this using a Platform.runLater call to schedule the additional change to be performed at some time in the future:
list.addListener((ListChangeListener<String>) c -> {
if (list.contains("second")) {
Platform.runLater(() -> list.remove("second"));
}
});
在执行此操作时要小心,以免引起级联的无限变化循环.
be careful when doing so that you don't cause a cascading infinite loop of changes.
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