java - NPE javafx.scene.control.behavior.ListViewBehavior.mousePressed

Question

感谢您花时间查看我的帖子。

我已经实现了带有嵌套 TitledPanes 的 ListViewListView 工作得很好 - 但是，当单击 ListView 中的 TitledPane(单击 Pane 而不是标题)时，会引发 NPE。

在目标区域内单击可以顺利进行，没有任何问题

单击此处将导致 NPE 被抛出。

代码:

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;

public class Example extends Application {

    @Override
    public void start(final Stage primaryStage) throws Exception {
        final ExpandableListView<Item> listView = new ExpandableListView<Item>();
        listView.setContentProvider(new ExpandableListView.ContentProvider<Item>() {
            @Override
            public String getTitleOf(final Item item) {
                return item.getTitle();
            }

            @Override
            public String getContentOf(final Item item) {
                return item.getContent();
            }
        });
        for (int i = 0; i < 100000; i++) {
            listView.getItems().add(new Item("title" + i, "content" + i));
        }

        final BorderPane group = new BorderPane();
        group.setCenter(listView);
        final Scene scene = new Scene(group);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static class Item {

        String title;
        String content;

        public Item(String title, String content) {
            this.title = title;
            this.content = content;
        }

        public String getTitle() {
            return title;
        }

        public String getContent() {
            return content;
        }
    }

    public static void main(String[] args) {
        launch(args);
    }
}



import java.util.HashSet;
import java.util.Set;

import javafx.collections.ObservableList;
import javafx.event.EventHandler;
import javafx.scene.control.ListCell;
import javafx.scene.control.ListView;
import javafx.scene.control.TitledPane;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.BorderPane;
import javafx.scene.text.Text;
import javafx.util.Callback;

public class ExpandableListView<E> extends ListView<E> {

    private ContentProvider<E> contentProvider=new ContentProvider<E>(){@Override public String getTitleOf(final E item){return item.toString();}

    @Override public String getContentOf(final E item){return getTitleOf(item);}};

    private final Set<E> expandedItems = new HashSet<E>();

    public ExpandableListView() {
        setSelectionModel(null);
        setCellFactory(new Callback<ListView<E>, ListCell<E>>() {
            @Override
            public ListCell<E> call(final ListView<E> param) {
                final TitledPane titledPane = new TitledPane();
                final Text contentArea = new Text();

                titledPane.setAnimated(false);
                titledPane.setCollapsible(true);
                titledPane.setExpanded(false);

                final BorderPane contentAreaWrapper = new BorderPane();
                contentAreaWrapper.setLeft(contentArea);
                titledPane.setContent(contentAreaWrapper);

                titledPane.addEventHandler(MouseEvent.MOUSE_CLICKED, new EventHandler<MouseEvent>() {
                    @Override
                    public void handle(final MouseEvent event) {
                        final boolean expanded = titledPane.isExpanded();
                        final E item = (E) titledPane.getUserData();
                        if (item == null) {
                            return;
                        }
                        if (expanded) {
                            expandedItems.add(item);
                        } else {
                            expandedItems.remove(item);
                        }
                    }
                });
                return new ListCell<E>() {
                    @Override
                    protected void updateItem(final E item, final boolean empty) {
                        super.updateItem(item, empty);
                        if (empty) {
                            titledPane.setText("");
                            contentArea.setText("");
                            return;
                        }
                        final boolean expanded = isExpanded(item);
                        titledPane.setUserData(item);
                        titledPane.setExpanded(expanded);
                        titledPane.setText(contentProvider.getTitleOf(item));
                        contentArea.setText(contentProvider.getContentOf(item));
                        setGraphic(titledPane);
                    }
                };
            }
        });

    }

    public void setContentProvider(final ContentProvider<E> contentProvider) {
        this.contentProvider = contentProvider;
    }

    public void expand(E item) {
        expand(item, true);
    }

    public void collapse(E item) {
        expand(item, false);
    }

    private void expand(E item, boolean expand) {
        if (expand) {
            this.expandedItems.add(item);
        } else {
            this.expandedItems.remove(item);
        }

        ObservableList<E> o = getItems();
        setItems(null);
        setItems(o);
    }

    public boolean isExpanded(E item) {
        return this.expandedItems.contains(item);
    }

    public static interface ContentProvider<E> {

        String getTitleOf(E item);

        String getContentOf(E item);

    }
}

NPE:

java.lang.NullPointerException
at com.sun.javafx.scene.control.behavior.ListViewBehavior.mousePressed(ListViewBehavior.java:366)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:95)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:394)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:432)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:410)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:431)
at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
at com.sun.glass.ui.View.notifyMouse(View.java:937)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$3(WinApplication.java:177)
at java.lang.Thread.run(Unknown Source)

Answer 1

NullPointerException 是由以下行引起的:

setSelectionModel(null);

提供您自己的自定义 no selection model .