JavaFx:TreeTableView 奇怪的 NullpointerException

Question

我注意到 TreeTableView 中有一个奇怪的 NPE

如果您双击不存在行的表，就会发生这种情况。我将附上屏幕截图来准确说明我的意思。

我纯粹来自JavaFx，与我的代码无关。我也做了研究，没有发现任何与此相关的内容。

这是一个简单的代码来重现它:

Controller :

public class Controller implements Initializable {
    @FXML
    private TreeTableColumn<Model, String> column;
    @FXML
    private TreeTableView<Model> treeTable;

    @Override
    public void initialize(URL location, ResourceBundle resources) {
        TreeItem<Model> root = new TreeItem<>(new Model("Root"));
        treeTable.setRoot(root);
        column.setCellValueFactory(value -> value.getValue().getValue().textProperty());

    }

    private class Model {
        private StringProperty text;

        Model(String text) {
            this.text = new SimpleStringProperty(text);
        }

        public StringProperty textProperty() {
            return text;
        }

        public String getText() {
            return text.get();
        }

        @Override
        public String toString() {
            return getText();
        }
    }
}

.fxml:

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.TreeTableColumn?>
<?import javafx.scene.control.TreeTableView?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane xmlns="http://javafx.com/javafx"
            xmlns:fx="http://javafx.com/fxml"
            fx:controller="stackoverflow.treeview.Controller">
    <TreeTableView fx:id="treeTable">
        <columns>
            <TreeTableColumn fx:id="column" text="Test"/>
        </columns>
    </TreeTableView>
</AnchorPane>

如果双击红色区域，则会抛出 NPE。

堆栈跟踪:

Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
    at com.sun.javafx.scene.control.behavior.TreeTableRowBehavior.handleClicks(TreeTableRowBehavior.java:89)
    at com.sun.javafx.scene.control.behavior.CellBehaviorBase.simpleSelect(CellBehaviorBase.java:259)
    at com.sun.javafx.scene.control.behavior.TableRowBehaviorBase.doSelect(TableRowBehaviorBase.java:120)
    at com.sun.javafx.scene.control.behavior.CellBehaviorBase.mousePressed(CellBehaviorBase.java:150)
    at com.sun.javafx.scene.control.behavior.TableRowBehaviorBase.mousePressed(TableRowBehaviorBase.java:64)
    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.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$MouseEventNotification.run(GlassViewEventHandler.java:381)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:417)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:416)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
    at com.sun.glass.ui.View.notifyMouse(View.java:937)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
    at java.lang.Thread.run(Thread.java:745)

Java版本:1.8u121

作为一个解决方案，我会接受任何真正有效的解决方法，或者任何表明他们正在处理它的解释/javafx错误报告，或者在以下版本中有修复。

Answer 1

当您单击没有列的空白区域时，您最终会单击 TreeTableRow。显然，控件的行为类中存在一个错误，这意味着它无法处理具有 null 项的行。如果您单击列的空白处，则不会看到此错误，因为单击的是 TreeTableCell，其行为类似乎没有遇到相同的问题。不确定确切的区别在哪里，但我只是快速浏览了一下源代码。

正如 @kleopatra 提到的，阻止抛出异常的一种方法是向 TreeTableRow 添加一个事件过滤器，该事件过滤器消耗对空行的双击。

var table = new TreeTableView<String>();
table.setRowFactory(ttv -> {
    var row = new TreeTableRow<String>();
    row.addEventFilter(MouseEvent.MOUSE_PRESSED, event -> {
        if (row.getItem() == null && event.getClickCount() % 2 == 0) {
            event.consume();
        }
    });
    return row;
});

注意:您需要 clickCount % 2 == 0，因为当点击次数为偶数时，行为类将尝试访问 TreeItem。