我实现了这个代码示例，以便从数据库加载数据：
...........
Tab tabdata = new Tab();
Task<VBox> task = createLoadImagesTask(data);
StackPane stack = createVeiledPane(task, 120, 120);
runTask(task);
tabdata.setContent(stack);
AgentsDataStage.addNewTab(tabdata, newValue.getValue().toString());
............
private static Task<VBox> createLoadImagesTask(final InternalData data)
{
return new Task<VBox>()
{
@Override
protected VBox call() throws Exception
{
TabContent contentc = new TabContent();
return contentc.initTestTabContentData();
}
};
}
private static void runTask(Task<? extends Node> task)
{
Thread taskThread = new Thread(task, "Task Runner");
taskThread.setDaemon(true);
taskThread.start();
}
private static StackPane createVeiledPane(Task<? extends Node> task, double prefWidth, double prefHeight)
{
Region veil = new Region();
veil.setStyle("-fx-background-color: transparent");
veil.setPrefSize(prefWidth, prefHeight);
ProgressIndicator progress = new ProgressIndicator();
double progressSize = Math.min(prefWidth, prefHeight);
clampSize(progress, progressSize * 0.75);
progress.progressProperty().bind(task.progressProperty());
StackPane stack = new StackPane();
stack.getChildren().setAll(veil, progress);
task.setOnSucceeded(new EventHandler<WorkerStateEvent>()
{
@Override
public void handle(WorkerStateEvent t)
{
stack.getChildren().setAll(task.getValue());
}
});
return stack;
}
private static void clampSize(Control control, double size)
{
control.setMinSize(ProgressIndicator.USE_PREF_SIZE, ProgressIndicator.USE_PREF_SIZE);
control.setPrefSize(size, size);
control.setMaxSize(ProgressIndicator.USE_PREF_SIZE, ProgressIndicator.USE_PREF_SIZE);
}
当我运行代码并在TreeView节点上多次单击我启动代码时，我得到了这个堆栈异常：
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at com.sun.javafx.css.StyleManager.findMatchingStyles(Unknown Source)
at javafx.scene.CssStyleHelper.createStyleHelper(Unknown Source)
at javafx.scene.Node.reapplyCss(Unknown Source)
at javafx.scene.Node.impl_reapplyCSS(Unknown Source)
at javafx.scene.Node.invalidatedScenes(Unknown Source)
at javafx.scene.Node.setScenes(Unknown Source)
at javafx.scene.Parent$1.onChanged(Unknown Source)
at com.sun.javafx.collections.TrackableObservableList.lambda$new$19(Unknown Source)
at com.sun.javafx.collections.ListListenerHelper$Generic.fireValueChangedEvent(Unknown Sourc
e)
at com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(Unknown Source)
at javafx.collections.ObservableListBase.fireChange(Unknown Source)
at javafx.collections.ListChangeBuilder.commit(Unknown Source)
at javafx.collections.ListChangeBuilder.endChange(Unknown Source)
at javafx.collections.ObservableListBase.endChange(Unknown Source)
at javafx.collections.ModifiableObservableListBase.add(Unknown Source)
at java.util.AbstractList.add(Unknown Source)
at com.sun.javafx.collections.VetoableListDecorator.add(Unknown Source)
at com.sun.javafx.scene.control.skin.ProgressIndicatorSkin$IndeterminateSpinner.rebuild(Unkn
own Source)
at com.sun.javafx.scene.control.skin.ProgressIndicatorSkin$IndeterminateSpinner.access$400(U
nknown Source)
at com.sun.javafx.scene.control.skin.ProgressIndicatorSkin$2.invalidated(Unknown Source)
at javafx.beans.property.IntegerPropertyBase.markInvalid(Unknown Source)
at javafx.beans.property.IntegerPropertyBase.set(Unknown Source)
at javafx.css.StyleableIntegerProperty.set(Unknown Source)
at javafx.beans.property.IntegerProperty.setValue(Unknown Source)
at javafx.css.StyleableIntegerProperty.applyStyle(Unknown Source)
at javafx.css.StyleableIntegerProperty.applyStyle(Unknown Source)
at javafx.scene.CssStyleHelper.transitionToState(Unknown Source)
at javafx.scene.Node.impl_processCSS(Unknown Source)
at javafx.scene.Parent.impl_processCSS(Unknown Source)
at javafx.scene.control.Control.impl_processCSS(Unknown Source)
at javafx.scene.Parent.impl_processCSS(Unknown Source)
at javafx.scene.Parent.impl_processCSS(Unknown Source)
at javafx.scene.Node.processCSS(Unknown Source)
at javafx.scene.Node.processCSS(Unknown Source)
at javafx.scene.Node.processCSS(Unknown Source)
at javafx.scene.Node.processCSS(Unknown Source)
at javafx.scene.Node.processCSS(Unknown Source)
at javafx.scene.Node.processCSS(Unknown Source)
at javafx.scene.Scene.doCSSPass(Unknown Source)
at javafx.scene.Scene.access$3600(Unknown Source)
at javafx.scene.Scene$ScenePulseListener.pulse(Unknown Source)
at com.sun.javafx.tk.Toolkit.lambda$runPulse$31(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.Toolkit.runPulse(Unknown Source)
at com.sun.javafx.tk.Toolkit.firePulse(Unknown Source)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(Unknown Source)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(Unknown Source)
at com.sun.javafx.tk.quantum.QuantumToolkit.lambda$runToolkit$401(Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(Unknown Source)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$146(Unknown Source)
at java.lang.Thread.run(Unknown Source)
您能告诉导致此异常的原因吗？ 这可能与线程有关吗？
更新
与此代码相同的结果：
public void addNewTab(DynamicTreeNodeModel nodeModel)
{
final Tab tab = new Tab();
final ProgressBar progressBar = new ProgressBar();
final Task<BorderPane> loadDataTask = new Task<BorderPane>()
{
@Override
public BorderPane call() throws Exception
{
Content content = new Content(primaryStage, treeView.getSelectionModel().getSelectedItem());
return content.initContentData();
}
};
tab.setContent(progressBar);
loadDataTask.setOnSucceeded(new EventHandler<WorkerStateEvent>()
{
@Override
public void handle(WorkerStateEvent event)
{
BorderPane data = loadDataTask.getValue();
tab.setContent(data);
}
});
final Thread thread = new Thread(loadDataTask);
thread.setDaemon(true);
thread.start();
newTabLabel = new Label(nodeModel.getName());
tab.setStyle("-fx-focus-color: transparent;"); // Remove the blue dashed label from label
tab.setGraphic(newTabLabel);
tab.setContextMenu(makeTabContextMenu(tab, newTabLabel, tabPane));
tabPane.getTabs().add(0, tab);
tabPane.getSelectionModel().select(tab);
tabPane.setTabClosingPolicy(TabPane.TabClosingPolicy.ALL_TABS);
}