我有一个多级树视图 . 它有几个树项 . 我加载时只展开一个级别 . 用户可以通过单击该树项的箭头逐个展开 . 随着我不断扩展，最后一个节点继续向下移动并离开视口 . 我向下滚动，然后单击箭头 . 我收到了错误 .
@FXML
private void createDescendantsTreeView(TreeView<APerson> thisTreeView) {
AnchorPane.setTopAnchor(thisTreeView, 10.0);
AnchorPane.setBottomAnchor(thisTreeView, 10.0);
AnchorPane.setLeftAnchor(thisTreeView, 5.0);
AnchorPane.setRightAnchor(thisTreeView, 5.0);
thisTreeView.getSelectionModel().setSelectionMode(SelectionMode.SINGLE);
thisTreeView.setPrefHeight(vBoxHt);
thisTreeView.setCellFactory(new Callback<TreeView<APerson>, TreeCell<APerson>>() {
@Override
public TreeCell<APerson> call(TreeView<APerson> thisTreeView) {
return new TreeCell<APerson>() {
protected void updateItem(final APerson thisPerson, boolean empty) {
super.updateItem(thisPerson, empty);
// if the item is not empty and is a root...
if (!empty) {
setTooltip(thisPerson.getToolTip());
// This will set Context menu for the node
if (thisPerson.getFatherID() != 0) {
this.setContextMenu(rightContextMenu);
}
if (thisPerson.getGender().charAt(0) == 'M') {
setText(thisPerson.getPersonName() + " [" + thisPerson.getPersonID() + "]");
ImageView maleIcon = new ImageView(maleImage);
setGraphic(maleIcon);
String cellStyle = " -fx-font-size: 16;\n" + " -fx-font-family: \"Times New Roman\";\n" + "-fx-text-fill: blue;";
setStyle(cellStyle);
} else {
setText(thisPerson.getPersonName() + " [" + thisPerson.getPersonID() + "]");
ImageView femaleIcon = new ImageView(femaleImage);
setGraphic(femaleIcon);
String cellStyle = " -fx-font-size: 16;\n" + " -fx-font-family: \"Times New Roman\";\n" + "-fx-text-fill: red;";
setStyle(cellStyle);
}
} else {
this.setText(null);
this.setGraphic(null);
}
}
};
}
});
childrenTreeView.setOnMouseClicked(new EventHandler<MouseEvent>() {
@Override
public void handle(MouseEvent mouseEvent) {
Node node = mouseEvent.getPickResult().getIntersectedNode();
System.out.println("Node click: " + node.toString());
if (node instanceof Text || (node instanceof TreeCell && ((TreeCell) node).getText() != null)) {
TreeItem TreeItemAtLocation = new TreeItem();
TreeItemAtLocation = childrenTreeView.getSelectionModel().getSelectedItem();
System.out.println("Child Tree - clicked on : " + TreeItemAtLocation.getValue().toString());
String name = childrenTreeView.getSelectionModel().getSelectedItem().getValue().toString();
APerson tmp = childrenTreeView.getSelectionModel().getSelectedItem().getValue();
if (TreeItemAtLocation.getParent() == null) {
removePicture.setDisable(true);
} else {
removePicture.setDisable(false);
}
if (mouseEvent.getButton().equals(MouseButton.SECONDARY)) {
if (TreeItemAtLocation != null) {
if (childrenTreeView.getRoot() == TreeItemAtLocation) {
addPerson.setDisable(false);
deletePerson.setDisable(true);
deleteThisFamily.setDisable(true);
modifyPerson.setDisable(true);
viewPerson.setDisable(true);
} else {
addPerson.setDisable(false);
deletePerson.setDisable(false);
if (TreeItemAtLocation.isLeaf()) {
deleteThisFamily.setDisable(true);
} else {
deleteThisFamily.setDisable(false);
}
modifyPerson.setDisable(false);
viewPerson.setDisable(false);
}
rightContextMenu.show(myMainApp.getMainStage());
} else {
rightContextMenu.hide();
}
} else {
rightContextMenu.hide();
}
}
}
});
}
此图显示了屏幕，我正在谈论右侧的树 . 随着我不断扩展节点，最后一个Tree Item向下滚动，在此图像中不可见 . 我向下滚动以查看Tree Item，当我单击该Tree项的箭头时，我收到以下错误 .
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
Node click: MainWindowController$5$1@1051fb6[styleClass=cell indexed-cell tree-cell]'Daughter [363]'
at familytreev01.MainWindowController$6.handle(MainWindowController.java:510)
at familytreev01.MainWindowController$6.handle(MainWindowController.java:501)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Scene$ClickGenerator.postProcess(Scene.java:3470)
at javafx.scene.Scene$ClickGenerator.access$8100(Scene.java:3398)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3766)
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$MouseEventNotification.run(GlassViewEventHandler.java:352)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:275)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$355(GlassViewEventHandler.java:388)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:387)
at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
at com.sun.glass.ui.View.notifyMouse(View.java:937)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$149(WinApplication.java:191)
at java.lang.Thread.run(Thread.java:745)
Node click: MainWindowController$5$1@36f8bc[styleClass=cell indexed-cell tree-cell]'null'
Node click: StackPane@b679e7[styleClass=tree-disclosure-node]
Deleting directory D:\JavaFXPrograms\FamilyTreeV01\dist\run8821460
jfxsa-run:
BUILD SUCCESSFUL (total time: 16 minutes 1 second)
但是，如果我先选择Tree Item然后单击该箭头，我就不会收到该错误 . 它没有任何麻烦地扩展 . 右键单击该Tree Item也可以正常工作 .
错误符合我将值赋给类变量的情况 . . childrenTreeView.getSelectionModel（）getSelectedItem（）的getValue（）;
为什么这只会发生在最后一个节点？
提前致谢 .