在 openviewerFX 中，当我调用 JFileChooser 来保存我的 pdf 时，它会保存，但在那之后，它应该打开一个 BaseViewerFX 窗口并显示所说的保存的 PDF。然而，当我运行程序时，JFileChooser 出现，它保存，然后当需要调用 .loadPDF 方法时，它返回一个空指针异常，即使文件在 if 块中初始化。错误如下：
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.fxml.FXMLLoader$MethodHandler.invoke(Unknown Source)
at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(Unknown Source)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)
at javafx.event.Event.fireEvent(Unknown Source)
at javafx.scene.Node.fireEvent(Unknown Source)
at javafx.scene.control.Button.fire(Unknown Source)
at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(Unknown Source)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(Unknown Source)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(Unknown Source)
at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(Unknown Source)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)
at javafx.event.Event.fireEvent(Unknown Source)
at javafx.scene.Scene$MouseHandler.process(Unknown Source)
at javafx.scene.Scene$MouseHandler.access$1500(Unknown Source)
at javafx.scene.Scene.impl_processMouseEvent(Unknown Source)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Unknown Source)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(Unknown Source)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(Unknown Source)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(Unknown Source)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(Unknown Source)
at com.sun.glass.ui.View.handleMouseEvent(Unknown Source)
at com.sun.glass.ui.View.notifyMouse(Unknown Source)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.reflect.misc.Trampoline.invoke(Unknown Source)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.reflect.misc.MethodUtil.invoke(Unknown Source)
... 53 more
Caused by: java.lang.NullPointerException
at org.jpedal.examples.baseviewer.BaseViewerFX.start(Unknown Source)
at fbla.rahulshah.database.dataManipulation.PDFCreationAndViewerLauncher.createDebtorPDF(PDFCreationAndViewerLauncher.java:53)
at fbla.rahulshah.database.view.MainScreenController.generateDebtReport(MainScreenController.java:114)
... 62 more
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Qt: Untested Windows version 10.0 detected!
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at org.jpedal.examples.baseviewer.BaseViewerFX.openFile(Unknown Source)
at org.jpedal.examples.baseviewer.BaseViewerFX.loadPDF(Unknown Source)
at org.jpedal.examples.baseviewer.BaseViewerFX$7$1.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$null$173(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(Unknown Source)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(Unknown Source)
at java.lang.Thread.run(Unknown Source)
正如你所看到的，它给了我一个空指针异常，以及这个奇怪的 QT 未经测试的东西（我忽略了它，因为我查了它是什么，它显然并不重要）。即使我尝试使用 BaseViewerFX 窗口上的打开按钮打开它，它也会做同样的事情。我意识到 nullPointerExceptions 是可以轻松修复的，并且是由未初始化的变量引起的，但该变量是在创建它的 if 块内初始化的。将它从 if 块中取出也不会做任何事情。这是您自己查看的代码：
public void createDebtorPDF() throws Exception {
File file;
JFileChooser fileChooser = new JFileChooser();
ArrayList<StudentData> listOfDebtors = new ArrayList<StudentData>();
int i = 0;
listOfDebtors = StudentData.getListOfDebtors(i, listOfDebtors);
PDDocument debtorDoc = new PDDocument();
PDPage page = new PDPage();
debtorDoc.addPage(page);
createPDF(debtorDoc, page, i, listOfDebtors, i);
Stage pdfStage = new Stage();
BaseViewerFX baseViewer = new BaseViewerFX();
if (fileChooser.showSaveDialog(fileChooser) == JFileChooser.APPROVE_OPTION) {
file = fileChooser.getSelectedFile();
file = checkFileName(file);
file = fileChooser.showSaveDialog(null);
file = checkFileName(file);
baseViewer.init();
debtorDoc.save(file);
pdfStage.setScene(baseViewer.setupViewer(600, 400));
baseViewer.setupViewer(600, 400);
pdfStage.show();
baseViewer.loadPDF(file);
baseViewer.start(pdfStage);
debtorDoc.close();
}
}