当我的javafx程序中的控制器调用我的Excel读取方法时，我收到此错误：
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1774)
at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
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:49)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Node.fireEvent(Node.java:8413)
at javafx.scene.control.Button.fire(Button.java:185)
at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
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.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$148(WinApplication.java:191)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
... 48 more
Caused by: java.lang.NumberFormatException: For input string: "null"
at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2043)
at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
at java.lang.Double.parseDouble(Double.java:538)
at java.lang.Double.valueOf(Double.java:502)
at sample.Tab.setTotal(Tab.java:47)
at sample.Tab.readFromExcelFile(Tab.java:122)
at sample.Controller.editTab(Controller.java:121)
... 58 more
这是我第一个使用Apache的javafx项目，我对excel写入方法没有任何麻烦，只是读者。我已经完成了几次代码，但似乎无法确定导致此错误的原因。请注意，我的代码可能看起来有点难看，因为这是一个原型，除了我缺乏与Apache的任何实践经验，并且与javafx没有太大关系。
以下是相关代码 -
主要方法：
package sample;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
import org.apache.poi.xssf.usermodel.*;
public class Main extends Application {
@Override
public void start(Stage primaryStage) throws Exception{
Parent root = FXMLLoader.load(getClass().getResource("TabTrackerUI.fxml"));
primaryStage.setTitle("The Final Tabs");
primaryStage.setScene(new Scene(root, 1200, 690));
primaryStage.show();
XSSFWorkbook workbook = new XSSFWorkbook();
XSSFSheet sheet = workbook.createSheet("Customers");
}
public static void main(String[] args) {
launch(args);
}
}
我创建编写和读取excel文件所需方法的类：
public class Tab{
private String custName;
private BigDecimal custTotal;
private String custLast;
public Tab(String custName, String custTotal, String custLast){
this.custName = custName;
this.custTotal = new BigDecimal(custTotal);
this.custLast = custLast;
}
public Tab() {
}
//Getters and Setters
public String getName(){return custName;}
public BigDecimal getTotal(){return custTotal;}
public String getLast(){return custLast;}
public void setName(String name){this.custName = name;}
public void setTotal(String price){
double current = Double.valueOf(String.valueOf(getTotal()));
this.custTotal = BigDecimal.valueOf(Long.parseLong(current + price));
}
public void setLast(String item){this.custLast = item;}
public static void writeExcel(Tab tab, String excelFilePath) throws IOException {
Workbook workbook = new HSSFWorkbook();
Sheet sheet = workbook.createSheet();
int rowCount = 0;
Row row = sheet.createRow(++rowCount);
writeTab(tab, row);
try (FileOutputStream outputStream = new FileOutputStream(excelFilePath)) {
workbook.write(outputStream);
}
}
private static void writeTab(Tab tab, Row row) {
Cell cell = row.createCell(1);
cell.setCellValue(tab.getName());
cell = row.createCell(2);
cell.setCellValue(String.valueOf(tab.getTotal()));
cell = row.createCell(3);
cell.setCellValue(tab.getLast());
}
//Read from excel docs
public String toString() {
return String.format("%s - %s - %f", custName, custTotal, custLast);
}
private Object getCellValue(Cell cell) {
switch (cell.getCellType()) {
case Cell.CELL_TYPE_STRING:
return cell.getStringCellValue();
case Cell.CELL_TYPE_BOOLEAN:
return cell.getBooleanCellValue();
case Cell.CELL_TYPE_NUMERIC:
return cell.getNumericCellValue();
case Cell.CELL_TYPE_ERROR:
return null;
}
return null;
}
List<Tab> readFromExcelFile(String excelFilePath) throws IOException {
List<Tab> listTab = new ArrayList<>();
FileInputStream inputStream = new FileInputStream(new File(excelFilePath));
Workbook workbook = new HSSFWorkbook(inputStream);
Sheet firstSheet = workbook.getSheetAt(0);
Iterator<Row> iterator = firstSheet.iterator();
while (iterator.hasNext()) {
Row nextRow = iterator.next();
Iterator<Cell> cellIterator = nextRow.cellIterator();
Tab aTab = new Tab();
while (cellIterator.hasNext()) {
Cell nextCell = cellIterator.next();
int columnIndex = nextCell.getColumnIndex();
switch (columnIndex) {
case 1:
aTab.setName((String) getCellValue(nextCell));
break;
case 2:
aTab.setTotal((String) getCellValue(nextCell));
break;
case 3:
aTab.setLast((String) getCellValue(nextCell));
break;
}
}
listTab.add(aTab);
}
workbook.close();
inputStream.close();
return listTab;
}
}
调用方法的控制器类（调用是暂时的，用于测试）：
@FXML
public void editTab(ActionEvent event) throws IOException {
Tab reader = new Tab();
List<Tab> listTabs = reader.readFromExcelFile(excelFilePath);
System.out.println(listTabs);
}
答案 0 :(得分：0)
public BigDecimal getTotal(){return custTotal;} //culprit --here
public BigDecimal getTotal(){return custTotal;}//culprit --here
public String getLast(){return custLast;}
public void setName(String name){this.custName = name;}
public void setTotal(String price){
double current = Double.valueOf(String.valueOf(getTotal())); //culprit --here
this.custTotal = BigDecimal.valueOf(Long.parseLong(current + price));
}
你面临NULL指针问题的原因是因为当你试图在这里转换为double值时，你还没有为custTotal分配一个值因此为NULL指针
double current = Double.valueOf(String.valueOf(getTotal()))
反过来调用
public BigDecimal getTotal(){return custTotal;} // custTotal is null still
<强>解
在构造函数中指定custTotal = 0;
Tab(){
custTotal = new BigDecimal(0);
}
此外，您仍然会遇到问题
this.custTotal = BigDecimal.valueOf(Long.parseLong(current + price));
因为价格仍然是String并且您尝试添加double和string将失败，将其更改为以下内容并且它将起作用
double dPrice = Double.valueOf(price);
this.custTotal = BigDecimal.valueOf(current + dPrice);
希望这有帮助：）