我的问题是关于 JavaFX-9。我正在尝试在一个 FXML 控制器类中处理两个表视图。但它给了我一个空指针异常。如何解决这个问题？
第一个 TableView (studentTable) 正在工作，第二个 table(rTable) 不工作。
主页.java：
package Home;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class home extends Application{
public void start(Stage stage)throws Exception{
Parent root=(Parent) FXMLLoader.load(getClass().getResource("Home.fxml"));
Scene scene=new Scene(root);
stage.setScene(scene);
stage.setTitle("Result Analysis System");
stage.show();
}
public static void main(String[] args){
launch(args);
}
}
homeController.java
package Home;
/*_____________________
Error in this file
_____________________*/
import dbUtils.dbConnection;
//import Home.rControl;
//import Home.resultData;
import javafx.collections.FXCollections;
import javafx.collections.ObservableArray;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.*;
//import javafx.scene.control.DatePicker;
import javafx.scene.control.cell.PropertyValueFactory;
//import Home.resultData;
import java.net.URL;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;
import java.util.ResourceBundle;
public class homeController /*extends resultController*/ implements Initializable{
//Student tab
@FXML
private TextField usn;
@FXML
private TextField name;
@FXML
protected TableView<studentData> studentTable;
@FXML
protected TableColumn<studentData,String> USNcolumn;
@FXML
protected TableColumn<studentData,String> Namecolumn;
//Result tab
@FXML
private TextField rusn;
@FXML
private ComboBox<option> rSelectSem;
@FXML
private TextField rSub1;
@FXML
private TextField rSub2;
@FXML
private TextField rSub3;
@FXML
private TextField rSub4;
@FXML
private TextField rSub5;
@FXML
private TextField rSub6;
@FXML
private TextField rSub7;
@FXML
private TextField rSub8;
@FXML
private Button rAdd;
@FXML
private Button rLoad;
@FXML
private Button rClear;
@FXML
private ComboBox<option> rSelectSem1;
@FXML
private Button rLoad1;
@FXML
private TableView<resultData> rTable;
@FXML
private TableColumn<resultData,String> rColusn;
@FXML
private TableColumn<resultData,String> rColname;
@FXML
private TableColumn<resultData,Integer> rColsub1;
@FXML
private TableColumn<resultData,Integer> rColsub2;
@FXML
private TableColumn<resultData,Integer> rColsub3;
@FXML
private TableColumn<resultData,Integer> rColsub4;
@FXML
private TableColumn<resultData,Integer> rColsub5;
@FXML
private TableColumn<resultData,Integer> rColsub6;
@FXML
private TableColumn<resultData,Integer> rColsub7;
@FXML
private TableColumn<resultData,Integer> rColsub8;
@FXML
private TableColumn<resultData,Integer> rColtotal;
//Analyze tab
@FXML
private ComboBox<option> aSelectSem;
@FXML
private Button aHighmarks;
@FXML
private Button aPassedstudent;
@FXML
private Button aFailedstudent;
@FXML
private Button aListallstudent;
@FXML
private Button adistiction;
@FXML
private Button aFirstclass;
@FXML
private Button aSecondclass;
@FXML
private TableView<analysisData> aTable;
@FXML
private TableColumn<analysisData,String> aColusn;
@FXML
private TableColumn<analysisData,String> aColname;
@FXML
private TableColumn<analysisData,Integer> aColsub1;
@FXML
private TableColumn<analysisData,Integer> aColsub2;
@FXML
private TableColumn<analysisData,Integer> aColsub3;
@FXML
private TableColumn<analysisData,Integer> aColsub4;
@FXML
private TableColumn<analysisData,Integer> aColsub5;
@FXML
private TableColumn<analysisData,Integer> aColsub6;
@FXML
private TableColumn<analysisData,Integer> aColsub7;
@FXML
private TableColumn<analysisData,Integer> aColsub8;
@FXML
private TableColumn<analysisData,Integer> aColtotal;
protected dbConnection dc;
protected ObservableList<studentData> data;
//private ObservableList<resultData> list;
protected String sql = "SELECT * FROM studentDet";
@Override
public void initialize(URL url, ResourceBundle rb){
this.dc = new dbConnection();
this.rSelectSem.setItems(FXCollections.observableArrayList(option.values()));
this.rSelectSem1.setItems(FXCollections.observableArrayList(option.values()));
this.aSelectSem.setItems(FXCollections.observableArrayList(option.values()));
// rTable.setItems(list);
}
//Load student data in student tab
//This is working
@FXML
private void loadStudentData(ActionEvent event) throws SQLException{
try {
Connection conn = dbConnection.getConnection();
this.data = FXCollections.observableArrayList();
ResultSet rs = conn.createStatement().executeQuery(sql);
while (rs.next()){
this.data.add(new studentData(rs.getString(1),rs.getString(2)));
}
}
catch (SQLException e){
System.err.println("error" + e);
}
this.USNcolumn.setCellValueFactory(new PropertyValueFactory<studentData,String>("USN"));
this.Namecolumn.setCellValueFactory(new PropertyValueFactory<studentData,String>( "Name"));
this.studentTable.setItems(null);
this.studentTable.setItems(this.data);
}
//This is working
//Add student in student tab
@FXML
private void addStudent(ActionEvent actionEvent) {
String sqlInsert="INSERT INTO studentDet(USN,Name) VALUES(?,?)";
try {
//here the name is same but it doesn't matter because this is a local variable
Connection conn=dbConnection.getConnection();
PreparedStatement statement=conn.prepareStatement(sqlInsert);
statement.setString(1,this.usn.getText());
statement.setString(2,this.name.getText());
statement.execute();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
//This is working
//Clear feilds in Student tab
@FXML
private void clearFields(ActionEvent actionEvent)
{
this.usn.setText("");
this.name.setText("");
}
@FXML
private void rclearFields(ActionEvent actionEvent)
{
this.rusn.setText("");
this.rSub1.setText("");
this.rSub2.setText("");
this.rSub3.setText("");
this.rSub4.setText("");
this.rSub5.setText("");
this.rSub6.setText("");
this.rSub7.setText("");
this.rSub8.setText("");
}
//This is working
//Add marks to sem in Result tab
@FXML
private void addSemMarks(ActionEvent actionEvent)
{
String sqlInsert;
try {
switch (((option) this.rSelectSem.getValue()).toString()) {
case "SEM1":
sqlInsert="INSERT INTO SEM1(USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E) VALUES(?,?,?,?,?,?,?,?,?)";
semMarksAdd(sqlInsert);
break;
case "SEM2":
sqlInsert="INSERT INTO SEM2(USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E) VALUES(?,?,?,?,?,?,?,?,?)";
semMarksAdd(sqlInsert);
break;
case "SEM3":
sqlInsert="INSERT INTO SEM3(USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E) VALUES(?,?,?,?,?,?,?,?,?)";
semMarksAdd(sqlInsert);
break;
case "SEM4":
sqlInsert="INSERT INTO SEM4(USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E) VALUES(?,?,?,?,?,?,?,?,?)";
semMarksAdd(sqlInsert);
break;
case "SEM5":
sqlInsert="INSERT INTO SEM5(USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E) VALUES(?,?,?,?,?,?,?,?,?)";
semMarksAdd(sqlInsert);
break;
case "SEM6":
sqlInsert="INSERT INTO SEM6(USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E) VALUES(?,?,?,?,?,?,?,?,?)";
semMarksAdd(sqlInsert);
break;
case "SEM7":
sqlInsert="INSERT INTO SEM7(USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E) VALUES(?,?,?,?,?,?,?,?,?)";
semMarksAdd(sqlInsert);
break;
case "SEM8":
sqlInsert="INSERT INTO SEM8(USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E) VALUES(?,?,?,?,?,?,?,?,?)";
semMarksAdd(sqlInsert);
break;
}
}
catch (Exception ex){
ex.printStackTrace();
}
}
private void semMarksAdd(String sqlinsert){
//String sqlInsert="INSERT INTO SEM1(USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E) VALUES(?,?,?,?,?,?,?,?,?)";
try {
//here the name is same but it doesn't matter because this is a local variable
Connection conn=dbConnection.getConnection();
PreparedStatement statement=conn.prepareStatement(sqlinsert);
statement.setString(1,this.rusn.getText());
statement.setString(2,this.rSub1.getText());
statement.setString(3,this.rSub2.getText());
statement.setString(4,this.rSub3.getText());
statement.setString(5,this.rSub4.getText());
statement.setString(6,this.rSub5.getText());
statement.setString(7,this.rSub6.getText());
statement.setString(8,this.rSub7.getText());
statement.setString(9,this.rSub8.getText());
statement.execute();
conn.close();
}
catch (SQLException e) {
e.printStackTrace();
}
}
//#########################################################Stable upto here
//From here it is giving error
//TO LOAD STUDENT MARKS DATA IN RESULT TABLE
/*@FXML
private void loadResultData(ActionEvent actionEvent){
String sqlLoad;
try {
switch (((option) this.rSelectSem.getValue()).toString()) {
case "SEM1":
sqlLoad = "SELECT USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E,TOTAL FROM SEM1";
loadRdata(sqlLoad);
break;
case "SEM2":
sqlLoad = "SELECT USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E,TOTAL FROM SEM2";
loadRdata(sqlLoad);
break;
case "SEM3":
sqlLoad = "SELECT USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E,TOTAL FROM SEM3";
loadRdata(sqlLoad);
break;
case "SEM4":
sqlLoad = "SELECT USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E,TOTAL FROM SEM4";
loadRdata(sqlLoad);
break;
case "SEM5":
sqlLoad = "SELECT USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E,TOTAL FROM SEM5";
loadRdata(sqlLoad);
break;
case "SEM6":
sqlLoad = "SELECT USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E,TOTAL FROM SEM6";
loadRdata(sqlLoad);
break;
case "SEM7":
sqlLoad = "SELECT USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E,TOTAL FROM SEM7";
loadRdata(sqlLoad);
break;
case "SEM8":
sqlLoad = "SELECT USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E,TOTAL FROM SEM8";
loadRdata(sqlLoad);
break;
}
}
catch (Exception ex){
ex.printStackTrace();
}
}*/
@FXML
public void loadResultData(ActionEvent actionEvent) {
String sqlLoad = "SELECT USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E,TOTAL FROM SEM1";
loadRdata(sqlLoad); //Error here
}
/*private void loadResultData(ActionEvent actionEvent) {
String sqlLoad = "SELECT USN,SUB1E,SUB2E,SUB3E,SUB4E,SUB5E,SUB6E,SUB7E,SUB8E,TOTAL FROM SEM1";
rc.loadRdata(sqlLoad);
}*/
private ObservableList<resultData> list = FXCollections.observableArrayList();
private void loadRdata(String sqlLoad) {
try {
Connection conn = dbConnection.getConnection();
this.list = FXCollections.observableArrayList();
//System.out.println("Hello"); //working
ResultSet rs = conn.createStatement().executeQuery(sqlLoad);
while (rs.next()) {
//System.out.println(rs.getString(1)); //Working
this.list.add(new resultData(rs.getString(1), rs.getInt(2), rs.getInt(3), rs.getInt(4), rs.getInt(5), rs.getInt(6), rs.getInt(7), rs.getInt(8), rs.getInt(9), rs.getInt(10)));
}
// this.rColusn.setCellValueFactory("Helloworld"); //working
this.rColusn.setCellValueFactory(new PropertyValueFactory<resultData, String>("rColUsn"));
this.rColsub1.setCellValueFactory(new PropertyValueFactory<resultData, Integer>("rColSub1"));
this.rColsub2.setCellValueFactory(new PropertyValueFactory<resultData, Integer>("rColSub2"));
this.rColsub3.setCellValueFactory(new PropertyValueFactory<resultData, Integer>("rColSub3"));
this.rColsub4.setCellValueFactory(new PropertyValueFactory<resultData, Integer>("rColSub4"));
this.rColsub5.setCellValueFactory(new PropertyValueFactory<resultData, Integer>("rColSub5"));
this.rColsub6.setCellValueFactory(new PropertyValueFactory<resultData, Integer>("rColSub6"));
this.rColsub7.setCellValueFactory(new PropertyValueFactory<resultData, Integer>("rColSub7"));
this.rColsub8.setCellValueFactory(new PropertyValueFactory<resultData, Integer>("rColSub8"));
this.rColtotal.setCellValueFactory(new PropertyValueFactory<resultData, Integer>("rColTotal"));
System.out.println("after block1");
list.clear();
System.out.println("after block2");
rTable.setItems(list);// CAUSING NULL POINTER EXCEPTION
System.out.println("after block3");//NOT PRINTING
}
catch (Exception e) {//System.out.println(" "+e);
System.err.println("error" + e);
}
}
}
结果数据.java
package Home;
import javafx.beans.property.IntegerProperty;
import javafx.beans.property.SimpleIntegerProperty;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
public class resultData {
private final StringProperty rColUsn;
//private final StringProperty rColName;
private final IntegerProperty rColSub1;
private final IntegerProperty rColSub2;
private final IntegerProperty rColSub3;
private final IntegerProperty rColSub4;
private final IntegerProperty rColSub5;
private final IntegerProperty rColSub6;
private final IntegerProperty rColSub7;
private final IntegerProperty rColSub8;
private final IntegerProperty rColTotal;
public resultData(String usn,Integer sub1,Integer sub2,Integer sub3,Integer sub4,Integer sub5,Integer sub6,Integer sub7,Integer sub8,Integer total){
System.out.println("result data");// TWO TIMES IT WORKS,BUT THE THERE ARE 10 COLUMNS AND IT SHOULD PRINT 10 TIMES.
rColUsn = new SimpleStringProperty(usn);
//this.rColName = new SimpleStringProperty(name);
rColSub1 = new SimpleIntegerProperty(sub1);
rColSub2 = new SimpleIntegerProperty(sub2);
rColSub3 = new SimpleIntegerProperty(sub3);
rColSub4 = new SimpleIntegerProperty(sub4);
rColSub5 = new SimpleIntegerProperty(sub5);
rColSub6 = new SimpleIntegerProperty(sub6);
rColSub7 = new SimpleIntegerProperty(sub7);
rColSub8 = new SimpleIntegerProperty(sub8);
rColTotal = new SimpleIntegerProperty(total);
}
public String getrColUsn() {
return rColUsn.get();
}
public StringProperty rColUsnProperty() {
return rColUsn;
}
public void setrColUsn(String rColUsn) {
this.rColUsn.set(rColUsn);
}
public int getrColSub1() {
return rColSub1.get();
}
public IntegerProperty rColSub1Property() {
return rColSub1;
}
public void setrColSub1(int rColSub1) {
this.rColSub1.set(rColSub1);
}
public int getrColSub2() {
return rColSub2.get();
}
public IntegerProperty rColSub2Property() {
return rColSub2;
}
public void setrColSub2(int rColSub2) {
this.rColSub2.set(rColSub2);
}
public int getrColSub3() {
return rColSub3.get();
}
public IntegerProperty rColSub3Property() {
return rColSub3;
}
public void setrColSub3(int rColSub3) {
this.rColSub3.set(rColSub3);
}
public int getrColSub4() {
return rColSub4.get();
}
public IntegerProperty rColSub4Property() {
return rColSub4;
}
public void setrColSub4(int rColSub4) {
this.rColSub4.set(rColSub4);
}
public int getrColSub5() {
return rColSub5.get();
}
public IntegerProperty rColSub5Property() {
return rColSub5;
}
public void setrColSub5(int rColSub5) {
this.rColSub5.set(rColSub5);
}
public int getrColSub6() {
return rColSub6.get();
}
public IntegerProperty rColSub6Property() {
return rColSub6;
}
public void setrColSub6(int rColSub6) {
this.rColSub6.set(rColSub6);
}
public int getrColSub7() {
return rColSub7.get();
}
public IntegerProperty rColSub7Property() {
return rColSub7;
}
public void setrColSub7(int rColSub7) {
this.rColSub7.set(rColSub7);
}
public int getrColSub8() {
return rColSub8.get();
}
public IntegerProperty rColSub8Property() {
return rColSub8;
}
public void setrColSub8(int rColSub8) {
this.rColSub8.set(rColSub8);
}
public int getrColTotal() {
return rColTotal.get();
}
public IntegerProperty rColTotalProperty() {
return rColTotal;
}
public void setrColTotal(int rColTotal) {
this.rColTotal.set(rColTotal);
}
}
学生数据.java
package Home;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
public class studentData{
private final StringProperty USN;
private final StringProperty Name;
public studentData(String usn,String name){
this.USN=new SimpleStringProperty(usn);
this.Name=new SimpleStringProperty(name);
}
public String getUSN() {
return USN.get();
}
public StringProperty USNProperty() {
return USN;
}
public void setUSN(String USN) {
this.USN.set(USN);
}
public String getName() {
return Name.get();
}
public StringProperty nameProperty() {
return Name;
}
public void setName(String name) {
this.Name.set(name);
}
}
命令行输出：
"C:\Program Files\Java\jdk-9.0.1\bin\java" "-javaagent:C:\Program
Files\JetBrains\IntelliJ IDEA 2017.2.5\lib\idea_rt.jar=55700:C:\Program
Files\JetBrains\IntelliJ IDEA 2017.2.5\bin" -Dfile.encoding=UTF-8 -
/* WHEN CLICKING TABLE DISPLAY BUTTON FIRST TIME */
result data
result data
after block1
after block2
errorjava.lang.NullPointerException
/* WHEN CLICKING TABLE DISPLAY BUTTON SECOND TIME*/
errorjava.lang.NullPointerException
result data
result data
after block1
after block2