我想将JTextfield转换为int，但java.lang.NullPointerException通过JTextfield获取numText。首先转换为String，然后将String转换为Integer，并将其放入其他类中。
package fitness_2;
import java.util.*;
import javax.swing.*;
import fitness_2.Person.Calculation;
import java.awt.event.*;
public class fitness extends JFrame {
Calculation cal = null;
public fitness() {
try {
}catch(NumberFormatException e) {
}catch(Exception e) {
}
JPanel panel = new JPanel();
JLabel numOfPerson = new JLabel("number of members:");
JTextField numText = new JTextField(4);
JButton submitBtn = new JButton ("SUBMIT");
panel.add(numOfPerson);
panel.add(numText);
panel.add(submitBtn);
String n = numText.getText();
submitBtn.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
}
});
submitBtn.addMouseListener(new MouseAdapter() {
@Override
public void mouseClicked(MouseEvent e) {
cal = new Calculation();
if(!checkStr(n)) {
int num = Integer.parseInt(n);
cal.CalculationPane(num);
}
}});
add(panel);
setVisible(true);
setSize(600,400);
setLocationRelativeTo(null);
setResizable(false);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
boolean checkStr(String s){
boolean result = false;
for(int i = 0 ;i < s.length();i++) {
if(!Character.isDigit(s.charAt(i))) {
result = false;
}else
result = true;
}
return result;
}
public static void main(String args[]) {
new fitness();
}
}
那么，错误是：
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at fitness_2.Person$Calculation.CalculationPane(Calculation.java:73)
at fitness_2.fitness$2.mouseClicked(fitness.java:44)
at java.desktop/java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:278)
at java.desktop/java.awt.Component.processMouseEvent(Component.java:6639)
at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342)
at java.desktop/java.awt.Component.processEvent(Component.java:6401)
at java.desktop/java.awt.Container.processEvent(Container.java:2263)
at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5012)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4844)
at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4918)
at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4556)
at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4488)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2307)
at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2762)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4844)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
和计算代码
package fitness_2;
import java.awt.*;
import java.sql.*;
import java.util.*;
import javax.swing.*;
import fitness_2.Person.Calculation;
import java.awt.event.*;
class Person {
String name;
int waitingTime;
int satisfaction;
int dissatisfaction;
int index;
Person () {
}
Person (String name, int waitingTime, int satisfaction, int
dissatisfaction, int index) {
this.name = name;
this.waitingTime = waitingTime;
this.satisfaction = satisfaction;
this.dissatisfaction = dissatisfaction;
this.index = index;
}
static class Calculation implements MouseListener{
JFrame frame;
JPanel panel;
JPanel panel1;
JPanel panel2;
JPanel panel3;
JTextField nameText, timeText, satisfactionText, dissatisfactionText;
JButton calBtn;
void CalculationPane(int n) {
frame = new JFrame("Scheduling");
panel = new JPanel();
panel1 = new JPanel(new GridLayout(3,1));
panel2 = new JPanel(new GridLayout(3,1));
panel3 = new JPanel();
Person p[] = new Person[n];
for(int i = 0;i < n;i++) {
JLabel nameLabel = new JLabel("Enter name: ", JLabel.CENTER);
JLabel timeLabel = new JLabel("Enter waiting time: ",JLabel.CENTER);
JLabel satisLabel = new JLabel("Enter satisfaction: ",JLabel.CENTER);
JLabel dissatisLabel = new JLabel("Enter dissatisfaction: ",JLabel.CENTER);
panel1.add(nameLabel);
panel1.add(timeLabel);
panel1.add(satisLabel);
panel1.add(dissatisLabel);
nameText = new JTextField(20);
nameText.addMouseListener(this);
timeText = new JTextField(3);
timeText.addMouseListener(this);
satisfactionText = new JTextField(4);
satisfactionText.addMouseListener(this);
dissatisfactionText = new JTextField(4);
dissatisfactionText.addMouseListener(this);
panel2.add(nameText);
panel2.add(timeText);
panel2.add(satisfactionText);
panel2.add(dissatisfactionText);
p[i].name = nameText.getText();
p[i].waitingTime =Integer.parseInt(timeText.getText().trim());
p[i].satisfaction = Integer.parseInt(satisfactionText.getText().trim());
p[i].dissatisfaction = Integer.parseInt(dissatisfactionText.getText().trim());
p[i].index = i;
}
calBtn = new JButton("Scheduling");
calBtn.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
}
});
calBtn.addMouseListener(new MouseAdapter() {
public void mouseClicked(MouseEvent e) {
for (int i = 0; i < n - 1; i++) {
for (int j = 0; j < n - i - 1; j++) {
if ((double)p[j].dissatisfaction / ((double)p[j].waitingTime + 1) < (double)p[j + 1].dissatisfaction / ((double)p[j + 1].waitingTime + 1)) {
Person temp = new Person();
temp = p[j + 1];
p[j + 1] = p[j];
p[j] = temp;
}
else if ((double)p[j].dissatisfaction / (double)p[j].waitingTime == (double)p[j + 1].dissatisfaction / (double)p[j + 1].waitingTime) {
if (p[j].dissatisfaction > p[j + 1].dissatisfaction * p[j + 1].waitingTime)
continue;
else
{
Person temp = new Person();
temp = p[j + 1];
p[j + 1] = p[j];
p[j] = temp;
}
}
else
continue;
}
}
int tot_satisfaction = 0;
System.out.println("Order of use: ");
for (int i = 0; i < n; i++) {
System.out.println(p[i].index);
if (i < p[i].waitingTime) {
tot_satisfaction += p[i].satisfaction;
}
else
tot_satisfaction += p[i].satisfaction - ((i - p[i].waitingTime) * p[i].dissatisfaction);
}
System.out.println();
System.out.println("Total satisfaction: " + tot_satisfaction);
}
});
}
@Override
public void mouseClicked(MouseEvent e) {
// TODO Auto-generated method stub
}
@Override
public void mousePressed(MouseEvent e) {
// TODO Auto-generated method stub
}
@Override
public void mouseReleased(MouseEvent e) {
// TODO Auto-generated method stub
}
@Override
public void mouseEntered(MouseEvent e) {
// TODO Auto-generated method stub
}
@Override
public void mouseExited(MouseEvent e) {
// TODO Auto-generated method stub
}
}
}
我该如何修复它们？我申请例外。但一切都没有改变。此外，替换"至"；0"；两者都不起作用。
您需要在点击按钮内添加numText值的获取，因为每次值都会改变，您需要在每次点击时获取：
您在Person类中定义了Calculation类及其静态，因此要访问计算，首先需要从calculation类中删除static，或者将CalculationPane方法定义为static以使其从类中可访问，我从Calculation中删除了static密钥
class Calculation {
}
并且您需要从Person类对象初始化Calculation类(更多详细信息(：
submitBtn.addMouseListener(new MouseAdapter() {
@Override
public void mouseClicked(MouseEvent e) {
cal = new Person();
String n = numText.getText();
if (!checkStr(n)) {
int num = Integer.parseInt(n);
Person.Calculation c = cal.new Calculation();
c.CalculationPane(num);
}
}
});