登陸界面和登錄功能，如果用戶名為“user”，密碼為“user”則彈出登錄成功對話框，否則彈出登錄失敗對話框。
在最后點擊登錄的時候會出這種錯誤
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at jjc.DL$DLListener.actionPerformed(DL.java:50)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6533)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6298)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4889)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)
at java.awt.Window.dispatchEventImpl(Window.java:2746)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:90)
at java.awt.EventQueue$4.run(EventQueue.java:731)
at java.awt.EventQueue$4.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
這是JAVA的代碼
package jjc;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class DL extends JFrame {
/**
*
*/
private static final long serialVersionUID = -2918915622569706727L;
TextField text,text2;
/**
* @param args
*/
public DL(){
JTextField text = new JTextField(150);
JTextField text2 = new JTextField(150);
JButton button1 = new JButton("登陸");
button1.addActionListener(new DLListener());
JLabel button2 = new JLabel("賬號");
JLabel button3 = new JLabel("密碼");
this.setLayout(null);
this.setTitle("用戶登陸");
text.setBounds(100,50,120,30);
text2.setBounds(100,100,120,30);
button1.setBounds(100,150,100,20);
button2.setBounds(30,50,30,30);
button3.setBounds(30,100,30,30);
this.add(text);
this.add(text2);
this.add(button1);
this.add(button2);
this.add(button3);
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
//視窗大小
this.setSize(300,300);
//生成視窗的位置
this.setLocation(600, 400);
this.setVisible(true);
}
class DLListener implements ActionListener {
@Override
public void actionPerformed(ActionEvent e) {
String s1=text.getText();
String s2=text2.getText();
String s3="user";
String s4="user";
if(s1.equals(s3)&&s2.equals(s4))
{
JOptionPane.showMessageDialog(null, "登錄成功", "注意", JOptionPane.INFORMATION_MESSAGE);
}
else {
JOptionPane.showMessageDialog(null, "登錄失敗", "注意", JOptionPane.INFORMATION_MESSAGE);
}
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
new DL();
}
}
被搞得有點蒙了，各位大佬幫我解答一下疑問可好，謝謝。
uj5u.com熱心網友回復：
好了，解決了。犯了一點錯誤修改代碼如下
package jjc;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class DL extends JFrame {
JTextField text = new JTextField(150);
JTextField text2 = new JTextField(150);
JButton button1 = new JButton("登陸");
JLabel button2 = new JLabel("賬號");
JLabel button3 = new JLabel("密碼");
/**
*
*/
private static final long serialVersionUID = -2918915622569706727L;
/**
* @param args
*/
public DL(){
button1.addActionListener(new DLListener());
text.addActionListener(new DLListener());
text2.addActionListener(new DLListener());
this.setLayout(null);
this.setTitle("用戶登陸");
text.setBounds(100,50,120,30);
text2.setBounds(100,100,120,30);
button1.setBounds(100,150,100,20);
button2.setBounds(30,50,30,30);
button3.setBounds(30,100,30,30);
this.add(text);
this.add(text2);
this.add(button1);
this.add(button2);
this.add(button3);
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
//視窗大小
this.setSize(300,300);
//生成視窗的位置
this.setLocation(600, 400);
this.setVisible(true);
}
class DLListener implements ActionListener {
@Override
public void actionPerformed(ActionEvent e) {
String s1=text.getText();
String s2=text2.getText();
String s3="user";
String s4="user";
if(s1.equals(s3)&&s2.equals(s4)) {
JOptionPane.showMessageDialog(null, "登錄成功", "注意", JOptionPane.INFORMATION_MESSAGE);
}
else {
JOptionPane.showMessageDialog(null, "登錄失敗", "注意", JOptionPane.INFORMATION_MESSAGE);
}
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
new DL();
}
}
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標籤：Java SE
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