如何从其他类访问输入的值“Username”？包内 我编码时遇到了麻烦。我应该公开一些变量吗？ 我宣布用户名是公开的，但我收到错误
这是我的代码：
package login;
import java.awt.HeadlessException;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.*;
import javax.swing.JOptionPane;
@SuppressWarnings("serial")
public class Login extends javax.swing.JFrame {
public Login() {
initComponents0();
}
@SuppressWarnings("unchecked")
private void initComponents0() {
jLabel1 = new javax.swing.JLabel();
jLabel2 = new javax.swing.JLabel();
uname = new javax.swing.JTextField();
jLabel3 = new javax.swing.JLabel();
login = new javax.swing.JButton();
reset = new javax.swing.JButton();
pwd = new javax.swing.JPasswordField();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jLabel1.setFont(new java.awt.Font("Tahoma", 0, 18)); // NOI18N
jLabel1.setText("Login Pane");
jLabel2.setText("User Name:");
jLabel3.setText("Password:");
login.setText("Login");
login.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
String un = uname.getText();
@SuppressWarnings("deprecation")
String pw = pwd.getText();
try{
FileInputStream fstream = new FileInputStream("data.dat");
try (DataInputStream in = new DataInputStream(fstream)) {
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String strLine;
boolean registered = false;
boolean registered0 = false;
while ((strLine = br.readLine()) != null) {
String values[] = strLine.split("\\|");
if ((strLine.startsWith(un))&&(pw.equals(values[1]))){
registered = true;
break;
}
if ((strLine.startsWith(un))&&(!pw.equals(values[1]))){
registered0 = true;
break;
}
}
if(registered){
JOptionPane.showMessageDialog(null,"Hello: "+un ,"Registration",JOptionPane.INFORMATION_MESSAGE);
File file = new File("temp.dat");
try {
try (FileWriter writer = new FileWriter(file, false)) {
String data0 = un;
writer.write(data0);
}}
catch (IOException | HeadlessException z) {
JOptionPane.showMessageDialog(null, e);
}
}
else if(registered0){JOptionPane.showMessageDialog(null,"It seems you entered a wrong password! \n Please try again " ,"Admin",JOptionPane.INFORMATION_MESSAGE);}
else
{
int sel = JOptionPane.showConfirmDialog(null,"It seems that you haven't registered yet? \n Launch Registration Pane?","Admin",JOptionPane.INFORMATION_MESSAGE);
if (sel == JOptionPane.YES_OPTION){
java.awt.EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
new Register().setVisible(true);
}});}
}}}
catch ( IOException | HeadlessException ez){
JOptionPane.showMessageDialog(null,"A null file was created in order to \n avoid File Catch errors","Admin",JOptionPane.INFORMATION_MESSAGE);
File file = new File("data.dat");
try {
try (FileWriter writer = new FileWriter(file, true)) {
String data0 = "null";
String data1 = "null";
writer.write(data0+" | "+data1+"\n");
}}
catch (IOException | HeadlessException z) {
JOptionPane.showMessageDialog(null, e);
}
}
}});
reset.setText("Reset Field");
reset.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
uname.setText("");
pwd.setText("");
}
});
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
.addComponent(jLabel1)
.addGroup(layout.createSequentialGroup()
.addComponent(jLabel2)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(uname, javax.swing.GroupLayout.PREFERRED_SIZE, 300, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGroup(layout.createSequentialGroup()
.addComponent(jLabel3)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addComponent(login, javax.swing.GroupLayout.PREFERRED_SIZE, 137, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(reset, javax.swing.GroupLayout.PREFERRED_SIZE, 137, javax.swing.GroupLayout.PREFERRED_SIZE))
.addComponent(pwd))))
.addContainerGap(30, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jLabel1)
.addGap(18, 18, 18)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel2)
.addComponent(uname, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(18, 18, 18)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel3)
.addComponent(pwd, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(18, 18, 18)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(login)
.addComponent(reset))
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
);
pack();
}
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
new Login().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JButton login;
private javax.swing.JPasswordField pwd;
private javax.swing.JButton reset;
private javax.swing.JTextField uname;
// End of variables declaration
}
编辑
package login;
import java.awt.HeadlessException;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.*;
import javax.swing.JOptionPane;
@SuppressWarnings("serial")
public class Login extends javax.swing.JFrame {
private String username,password;
public String getUsername() {
return username;
}
public String getPassword() {
return password;
}
public Login() {
initComponents0();
}
@SuppressWarnings("unchecked")
private void initComponents0() {
jLabel1 = new javax.swing.JLabel();
jLabel2 = new javax.swing.JLabel();
uname = new javax.swing.JTextField();
jLabel3 = new javax.swing.JLabel();
login = new javax.swing.JButton();
reset = new javax.swing.JButton();
pwd = new javax.swing.JPasswordField();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jLabel1.setFont(new java.awt.Font("Tahoma", 0, 18)); // NOI18N
jLabel1.setText("Login Pane");
jLabel2.setText("User Name:");
jLabel3.setText("Password:");
login.setText("Login");
login.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
String un = uname.getText();
@SuppressWarnings("deprecation")
String pw = pwd.getText();
username = un;
password = pw;
try{
FileInputStream fstream = new FileInputStream("data.dat");
try (DataInputStream in = new DataInputStream(fstream)) {
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String strLine;
boolean registered = false;
boolean registered0 = false;
while ((strLine = br.readLine()) != null) {
String values[] = strLine.split("\\|");
if ((strLine.startsWith(un))&&(pw.equals(values[1]))){
registered = true;
break;
}
if ((strLine.startsWith(un))&&(!pw.equals(values[1]))){
registered0 = true;
break;
}
}
if(registered){
username = un;
password = pw;
JOptionPane.showMessageDialog(null,"Hello: "+un ,"Registration",JOptionPane.INFORMATION_MESSAGE);
File file = new File("temp.dat");
try {
try (FileWriter writer = new FileWriter(file, false)) {
String data0 = un;
writer.write(data0);
}}
catch (IOException | HeadlessException z) {
JOptionPane.showMessageDialog(null, e);
}
}
else if(registered0){JOptionPane.showMessageDialog(null,"It seems you entered a wrong password! \n Please try again " ,"Admin",JOptionPane.INFORMATION_MESSAGE);}
else
{
int sel = JOptionPane.showConfirmDialog(null,"It seems that you haven't registered yet? \n Launch Registration Pane?","Admin",JOptionPane.INFORMATION_MESSAGE);
if (sel == JOptionPane.YES_OPTION){
java.awt.EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
new Register().setVisible(true);
}});}
}}}
catch ( IOException | HeadlessException ez){
JOptionPane.showMessageDialog(null,"A null file was created in order to \n avoid File Catch errors","Admin",JOptionPane.INFORMATION_MESSAGE);
File file = new File("data.dat");
try {
try (FileWriter writer = new FileWriter(file, true)) {
String data0 = "null";
String data1 = "null";
writer.write(data0+" | "+data1+"\n");
}}
catch (IOException | HeadlessException z) {
JOptionPane.showMessageDialog(null, e);
}
}
}});
reset.setText("Reset Field");
reset.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
uname.setText("");
pwd.setText("");
}
});
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
.addComponent(jLabel1)
.addGroup(layout.createSequentialGroup()
.addComponent(jLabel2)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(uname, javax.swing.GroupLayout.PREFERRED_SIZE, 300, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGroup(layout.createSequentialGroup()
.addComponent(jLabel3)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addComponent(login, javax.swing.GroupLayout.PREFERRED_SIZE, 137, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(reset, javax.swing.GroupLayout.PREFERRED_SIZE, 137, javax.swing.GroupLayout.PREFERRED_SIZE))
.addComponent(pwd))))
.addContainerGap(30, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jLabel1)
.addGap(18, 18, 18)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel2)
.addComponent(uname, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(18, 18, 18)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel3)
.addComponent(pwd, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(18, 18, 18)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(login)
.addComponent(reset))
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
);
pack();
}
/*
* @param args the command line arguments
*/
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
new Login().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JButton login;
private javax.swing.JPasswordField pwd;
private javax.swing.JButton reset;
private javax.swing.JTextField uname;
// End of variables declaration
}
答案 0 :(得分：2)
当您接受输入时，将private个全局非静态字段保留username和password字段，将值分配给全局username和{{1变量。然后使用password的getter方法并返回该实例的public和username。
类似的东西：
passwordpublic class Login extends javax.swing.JFrame {
private String username,password;//assign private global fields for the instance
//the variables are assigned when you accept user input
public String getUsername() {
return username;
}
public String getPassword() {
return password;
}
}
答案 1 :(得分：2)
您需要为您的私有变量设置公共setter和getter，以便从您的类的外部调用或编辑您的私有变量。这称为encapsulation OOP的重要概念之一{{1}}。你可能想谷歌知道更多。
答案 2 :(得分：1)
在全局范围内声明变量，并使用Public访问说明符声明这些变量。或者
对Private声明的变量使用getter方法。并制作那些getter方法Public。