Java摇摆 | JPasswordField

PasswordField 是 javax.swing 包的一部分。 JPasswordField 类是一个组件，它允许编辑单行文本，其中视图指示输入的内容不显示实际字符。 JPasswordField 继承了 javax.swing 包中的 JTextField 类。
该类的构造函数是：

1. JPasswordField() ：创建新 PasswordField 的构造函数
   
2. JPasswordField(int columns) ：创建具有指定列数的新的空 PasswordField 的构造函数。
   
3. JPasswordField(String Password) ：创建一个新的空密码字段的构造函数，用给定的字符串初始化。
   
4. JPasswordField(String Password, int columns) ：使用给定字符串和指定列数创建一个新的空 PasswordField 的构造函数。
   
5. JPasswordField(Document doc, String Password, int columns) ：创建使用给定文本存储模型和给定列数的 Passwordfield 的构造函数。
   

JPasswordField 的常用方法：

1. char getEchoChar() ：返回用于在 JPasswordField 中回显的字符。
   
2. setEchoChar(char c) : 设置 JPasswordField 的回显字符。
   
3. String getPassword() ：返回 JPasswordField 中包含的文本。
   
4. String getText() ：返回 JPasswordField 中包含的文本。
   

1.程序使用JTextField和JPasswordField输入名称和密码

Java

// Java Program to enter name and password
// using JTextField and JPasswordField
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
class text extends JFrame implements ActionListener {
    // JTextField
    static JTextField t;
 
    // JPasswordField
    static JPasswordField pass;
 
    // JFrame
    static JFrame f;
 
    // JButton
    static JButton b;
 
    // label to display text
    static JLabel l;
 
    // default constructor
    text()
    {
    }
 
    // main class
    public static void main(String[] args)
    {
        // create a new frame to store text field and button
        f = new JFrame("textfield");
 
        // create a label to display text
        l = new JLabel("nothing entered");
 
        // create a new button
        b = new JButton("submit");
 
        // create a object of the text class
        text te = new text();
 
        // addActionListener to button
        b.addActionListener(te);
 
        // create a object of JTextField with 16 columns and initial text
        t = new JTextField("enter name", 16);
 
        // create a object of passwordField with 16 columns
        pass = new JPasswordField(16);
 
        // create an object of font type
        Font fo = new Font("Serif", Font.ITALIC, 20);
 
        // set the font of the textfield
        t.setFont(fo);
 
        // create a panel to add buttons and textfield
        JPanel p = new JPanel();
 
        // add buttons and textfield to panel
        p.add(t);
        p.add(pass);
        p.add(b);
        p.add(l);
 
        // add panel to frame
        f.add(p);
 
        // set the size of frame
        f.setSize(300, 300);
 
        f.show();
    }
 
    // if the button is pressed
    public void actionPerformed(ActionEvent e)
    {
        String s = e.getActionCommand();
        if (s.equals("submit")) {
            // set the text of the label to the text of the field
            l.setText("name = " + t.getText() + "\t Password = " + pass.getText());
 
            // set the text of field to blank
            t.setText("  ");
 
            // set the text of password field to blank
            pass.setText("");
        }
    }
}

输出 ：

2.更改JPasswordField的回显字符并设置密码字段的初始文本的程序

Java

// Java Program to change the echo character of
// JPasswordField and set initial text for password field
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
class text extends JFrame implements ActionListener, FocusListener {
    // JTextField
    static JTextField t;
 
    // JPasswordField
    static JPasswordField pass;
 
    // JFrame
    static JFrame f;
 
    // JButton
    static JButton b;
 
    // label to display text
    static JLabel l;
 
    // default constructor
    text()
    {
    }
 
    // main class
    public static void main(String[] args)
    {
        // create a new frame to store text field and button
        f = new JFrame("textfield");
 
        // create a label to display text
        l = new JLabel("nothing entered");
 
        // create a new button
        b = new JButton("submit");
 
        // create a object of the text class
        text te = new text();
 
        // addActionListener to button
        b.addActionListener(te);
 
        // create a object of JTextField with 16 columns and initial text
        t = new JTextField("enter name", 16);
 
        // create a object of passwordField with 16 columns
        pass = new JPasswordField(16);
 
        // add FocusListener to passwordField
        pass.addFocusListener(te);
 
        // set the echo character of the password field
        pass.setEchoChar((char)0);
 
        // set initial text for password field
        pass.setText("enter password");
 
        // set the echo character of the password field
        // create an object of font type
        Font fo = new Font("Serif", Font.ITALIC, 20);
 
        // set the font of the textfield
        t.setFont(fo);
 
        // create a panel to add buttons and textfield
        JPanel p = new JPanel();
 
        // add buttons and textfield to panel
        p.add(t);
        p.add(pass);
        p.add(b);
        p.add(l);
 
        // add panel to frame
        f.add(p);
 
        // set the size of frame
        f.setSize(300, 300);
 
        f.show();
    }
    // flag to set the text to blank for the first time when the component gets focus
    boolean flag = true;
 
    // events of focus listener
    // when focus is gained
    public void focusGained(FocusEvent e)
    {
        if (flag) {
            // set a definite echo char
            pass.setEchoChar('*');
 
            // only set the text to blank for 1st time
            // set the text to blank
            pass.setText("");
            flag = false;
        }
    }
 
    // when the focus is lost
    public void focusLost(FocusEvent e)
    {
    }
 
    // if the button is pressed
    public void actionPerformed(ActionEvent e)
    {
        String s = e.getActionCommand();
        if (s.equals("submit")) {
            // set the text of the label to the text of the field
            l.setText("name = " + t.getText() + "\t, Password = " + pass.getText());
 
            // set the text of field to blank
            t.setText("  ");
 
            // set the text of password field to blank
            pass.setText("");
        }
    }
}

注意：上述程序可能无法在使用离线 IDE 的在线编译器中运行。
程序员可以根据需要更改密码的默认文本和列数。