JTextField of Swing Series (Single Line Textbox)

JTextField.RIGHT

JTextField.LEADING (the default)

JTextField.TRAILING

• setFont(Font font) Setting Font

• SetScrollOffset (int scroll Offset) gets the scroll offset in pixels.

• setDocument(Document doc) associates the editor with a text document, which means associating the text box with a text document. This will keep the content consistent, and if one changes, the other will change.

• setInputVerifier(verifier) sets the validation method, and if the text fails to validate, it cannot focus on the next component, and it will focus on the text box all the time.

• Whether setDragEnabled(boolean x) can drag and drop text in the text box, or true, means whether it can drag and drop text when it is selected.

• Additional ActionListener (ActionListener Action) adds a listening mechanism, which triggers input text by pressing Enter, the same as the button listening mechanism.

• Writer (InfileWriter writer) enters the contents of the text box into the file

• Add KeyListener (KeyListener event) adds keyboard monitoring, triggering the keyboard when entering content in the text box. There are press, release, and type actions. For more information, see Official Documents

A simple example

import javax.swing.*;
import java.awt.*;

class text extends JFrame {
    private JTextField textField1;
    private JTextField textField2;

    public static void main(String args[]) {
        text my = new text();
        my.setVisible(true);

    }

    public text() {
        //this.setBounds(100,100,300,200);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel panel = new JPanel(new GridLayout(2, 1));
        textField1 = new JTextField(10);
        textField2 = new JTextField();
        panel.add(textField1);
        panel.add(textField2);
        this.getContentPane().add(panel, BorderLayout.CENTER);
        this.pack();
        InputVerifier verifier = new InputVerifier() {    //Adding validation methods
            @Override
            public boolean verify(JComponent input) {     //overloaded function
                boolean value;
                textField1 = (JTextField) input;    //Force the input component into a single-line text box of JTextField type
                return textField1.getText().equals("pass");  //pass when judging whether or not the input is entered, if not, the error will be validated

            }
        };
        textField1.setInputVerifier(verifier);   //Setting up authentication mode
        textField1.setHorizontalAlignment(JTextField.CENTER);   //Setting Horizontal Alignment
        Font font = new Font("Regular script", Font.BOLD + Font.ITALIC, 20);
        textField1.setFont(font);   //Setting fonts
        textField1.setDragEnabled(true);  //Setting it in a single line text box can drag and drop text, but if it is false, it can't drag and drop text.


    }
}

Associated Text Documents

import java.awt.Container;
import java.awt.GridLayout;
/*from   w  ww.jav  a  2s . co m*/
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.text.Document;

public class Main extends JFrame {
  JLabel nameLabel = new JLabel("Name:");
  JLabel mirroredNameLabel = new JLabel("Mirrored:");
  JTextField name = new JTextField(20);
  JTextField mirroredName = new JTextField(20);

  public Main() {
    this.setDefaultCloseOperation(EXIT_ON_CLOSE);
    this.setLayout(new GridLayout(2, 0));

    Container contentPane = this.getContentPane();
    contentPane.add(nameLabel);
    contentPane.add(name);
    contentPane.add(mirroredNameLabel);
    contentPane.add(mirroredName);

    Document nameModel = name.getDocument();    //Get the text document of the text box and associate it with the second text box
    mirroredName.setDocument(nameModel);           //The contents of the two text boxes are interrelated, so that only one text needs to be entered and displayed in another text box.
    
    pack();
    setVisible(true);    
  }

  public static void main(String[] args) {
    Main frame = new Main();

  }
}

Explanation: Here we associate two text boxes, so that we can input one text box and update the content at the same time.

Action Listener

Enter text and press Enter to trigger

import java.awt.event.ActionEvent;
//from  w  w  w. ja va2s  .c o m
import javax.swing.JFrame;
import javax.swing.JTextField;

public class Main {

  public static void main(String[] a) {
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JTextField jTextField1 = new JTextField();

    jTextField1.setText("jTextField1");
    //Adding monitoring mechanism
    jTextField1.addActionListener(new   java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        System.out.println("action");
      }
    });
    frame.add(jTextField1);

    frame.setSize(300, 200);
    frame.setVisible(true);
  }

}

Verify text content

Use InputVerifier ) Verification

import java.awt.BorderLayout;
import javax.swing.InputVerifier;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JTextField;
public class Main {
  public static void main(String args[]) {
    JFrame frame = new JFrame("Verifier Sample");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JTextField textField1 = new JTextField();
    JTextField textField2 = new JTextField();
    InputVerifier verifier = new InputVerifier() {     //Create a validation
      public boolean verify(JComponent comp) {
        boolean returnValue;
        JTextField textField = (JTextField) comp;      //Force conversion, converting comp of control type to JTextFiled type
        try {
          Integer.parseInt(textField.getText());    //Converting input to int type triggers a //NumberFormateException error if the input string is not decimal
          returnValue = true;
        } catch (NumberFormatException e) {   
          returnValue = false;
        }
        return returnValue;        //If false is returned, the pointer will always be focused in this text box and cannot be moved to other components.
      }
    };
    textField1.setInputVerifier(verifier);
    frame.add(textField1, BorderLayout.NORTH);
    frame.add(textField2, BorderLayout.CENTER);
    frame.setSize(300, 100);
    frame.setVisible(true);
  }
}

Note: If you return false, the pointer will always be focused in this text box and cannot be moved to other components.

Save the contents of the text box to a file

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

class Main extends JFrame {
    private JTextField textField;
    private FileWriter writer;

    public static void main(String args[]) {
        Main my = new Main();
        my.setVisible(true);
    }

    public Main() {
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel panel = new JPanel(new BorderLayout());
        JButton button = new JButton("Function");
        JLabel label = new JLabel("name");
        textField = new JTextField();
        panel.add(label, BorderLayout.WEST);
        panel.add(textField, BorderLayout.CENTER);
        String filename = "text.txt";
        button.addActionListener(new ActionListener() {    //Add a button trigger, where just click anniu to enter the contents of the text box into the file
            @Override
            public void actionPerformed(ActionEvent e) {
                try {
                    writer = new FileWriter(filename, false);   //Create an object to write to a file, where false means that it is not added at the end of the file
                    textField.write(writer);     //Write input from a single line of text to a file
                    writer.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                    System.out.println("false");
                }
            }
        });
        panel.add(button, BorderLayout.SOUTH);
        this.getContentPane().add(panel, BorderLayout.CENTER);
        this.pack();
    }

}

Note: FileWriter class is used here to write content to a file. See my last article for details. Article

Copy, paste, and cut text

The time copy(), paste(), cut() functions used here

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.event.CaretEvent;
import javax.swing.event.CaretListener;

public class Main {
  public static void main(String args[]) {
    final JTextField textField = new JTextField(15);
    JButton buttonCut = new JButton("Cut");
    JButton buttonPaste = new JButton("Paste");
    JButton buttonCopy = new JButton("Copy");

    JFrame jfrm = new JFrame("Cut, Copy, and Paste");
    jfrm.setLayout(new FlowLayout());
    jfrm.setSize(230, 150);
    jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    buttonCut.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent le) {
        textField.cut();
      }
    });

    buttonPaste.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent le) {
        textField.paste();
      }
    });

    buttonCopy.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent le) {
        textField.copy();
      }
    });

    textField.addCaretListener(new CaretListener() {
      public void caretUpdate(CaretEvent ce) {
        System.out.println("All text: " + textField.getText());
        if (textField.getSelectedText() != null)
          System.out.println("Selected text: " + textField.getSelectedText());
        else
          System.out.println("Selected text: ");
      }
    });

    jfrm.add(textField);
    jfrm.add(buttonCut);
    jfrm.add(buttonPaste);
    jfrm.add(buttonCopy);
    jfrm.setVisible(true);
  }
}

Explanation: Three buttons are used to monitor the operation. Just press the corresponding button to trigger the mechanism.

Adding keyboard monitoring mechanism

import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.HeadlessException;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;

public class Main extends JFrame {
  public Main() throws HeadlessException {
    setSize(200, 200);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setLayout(new FlowLayout(FlowLayout.LEFT));

    JLabel usernameLabel = new JLabel("Username: ");
    JTextField usernameTextField = new JTextField();
    usernameTextField.setPreferredSize(new Dimension(100, 20));
    add(usernameLabel);
    add(usernameTextField);

    usernameTextField.addKeyListener(new KeyAdapter() {   //Creating mechanisms
      public void keyReleased(KeyEvent e) {        //Overload function, release key trigger
        JTextField textField = (JTextField) e.getSource();  //Get the component object that originally occurred event, which is both a text box object
        String text = textField.getText();
        textField.setText(text.toUpperCase());      //Convert all lowercase letters to uppercase letters
      }
       public void keyTyped(KeyEvent e) {           //Triggered when typing
      }

      public void keyPressed(KeyEvent e) {       //Functions triggered when releasing keys
      }   
    });
  }

  public static void main(String[] args) {
    new Main().setVisible(true);
  }
}

Reference Documents

• Official website)

• English Documents

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