Java-How to extend InputStream to read from a JTextField?

Question

Working on a project I got into running java applications through a small console-like window. Thanks to the wonderful community in here I managed to solve the problem with

Answer 1

What I don't understand if why you need a JTextField that extends InputStream? Basically, what you are looking for is:

1. Add an ActionListener on the JTextField (ie, when use presses Enter, actionPerformed will be invoked)
2. You need to grab the text of the JTextField using getText()
3. You can then "transform" the String text to an InputStream with new ByteArrayInputStream(text.getBytes("UTF-8"));

Here is a small snippet that should get you the basic idea:

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;

import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class TestTextField {

    private void initUI() {
        JFrame frame = new JFrame(TestTextField.class.getSimpleName());
        frame.setLayout(new FlowLayout());
        final JTextField textfield = new JTextField(20);
        textfield.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                try {
                    String text = textfield.getText();
                    InputStream is = new ByteArrayInputStream(text.getBytes("UTF-8"));
                    // Here do something with your input stream (something non-blocking)
                    System.err.println(text);
                } catch (UnsupportedEncodingException e1) {
                    e1.printStackTrace();
                }

            }
        });
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(textfield);
        frame.setSize(300, 300);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                new TestTextField().initUI();
            }
        });
    }

}

Answer 2

How about this implementation

import java.io.IOException;
import java.io.InputStream;

import javax.swing.JTextField;


public class JTextFieldInputStream extends InputStream {
    byte[] contents;
    int pointer = 0;

    public JTextFieldInputStream(final JTextField text) {

        text.addKeyListener(new KeyAdapter() {
            @Override
            public void keyReleased(KeyEvent e) {
                if(e.getKeyChar()=='\n'){
                    contents = text.getText().getBytes();
                    pointer = 0;
                    text.setText("");
                }
                super.keyReleased(e);
            }
        });
    }

    @Override
    public int read() throws IOException {
        if(pointer >= contents.length) return -1;
        return this.contents[pointer++];
    }

}

to use this input stream, do the following

 InputStream in = new JTextFieldInputStream( someTextField );
 char c;
 while( (c = in.read()) != -1){
    //do whatever with c
 }

does it read only when I hit enter?

it reads when you call in.read() if the return value -1 it means end of the stream

(And will I be able to modify so that the Enter key empties the JTextField?)

you need to add an action listener and this functionality has nothing to do with the job of input stream