Is there any function operates as JButton pressed?

Question

I'm making KeyListener for JTextArea in chatting program

If I press ENTER key, JTextArea gets new line

However, I want to make ENTER key operates as "SEND" function

This is my code

public void keyPressed(KeyEvent ke) {
            if(ke.getKeyCode() == KeyEvent.VK_ENTER)
                sendButton.???
            else if(ke.getKeyCode() == KeyEvent.VK_ALT + KeyEvent.VK_ENTER)
                inputTextArea.setText(inputTextArea.getText() + "\n");
        }

What should I do at the point -> ???

And is there any useful advice, teach me and let my program develop :)

Answer 1

Don't use KeyListener with text components, it's just generally bad practice, instead, you want to take control of the KeyEvent.VK_ENTER key binding action and insert your custom functionality there...

Now, the trick is, letting the existing Action still work, cause you don't want any more work then you need...

This can be achieved by getting the Action associated with the KeyEvent.VK_ENTER...

InputMap im = ta.getInputMap(JTextArea.WHEN_FOCUSED);
ActionMap am = ta.getActionMap();

Object key = im.get(KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, 0));
Action insertBreak = am.get(key);

Then, you would set your own action to be triggered in it's place, passing the previous action to it, so it can called when you want it to be...

am.put(key, new MyNewOnEnterAction(insertBreak));

//...

public class MyNewOnEnterAction extends AbstractAction {

    private Action proxy;

    public MyNewOnEnterAction(Action proxy) {
        this.proxy = proxy;
    }


    @Override
    public void actionPerformed(ActionEvent e) {
        // Your custom functionality here...
        proxy.actionPerformed(e);
    }

}

For example...

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.KeyStroke;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.text.BadLocationException;
import javax.swing.text.Document;
import javax.swing.text.Element;
import javax.swing.text.JTextComponent;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    private JLabel status;

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JTextArea ta = new JTextArea(10, 10);
                InputMap im = ta.getInputMap(JTextArea.WHEN_FOCUSED);
                ActionMap am = ta.getActionMap();

                Object key = im.get(KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, 0));
                Action insertBreak = am.get(key);

                am.put(key, new MyNewOnEnterAction(insertBreak));

                status = new JLabel("...");

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new JScrollPane(ta));
                frame.add(status, BorderLayout.SOUTH);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public void sendMessage(String message) {

    }

    public class MyNewOnEnterAction extends AbstractAction {

        private Action proxy;

        public MyNewOnEnterAction(Action proxy) {
            this.proxy = proxy;
        }

        public int getLineAtCaret(JTextComponent component) {
            int caretPosition = component.getCaretPosition();
            Element root = component.getDocument().getDefaultRootElement();

            return root.getElementIndex(caretPosition) + 1;
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            JTextArea ta = (JTextArea) e.getSource();
            int line = getLineAtCaret(ta);
            try {
                int startPos = ta.getLineStartOffset(line - 1);
                int endPos = ta.getLineEndOffset(line - 1);
                Document doc = ta.getDocument();

                String text = doc.getText(startPos, endPos - startPos);
                status.setText(text);
            } catch (BadLocationException ex) {
                ex.printStackTrace();
            }

            proxy.actionPerformed(e);
        }

    }

}

This will get the current line of text and set it to the status JLabel's text...

Personally, I would setup either a class or method that both your key binding Action and your button can call...or you could even use the same Action, who knows ;)

See How to Use Key Bindings and How to Use Actions for more details