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POKeyEvent not functioning for JTextArea, but works for the JFrame containing the JTextArea
 

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  1. POKeyEvent not functioning for JTextArea, but works for the JFrame containing the JTextArea
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    <p>I searched for answers, but all i found is workaounds, not the reason, so i am asking this question:</p> <p>I am new to GUI programming. While practicing some code regarding key event handling, i came accross an example that has a JTextArea contained inside a JFrame. The keylistener interface is implemented by the Frame itself. When a key is pressed some relevant information are shown on the text area based on the key pressed. the code works fine.</p> <p>but i tried to go differently and tried to register the JTextarea to a keyListenr instead of the JFrame. However, this does not respond to key events. Here is the code below. Please help.</p> <pre><code>public class KeyDemoFrame extends JFrame { private String line1 = ""; private String line2 = ""; private String line3 = ""; private JTextArea textArea; public KeyDemoFrame() { super("Demonstrating Keystrong events"); textArea = new JTextArea(10,21); textArea.setText("Press any key on keyboard"); textArea.setEnabled(false); textArea.setDisabledTextColor(Color.BLACK); add(textArea); //addKeyListener( this ); KeyEventHandler keyStrokeHandler = new KeyEventHandler(); addKeyListener(keyStrokeHandler); } private class KeyEventHandler implements KeyListener { public void keyPressed(KeyEvent event) { line1 = String.format("Your pressed the %s key", KeyEvent.getKeyText(event.getKeyCode())); setLines2and3(event); } public void keyReleased(KeyEvent event) { line1 = String.format("You released %s key", KeyEvent.getKeyText(event.getKeyCode())); setLines2and3(event); } public void keyTyped(KeyEvent event) { line1 = String.format("You typed %s key",KeyEvent.getKeyText(event.getKeyCode())); setLines2and3(event); } private void setLines2and3(KeyEvent event) { line2 = String.format("This key is %san action key", (event.isActionKey()?"":"not ")); String temp = KeyEvent.getKeyModifiersText( event.getModifiers() ); line3 = String.format( "Modifier keys pressed: %s",( temp.equals( "" ) ? "none" : temp ) ); textArea.setText( String.format( "%s\n%s\n%s\n",line1, line2, line3 ) ); } } </code></pre> <p>}</p> <pre><code>import javax.swing.JFrame; public class KeyDemo { public static void main(String[] args) { KeyDemoFrame keyDemoFrame = new KeyDemoFrame(); keyDemoFrame.setSize(300, 100); keyDemoFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); keyDemoFrame.setVisible(true); } } </code></pre>
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    1. COTo be more precise, as to why is this happening, is because, you are extending `JFrame` , and you are adding `Listener` to the Frame itself instead of adding it to the `JTextArea` as desired by you. And as adviced by @mKorbel , you should be using `DocumentListener` for `JTextComponent` :-)
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