CODEWITHSUNDEEP
javainputconsolekeylistener
Konrad
Konrad

Reputation: 24661

Java easiest keylistener

I know there was milions of questions about that, but I can't understand most of them. I've seen that people make something like that:

public void keyPressed(KeyEvent e)
{
    if (e.getKeyCode()== KeyEvent.VK_Q)
        //do something
}

but keyPressed must override methos of some class to work or be runned in other thread. I really don't know how to do that. Can someone give me code of the easiest keylistener for java.
It should work even when program is not focused (it's just console program).

import java.awt.AWTException;
import java.awt.Robot;
import java.awt.event.*;

import javax.swing.JFrame;

public class SquatCounter {

class MyKeyListener extends KeyAdapter{
    public void keyPressed(KeyEvent e)
    {
        if (e.getKeyCode()== KeyEvent.VK_Q)
            System.out.println("Key Q pressed!");
    }
}

JFrame jf = new JFrame("title");
public SquatCounter() {
    jf.addKeyListener(new MyKeyListener());
}
public static void main(String[] args) {
    Key1 key = new Key1 ();
    SquatCounter test = new SquatCounter();
}
}

Upvotes: 1

Views: 3654

Answers (2)

John S.
John S.

Reputation: 646

Just add a KeyListener.

import java.awt.AWTException;
import java.awt.Robot;
import java.awt.event.*;

import javax.swing.JFrame;

public class SquatCounter {
    JFrame jf = new JFrame("title") {{
        setVisible(true);
        setDefaultCloseOperation(3); // EXIT_ON_CLOSE
    }};

    public SquatCounter() {
        jf.addKeyListener(new KeyListener() {
            @Override
            public void keyPressed(KeyEvent event) {
                if (e.getKeyCode()== KeyEvent.VK_Q)
                    //do something
            }
            @Override
            public void keyReleased(KeyEvent event) {
                // different stuff
            }
            @Override
            public void keyTyped(KeyEvent event) {
                // more stuff
            }
        });
    }

    public static void main(String[] args) {
        SquatCounter test = new SquatCounter();
    }
}

Doing something out of focus has an answer here: Stackoverflow: Listening for input without focus in Java

Upvotes: 0

tagh
tagh

Reputation: 1037

When you setup the JFrame, add a KeyListener like this:

JFrame jf = new JFrame("title");
jf.addKeyListener(new MyKeyListener());
jf.setVisible(false);

(The jf.setVisible(false); stops the program window from appearing (only command line)

Then create a new class called MyKeyListener that extends KeyAdapter.

class MyKeyListener extends KeyAdapter{
    public void keyPressed(KeyEvent e)
    {
        if (e.getKeyCode()== KeyEvent.VK_Q)
            System.out.println("Key Q pressed!");
    }
}

Now let me explain things a bit.

First, when you create a JFrame, it has no default KeyListener attached. Therefore, we have to create a class MyKeyListener to do that.

Secondly, we extended KeyAdapter instead of implementing KeyListener because there are a lot more methods than what you need in there. You only need to override the keypressed() method when you extends KeyAdapter but you have to implement all (I think it's 3) the other methods that you don't need for your purposes.

Lastly, if you want to do other methods like keyreleased(), just add it in to the MyKeylistener class and it will work.

Hope this helps!

EDIT: Per OP's request, it should be like this:

BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
String line = "";

while (line.equalsIgnoreCase("q") == false) {
   line = in.read();

   System.out.println("Q is pressed!");
}

in.close();

Upvotes: 2

Related Questions