CODEWITHSUNDEEP
java
Ben Stoler
Ben Stoler

Reputation: 21

On mac, in Java, keyPressed event doesn't fire for certain keys

This is a really weird issue, but I just have a simple keyListener added to a JPanel that prints on keyPressed and on keyReleased. Usually it works fine, but on certain keys like 'A', if I press and hold before releasing, no other keys will fire keyPressed after that release until I press and hold on certain keys like 'D'. After that, it's back to usual unless I press a "bad" key and hold it for too long.

One last note, keyReleased ALWAYS triggers properly, it's just keyPressed which fails.

EDIT2: I've simplified the code to simply the following and it still behaves as described above:

import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JFrame;

public class Test {
    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setSize(800, 600);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);

        frame.addKeyListener(new KeyListener() {

            @Override
            public void keyTyped(KeyEvent e) {

            }

            @Override
            public void keyPressed(KeyEvent e) {
                System.out.println("Pressed");
            }

            @Override
            public void keyReleased(KeyEvent e) {
                System.out.println("Released");
            }

        });
    }
}

EDIT: code extract: 

JFrame frame = new JFrame("test");
frame.setSize(WIDTH, HEIGHT);
frame.setLocationRelativeTo(null);
frame.setLayout(null);
frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
frame.setResizable(false);

JLayeredPane panel = new JLayeredPane();
panel.setBounds(0, 0, WIDTH, HEIGHT);
panel.setLayout(null);


frame.add(panel);
KeyListener listener = new KeyListener() {

    public void keyTyped(KeyEvent e) {
        System.out.println("typed: "+e.getKeyCode());
    }

    @Override
    public void keyPressed(KeyEvent e) {
        System.out.println("pressed: "+e.getKeyCode());
    }

    @Override
    public void keyReleased(KeyEvent e) {
        System.out.println("released: "+e.getKeyCode());
        System.out.println();
    }

};
panel.addKeyListener(listener);
frame.addKeyListener(listener);
frame.setVisible(true);

Upvotes: 2

Views: 2293

Answers (4)

NickD
NickD

Reputation: 506

I ran into this issue recently, it is caused by the MacOS showing a context menu when you hold certain keys down (To allow you to chose alternative language characters) and the bug report page had a good solution that worked for me:

https://bugs.java.com/bugdatabase/view_bug.do?bug_id=JDK-8167263

To disabled the character accent menu and enable auto-repeat, type the following at the command prompt:

defaults write -g ApplePressAndHoldEnabled -bool false

This can be reversed with the following:

defaults write -g ApplePressAndHoldEnabled -bool true

I just tried this on the mac console and my java application no longer has the key problem.

Upvotes: 1

wouter
wouter

Reputation: 1

More troublesome keys were reported here

https://community.oracle.com/thread/4115318

It seems at this moment the best workaround is to avoid the use of

z, c, n, a, s, e, y, u, i, o

Upvotes: 0

user41871
user41871

Reputation:

It appears that this is a Java bug that arose after people upgraded to MacOS Sierra:

As a temporary workaround you might try using keys other than the standard WASD for controlling movement.

Upvotes: 0

Ben Stoler
Ben Stoler

Reputation: 21

I fixed it by going into my system preferences -> keyboard and moving the key repeat slider all the way to the left to "Off".

Upvotes: 0

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