Java InputMap does not register Shift presses

Question

I am currently creating a small jump and run in Java. I recently wanted to switch from a KeyListener to a Inputmap because the KeyListener seemed unresponsive at times.

I have a custom JFrame named Window with a JPanel and the following code:

public class EditorGamePanel extends JPanel {

    Window parent;
    MainGame maingame;

    public EditorGamePanel(Window parent) {
        this.parent = parent;
        setLayout(null);

        Canvas canvas = new MainGame(parent);
        canvas.setBounds(0, 0, 1920, 1080);
        add(canvas);
        maingame = (MainGame) canvas;

        InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
        ActionMap am = getActionMap();

        im.put(KeyStroke.getKeyStroke(KeyEvent.VK_SHIFT, 0, false), "pressed");
        im.put(KeyStroke.getKeyStroke(KeyEvent.VK_SHIFT, 0, true), "released");

        am.put("pressed", new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println("Pressed");
            }
        });

        am.put("released", new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println("released");
            }
        });
    }
}

The problem is that it does not register me pressing Shift but it DOES register me letting go of Shift. Other keys like w seem to work just fine both ways. I cant seem to find any error or any help in the documentation.

Answer 1

You may be using the wrong KeyStroke for the shift-down key stroke. Instead of:

im.put(KeyStroke.getKeyStroke(KeyEvent.VK_SHIFT, 0, false), "pressed");

try:

im.put(KeyStroke.getKeyStroke(KeyEvent.VK_SHIFT, InputEvent.SHIFT_DOWN_MASK, false), "pressed");

Since this key stroke is not valid if the mask is set to 0.