LibGDX - Multiple actors receiving key events

Question

I have more than one actor (for a local coop game) that need to receive key events (e.g. Player 1 uses arrow keys, Player 2 uses WASD etc...). If I just add Actors to a Stage, they don't receive key events through the InputListener, and if I do this:

stage.setKeyboardFocus(p1);
stage.setKeyboardFocus(p2);

Only Player 2 receives key events, of course. How can I have two (or more) actors receive key events?

Answer 1

You can use a Group or a Table which are actors that can contain other actors, and add the actors

Gdx.setInputProcessor(stage);
group = new Group();
group.addActor(actor1);
group.addActor(actor2);

group.addListener(new InputListener(){
   @Override
   public boolean keyDown(InputEvent event, int keycode){
    if (keycode == Keys.A){
       update(actor1)
    }
    if (keycode == Keys.LEFT{
       update(actor2)
    }
    return true;
    });

stage.addActor(group);
stage.setKeyboardFocus(group);

Answer 2

Libgdx Stage extends InputAdapter, which gives you access to the methods keyDown(int keyCode) and keyUp(int keyCode). If you set the Stage as your InputProcessor by using: Gdx.setInputProcessor(stage); you can handle key inputs in the Stage. Some Pseudocode:

public boolean keyDown(int keyCode) {
    switch (keyCode) {
    case Input.Keys.A:
         player2.moveLeft();
    case Input.Keys.NUMPAD_4:
         player1.moveLeft();
    }
}

Hope it helps.

Answer 3

It's curious that nobody mentioned InputMultiplexer. Try it for your situation.

Answer 4

Figured it out. Instead of setting the keyboard focus to the individual Actors, set it to a common actor, and then just add a listener to that actor. E.G.:

public class Scene extends Stage
{
    public Scene()
    {
        setKeyboardFocus(getRoot()); // getRoot() returns the parent actor group
        addActor(new Player(1));
        addActor(new Player(2));
    }
}

public class Player extends Actor
{
    public Player(Stage stage)
    {
        stage.getRoot().addListener(inputListener);
    }
}