LibGDX player movment

Question

I'm working on a project in LibGDX. It's a 2d platform game; you can say it's like Super Mario.

So this is how I move my player to the right:

if (Gdx.input.isKeyPressed(Input.Keys.RIGHT)){
    player.b2body.applyLinearImpulse(
               new Vector2(0.1f, 0), 
               player.b2body.getWorldCenter(),
               true);
}

When I release the key, the player is still moving a bit. (It still has a "Linear Impulse" force on its physical body, I think).

How can I make it stop?

My question could be simple as: What is the best way to move a physical body on LibGDX in one direction while holding a key. When I release the key, the body stops immediately.

I have tried with "setTransform" and it's causing issues when the body is touching other objects - plus the shape comes "before" the rest of the game in the screen (you can see it on debug)

Thanks.

Answer 1

You can set linear velocity when you release the movement key. It's as simple as doing body.setLinearVelocity(x, y) then just set the appropriate axis to 0.

Example:

if (Gdx.input.isKeyPressed(Keys.W)) {
    // Move forward
} else if (Gdx.input.isKeyPressed(Keys.S)) {
    // Move backwards
} else {
    // Stop moving in the Y direction
    body.setLinearVelocity(body.getLinearVelocity().x, 0);
}

---

Modifying your existing code to this should probably fix it:

boolean moveRight = (Gdx.input.isKeyPressed(Input.Keys.RIGHT) || JOYSTICK_RIGHT_PRESSED);
boolean moveLeft = (Gdx.input.isKeyPressed(Input.Keys.LEFT) || JOYSTICK_LEFT_PRESSED);

if (moveRight && player2body.getLinearVelocity().x < 3.00f) {
    player2body.applyLinearImpulse(new Vector2(0.15f, 0), player2body.getWorldCenter(), true);
} else if (moveLeft && player2body.getLinearVelocity().x > -3.00f) {
    player2body.applyLinearImpulse(new Vector2(-0.15f, 0), player2body.getWorldCenter(), true);
} else if (moveRight == moveLeft) {
    player2body.setLinearVelocity(0f, player2body.getLinearVelocity().y);
}

The change is in the last else statement. I changed it to an else if statement that checks if you are either:

• Not moving right or left
• Moving both right and left

If any of these two cases are true you should be standing still. The reason your old code did not work is because if the player was moving at max speed (velocity >= 3) or min speed (velocity <= -3) the final else statement would run and stop the player completely.