Question

所以我遇到了一个我真的不明白的问题。在试图弄清楚什么是错的之后，我决定录制一个video并在这里问一下。

在视频中，请注意左下角的True / False布尔值。这是我的变量canJump的值。在开始时，只需左右移动“播放器”，值就会在true和false之间。当玩家上坡和下坡时也会发生这种情况。

使用Tiled创建地图/碰撞图层。

我的TiledObject类：

public class TiledObjectUtil {

public static float PPM = 32;

public static void parseTiledObjectLayer(World world, MapObjects objects) {
    for(MapObject object : objects) {
        Shape shape;

        if(object instanceof PolylineMapObject) {
            shape = createPolyLine((PolylineMapObject) object);

        } else {
            continue;
        }

        Body body;
        BodyDef bdef = new BodyDef();
        bdef.type = BodyDef.BodyType.StaticBody;
        body = world.createBody(bdef);
        body.createFixture(shape, 1.0f);

        shape.dispose();
    }
}

private static ChainShape createPolyLine(PolylineMapObject polyline) {
    float[] vertices = polyline.getPolyline().getTransformedVertices();
    Vector2[] worldVertices = new Vector2[vertices.length / 2];

    for(int i = 0; i<worldVertices.length; i++) {
        worldVertices[i] = new Vector2(vertices[i * 2] / PPM, vertices[i*2+1] / PPM);
    }
    ChainShape cs = new ChainShape();
    cs.createChain(worldVertices);
    return cs;
}}

我的玩家类：

public class Player {

private BodyDef def = new BodyDef();
public Body playerBody;


private float speed = 10;

public Player() {

}

public void update() {

    if (InputUtil.moveLeft)  {
        playerBody.setLinearVelocity(-speed, playerBody.getLinearVelocity().y);
    }
    if (InputUtil.moveRight)  {
        playerBody.setLinearVelocity(speed, playerBody.getLinearVelocity().y);
    }

    if (!InputUtil.moveLeft && !InputUtil.moveRight) {

        playerBody.setLinearVelocity(0, playerBody.getLinearVelocity().y);
    }
}

public void jump() {
    if (ContactUtil.canJump) {
        playerBody.applyLinearImpulse(0, 80, 0, 0, true);

    }

}


public Body createPlayer(World world) {
    def.type = BodyDef.BodyType.DynamicBody;
    def.position.set(20, 20);
    def.fixedRotation = true;

    playerBody = world.createBody(def);

    PolygonShape shape = new PolygonShape();
    shape.setAsBox(2f / 2, 2f / 2);

    FixtureDef playerFixture = new FixtureDef();
    playerFixture.density = 1f;
    playerFixture.shape = shape;
    playerFixture.restitution = 0f;
    playerFixture.friction = 1f;
    playerBody.createFixture(playerFixture);

    shape.setAsBox(2f / 2, 1f / 2, new Vector2(0, 0 - 1), 0);
    playerFixture.shape = shape;
    playerFixture.isSensor = true;
    playerBody.createFixture(playerFixture).setUserData("player");

    shape.dispose();

    return playerBody;
} }

最后，我的ContactListener：

public class ContactUtil implements ContactListener {

public static boolean canJump;


public ContactUtil() {

}

@Override
public void beginContact(Contact contact) {

    Fixture fixtureA = contact.getFixtureA();
    Fixture fixtureB = contact.getFixtureB();

    System.out.println(fixtureA.getUserData() + ", " + fixtureB.getUserData());

    if (fixtureA.getUserData() == "player" && fixtureB.getUserData() == null) {
        canJump = true;
    }
    if (fixtureA.getUserData() == null && fixtureB.getUserData() == "player") {
        canJump = true;
    }

}

@Override
public void endContact(Contact contact) {

    Fixture fixtureA = contact.getFixtureA();
    Fixture fixtureB = contact.getFixtureB();

    System.out.println(fixtureA.getUserData() + ", " + fixtureB.getUserData());

    if (fixtureA.getUserData() == "player" && fixtureB.getUserData() == null) {
        canJump = false;
    }
    if (fixtureA.getUserData() == null && fixtureB.getUserData() == "player") {
        canJump = false;
    }

}

另外，我的玩家每次在斜坡上停下来都会跳一点。我知道这是由于这一行：playerBody.setLinearVelocity(0, playerBody.getLinearVelocity().y);

如果有人知道更好的方式来处理这个动作，那将非常感激。

Answer 1

我似乎记得过去有过这个问题！我认为问题在于beginContact和endContact中的逻辑。

我将打破我粗糙的MS Paint技能来解释这个问题。想象一下以下情况：你的玩家在空中，朝着下面的平台坠落。正如您所料，canJump是错误的：

玩家跌落并降落，并且调用beginContact平台1。这会将canJump设置为true。再次，这是我们所期望的：

现在玩家向右移动，直到他们接触到平台2。调用平台2的beginContact。然而，canJump被设置为真。

这就是问题所在。在最后一步，玩家仍然与平台一接触。但现在他们不是，所以调用平台一endContact。 canJump现已设置为false。这解释了您获得的意外行为。

解决方案非常简单。您需要维护播放器底部正在触摸的联系人列表。在这篇iforce2d文章中有一个指南可以做到这一点：http://www.iforce2d.net/b2dtut/jumpability

祝你好运！

Box2D碰撞检测失败

1 个答案: