Question

我已经尝试设置我自己的类来处理冲突，但它似乎只是输出下面的错误。程序打开很好，它只在球和尖峰碰撞时输出错误。感谢

 Exception in thread "LWJGL Application" java.lang.NullPointerException
    at com.alexcz.mariobros.Tiles.HandleCollisions.ballSpike(HandleCollisions.java:20)
    at com.alexcz.mariobros.Tools.WorldContactListener.beginContact(WorldContactListener.java:41)
    at com.badlogic.gdx.physics.box2d.World.beginContact(World.java:982)

public class HandleCollisions {
    Character player;
    World world;

    public HandleCollisions(Character player, World world) {
        this.player = player;
        this.world = world;
    }

    public void ballSpike(){
        player.hitSpike();
        System.out.println("collided");
    }
}

public class WorldContactListener implements ContactListener {
    public World world;
    public Character player;
    public HandleCollisions handleCollisions;

    public WorldContactListener(Character player,World world) {
        world = this.world;
        player = this.player;

        handleCollisions = new HandleCollisions(player, world);
    }

    @Override
    public void beginContact(Contact contact) {
        Fixture fixtureA = contact.getFixtureA();
        Fixture fixtureB = contact.getFixtureB();

        if(fixtureA.getUserData() == "ball" || fixtureB.getUserData() == "ball"){
            Fixture ball = fixtureA.getUserData() == "head" ? fixtureA : fixtureB;
            Fixture object = ball == fixtureA ? fixtureB : fixtureA;

            if(object.getUserData() instanceof InteractiveTileObject)
            {
                ((InteractiveTileObject)object.getUserData()).hit();
                handleCollisions.ballSpike();
            }
        }
    }

Answer 1

这是您的问题：

    world = this.world;    // this.world is null
    player = this.player;  // this.player is null

应该是：

    this.world = world;
    this.player = player;

因为this是您的实例，所以您将如何分配类变量。

我猜这就是为什么你的handleCollisions是null，并在执行java.lang.NullPointerException时抛出handleCollisions.ballSpike()。

这里有一个调试检查器派上用场。

Libgdx On Collision错误

1 个答案: