Libgdx空指针2d跳转并运行游戏

我想在我的2D跳跃和运行游戏中实现我的玩家可以拍摄但我总是得到一个空指针异常 . 有谁知道为什么？

在这个类中我检查输入：public class InputIngame实现InputProcessor {

Player player;

public void handleInput(){
    //control our player using immediate impulses
        if (Gdx.input.isKeyJustPressed(Input.Keys.W) && PlayScreen.player.b2body.getLinearVelocity().y == 0)
            PlayScreen.player.b2body.applyLinearImpulse(new Vector2(0, 6f), PlayScreen.player.b2body.getWorldCenter(), true);
        if (Gdx.input.isKeyPressed(Input.Keys.D) && PlayScreen.player.b2body.getLinearVelocity().x <= 2)
            PlayScreen.player.b2body.applyLinearImpulse(new Vector2(0.2f, 0), PlayScreen.player.b2body.getWorldCenter(), true);
        if (Gdx.input.isKeyPressed(Input.Keys.A) && PlayScreen.player.b2body.getLinearVelocity().x >= -2)
            PlayScreen.player.b2body.applyLinearImpulse(new Vector2(-0.2f, 0), PlayScreen.player.b2body.getWorldCenter(), true);
        if (Gdx.input.isKeyPressed(Input.Keys.D) && Gdx.input.isKeyPressed(Input.Keys.SHIFT_LEFT) && PlayScreen.player.b2body.getLinearVelocity().x > 1)
            PlayScreen.player.b2body.setLinearVelocity(1, PlayScreen.player.b2body.getLinearVelocity().y);
        if (Gdx.input.isKeyPressed(Input.Keys.A) && Gdx.input.isKeyPressed(Input.Keys.SHIFT_LEFT) && PlayScreen.player.b2body.getLinearVelocity().x < -1)
            PlayScreen.player.b2body.setLinearVelocity(-1, PlayScreen.player.b2body.getLinearVelocity().y);
        if (Gdx.input.isKeyJustPressed(Input.Keys.SPACE))
            player = new Player();
            player.fire();
}

在我的屏幕课上我画了火球：

@Override
public void render(float delta) {
    //separate our update logic from render
    update(delta);

    //Clear the game screen with Black
    Gdx.gl.glClearColor(0, 0, 0, 1);
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

    //render our game map
    renderer.render();
    if (player.isDead == true)
        player.die();
    player.draw(runner.batch);

    //renderer our Box2DDebugLines
    b2dr.render(world, gamecam.combined);

    runner.batch = new SpriteBatch();
    runner.batch.setProjectionMatrix(gamecam.combined);
    runner.batch.begin();
    player.draw(runner.batch);
    runner.batch.end();

    if (TimeUtils.timeSinceNanos(startTime) > 1000000000) {
        startTime = TimeUtils.nanoTime();
    }

    Gdx.app.log("FPSLogger", "fps: " + Gdx.graphics.getFramesPerSecond());
}

在我的播放器类中，我设置了我的变量：

private PlayScreen screen;
private Array<FireBall> fireballs;

并初始化他们：

public Player(PlayScreen screen){
    //initialize default values
    runner = new HardwareRunner();
    this.screen = screen;
    fireballs = new Array<FireBall>();

并且此方法在render方法中执行：

public void update(float dt){
    //update our sprite to correspond with the position of our Box2D body
    setPosition(b2body.getPosition().x - getWidth() / 2, b2body.getPosition().y - getHeight() / 2);
    //update sprite with the correct frame depending on marios current action
    setRegion(getFrame(dt));

    for(FireBall  ball : fireballs) {
        ball.update(dt);
    }

}

还有这些方法：

public void fire(){
    fireballs.add(new FireBall(screen, b2body.getPosition().x, b2body.getPosition().y, runningRight ? true : false));
}

public void draw(Batch batch){
    super.draw(batch);
    for(FireBall ball : fireballs)
        ball.draw(batch);

}

然后是我的火球课：

public class FireBall extends Sprite {

PlayScreen screen;
World world;
Array<TextureRegion> frames;
Animation fireAnimation;
float stateTime;
boolean destroyed;
boolean setToDestroy;
boolean fireRight;

Body b2body;
public FireBall(PlayScreen screen, float x, float y, boolean fireRight){
    this.fireRight = fireRight;
    this.screen = screen;
    this.world = screen.getWorld();
    frames = new Array<TextureRegion>();
    for(int i = 0; i < 4; i++){
        frames.add(new TextureRegion(screen.getAtlas().findRegion("fireball"), i * 8, 0, 8, 8));
    }
    fireAnimation = new Animation(0.2f, frames);
    setRegion(fireAnimation.getKeyFrame(0));
    setBounds(x, y, 6 / HardwareRunner.PPM, 6 / HardwareRunner.PPM);
    defineFireBall();
}

public void defineFireBall(){
    BodyDef bdef = new BodyDef();
    bdef.position.set(fireRight ? getX() + 12 /HardwareRunner.PPM : getX() - 12 /HardwareRunner.PPM, getY());
    bdef.type = BodyDef.BodyType.DynamicBody;
    if(!world.isLocked())
    b2body = world.createBody(bdef);

    FixtureDef fdef = new FixtureDef();
    CircleShape shape = new CircleShape();
    shape.setRadius(3 / HardwareRunner.PPM);
    fdef.filter.categoryBits = HardwareRunner.PROJECTILE_BIT;
    fdef.filter.maskBits = HardwareRunner.GROUND_BIT |
            HardwareRunner.BRICK_BIT |
            HardwareRunner.OBJECT_BIT;

    fdef.shape = shape;
    fdef.restitution = 1;
    fdef.friction = 0;
    b2body.createFixture(fdef).setUserData(this);
    b2body.setLinearVelocity(new Vector2(fireRight ? 2 : -2, 2.5f));
}

public void update(float dt){
    stateTime += dt;
    setRegion(fireAnimation.getKeyFrame(stateTime, true));
    setPosition(b2body.getPosition().x - getWidth() / 2, b2body.getPosition().y - getHeight() / 2);
    if((stateTime > 3 || setToDestroy) && !destroyed) {
        world.destroyBody(b2body);
        destroyed = true;
    }
    if(b2body.getLinearVelocity().y > 2f)
        b2body.setLinearVelocity(b2body.getLinearVelocity().x, 2f);
    if((fireRight && b2body.getLinearVelocity().x < 0) || (!fireRight && b2body.getLinearVelocity().x > 0))
        setToDestroy();
}

public void setToDestroy(){
    setToDestroy = true;
}

public boolean isDestroyed(){
    return destroyed;
}

}

但是，如果我尝试启动游戏，我会收到此错误：

Exception in thread "LWJGL Application" java.lang.NullPointerException
at de.tobls.hardwarerunner.Input.InputIngame.handleInput(InputIngame.java:30)
at de.tobls.hardwarerunner.Screens.PlayScreen.update(PlayScreen.java:109)
at de.tobls.hardwarerunner.Screens.PlayScreen.render(PlayScreen.java:130)
at com.badlogic.gdx.Game.render(Game.java:46)
at de.tobls.hardwarerunner.HardwareRunner.render(HardwareRunner.java:71)
at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:215)
at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:120)

line 30 is player.fire();
line 109 is input.handleInput();
line 130 is update(delta);
and line 71 is update(delta); in my main class

我希望有人能帮助我！