如何创建 movingPlatform？

Question

我想用 box2d 创建移动 right/left 的平台，但我不知道怎么做？

我创建了 platform-body 并给了他 KinematicType，并尝试用 setLinearVelocity 移动它，但没有帮助

这就是我创建平台的方式 "bucket":

package com.niceboy.game.Objects;

import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.physics.box2d.Body;
import com.badlogic.gdx.physics.box2d.BodyDef;
import com.badlogic.gdx.physics.box2d.FixtureDef;
import com.badlogic.gdx.physics.box2d.PolygonShape;
import com.badlogic.gdx.physics.box2d.World;

import java.util.Random;

import static com.niceboy.game.Constants.PLATFORM_MARGIN;
import static com.niceboy.game.Constants.PPM;

public class Bucket {
  private Random rand = new Random();

  private World world;
  private Body body;

  public Bucket(World world){
      this.world = world;
  }

  public void createBucket(int y){
      BodyDef bdef = new BodyDef();    
      bdef.position.set(rand.nextInt(Gdx.graphics.getWidth())/PPM,PLATFORM_MARGIN/PPM*y);
      bdef.type = BodyDef.BodyType.KinematicBody;

      body = world.createBody(bdef);

      PolygonShape box = new PolygonShape();
      box.setAsBox(50/PPM,20/PPM);
      FixtureDef fdef = new FixtureDef();
      fdef.shape = box;

      body.createFixture(fdef).setUserData("bucket");
  }

  public void repos(int y){
    body.getPosition().set(rand.nextInt(Gdx.graphics.getWidth())/PPM,PLATFORM_MARGIN/PPM*y);
  }
}

但是不知道怎么移动

Answer 1

kinematicBody->setLinearVelocity(1,0); //每秒向右移动1个单位

我已经创建了 KinematicBody 主体并为其提供了 PolygonShape 并应用了线速度，然后主体开始移动，当您想要改变方向时，应用相同的负大小的速度，以便它开始向相反的方向移动。

public class MainGame extends InputAdapter implements ApplicationListener {

    private SpriteBatch batch;
    private ExtendViewport extendViewport;
    private OrthographicCamera cam;

    private float w=20;
    private float h=22;

    private World world;
    private Box2DDebugRenderer debugRenderer;

    private Array<Body> array;
    private Vector3 vector3;
    private Body platform;
    Vector2 vector2;
    boolean isLeft;

    @Override
    public void create() {

        vector2=new Vector2();
        isLeft=true;
        cam=new OrthographicCamera();
        extendViewport=new ExtendViewport(w,h,cam);

        batch =new SpriteBatch();
        Gdx.input.setInputProcessor(this);

        world=new World(new Vector2(0,-9.8f),true);
        array=new Array<Body>();
        debugRenderer=new Box2DDebugRenderer();
        vector3=new Vector3();

        BodyDef bodyDef=new BodyDef();
        bodyDef.type= BodyDef.BodyType.KinematicBody;
        bodyDef.position.set(0,0);
        platform=world.createBody(bodyDef);

        PolygonShape polygonShape=new PolygonShape();
        polygonShape.setAsBox(3,1);

        FixtureDef fixtureDef=new FixtureDef();
        fixtureDef.shape=polygonShape;
        fixtureDef.restitution=.5f;
        platform.createFixture(fixtureDef);
        polygonShape.dispose();
        platfrom.setLinearVelocity(1,0);
    }

    @Override
    public void render() {

        Gdx.gl.glClearColor(0,1,1,1);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

        world.step(1/60f,6,2);
        batch.setProjectionMatrix(cam.combined);
        batch.begin();

        world.getBodies(array);
        for (Body body:array){
            if(body.getUserData()!=null) {
                Sprite sprite = (Sprite) body.getUserData();
                sprite.setPosition(body.getPosition().x-sprite.getWidth()/2, body.getPosition().y-sprite.getHeight()/2);
                sprite.setRotation(body.getAngle()*MathUtils.radDeg);
                sprite.draw(batch);
            }
        }
        batch.end();
        debugRenderer.render(world,cam.combined);


        Vector2 pos=platfrom.getTransform().getPosition();
        if(pos.x>20-3) {
            platfrom.setLinearVelocity(-1,0);
        }
        if(pos.x<3) {
            platfrom.setLinearVelocity(1,0);
        }

    }

    @Override
    public void pause() {

    }

    @Override
    public void resume() {

    }

    @Override
    public void resize(int width, int height) {

        extendViewport.update(width,height);
        cam.position.x = w /2;
        cam.position.y = h/2;
        cam.update();
    }

    private void createPhysicsObject(float x,float y){

        float sizeX=0.5f,sizeY=0.5f;
        BodyDef bodyDef=new BodyDef();
        bodyDef.position.set(x,y);
        bodyDef.type= BodyDef.BodyType.DynamicBody;

        Body body=world.createBody(bodyDef);

        PolygonShape polygonShape=new PolygonShape();
        polygonShape.setAsBox(sizeX,sizeY);
        FixtureDef fixtureDef=new FixtureDef();
        fixtureDef.shape=polygonShape;
        fixtureDef.restitution=.2f;
        fixtureDef.density=2;

        body.createFixture(fixtureDef);
        body.setFixedRotation(false);
        polygonShape.dispose();

        Sprite sprite=new Sprite(new Texture("badlogic.jpg"));
        sprite.setSize(2*sizeX,2*sizeY);
        sprite.setPosition(x-sprite.getWidth()/2,y-sprite.getHeight()/2);
        sprite.setOrigin(sizeX,sizeY);

        body.setUserData(sprite);
    }

    @Override
    public void dispose() {
        batch.dispose();
        debugRenderer.dispose();
        world.dispose();
    }

    @Override
    public boolean touchDown(int screenX, int screenY, int pointer, int button) {

        vector3.set(screenX,screenY,0);
        Vector3 position=cam.unproject(vector3);
        createPhysicsObject(vector3.x,vector3.y);

        return false;
    }
}

如何创建 movingPlatform？

How to create movingPlatform?

java

android

box2d

libgdx