使用 libgdx 进行触摸滚动

I'm trying to implement touch scrolling in a libgdx game. I have a wide image that is a panorama of a room. I want to be able to scroll the image so the user can see around the room. I have it so that I can scroll a certain distance but when a new touchDragged event is registered the image is moved back to the original position.

这就是我的实现方式

public class AttackGame implements ApplicationListener {

AttackInputProcessor inputProcessor;
Texture backgroundTexture; 
TextureRegion region;
OrthographicCamera cam;
SpriteBatch batch;
float width;
float height;
float posX;
float posY;

@Override
public void create() {
    posX = 0;
    posY = 0;
    width = Gdx.graphics.getWidth();
    height = Gdx.graphics.getHeight();  
    backgroundTexture = new Texture("data/pancellar.jpg");
    region = new TextureRegion(backgroundTexture, 0, 0, width, height);
    batch = new SpriteBatch();

}

@Override
public void resize(int width, int height) {
    cam = new OrthographicCamera();
    cam.setToOrtho(false, width, height);
    cam.translate(width / 2, height / 2, 0);
    inputProcessor = new AttackInputProcessor(width, height, cam);
    Gdx.input.setInputProcessor(inputProcessor);

}

@Override
public void render() {

    Gdx.gl.glClearColor(0,0,0,1);
    Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);    
    batch.setProjectionMatrix(cam.combined);
    batch.begin();
    batch.draw(backgroundTexture, 0, 0, 2400, 460);
    batch.end();

}

@Override
public void pause() {
    // TODO Auto-generated method stub

}

@Override
public void resume() {
    // TODO Auto-generated method stub

}

@Override
public void dispose() {
    backgroundTexture.dispose();

}

}

在输入处理器中

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

    cam.position.set(screenX, posY / 2, 0);
    cam.update();
    return false;
}

在这个问题LibGdx How to Scroll using OrthographicCamera?.但是它并没有真正解决我的问题.

public class MapInputProcessor implements InputProcessor {
    Vector3 last_touch_down = new Vector3();

    ...

    public boolean touchDragged(int x, int y, int pointer) {
        moveCamera( x, y );     
        return false;
    }

    private void moveCamera( int touch_x, int touch_y ) {
        Vector3 new_position = getNewCameraPosition( touch_x, touch_y );

        if( !cameraOutOfLimit( new_position ) )
            stage.getCamera().translate( new_position.sub( stage.getCamera().position ) );

        last_touch_down.set( touch_x, touch_y, 0);
    }

    private Vector3 getNewCameraPosition( int x, int y ) {
        Vector3 new_position = last_touch_down;
        new_position.sub(x, y, 0);
        new_position.y = -new_position.y;
        new_position.add( stage.getCamera().position );

        return new_position;
    }

    private boolean cameraOutOfLimit( Vector3 position ) {
        int x_left_limit = WINDOW_WIDHT / 2;
        int x_right_limit = terrain.getWidth() - WINDOW_WIDTH / 2;
        int y_bottom_limit = WINDOW_HEIGHT / 2;
        int y_top_limit = terrain.getHeight() - WINDOW_HEIGHT / 2;

        if( position.x < x_left_limit || position.x > x_right_limit )
            return true;
        else if( position.y < y_bottom_limit || position.y > y_top_limit )
            return true;
        else
          return false;
}


    ...
}