暂停/恢复适用于Android的简单Libgdx游戏

目前，我正在尝试使用针对Android平台的libgdx实现简单的游戏。我已经实现了游戏，但不知道如何根据用户输入来暂停和继续游戏。请提出想法以及一些实现该想法的实用代码。我使用的是libgdx库中演示的简单游戏代码。谢谢。

这是代码：

public class Drop implements ApplicationListener {
   Texture dropImage;
   Texture bucketImage;
   Sound dropSound;
   Music rainMusic;
   SpriteBatch batch;
   OrthographicCamera camera;
   Rectangle bucket;
   Array<Rectangle> raindrops;
   long lastDropTime;

   @Override
   public void create() {
      // load the images for the droplet and the bucket, 64x64 pixels each
      dropImage = new Texture(Gdx.files.internal("droplet.png"));
      bucketImage = new Texture(Gdx.files.internal("bucket.png"));

      // load the drop sound effect and the rain background "music"
      dropSound = Gdx.audio.newSound(Gdx.files.internal("drop.wav"));
      rainMusic = Gdx.audio.newMusic(Gdx.files.internal("rain.mp3"));

      // start the playback of the background music immediately
      rainMusic.setLooping(true);
      rainMusic.play();

      // create the camera and the SpriteBatch
      camera = new OrthographicCamera();
      camera.setToOrtho(false, 800, 480);
      batch = new SpriteBatch();

      // create a Rectangle to logically represent the bucket
      bucket = new Rectangle();
      bucket.x = 800 / 2 - 64 / 2; // center the bucket horizontally
      bucket.y = 20; // bottom left corner of the bucket is 20 pixels above the bottom screen edge
      bucket.width = 64;
      bucket.height = 64;

      // create the raindrops array and spawn the first raindrop
      raindrops = new Array<Rectangle>();
      spawnRaindrop();
   }

   private void spawnRaindrop() {
      Rectangle raindrop = new Rectangle();
      raindrop.x = MathUtils.random(0, 800-64);
      raindrop.y = 480;
      raindrop.width = 64;
      raindrop.height = 64;
      raindrops.add(raindrop);
      lastDropTime = TimeUtils.nanoTime();
   }

   @Override
   public void render() {
      // clear the screen with a dark blue color. The
      // arguments to glClearColor are the red, green
      // blue and alpha component in the range [0,1]
      // of the color to be used to clear the screen.
      Gdx.gl.glClearColor(0, 0, 0.2f, 1);
      Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);

      // tell the camera to update its matrices.
      camera.update();

      // tell the SpriteBatch to render in the
      // coordinate system specified by the camera.
      batch.setProjectionMatrix(camera.combined);

      // begin a new batch and draw the bucket and
      // all drops
      batch.begin();
      batch.draw(bucketImage, bucket.x, bucket.y);
      for(Rectangle raindrop: raindrops) {
         batch.draw(dropImage, raindrop.x, raindrop.y);
      }
      batch.end();

      // process user input
      if(Gdx.input.isTouched()) {
         Vector3 touchPos = new Vector3();
         touchPos.set(Gdx.input.getX(), Gdx.input.getY(), 0);
         camera.unproject(touchPos);
         bucket.x = touchPos.x - 64 / 2;
      }
      if(Gdx.input.isKeyPressed(Keys.LEFT)) bucket.x -= 200 * Gdx.graphics.getDeltaTime();
      if(Gdx.input.isKeyPressed(Keys.RIGHT)) bucket.x += 200 * Gdx.graphics.getDeltaTime();

      // make sure the bucket stays within the screen bounds
      if(bucket.x < 0) bucket.x = 0;
      if(bucket.x > 800 - 64) bucket.x = 800 - 64;

      // check if we need to create a new raindrop
      if(TimeUtils.nanoTime() - lastDropTime > 1000000000) spawnRaindrop();

      // move the raindrops, remove any that are beneath the bottom edge of
      // the screen or that hit the bucket. In the later case we play back
      // a sound effect as well.
      Iterator<Rectangle> iter = raindrops.iterator();
      while(iter.hasNext()) {
         Rectangle raindrop = iter.next();
         raindrop.y -= 200 * Gdx.graphics.getDeltaTime();
         if(raindrop.y + 64 < 0) iter.remove();
         if(raindrop.overlaps(bucket)) {
            dropSound.play();
            iter.remove();
         }
      }
   }

   @Override
   public void dispose() {
      // dispose of all the native resources
      dropImage.dispose();
      bucketImage.dispose();
      dropSound.dispose();
      rainMusic.dispose();
      batch.dispose();
   }

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

   @Override
   public void pause() {
   }

   @Override
   public void resume() {
   }
}