android - Firebase complex "contain" queries

Question

I am moving an Android app from rdbms to firebase and like a newbie in Firebase I am struggling with some queries.

I have the DB below in FB:

{
  "posts" : {
    "-KNnbTHJGm83zpSELWwB" : {
      ".priority" : "6gydj46kg0",
      "branch" : "Branch",
      "category" : "Categoria",
      "expiration" : "24h",
      "g" : "6gydj46kg0",
      "l" : [ -23.5415083, -46.88642 ],
      "photo" : "mPostPic_20160728192627.jpeg",
      "price" : 10,
      "priority" : 0,
      "product" : "ipad",
      "userKey" : "BNd8RP5qHoc0q7f9gn8cLjPy5Ux1",
      "offerMessage": "Valido ate as 14:00 hs",
      "likeCount": 0
    }
  }
}

in this post db I have a child "category". I have a list of some categories and I need to query only the posts where value category is inside this categories list.

I tried .start() and .end() but is not working.

Answer 1

Waitting for answers