Firebase RecyclerView Displays One Item

The problem is with your json structure. In this situation, you'd want to be using a json array for the songs, and likely have a Song object. Right now, they're likely parsed out as just an individual "song" which is really a String. Something like the following json structure would be a start to something that would work as intended:

  "DjSunGazer" : {
    "songs" : [
      { "id" : "-LmHrkYkU1qD2GND9wY2", "name" : "Ginuwine - So Anxious" },
      { "id" : "-LmHrlalIVUStU6nqBJI", "name" : "Ginuwine - So Anxious" },
      { "id" : "-LmHrmRRXy4UYoF7DNZz", "name" : "Ginuwine - So Anxious" },
      { "id" : "-LmHrpZzOKOtY_8AGQ_S", "name" : "Rick Ross - Gold Roses (feat. Drake) }"
    ]
  }

I'd still recommend updating the json structure further, so it's easier to parse. Right now it seems like you're including the artist's name as the key value for the song set, which I could see also causing problems or making things more difficult than they need to be.