您需要使用Map<String, Object>，而不是HashMap<Integer, String>.

请使用以下代码:

private Map<String, Object> episodes;

public HashMap<String, Object> getEpisodes() {
    return episodes;
}

public void setEpisodes(HashMap<String, Object> episodes) {
    this.episodes = episodes;

}

要查询数据库，请使用以下代码:

To query your database please use this code:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference episodesRef = rootRef..child("users").child(auth.getCurrentUser().getUid()).child("episodes");
ValueEventListener eventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            String key = ds.getKey();
            String value = ds.getValue(String.class)
            Log.d("TAG", "key= " + key + " -> value: " + value);
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
episodesRef.addListenerForSingleValueEvent(eventListener);

输出将是:

 key: 0 -> value: -Kno0IYdlSjjfFsXkGQ7
 key: 1 -> value: -Kno0IYdlSjjfFsXkGQ8

肯定会起作用.