code: public List<Channel> getCurrentChannels(Context mContext) {
          try {
              ApplicationInfo app = getApplicationContext().getPackageManager().getApplicationInfo(getApplicationContext().getPackageName(), PackageManager.GET_META_DATA);
              Bundle bundle = app.metaData;
              final String service = bundle.getString("TvInputService");
              String channels = TvContract.buildInputId(new ComponentName(getPackageName(), service.substring(getPackageName().length())));
              Uri channelsQuery = TvContract.buildChannelsUriForInput(channels);
              Log.d(TAG, channels + " " + channelsQuery.toString());
              List<Channel> list = new ArrayList<>();
              Cursor cursor = null;
              try {
                  cursor = mContext.getContentResolver().query(channelsQuery, null, null, null, null);
                  while(cursor != null && cursor.moveToNext()) {
                      Channel channel = new Channel()
                              .setNumber(cursor.getString(cursor.getColumnIndex(TvContract.Channels.COLUMN_DISPLAY_NUMBER)))
                              .setName(cursor.getString(cursor.getColumnIndex(TvContract.Channels.COLUMN_DISPLAY_NAME)))
                              .setOriginalNetworkId(cursor.getInt(cursor.getColumnIndex(TvContract.Channels.COLUMN_ORIGINAL_NETWORK_ID)))
                              .setTransportStreamId(cursor.getInt(cursor.getColumnIndex(TvContract.Channels.COLUMN_TRANSPORT_STREAM_ID)))
                              .setServiceId(cursor.getInt(cursor.getColumnIndex(TvContract.Channels.COLUMN_SERVICE_ID)))
                              .setVideoHeight(1080)
                              .setVideoWidth(1920)
                              .setPrograms(getPrograms(getApplicationContext(),
                                      TvContract.buildChannelUri(cursor.getInt(cursor.getColumnIndex(TvContract.Channels._ID)))));
                      list.add(channel);
                  }
              } finally {
                  if (cursor != null) {
                      cursor.close();
                  }
              }
              return list;
          } catch (PackageManager.NameNotFoundException e) {
              e.printStackTrace();
          }
          return null;
      }
docs: Goes into the TV guide and obtains the channels currently registered
  @return An ArrayList of channels