NFT Price History in Mobile App

NFT Price History in Mobile App

An NFT collection looks like a set of JPEGs until you see its floor price grow from 0.05 to 12 ETH in three weeks. It's price history that turns an NFT tracker from a static catalog into an analytical tool.

Price History Source

Blockchain itself doesn't store "price history" as an entity. An NFT sale is a Transfer event in an ERC-721 smart contract plus ETH movement between addresses in the same transaction. To build price history, you need to aggregate on-chain events. Self-parsing Ethereum is expensive. So use specialized APIs:

OpenSea API v2 (/api/v2/events/collection/{slug}) returns sale type events with price in wei and timestamp. Limitation—4 requests per second on free key. For history deeper than 30 days, need paid plan.

Reservoir API (/sales/v6)—more generous with history depth and rate limits. Supports multiple marketplaces simultaneously (OpenSea, Blur, X2Y2). Pagination via continuation token.

Alchemy NFT API (/getNFTSales)—convenient if already using Alchemy for other on-chain requests.

On Flutter typical repository looks like:

class NftSalesRepository {
  final Dio _dio;
  final String _reservoirKey;

  Future<List<NftSale>> getSalesHistory({
    required String contractAddress,
    required String tokenId,
    DateTime? from,
  }) async {
    final params = {
      'tokens': '$contractAddress:$tokenId',
      'startTimestamp': from?.millisecondsSinceEpoch ~/ 1000,
      'limit': 100,
    };
    final resp = await _dio.get(
      'https://api.reservoir.tools/sales/v6',
      queryParameters: params,
      options: Options(headers: {'x-api-key': _reservoirKey}),
    );
    return (resp.data['sales'] as List)
        .map((e) => NftSale.fromJson(e))
        .toList();
  }
}

Price comes in ETH (or other network native currency), but users expect to see USD. ETH/USD rate must be pulled separately—via CoinGecko API or Alchemy Price API, cached with TTL 60 seconds and applied to historical points post-factum.

Visualization

For chart rendering on Flutter, fl_chart works well. Sales data needs normalization before render: remove obvious wash-trade outliers (sale between related wallets at off-market price), aggregate by days or weeks depending on history depth.

On React Native—Victory Native XL (works on Reanimated 3, no bridge redraws) or react-native-gifted-charts.

LineChart(
  LineChartData(
    lineBarsData: [
      LineChartBarData(
        spots: sales.map((s) => FlSpot(
          s.timestamp.toDouble(),
          s.priceUsd,
        )).toList(),
        isCurved: true,
        gradient: LinearGradient(colors: [Colors.purple, Colors.blue]),
        belowBarData: BarAreaData(show: true, color: Colors.purple.withOpacity(0.1)),
      ),
    ],
    titlesData: FlTitlesData(
      bottomTitles: AxisTitles(
        sideTitles: SideTitles(
          showTitles: true,
          getTitlesWidget: (value, meta) => _formatDate(value),
        ),
      ),
    ),
  ),
)

What's Included

• Reservoir API or OpenSea API integration with pagination
• Data models: NftSale, PricePoint with wei → ETH → USD conversion
• SQLite caching (drift/floor) with TTL
• Chart with time range selection (7d / 30d / All)
• Empty history and network error handling

Timeline

2–4 business days depending on platform and chart design complexity. Cost is calculated individually after requirements analysis.