NativeScript + Fresco example for downloading images with headers

app.module.ts

if (applicationModule.android) {
    applicationModule.on("launch", () => {
        var fetcher = new NSNetworkFetcher();
        var config = com.facebook.imagepipeline.core.ImagePipelineConfig
          .newBuilder(application.android.context)
          .setNetworkFetcher(fetcher)
          .build();
        com.facebook.drawee.backends.pipeline.Fresco.initialize(application.android.context, config);      
    });
}

nsfetchstate.ts

export class NSFetchState extends com.facebook.imagepipeline.producers.FetchState
{
  public submitTime: number;
  public responseTime: number;
  public fetchCompleteTime: number;

  constructor(consumer, producerContext) {
    super(consumer, producerContext);
    return global.__native(this);
  }
}

nsnetworkfetcher.ts

export class NSNetworkFetcher extends com.facebook.imagepipeline.producers.BaseNetworkFetcher {

  constructor() {
    super();
    return global.__native(this);
  }

  createFetchState(consumer, context) {
    return new NSFetchState(consumer, context);
  }

  fetch(fetchState, callback) {
    var uri = fetchState.getUri();
    fetchState.submitTime = android.os.SystemClock.elapsedRealtime();

    try {
      http.request({
        url: uri.toString(),
        method: "GET",
        headers: {
          "User-Agent": "NativeScript"
        }
      })
      .then((response) => {   
        if (response.statusCode >= 200 && response.statusCode <= 300) {
          console.log("Response length: " + response.content.raw.size() + " code : " + response.statusCode);
          var inputStream = new java.io.ByteArrayInputStream(response.content.raw.toByteArray());          
          callback.onResponse(inputStream, response.content.raw.size());
        } else {
          callback.onFailure(new java.io.IOException("Request failed"));
        }
      })
      .catch((e) => {
        callback.onFailure(new java.io.IOException("Unknown error"))
      });
    } catch (e)
    {
      callback.onFailure(new java.io.IOException("Unknown error"));
    }
  }

  onFetchCompletion(fetchState, byteSize) {
    fetchState.fetchCompleteTime = android.os.SystemClock.elapsedRealtime();
  }

  getExtraMap() {
    return null;
  }
}