Dart

Download Binary File to In-Memory Bytes

See more Google Drive Examples

This example demonstrates how to download the binary content of a file from Google Drive directly into local memory. Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // It requires the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  // This example uses a previously obtained access token having permission for the 
  // Google Drive scope.

  final gAuth = CkAuthGoogle();
  gAuth.accessToken = 'GOOGLE-DRIVE-ACCESS-TOKEN';

  final rest = CkRest();

  // Connect using TLS.
  // A single REST object, once connected, can be used for many Google Drive REST API calls.
  // The auto-reconnect indicates that if the already-established HTTPS connection is closed,
  // then it will be automatically re-established as needed.
  final bAutoReconnect = true;
  rest.connect('www.googleapis.com', 443, true, bAutoReconnect);

  // Provide the authentication credentials (i.e. the access token)
  rest.setAuthGoogle(gAuth);

  // ------------------------------------------------------------------------------
  // To download a file, we must know the file ID.
  // In a previous example (see Build Local Metadata Cache
  // we built a local cache to make it easy to lookup file IDs given a file path.
  // Let's say we want to download "testFolder/abc/123/penguins.jpg".
  // First we lookup the fileId in the cache.  With the fileId, we can download the file.
  final gdCache = CkCache();
  gdCache.level = 0;
  gdCache.addRoot('C:/ckCache/googleDrive');

  final String fileId;
  try {
    fileId = gdCache.fetchText('testFolder/abc/123/penguins.jpg');
  } on ChilkatException {
    print('Filepath not found in cache.');
    return;
  }

  // We need to send a GET request like this:
  // GET https://www.googleapis.com/drive/v3/files/fileId?alt=media
  // The fileId is part of the path.
  final sbPath = CkStringBuilder();
  sbPath.append('/drive/v3/files/');
  sbPath.append(fileId);
  rest.addQueryParam('alt', 'media');

  // To download to memory, we'll send the request in one call, then receive
  // the response header, and then the response body.
  // If the response header indicates failure or an unexpected response, then the
  // body is not the data we desire.

  // First send the HTTP request.
  try {
    rest.sendReqNoBody('GET', sbPath.getAsString());
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Get the response header.
  final statusCode = rest.readResponseHeader();
  if (statusCode != 200) {
    print('response status code = ${rest.responseStatusCode}');
    print('response status text = ${rest.responseStatusText}');
    print('response header: ${rest.responseHeader}');

    // Read the response body (which should be error text or HTML)
    try {
      final errResponseBody = rest.readRespBodyString();
      print('response body: $errResponseBody');
    } on ChilkatException {
      // rest.readRespBodyString() failed; continue anyway.
    }

    return;
  }

  // Read the response body, which should contain the file data.
  final jpgBytes = rest.readRespBodyBinary();
  if (!rest.lastMethodSuccess) {
    print(rest.lastErrorText);
    return;
  }

  // Save jpgBytes to a file so we can examine the file to verify that it worked.
  final fac = CkFileAccess();
  fac.writeEntireFile('qa_output/penguins_out.jpg', jpgBytes);

  print('File downloaded.');
}