index.js

import { NativeModules, Platform } from 'react-native';

const resolveAssetSource = require('react-native/Libraries/Image/resolveAssetSource');

const callbacks = {};

const DocumentPicker = {
  show: (options, callback) => {
    if (options.customActions) {
      options.customActions = options.customActions.map(item => {
        callbacks[item.key] = item.action;
        let image = null;
        if (item.image) {
          image = resolveAssetSource(item.image);
        }
        return {
          ...item,
          isCustomAction: true,
          image
        };
      });
    }

    NativeModules.RNDocumentPicker.show(options, (err, res) => {
      if (res && res.isCustomAction) {
        callbacks[res.key](res, newRes => callback(null, newRes));
      } else {
        callback(err, res);
      }
    });
  }
};

/**
 * Android requires mime types, iOS is a bit more complicated:
 *
 * @see https://developer.apple.com/library/ios/documentation/Miscellaneous/Reference/UTIRef/Articles/System-DeclaredUniformTypeIdentifiers.html
 */
class DocumentPickerUtil {
  static allFiles() {
    return Platform.OS === 'android' ? '*/*' : 'public.content';
  }

  static images() {
    return Platform.OS === 'android' ? 'image/*' : 'public.image';
  }

  static plainText() {
    return Platform.OS === 'android' ? 'text/plain' : 'public.plain-text';
  }

  static audio() {
    return Platform.OS === 'android' ? 'audio/*' : 'public.audio';
  }

  static video() {
    return Platform.OS === 'android' ? 'video/*' : 'public.video';
  }

  static pdf() {
    return Platform.OS === 'android' ? 'application/pdf' : 'com.adobe.pdf';
  }
}

module.exports = { DocumentPickerUtil, DocumentPicker };