Access portal content

Portals such as ArcGIS Online and ArcGIS Enterprise can store many types of data. Perhaps the type most commonly used by apps is a web map—a JSON description of the data in a map, along with other display and behavioral properties. Other types include tile packages, feature collections, and services. Some types, such as globe documents and map templates, may only be relevant to desktop systems. Although you can access these types of data using the API, you may not be able to use them on a mobile device. Some types of data can be taken offline.

PortalItem represents an individual item stored on a portal. Each item includes the following:

  • Metadata, such as a unique identifier (ID), title, summary, description, thumbnail image, and tags
  • Binary or text-based data—for example, the JSON that defines a web map or a feature collection, or a URL pointing to a map service, or the binary data of a tile package or shapefile

Web page showing properties of a portal item including the item ID

Apps use portal items in different ways. They may show a user a range of items from a portal by combining the title, thumbnail image, and other metadata. This approach is often used to allow users to browse web maps, basemaps, or map services, and identify the item to work with. If a user selects an item, the app may then download the data stored in the portal item, for example, by opening and displaying a web map in a map, or downloading a tile package. Apps sometimes access items directly by ID if a specific item should always be used.

Your app can also add new portal items and alter existing items by adding comments and ratings, updating item information, sharing, unsharing, and deleting them, as long as the authenticated user has access permissions to do so.

You access the content of a portal item differently depending on its type. Below you can find examples of accessing different types of portal items. For more information on connecting to a portal, see Access the ArcGIS platform.

Display a web map by ID

A very common task is to display a web map from a portal. Web maps are stored as portal items and can be opened by using the ID of the item, along with the URL of the portal. If the map is not public (for example, if it is shared only with a specific group), you also need to pass in valid credentials with permission to view the map. See Access the ArcGIS platform for more information on accessing secured items.

The code below sets a map into a map view by creating a portal item from the ID of a known web map portal item. This assumes that the portal item is publicly shared, as no credentials are used.

Portal* portal = new Portal(this);


PortalItem* portalItem = new PortalItem(portal, "01f052c8995e4b9e889d73c3e210ebe3", this);


Map* webMap = new Map(portalItem, this);


mapView->setMap(webMap);

There are different ways to display a map from a web map.

Open a map

You can create a map from a web map portal item without needing to display it immediately. From this, you could find out more about the contents of the map before displaying it if required—for example, getting the basemap, operational layers, bookmarks, and initial extent. To do this, load the map before setting it into a map view—see Loadable pattern for more information.

The following example gets a web map portal item, finds one of its bookmarks, and obtains its viewpoint.

Portal* portal = new Portal(this);
PortalItem* portalItem = new PortalItem(portal, "01f052c8995e4b9e889d73c3e210ebe3", this);
Map* webMap = new Map(portalItem, this);


connect(webMap, &Map::doneLoading, this, [webMap, mapView](Error loadError)
{
  if (!loadError.isEmpty())
    return;


  BookmarkListModel* bookmarks = webMap->bookmarks();
  if (!bookmarks)
    return;


  for( int i = 0; i < bookmarks->rowCount(); ++i)
  {
    Bookmark* bm = bookmarks->at(i);
    if (bm->name().compare("Chula Vista", Qt::CaseInsensitive) == 0)
    {
      mapView->setViewpointAndWait(bm->viewpoint());
      return;
    }
  }


  mapView->setMap(webMap); // if no bookmark was found just set the webmap
});


webMap->load();
mapView.map = webmapFromItem;

Note:

Remember that you must also specify credentials for a valid user with access to the item, if the item is not publicly shared.

Find information about any portal item by ID

You can use the ID of any item stored in a portal to access it, and also to find its fields—properties such as its title, description, thumbnail image, owner, and any ratings or comments added by portal users. You can also find out the type of data it contains.

// connect to ArcGIS online
Portal* portal = new Portal(parent);


// find info about a PortalItem by ID
PortalItem* portalItem = new PortalItem(portal, itemId, parent);


QString title;
QDateTime createdOn;
int numViews = -1;


connect(portalItem, &PortalItem::doneLoading, this, [portalItem, &title, &createdOn, &numViews](Error error)
{
  if (!error.isEmpty())
    return;


  title = portalItem->title();
  createdOn = portalItem->created();
  numViews = portalItem->viewCount();


  qDebug() << QString("%1 was created on %2 and has been viewed %3 times")
              .arg(title).arg(createdOn.toString()).arg(numViews);
});


portalItem->load();

Note:

The thumbnail of a portal item, along with the ratings and data, is not returned from the portal when you initially load the item, in order to reduce the network traffic and memory requirements. See the section below on how to access these properties.

Fetch thumbnails of items

When you create a portal item object, not all information associated with it is immediately returned. This allows you to work with the item using a minimum amount of memory and delay fetching the larger pieces of data unless, or until, you really need them. Information you need to fetch, if required, includes thumbnail images, ratings and comments, item data, group memberships, and user folder contents.

The following example shows how to get the thumbnail image of an item, assign it to an Image component and print its dimensions

// fetch the (already loaded) portaltem's thumbnail
QSize imgSize;
connect(portalItem, &PortalItem::fetchThumbnailCompleted, this, [portalItem, &imgSize](bool success)
{
  if (!success)
    return;


  QImage thumbnailImg = portalItem->thumbnail();
  if (thumbnailImg.isNull())
    return;


  imgSize = thumbnailImg.size();
  qDebug() << QString("thumbnail image is %1 x %2 pixels").arg(imgSize.width()).arg(imgSize.height());
});


connect(portalItem, &Object::errorOccurred, this, [=](Error error)
{
  qDebug() << error.message() << error.additionalMessage();
});


portalItem->fetchThumbnail();

The same applies to the thumbnails of other classes, like users, groups, and organizations. Use fetchThumbnail on PortalItem, PortalGroup, and PortalUser. Additionally, PortalInfo provides thumbnailUrl (for the organization) and portalThumbnailUrl.

Access item data

Portal items that represent files, such as tile packages, images, documents, PDF files, and so on, can be opened, downloaded, and then stored or opened in your app or in another app. As in the previous example, you will need to specifically fetch the data of a portal item after you create it. Use the fetchData method to do this.

The following example gets the data for an image (.jpg) stored in the portal and saves it to a local file.

// check the item type to make sure it is an Image
if (portalItem->type() != PortalItemType::Image)
  return;


connect(portalItem, &PortalItem::fetchDataCompleted, this, [portalItem, filename](bool success)
{
  if (!success)
    return;


  QImage img(filename);
  qDebug() << "Image size:" << img.size();
});


// fetch the (already loaded) portaltem's data into the temporary file
portalItem->fetchData(filename);

Fetch a user's content

Many apps present a list of maps or other items that belong to the current user. Users can create folders within their portal accounts to help organize their work. Apps should respect the user's view of their content and present the list of folders to the user, allowing the user to choose which folder to look at in detail.

It's easy to get all the portal items owned by the authenticated user (that represent the content and services items created by that user). PortalUser represents information about a user, and from this you can retrieve all of the items and folders (represented by PortalFolder) owned by the user.

The code below iterates all of the items belonging to the authenticated user of the portal that are in the default (or root) user folder, using the PortalItemsListModel and PortalFolderListModel returned from PortalUser.fetchContent. Next, each folder and its contents are iterated, using fetchContentInFolder.

connect(&portalUser, &PortalUser::fetchContentCompleted, this, [&portalUser, &folderTitles](bool success)
{
  if (!success)
    return;


  PortalItemListModel* items = portalUser.items();
  Q_CHECK_PTR(items);


  // report the title of each portalItem
  for(int i = 0; i < items->size(); ++i)
  {
    PortalItem* item = items->at(i);
    if (!item)
      continue;


    QString folderTitle = folderTitles[item->folderId()];
    qDebug() << folderTitle << item->title() << item->typeName() << item->itemId();
  }
});


// fetch content for each folder
for (QString folderId: folderTitles.keys())
{
  portalUser.fetchContentInFolder(folderId);
}

Note:

As seen in the code above, user content is another example of information that you must explicitly fetch, like portal item thumbnails and content.

To get items shared with the current user, or items owned by a different user, you need to search for content.

List the groups a user belongs to

Groups can be configured in different ways—some groups are open to all users; some are only accessible by invitation; and for others, any user can request to join. The groups to which the authenticated user belongs can be accessed, and for any group, the identities of the members can be found.

The PortalGroup class represents a group. You can get a list of the groups a user belongs to by calling the PortalUser. Use groups method to retrieve the users in each group—after that, you can get the members from the PortalGroup objects contained in the PortalGroupListModel.

for (int i = 0; i < groups->size(); ++i)
{
  PortalGroup* group = groups->at(i);
  Q_CHECK_PTR(group);


  connect(group, &PortalGroup::fetchGroupUsersCompleted, this, [group, &portalUser](bool succes)
  {
    if (!succes)
      return;


    const int numUsers = group->users().size();
    const int numAdmin = group->admins().size();
    const QString role = group->admins().contains(portalUser.username()) ? "admin" : "user";


    qDebug() << QString("Your role in '%1' is %2").arg(group->title()).arg(role);
    qDebug() << QString("It has %1 users and %2 admins").arg(QString::number(numUsers)).arg(QString::number(numAdmin));
  });


  group->fetchGroupUsers();
}

From the group, you can find out if membership is by invitation only by examining the property, and if the user can share items with the group using the isInvitationOnly property.