Implementing Facebook

This guide discusses how to implement common Facebook tasks and processes in your Corona app.

Note

If you just need to perform basic tasks like posting a Facebook user's status update, the Social Popup plugin (Android) or the Activity Popup plugin (iOS) is the easiest method. However, if you need to perform more advanced tasks or create a more complete integration of Facebook within an app, please proceed with the instructions in this guide.

Including the Plugin

Important

To begin using the Facebook plugin, you must first register as a Facebook developer and configure your app in the Facebook Developer Portal. Please see the Facebook Portal Setup guide for assistance with this process — it requires some very precise information and it's imporant to follow every step carefully.

As with all Corona plugins, you must include the Facebook plugin within the plugins table of build.settings:

settings = {

    plugins =
    {
        ["plugin.facebook.v4a"] =
        {
            publisherId = "com.coronalabs"
        },
    },
}

Then, you must require() the plugin in any module where you need to access its methods and properties:

local facebook = require( "plugin.facebook.v4a" )

User Experience

The user experience for different components of the Facebook plugin vary depending on the presence of a native Facebook app. In many cases, if a native Facebook app is on the device, operations like logging in or presenting the Share Dialog may try to redirect the heavy lifting to the Facebook app. The cases where a redirect to the Facebook app occurs has changed a lot throughout the history of the Facebook SDK, so your app should be prepared for a Facebook operation to suspend and then resume your app after the Facebook operation completes.

Note

On Android, a native Facebook app could be the standard Facebook app or the Facebook Lite app. Each native app may result in a different user experience.

Login Considerations

Before the Facebook Graph API can be used, the app must successfully log in to Facebook. Then, it must gather the required authentication information and the specific permissions required by the app.

  • If the mobile device has a native Facebook app installed, your app will launch it and ask for the necessary permissions. When this happens, your app is temporarily suspended and placed into the background while the native Facebook app runs. When complete (the user has either granted permission or has cancelled), the Facebook app will try to restore your app and put it in the foreground, bringing with it the information about your permission request.

  • If the mobile device does not have a native Facebook app installed, it will use Facebook's website to log in. This happens through a web view, so your app is never actually suspended to the background. In general, the web-based login method is very reliable, but you (the developer) cannot control if your app's user does or doesn't have the native Facebook app installed. Therefore, you must support both methods.

  • Facebook encourages developers to delay logging in to Facebook until necessary, and at the user's choosing. Automatically logging the user in within main.lua is discouraged.

Notes
  • The Facebook v4 plugin uses a SFSafariViewController to log in on iOS 9 and above.

  • On low-end Android devices, it's more likely that a Facebook app will fail to restore your app when used for logging in. This may be caused by the Android OS terminating your app because it's running low on memory.

iOS Requirements

If your app is for iOS, you must include specific aspects within your build.settings file to ensure that the native Facebook app functions properly. Please see the plugin documentation for details.

Note

If you want to publish multiple iOS apps that use the same Facebook App ID, for example a trial version and full version of the same app, this can be accomplished via a FacebookUrlSchemeSuffix key in the iphoneplist table of build.settings, along with other minor edits as noted below. See Facebook's iOS SDK FAQ for more info.

settings = {

    iphone =
    {
        plist =
        {
            FacebookUrlSchemeSuffix = "suffix",
            ["URL types"] =
            {
                item =
                {
                    ["URL Schemes"] = { ["Item 0"] = "fbXXXXXXXXXXsuffix" },  -- Replace XXXXXXXXXX with your Facebook App ID
                },
            },

            MinimumOSVersion = "8.0",
            UIApplicationExitsOnSuspend = false,
            FacebookAppID = "XXXXXXXXXX",  -- Replace XXXXXXXXXX with your Facebook App ID
            CFBundleURLTypes =
            {
                { CFBundleURLSchemes = { "fbXXXXXXXXXXsuffix", } }  -- Replace XXXXXXXXXX with your Facebook App ID
            },
        }
    }
}

Android Requirements

On Android, Facebook uses your app Package Name, for example com.yoursite.yourapp. To ensure that the native Facebook app functions properly, you must provide Facebook's portal with two important pieces of information — these include the Class Name of com.ansca.corona.CoronaActivity and the Key Hash gathered from the keystore you built your app with. These are discussed in the Facebook Portal Setup guide.

Furthermore, the Facebook v4 plugin needs to know about your unique Facebook App ID (facebookAppId):

settings =
{
    android =
    {
        facebookAppId = "XXXXXXXXXX",  -- Replace XXXXXXXXXX with your Facebook App ID
    },
}

Initialization

The Facebook plugin begins initializing when you require the plugin the first time. Depending on network conditions, this could take several seconds. In your main.lua file, you can create a listener function to notify you when initialization is complete and reference that function within facebook.init():

local function facebookListener( event )

    if ( "fbinit" == event.name ) then

        print( "Facebook initialized" )

        -- Initialization complete; call "facebook.publishInstall()"
        facebook.publishInstall()

    elseif ( "fbconnect" == event.name ) then

        if ( "session" == event.type ) then
            -- Handle login event and try to share the link again if needed
        elseif ( "dialog" == event.type ) then
            -- Handle dialog event
        end
    end
end

-- Set the "fbinit" listener to be triggered when initialization is complete
facebook.init( facebookListener )
Note

This listener function can be the same function that you'll use for Facebook requests, dialogs, and logging in, but if you prefer to use a different function for those aspects, simply specify that function reference within facebook.login().

Logging In/Out

Logging in to Facebook is accomplished through facebook.login(). If you didn't already set a listener function via facebook.init() or facebook.setFBConnectListener(), you can set it by passing the listener reference as the first argument to facebook.login().

Secondly, via facebook.login(), you can request an array of permissions. Both read-only and publishable permissions can be specified, with some caveats which are outlined in the facebook.login() documentation.

Putting these two aspects together, a login call might look like this:

facebook.login( facebookListener, { "email", "user_birthday" } )

Logging the user out is even easier. To disconnect the app from Facebook's services, simply call facebook.logout(). Note, however, that this does not log the device's user out of Facebook entirely — if the user is logged into Facebook through a native Facebook app or the device's browser, they will remain logged in via those means.

facebook.logout()

Facebook Listener

All Facebook requests will call the listener function you passed to facebook.init(), facebook.login(), or set via facebook.setFBConnectListener(). For example:

local function facebookListener( event )

    if ( "fbinit" == event.name ) then

        print( "Facebook initialized" )

    elseif ( "fbconnect" == event.name ) then

        -- Event type of "session" covers various login/logout events
        if ( "session" == event.type ) then
            -- Handle login event and try to share the link again if needed

        -- Event.type of "request" handles calls to various Graph API functionalities
        elseif ( "request" == event.type ) then
            if not event.isError then
                -- Process response data here
            end

        -- Event.type of "dialog" indicates standard popup boxes that can be displayed
        elseif ( "dialog" == event.type ) then
            -- Handle dialog event
        end
    end
end

Making Requests

To make different Graph API requests, use the facebook.request() call. By default, this call makes HTTP GET requests to Facebook. If you wish to use another method, set the second parameter (httpMethod) to a value outlined in the facebook.request() documentation.

facebook.request( path [, httpMethod] [, params] )

The only required parameter is path which is based on the Facebook Graph API path. This will typically be the REST object that you want to access. For example, the following command will retrieve the latest posts from the user's account feed:

facebook.request( "me/feed" )

Some Graph API calls also require parameters to be passed to facebook.request(). This is done via the optional params table, for instance:

facebook.request( "me/feed", "POST", { message="Hello Facebook" } )

To upload a photo to your Facebook photo album, the params table can be filled in based on the standard Graph API parameters found here:

local attachment = {
    caption = "Corona icon file",
    url = "http://www.coronalabs.com/links/demo/Corona90x90.png",
}
facebook.request( "me/photos", "POST", attachment )

When facebook.request() calls complete, your Facebook listener function will be called with an event.type of "request". Facebook generally returns your data as event.response, a JSON-encoded table of data. To convert this into a Lua table, call json.decode(), remembering to first require() the JSON library.

To learn more about which requests, parameters, and data Facebook provides, please see the Facebook Graph API documentation.

Using Dialogs

Facebook requires that some tasks be done through dialogs they control. To use a dialog, call the facebook.showDialog() function:

facebook.showDialog( action, params )

For this call, the action parameter specifies the dialog type:

facebook.showDialog( "link",
{
    name = "Implementing Facebook with Corona",
    link = "https://docs.coronalabs.com/guide/social/usingFacebook/index.html"
})
facebook.showDialog( "requests",
{
    message = "You should download this game!",
    filter = "APP_NON_USERS"
})

Observe how the params argument is a table of key/value pairs which gets passed to the Facebook API call. The keys that you pass correspond to specific options which are available for the dialog. See the facebook.showDialog() documentation for details.

Published Installs

While not part of the Graph API, Published Installs is a way for apps to participate in Facebook's mobile ad campaign which can report (to Facebook) that the app has been installed. This process is simple and there is no callback information or need to call facebook.login() — just call facebook.publishInstall():

facebook.publishInstall()