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Android Components > Service > Firefox Accounts (FxA)

A library for integrating with Firefox Accounts.

Motivation

The Firefox Accounts Android Component provides a way for Android applications to do the following:

  • Obtain OAuth tokens that can be used to access the user's data in Mozilla-hosted services like Firefox Sync
  • Fetch client-side scoped keys needed for end-to-end encryption of that data
  • Fetch a user's profile to personalize the application

See also the sample app for help with integrating this component into your application.

Usage

Setting up the dependency

Use Gradle to download the library from maven.mozilla.org (Setup repository):

implementation "org.mozilla.components:service-firefox-accounts:{latest-version}"

Start coding

First you need some OAuth information. Generate a client_id, redirectUrl and find out the scopes for your application. See Firefox Account documentation for that.

Once you have the OAuth info, you can start adding FxAClient to your Android project. As part of the OAuth flow your application will be opening up a WebView or a Custom Tab. Currently the SDK does not provide the WebView, you have to write it yourself.

Create a global account object:

var account: FirefoxAccount? = null

You will need to save state for FxA in your app, this example just uses SharedPreferences. We suggest using the Android Keystore for this data. Define variables to help save state for FxA:

val STATE_PREFS_KEY = "fxaAppState"
val STATE_KEY = "fxaState"

Then you can write the following:

account = getAuthenticatedAccount()
if (account == null) {
  // Start authentication flow
  val config = Config(CONFIG_URL, CLIENT_ID, REDIRECT_URL)
  // Some helpers such as Config.release(CLIENT_ID, REDIRECT_URL)
  // are also provided for well-known Firefox Accounts servers.
  account = FirefoxAccount(config)
}

fun getAuthenticatedAccount(): FirefoxAccount? {
    val savedJSON = getSharedPreferences(FXA_STATE_PREFS_KEY, Context.MODE_PRIVATE).getString(FXA_STATE_KEY, "")
    return savedJSON?.let {
        try {
            FirefoxAccount.fromJSONString(it)
        } catch (e: FxaException) {
            null
        }
    } ?: null
}

The code above checks if you have some existing state for FxA, otherwise it configures it. All asynchronous methods on FirefoxAccount are executed on Dispatchers.IO's dedicated thread pool. They return Deferred which is Kotlin's non-blocking cancellable Future type.

Once the configuration is available and an account instance was created, the authentication flow can be started:

launch {
    val url = account.beginOAuthFlow(scopes, wantsKeys).await()
    openWebView(url)
}

When spawning the WebView, be sure to override the OnPageStarted function to intercept the redirect url and fetch the code + state parameters:

override fun onPageStarted(view: WebView?, url: String?, favicon: Bitmap?) {
    if (url != null && url.startsWith(redirectUrl)) {
        val uri = Uri.parse(url)
        val mCode = uri.getQueryParameter("code")
        val mState = uri.getQueryParameter("state")
        if (mCode != null && mState != null) {
            // Pass the code and state parameters back to your main activity
            listener?.onLoginComplete(mCode, mState, this@LoginFragment)
        }
    }

    super.onPageStarted(view, url, favicon)
}

Finally, complete the OAuth flow, retrieve the profile information, then save your login state once you've gotten valid profile information:

launch {
    // Complete authentication flow    
    account.completeOAuthFlow(code, state).await()

    // Display profile information
    val profile = account.getProfile().await()    
    txtView.txt = profile.displayName

    // Persist login state    
    val json = account.toJSONString()
    getSharedPreferences(FXA_STATE_PREFS_KEY, Context.MODE_PRIVATE).edit()
        .putString(FXA_STATE_KEY, json).apply()
}

License

This Source Code Form is subject to the terms of the Mozilla Public
License, v. 2.0. If a copy of the MPL was not distributed with this
file, You can obtain one at http://mozilla.org/MPL/2.0/
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