{"id":1031,"date":"2013-06-18T01:00:00","date_gmt":"2013-06-17T23:00:00","guid":{"rendered":"https:\/\/www.fussylogic.co.uk\/blog\/?p=1031"},"modified":"2014-10-10T12:08:26","modified_gmt":"2014-10-10T11:08:26","slug":"android-authenticators-i","status":"publish","type":"post","link":"https:\/\/www.fussylogic.co.uk\/blog\/?p=1031","title":{"rendered":"Android Authenticators I"},"content":{"rendered":"

I found a blog that gave an example<\/a> of how to make a custom authenticator for Android. I didn\u00e2\u20ac\u2122t find it very clear, so this article covers my understanding that I\u00e2\u20ac\u2122ve pulled this together from the example<\/a> given by that blog author, and from the Android documentation, and then building something that works.<\/p>\n

To make a custom account type<\/a> available in Android\u00e2\u20ac\u2122s account page, your app must supply an authenticator <service><\/code> in your AndroidManifest.xml<\/code> that includes the following intent filter:<\/p>\n

    <intent-filter><\/span>\n        <action<\/span> android:name=<\/span>"android.accounts.AccountAuthenticator"<\/span> \/><\/span>\n    <\/intent-filter><\/span><\/code><\/pre>\n
Which in turn will need the following permission:<\/p>\n
    <uses-permission<\/span> android:name=<\/span>"android.permission.AUTHENTICATE_ACCOUNTS"<\/span> \/><\/span><\/code><\/pre>\n
When the OS finds support for this Intent<\/code> in an app, it will then go looking for information about how it should display it on its settings screen. That\u00e2\u20ac\u2122s done by including the following in that same <service><\/code> section:<\/p>\n
    <meta-data<\/span>\n        android:name=<\/span>"android.accounts.AccountAuthenticator"<\/span>\n        android:resource=<\/span>"@xml\/authenticator"<\/span> \/><\/span><\/code><\/pre>\n
The actual account description is then in the XML resource file referenced in this meta-data<\/code> section, res\/xml\/authenticator.xml<\/code> in this case. That file contains the actual help that the OS settings module needs:<\/p>\n
    <?xml<\/span> version="1.0" encoding="utf-8"?><\/span>\n    <account-authenticator<\/span> xmlns:android=<\/span>"http:\/\/schemas.android.com\/apk\/res\/android"<\/span>\n        android:accountPreferences=<\/span>"@xml\/authenticator_preferences"<\/span>\n        android:accountType=<\/span>"@string\/authenticator_account_type"<\/span>\n        android:label=<\/span>"@string\/authenticator_label"<\/span>\n        android:icon=<\/span>"@drawable\/ic_launcher"<\/span>\n        android:smallIcon=<\/span>"@drawable\/ic_launcher"<\/span> \/><\/span><\/code><\/pre>\n
The most important setting above is the android:accountType<\/code> attribute. That\u00e2\u20ac\u2122s the unique name that causes your interface rather than any other (Google, Facebook, or Twitter, say) to be used when the user picks this type when they click \u00e2\u20ac\u0153Add Account\u00e2\u20ac\u009d \u00e2\u20ac\u201c it\u00e2\u20ac\u2122s best defined as a resource reference because you\u00e2\u20ac\u2122ll want it available in the code later.<\/p>\n
Note that we\u00e2\u20ac\u2122ve also referred to another resource, res\/xml\/authenticator_preferences.xml<\/code>. This file defines the user interface for configuring the authentication service as a whole \u00e2\u20ac\u201c this is not the same thing as configuring an individual account, this is settings for the account type.<\/p>\n
    <PreferenceScreen<\/span> xmlns:android=<\/span>"http:\/\/schemas.android.com\/apk\/res\/android"<\/span> ><\/span>\n        <PreferenceCategory<\/span> android:title=<\/span>"FussyLogic Authenticator"<\/span> \/><\/span>\n        <CheckBoxPreference<\/span>\n            android:key=<\/span>"isDebug"<\/span>\n            android:summary=<\/span>"Connecting to a debug server instead of production server"<\/span>\n            android:title=<\/span>"Use debug server"<\/span> \/><\/span>\n        <SwitchPreference<\/span>\n            android:key=<\/span>"logsVerbose"<\/span>\n            android:summary=<\/span>"Increase logging verbosity for LogCat output"<\/span>\n            android:title=<\/span>"Debug Logs"<\/span> \/><\/span>\n    <\/PreferenceScreen><\/span><\/code><\/pre>\n
These are just examples, you could use whatever you want. I\u00e2\u20ac\u2122m missing one piece of information however \u00e2\u20ac\u201c how you access these settings. I\u00e2\u20ac\u2122d be delighted if someone more knowledgeable can tell me, as the Android documentation is lacking. It certainly seems possible, the Skype app does it.<\/p>\n
    package uk.co.fussylogic.accounttester;<\/span>\n    \n    import android.app.Service;<\/span>\n    import android.content.Intent;<\/span>\n    import android.os.IBinder;<\/span>\n    \n    public<\/span> class<\/span> AuthenticatorService extends<\/span> Service {\n        @Override<\/span>\n        public<\/span> IBinder onBind<\/span>(Intent intent) {\n            if<\/span> (intent.getAction<\/span>().equals<\/span>(\n                    android.accounts<\/span>.AccountManager<\/span>.ACTION_AUTHENTICATOR_INTENT<\/span>))\n                return<\/span> null<\/span>;\n            \n            AbstractAccountAuthenticator authenticator =\n                new<\/span> FussyLogicAuthenticator<\/span>(this<\/span>);\n            return<\/span> authenticator.getIBinder<\/span>();\n        }\n\n        \/\/ --------------------------------<\/span>\n\n        public<\/span> class<\/span> FussyLogicAuthenticator extends<\/span> AbstractAccountAuthenticator {\n            protected<\/span> Context mContext;\n\n            public<\/span> FussyLogicAuthenticator<\/span>(Context context) {\n                super<\/span>(context);\n                this<\/span>.mContext<\/span> = context;\n            }\n\n            \/\/ ... implement abstract methods ...<\/span>\n        };\n    }<\/code><\/pre>\n
Android calls onBind()<\/code> in a Service<\/code> when another component wants to connect to it for a dialogue (this is in contrast to onStartCommand()<\/code>, which is used when the service only undertakes actions, it doesn\u00e2\u20ac\u2122t return answers). The IBinder<\/code> class defines the RPC interface \u00e2\u20ac\u201c that is, it describes the functions that may be called by the binding client. This is the case for all bound services. In the particular case of an authenticator service, the IBinder<\/code> class must be one that describes the calls that the Android accounts system requires. Fortunately, we needn\u00e2\u20ac\u2122t worry about creating an appropriate IBinder<\/code>, Android can provide an appropriate IBinder<\/code> using its AbstractAccountAuthenticator<\/code> class, which you can see above as the call to FussyLogicAuthenticator.getIBinder()<\/code> \u00e2\u20ac\u201c that is a child class of AbstractAccountAuthenticator<\/code>, which, being abstract, we<\/em> have to subclass to provide a concrete implementation, FussyLogicAuthenticator<\/code>. There are a number of abstract methods that we have to implement, that the AbstractAccountAuthenticator.getIBinder()<\/code> will have described. For the most part, the pattern for implementing these abstract methods is the same:<\/p>\n
The presence of the Service<\/code>, and the above settings are enough to make Android offer your authenticator when the user adds an account. The authenticator Service<\/code><\/a> code itself is short:<\/p>\n