sdk/src/com/socialize/facebook/Facebook.java
private boolean startSingleSignOn(Activity activity, String applicationId,
            String[] permissions, int activityCode) {
        boolean didSucceed = true;
        Intent intent = new Intent();

        intent.setClassName("com.facebook.katana",
                "com.facebook.katana.ProxyAuth");
        intent.putExtra("client_id", applicationId);
        if (permissions.length > 0) {
            intent.putExtra("scope", TextUtils.join(",", permissions));
        }

        // Verify that the application whose package name is
        // com.facebook.katana.ProxyAuth
        // has the expected FB app signature.
        if (!validateActivityIntent(activity, intent)) {
            return false;
        }

        mAuthActivity = activity;
        mAuthPermissions = permissions;
        mAuthActivityCode = activityCode;
        try {
            activity.startActivityForResult(intent, activityCode);
        } catch (ActivityNotFoundException e) {
            didSucceed = false;
        }

        return didSucceed;
    }
private boolean startSingleSignOn(Activity activity, String applicationId,
            String[] permissions, int activityCode) {
        boolean didSucceed = true;
        Intent intent = new Intent();

        intent.setClassName("com.facebook.katana",
                "com.facebook.katana.ProxyAuth");
        intent.putExtra("client_id", applicationId);
        if (permissions.length > 0) {
            intent.putExtra("scope", TextUtils.join(",", permissions));
        }

        // Verify that the application whose package name is
        // com.facebook.katana.ProxyAuth
        // has the expected FB app signature.
        if (!validateActivityIntent(activity, intent)) {
            return false;
        }

        mAuthActivity = activity;
        mAuthPermissions = permissions;
        mAuthActivityCode = activityCode;
        try {
            activity.startActivityForResult(intent, activityCode);
        } catch (ActivityNotFoundException e) {
            didSucceed = false;
        }

        return didSucceed;
    }
Internal method to handle single sign-on backend for authorize().

@param activity
The Android Activity that will parent the ProxyAuth Activity.
@param applicationId
The Facebook application identifier.
@param permissions
A list of permissions required for this application. If you do
not require any permissions, pass an empty String array.
@param activityCode
Activity code to uniquely identify the result Intent in the
callback.