java.lang.IllegalStateException：GoogleApiClient尚未连接

我试图通过使用Google Play游戏服务为我的游戏添加成就。我的游戏中负责提供成就的活动已经扩展了BaseGameActivity，并且在必须提供成就时调用beginUserInitiatedSignIn，因此用户必须登录，但在我解锁用户成就时，我保留得到java.lang.IllegalStateException：GoogleApiClient尚未连接。谁能告诉我我做错了什么？这里是负责解锁成就的代码（它在BaseGameUtils中扩展BaseGameActivity的类中）：

I'm trying to add achievements to my game by using google play game services. The activity in my game that is responsible for giving the achievement already extends BaseGameActivity and it calls the beginUserInitiatedSignIn when it has to give the achievement, so the user must be signing in, but at the time I unlock the achievement for the user, I keep getting "java.lang.IllegalStateException: GoogleApiClient is not connected yet". Can anyone tell me what I am doing wrong? Here's the code responsible for unlocking the achievement(it's in the class that extends BaseGameActivity, from BaseGameUtils):

private void darConquistaDerrubouArvore(int numeroDeAcertos) {
     // start the asynchronous sign in flow
    mSignInClicked = true;
    mGoogleApiClient.connect();
    if(numeroDeAcertos <= 40)
    {
        try
        {
                beginUserInitiatedSignIn();
                Games.Achievements.unlock(gameHelper.getApiClient(), "CgkIs_27xcoSEAIQAQ");
                Log.i("TelaModoCasual", "usuário não está logado");
                this.onSignInFailed();

        }
        catch(Exception exc)
        {
            exc.printStackTrace();
            this.onSignInFailed();
        }
    }

}