Flutter 集成Jmessage 获取好友的appkey

你好，我是个前端小菜鸟，最近在想写一个flutter的及时聊天，在sdk中

 private void addFrieds(String name,String appkey,String reason,final Callback callback){
        ContactManager.sendInvitationRequest(name, appkey, reason, new BasicCallback() {
            @Override
            public void gotResult(int i, String s) {
                if (i == 0) {
                   callback.callback("申请成功");
                }else {
                    Log.i("AddFriendActivity", "ContactManager.sendInvitationRequest" + ", responseCode = " + i + " ; Desc = " + s);
                    callback.callback("申请失败");
                }
            }
        });

    }

这是我写的 methodCall 方法但是有个问题是我应该怎么获取好友的appkey呢？