1. 获取按钮并设置点击事件

using UnityEngine.UI;

var button = transform.Find("Btn_login").gameObject.GetComponent<Button>();
if (button != null) {
    button.onClick.RemoveAllListeners();
    button.onClick.AddListener(
        delegate {
            this.onLogin(button);
        }
    );
}

2. JSON解析

using SimpleJSON;

var json = JSON.Parse("{\"array\":[1,2,3],\"boolean\":true,\"null\":null,\"number\":123,\"object\":{\"a\":\"b\",\"c\":\"d\",\"e\":\"f\"},\"string\":\"Hello World\"}");
Debug.Log(json["string"].Value);
Debug.Log(json["boolean"].AsBool);
Debug.Log(json["array"].AsArray);