Facebook SDK v5.1 cannot login on android device

Hi, I get the trouble with using Facebook SDK on android. Below is what I have done:

1. I'm using Facebook sdk 5.1.0 and Unity version is 4.3.4

2. In "`Assets\Facebook\Editor\android\FacebookAndroidUtil.cs`", I add "`System.Environment.GetEnvironmentVariable("HOMEDRIVE")`" in line 62 so that "Debug Android Key Hash" can be generated.

3. I using C# to type the main script, in "Awake()" I add "FB.Init(SetInit, InitCallback);". It just like the tutorial from developers.facebook.com, and enable is give out "true". (I think that mean FB.init() is success.)

After that, I build up a GUI button for log in. I have try "`FB.Login("basic_infos", AfterLogin);`", " FB.Login("publish_actions", AfterLogin); " and " FB.Login("email", AfterLogin); ", both the FB.isLoggedIn is false on android device.

Actually I can log in on unity environment using "User Access Token". On android device, after I press the Login button, it give out a permission and then I press "OK", nothing happen...(`FB.isLoggedIn` still false)

Anyone can give a help? I get the trouble a few week already...
p.s. My English is not good, please let me know if you don't understand.

Below is my coding,

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 using Facebook.MiniJSON;
 using System;
 
 public class FB_control : MonoBehaviour {
 
     public Texture2D texture_btn_Login;    
 
     void Awake ()
     {
         FB.Init(SetInit);
     }
 
     public void SetInit()
     {
         enabled = true;
     }
 
     void OnGUI()
     {
         // Click
         if (GUI.Button(new Rect(10, 50, texture_btn_Login.width * 2, texture_btn_Login.height * 2), texture_btn_Login))
         {
             FB.Login("basic_infos", AfterLogin);
         }
 
         // Display
         GUI.Label(new Rect(10, 300, 400, 30), "Login: "+ FB.IsLoggedIn +"      ||  init.enabled: "+ enabled);
 
         if(api_get_result == true)
         {
             GUI.Label(new Rect(10, 500, 400, 30), "ID: "+ profile["id"]);
             GUI.Label(new Rect(10, 550, 400, 30), "Name: "+ profile["name"]);
         }
     }
     
     void AfterLogin(FBResult result)
     {
         if(FB.IsLoggedIn)
         {
             FB.API("/me?fields=id,name", Facebook.HttpMethod.GET, APICallback);
         }
     }
     
     void APICallback(FBResult result)                                                                                              
     {
         result_str = result.Text;
         profile = Util.DeserializeJSONProfile(result.Text);
     }
 }