Android facebook图表Api GraphRequest.newMeRequest不起作用

我是Android的新手，我正在尝试使用“Android脸谱图Api GraphRequest.newMeRequest”，但我的代码不起作用，当我登录时应用程序崩溃 . 这是我的代码，也许有人可以帮助我 .

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    facebookSDKInitialize();
    setContentView(R.layout.activity_main);
    LoginButton loginButton = (LoginButton) findViewById(R.id.login_button);
    loginButton.setReadPermissions("email");
    getLoginDetails(loginButton);
}
/*
   Initialize the facebook sdk 
 */
protected void facebookSDKInitialize() {
    FacebookSdk.sdkInitialize(getApplicationContext());
    callbackManager = CallbackManager.Factory.create();
}
/*
Register a callback function with LoginButton to respond to the login result.
*/
protected void getLoginDetails(LoginButton login_button){
    // Callback registration
    login_button.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
        @Override
        public void onSuccess(LoginResult login_result) {
            getUserInfo(login_result);
        }
        @Override
        public void onCancel() {
            // code for cancellation
        }
        @Override
        public void onError(FacebookException exception) {
            //  code to handle error
        }
    });
}
/*To get the facebook user's own profile information via  creating a new request.*/
protected void getUserInfo(LoginResult login_result){
    GraphRequest data_request = GraphRequest.newMeRequest(
            login_result.getAccessToken(),
            new GraphRequest.GraphJSONObjectCallback() {
                @Override
                public void onCompleted(
                        JSONObject json_object,
                        GraphResponse response) {
                    Intent intent = new Intent(MainActivity.this,HomeActivity.class);

                    intent.putExtra("jsondata",json_object.toString());

                    startActivity(intent);
                }
            });
    Bundle permission_param = new Bundle();
    permission_param.putString("fields", "id,name,email,picture.width(120).height(120)");
    data_request.setParameters(permission_param);
    data_request.executeAsync();
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    callbackManager.onActivityResult(requestCode, resultCode, data);
    Log.e("data",data.toString());
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    // getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}
@Override
protected void onResume() {
    super.onResume();
    // Logs 'install' and 'app activate' App Events.
    AppEventsLogger.activateApp(this);
}
@Override
protected void onPause() {
    super.onPause();
    // Logs 'app deactivate' App Event.
    AppEventsLogger.deactivateApp(this);
}

}

在Android Studio中我收到错误：

E / AndroidRuntime：FATAL EXCEPTION：main进程：com.example.novella.auto，PID：11300主题：themes：{} java.lang.NullPointerException：尝试调用虚方法'java.lang.String org.json.JSONObject com.facebook.GraphRequest $ 1.onCompleted（GraphRequest.java :)在com.facebook上的com.example.novella.autofa.MainActivity $ 2.onCompleted（MainActivity.java:73）上的空对象引用上的.toString（）' .GraphRequest $ 5.run（GraphRequest.java:1368）在android.os.Handler.handleCallback（Handler.java:739）android.os.Handler.dispatchMessage（Handler.java:95）android.os.Looper.loop （looper.java:148）位于android.app.ActivityThread.main（ActivityThread.java:5475）的java.lang.reflect.Method.invoke（Native Method）at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run （ZygoteInit.java:726）com.android.internal.os.ZygoteInit.main（ZygoteInit.java:616）

错误“尝试在空对象引用上调用虚方法'java.lang.String org.json.JSONObject.toString（）'”引用此字符串：

intent.putExtra("jsondata",json_object.toString());

我做错了什么？拜托，帮助我！ :)