android 问题，动态修改 textview 修改后UI不更新

LayoutInflater inflater = (LayoutInflater)this.getSystemService(this.LAYOUT_INFLATER_SERVICE);
View nav_header_view = inflater.inflate(R.layout.nav_header_main, null);

    app = (MyApplication) getApplication();

    TextView tvUserName = (TextView)nav_header_view.findViewById(R.id.userName);
    String userName = app.getUserName();
    tvUserName.setText(userName);
    TextView tvUserEmail = (TextView)nav_header_view.findViewById(R.id.userEmail);
    String userEmail = app.getUserId();
    tvUserEmail.setText(userEmail);


            这里修改的是当前Activity对应xml下的一个子xml，就是导航菜单的头部信息
            ![图片说明](https://img-ask.csdn.net/upload/201612/19/1482121367_532086.png)
            ![图片说明](https://img-ask.csdn.net/upload/201612/19/1482121250_2046.png)

图片没上来

改完后 重新绘制一下