试试这个

Intent intent = new Intent(this, LoginActivity.class);
startActivityForResult(intent, 1); 

而在你的 onActivityResult（）用这个。

  @Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    // TODO Auto-generated method stub
    super.onActivityResult(requestCode, resultCode, data);

    if(requestCode == 1 && resultCode == RESULT_OK && data != null )
    {                       
      // Here you can get the username and password         
    }       
}

而在你登录活动

And in your Login Activity

 Intent intent = getIntent();
 intent.putExtra("UserName", user_id); // Place your information.
 intent.putExtra("Password", password);
 setResult(RESULT_OK, intent);  
 finish();

好运气