如何从活动中更改TextView文本片段

Question

我重复this问题的回答，失败了。 我需要更改位于片段中的cardView中的textView（文本）。这是Fragment的code，我想在方法 updateTextView 中更改文本，但我崩溃了。 这是我用Activity调用方法的代码

private void makeView(String wallPhoto, String wallText){

    Fragment fr =  TabFragment1.newInstance();
    getSupportFragmentManager().beginTransaction().replace(R.id.tab_fragment_1, fr, "tag").commit();
    TabFragment1 tabFragment1_text = (TabFragment1) getSupportFragmentManager().findFragmentByTag("tag");
    tabFragment1_text.updateTextView("walll");
    Log.d("", wall_text);
}

崩溃似乎是：java.lang.NullPointerException: Attempt to invoke virtual method 'void pc.dd.tabhost.TabFragment1.updateTextView(java.lang.String)' on a null object reference 更新： 如果按照Nfear的建议，现在没有错误，但文本不会改变。像这样：

private void makeView(String wallPhoto, String wallText){

    Fragment fr =  TabFragment1.newInstance();
    getSupportFragmentManager(). beginTransaction().replace(R.id.tab_fragment_1, fr, "tag").commit();
    getSupportFragmentManager().executePendingTransactions();

    TabFragment1 tabFragment1_text = (TabFragment1) getSupportFragmentManager().findFragmentByTag("tag");
    tabFragment1_text.updateTextView("walll");
    Log.d("", wall_text);
}

调用Activity asynktask，如下所示：

  @Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (!VKSdk.onActivityResult(requestCode, resultCode, data, new VKCallback<VKAccessToken>() {
        @Override
        public void onResult(VKAccessToken res) {
            _VKLogin = true;
            Toast.makeText(getApplicationContext(),"Login succes ",Toast.LENGTH_LONG).show();
            VKRequestResponse _response = new VKRequestResponse();
            _response.execute(res);
        }
        @Override
        public void onError(VKError error) {
            _VKLogin = false;

            Toast.makeText(getApplicationContext(),"Login Error",Toast.LENGTH_LONG).show();
        }

    }))
    super.onActivityResult(requestCode, resultCode, data);
}
class VKRequestResponse extends AsyncTask{

    @Override
    protected Object doInBackground(Object[] params1) {
          VKParameters _params = new VKParameters();
        _params.put(VKApiConst.COUNT, "1");
       VKRequest _vkRequest = VKApi.wall().get(_params);
        _vkRequest.executeWithListener(new VKRequest.VKRequestListener() {
            @Override
            public void onComplete(VKResponse response) {
                    parsingFromJson(response.responseString);
                    makeView(null, wall_text);
                    Toast.makeText(getApplicationContext(),"Otvet "+response.responseString,Toast.LENGTH_LONG).show();
                 super.onComplete(response);
            }

            @Override
            public void onError(VKError error) {
                Toast.makeText(getApplicationContext(),"Ошибка "+error,Toast.LENGTH_LONG).show();
                super.onError(error);
            }

        });

        return null;
    }
}