Android 尝试更改片段中的textView文本时出现NullPointerException

当我尝试在片段中更改textView的文本时，我得到了一个nullPointerException，我尝试了将

getView（）

和

getActivity（）

放在

findByViewId

之前的建议，但它们都会导致错误。多谢各位

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将设置日期更改为：

public void setDate(View v){
    String mydate = java.text.DateFormat.getDateTimeInstance().format(Calendar.getInstance().getTime());
    //need to use calendar class as Date is deprecated (old)


    TextView textView = (TextView) v.findViewById(R.id.info_text);
    textView.setText("updated");
}

并称之为：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View rootview = inflater.inflate(R.layout.fragment_main, container, false);

    //calls setdate function
    setDate(rootview);

    return rootview;
}

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
                                                                           at au.com.alexh.dayrater.MainFragment.setDate(MainFragment.java:43)
                                                                           at au.com.alexh.dayrater.MainFragment.onCreateView(MainFragment.java:33)

public void setDate(View v){
    String mydate = java.text.DateFormat.getDateTimeInstance().format(Calendar.getInstance().getTime());
    //need to use calendar class as Date is deprecated (old)


    TextView textView = (TextView) v.findViewById(R.id.info_text);
    textView.setText("updated");
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View rootview = inflater.inflate(R.layout.fragment_main, container, false);

    //calls setdate function
    setDate(rootview);

    return rootview;
}