我有mainActivity.java一個叫做布局類activity_main.xml和一個名為.xml文件drawer_menu.xml具有textView這顯示在應用程序的drawer menu。我想抽屜菜單的設置textView文本的String價值，我有我的mainActivity.java課。我如何訪問 mainActivity 類中的那個 textView？activity_main.java（訪問textView的部分）：    /** * Prompts the user for his/her username * when the tutorial is done */private void promptForUsername() {    UsernameDialog dialog = new UsernameDialog();    dialog.setCancelable(false);    dialog.show(getFragmentManager(),"USERNAME_DIALOG");    username.setText(getUsername());}public void setUsername(String name) {    tempName = name;}public String getUsername() {    return tempName;}UsernameDialog.java 類：public class UsernameDialog extends DialogFragment {@BindView(R.id.editText) EditText mEditText;@Overridepublic void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);}@Overridepublic Dialog onCreateDialog(Bundle savedInstanceState) {    // inflate the layout using the dialog themed context    final Context context = getActivity();    final LayoutInflater inflater = LayoutInflater.from(context);    final View view = inflater.inflate(R.layout.username_dialog,null,false);    final MainActivity activity = new MainActivity();    ButterKnife.bind(this,view);    DialogInterface.OnClickListener posListener = new DialogInterface.OnClickListener() {        @Override        public void onClick(DialogInterface dialogInterface, int i) {            activity.setUsername(mEditText.getText().toString());            Log.d("USERNAME",mEditText.getText().toString());        }    };    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity())            .setTitle("Choose your username")            .setView(view)            .setPositiveButton("OK",posListener);    return builder.create();}}