如何在Android Gridview中将第一个孩子设置为Add按钮？

public class MyAdapter extends BaseAdapter {
    private Context mContext;
    private List<String> mData;

    public MyAdapter(Context context, List<String> data) {
        mContext = context;
        mData = data;
    }

    @Override
    public int getCount() {
        return mData.size();
    }

    @Override
    public Object getItem(int position) {
        return mData.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;
        if (convertView == null) {
            convertView = LayoutInflater.from(mContext).inflate(R.layout.grid_item, parent, false);
            holder = new ViewHolder();
            holder.button = convertView.findViewById(R.id.button);
            holder.textView = convertView.findViewById(R.id.textView);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        if (position == 0) {
            holder.button.setVisibility(View.VISIBLE);
            holder.textView.setVisibility(View.GONE);
        } else {
            holder.button.setVisibility(View.GONE);
            holder.textView.setVisibility(View.VISIBLE);
            holder.textView.setText(mData.get(position));
        }

        return convertView;
    }

    private static class ViewHolder {
        Button button;
        TextView textView;
    }
}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Add"
        android:visibility="gone" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="16sp"
        android:layout_centerInParent="true" />

</RelativeLayout>

public class MainActivity extends AppCompatActivity {
    private GridView mGridView;
    private List<String> mData;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mGridView = findViewById(R.id.gridView);
        mData = new ArrayList<>();
        mData.add("Item 1");
        mData.add("Item 2");
        mData.add("Item 3");
        // 添加更多数据...

        MyAdapter adapter = new MyAdapter(this, mData);
        mGridView.setAdapter(adapter);
    }
}

<GridView
    android:id="@+id/gridView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:numColumns="3"
    android:horizontalSpacing="10dp"
    android:verticalSpacing="10dp" />