如何在ListView中将backgroundColor更改为item？

// 自定义适配器类
public class CustomAdapter extends BaseAdapter {
    private List<String> itemList;
    private Context context;

    public CustomAdapter(List<String> itemList, Context context) {
        this.itemList = itemList;
        this.context = context;
    }

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

    @Override
    public Object getItem(int position) {
        return itemList.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(context).inflate(R.layout.list_item_layout, parent, false);
            holder = new ViewHolder();
            holder.itemTextView = convertView.findViewById(R.id.itemTextView);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        String item = itemList.get(position);
        holder.itemTextView.setText(item);

        // 设置背景颜色
        if (position % 2 == 0) {
            convertView.setBackgroundColor(Color.BLUE);
        } else {
            convertView.setBackgroundColor(Color.GREEN);
        }

        return convertView;
    }

    static class ViewHolder {
        TextView itemTextView;
    }
}

// 在Activity或Fragment中使用适配器
public class MainActivity extends AppCompatActivity {
    private ListView listView;
    private CustomAdapter adapter;

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

        listView = findViewById(R.id.listView);

        List<String> itemList = new ArrayList<>();
        itemList.add("Item 1");
        itemList.add("Item 2");
        itemList.add("Item 3");
        itemList.add("Item 4");
        itemList.add("Item 5");

        adapter = new CustomAdapter(itemList, this);
        listView.setAdapter(adapter);
    }
}