具有Viewholder和复选框状态保存的ListView

简单的购物清单应用程序。ListView（带有自定义适配器的TextView + CheckBox。试图实现viewHolder模式并完全丢失。对吗？请检查我的代码。还要如何保存复选框状态？我创建了大量但不知道如何实现的方法（滚动bug时取消选中）。

适配器：

public class ShopAdapter extends BaseAdapter {
private Context mainContex;
private ArrayList<ShopItem> shopItems;
boolean[] checkBoxState = new boolean[shopItems.size()];

static class ViewHolder {
    CheckBox checkBox;
    TextView textView;
}

public ShopAdapter(Context mainContex, ArrayList<ShopItem> shopItems) {
    this.mainContex = mainContex;
    this.shopItems = shopItems;
}

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

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

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

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    final ShopItem shopItem = shopItems.get(position);
    View item = convertView;
    if (item == null) {

        item = LayoutInflater.from(mainContex).inflate(R.layout.shoplist_item, null);

        final ViewHolder viewHolder = new ViewHolder();
        viewHolder.textView = (TextView) item.findViewById(R.id.itemTextView);
        viewHolder.checkBox = (CheckBox) item.findViewById(R.id.doneCheckBox);
        viewHolder.textView.setText(shopItem.getDescription());
        viewHolder.checkBox.setChecked(shopItem.isDone());
        viewHolder.checkBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                if (isChecked) {
                    shopItem.setDone(true);
                    viewHolder.textView.setTextColor(mainContex.getResources()
                            .getColor(R.color.done_text_color));
                } else {
                    shopItem.setDone(false);
                    viewHolder.textView.setTextColor(mainContex.getResources()
                            .getColor(R.color.secondary_text));
                }
            }
        });
        item.setTag(viewHolder);
        viewHolder.checkBox.setTag(shopItems.get(position));
    } else {
        item = convertView;
        ((ViewHolder) item.getTag()).checkBox.setTag(shopItems.get(position));
    }
    ViewHolder holder = (ViewHolder) item.getTag();
    holder.textView.setText(shopItems.get(position).getDescription());
    holder.checkBox.setChecked(shopItems.get(position).isDone());
    return item;
}

}

物品：

public class ShopItem {

private String description;
private boolean done;

public String getDescription() {
    return description;
}

public void setDescription(String description) {
    this.description = description;
}

public boolean isDone() {
    return done;
}

public void setDone(boolean done) {
    this.done = done;
}

}