Android购物车项目快速开发

购物车项目，业务需要实现了一个购物车的项目，简单的了解下实现逻辑：数据计算等是在Adapter中计算出来的，通过在Adapter中计算出来的数据就可以回调到Activity中进行订单操作等功能业务逻辑，每一个店铺产生的数据是走一条流程的，（业务需求：不是作为一个类似淘宝，京东的平台数据又由平台分发，所以我们实现的是一对一的客户交易的交易流程)接着往下看：

1.界面使用到的控件

goodsAdapter = new GoodsCarAdapter(ShopCarAvtivity.this, result);
lv_refresh.setAdapter(goodsAdapter);
goodsAdapter.setCheckInterface(ShopCarAvtivity.this);// 关键步骤1,设置复选框接口
goodsAdapter.setModifyCountInterface(ShopCarAvtivity.this);// 关键步骤2,设置数量增减接口
for (int i = 0; i < goodsAdapter.getGroupCount(); i++) {
lv_refresh.expandGroup(i);// 关键步骤3,初始化时，将ExpandableListView以展开的方式呈现
}

2.项目中使用到的数据接口

界面当中的复选框的接口回调

public interface CheckGoodsListener {
/**
* 组选框状态改变触发的事件
*
* @param groupPosition 组元素位置
* @param isChecked  组元素选中与否
*/
void checkGroup(int groupPosition, boolean isChecked);

/**
* 子选框状态改变时触发的事件
*
* @param groupPosition 组元素位置
* @param childPosition 子元素位置
* @param isChecked  子元素选中与否
*/
void checkChild(int groupPosition, int childPosition, boolean isChecked);

/**
* 购买
* @param groupPosition
* @param childPosition
* @param isChecked
*/
void checkGoodsBuy(ShopCarModel shopCarModel, double totalMonery, int totalCount);

}

商品增加和修改的接口

/**
* 改变数量的接口
* Created by zhuangAH on 2016-11-7.
*/

public interface ModifyCountListener {

/**
 * 增加操作
 *
 * @param groupPosition 组元素位置
 * @param childPosition 子元素位置
 * @param showCountView 用于展示变化后数量的View
 * @param isChecked  子元素选中与否
 */
void doIncrease(int groupPosition, int childPosition, View showCountView, boolean isChecked);

/**
 * 删减操作
 *
 * @param groupPosition 组元素位置
 * @param childPosition 子元素位置
 * @param showCountView 用于展示变化后数量的View
 * @param isChecked  子元素选中与否
 */
void doDecrease(int groupPosition, int childPosition, View showCountView, boolean isChecked);

/**
 * 删除子item
 *
 * @param groupPosition
 * @param childPosition
 */
void childDelete(int groupPosition, int childPosition);

}

3.在Adapter中计算商品的金额数量

单个店铺中有多个商品，所以这个店铺的布局，包含选择全组的按钮，使用了接口的回调 checkInterface.checkGroup(groupPosition, ((CheckBox) v).isChecked());来判断是否选中全组，在Activity中进行数据的便利是否选中商品之后再刷新数据。

@Override
public View getGroupView(final int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {

GroupViewHolder gholder = null;
 if (convertView != null && !(convertView.getTag() instanceof GroupViewHolder)) {
  convertView = null;
 }
 if (convertView == null) {
  gholder = new GroupViewHolder();
  convertView = View.inflate(context, R.layout.item_shopcart_group, null);
  gholder.determineChekbox = (CheckBox) convertView.findViewById(R.id.determine_chekbox);
  gholder.tvSourceName = (TextView) convertView.findViewById(R.id.tv_source_name);
  convertView.setTag(gholder);
 } else {
  gholder = (GroupViewHolder) convertView.getTag();
 }

final ShopCarModel group = (ShopCarModel) getGroup(groupPosition);
 gholder.tvSourceName.setText(group.getFactoryName());
 gholder.determineChekbox.setOnClickListener(new View.OnClickListener() {
  @Override
  public void onClick(View v) {
   group.setChoosed(((CheckBox) v).isChecked());
   checkInterface.checkGroup(groupPosition, ((CheckBox) v).isChecked());
  }
 });
 gholder.determineChekbox.setChecked(group.isChoosed());
 return convertView;
}

在Activity中计算便利数据

/***
 * 校对组元素
 *
 * @param groupPosition 组元素位置
 * @param isChecked  组元素选中与否
 */
@Override
public void checkGroup(int groupPosition, boolean isChecked) {

List<GoodsModel> goodsModelList = shopCarModelList.get(groupPosition).getGoodsModel();
 for (int i = 0; i < goodsModelList.size(); i++) {
  goodsModelList.get(i).setChoosed(isChecked);
 }
 goodsAdapter.notifyDataSetChanged();
}

在商品中计算数据结果：

@Override
public View getChildView(final int groupPosition, final int childPosition, final boolean isLastChild, View convertView, final ViewGroup parent) {
GoodsViewHolder goodsViewHolder = null;
int totalCount = 0;
double totalPrice = 0.00;

if (convertView != null && !(convertView.getTag() instanceof GoodsViewHolder)) {
 convertView = null;
}
if (convertView == null) {
 goodsViewHolder = new GoodsViewHolder();
 convertView = View.inflate(context, R.layout.item_shopcart_product, null);
 goodsViewHolder.checkBox = (CheckBox) convertView.findViewById(R.id.check_box);
 goodsViewHolder.ivAdapterListPic = (ImageView) convertView.findViewById(R.id.iv_adapter_list_pic);
 goodsViewHolder.tvIntro = (TextView) convertView.findViewById(R.id.tv_intro);
 goodsViewHolder.tvPrice = (TextView) convertView.findViewById(R.id.tv_price);
 goodsViewHolder.tvBuyNum = (TextView) convertView.findViewById(R.id.tv_buy_num);
 goodsViewHolder.rlNoEdtor = (RelativeLayout) convertView.findViewById(R.id.rl_no_edtor);
 goodsViewHolder.tvReduce = (TextView) convertView.findViewById(R.id.tv_reduce);
 goodsViewHolder.tvNum = (TextView) convertView.findViewById(R.id.tv_num);
 goodsViewHolder.tvAdd = (TextView) convertView.findViewById(R.id.tv_add);
 goodsViewHolder.llChangeNum = (LinearLayout) convertView.findViewById(R.id.ll_change_num);
 goodsViewHolder.layout_item_foot = (LinearLayout) convertView.findViewById(R.id.layout_item_foot);
 goodsViewHolder.tv_goods_number = (TextView) convertView.findViewById(R.id.tv_goods_number);
 goodsViewHolder.tv_goods_menoy = (TextView) convertView.findViewById(R.id.tv_goods_menoy);
 goodsViewHolder.tv_buys = (TextView) convertView.findViewById(R.id.tv_buys);
 goodsViewHolder.laytou_car = (LinearLayout) convertView.findViewById(R.id.laytou_car);
 convertView.setTag(goodsViewHolder);
} else {
 goodsViewHolder = (GoodsViewHolder) convertView.getTag();
}
//进行数据操作
final GoodsModel goodsInfo = (GoodsModel) getChild(groupPosition, childPosition);
if (goodsInfo != null) {
 //数量初始化为0,金额初始化为0
 goodsViewHolder.tv_goods_number.setText(TypeUtils.toString(0));
 goodsViewHolder.tv_goods_menoy.setText("￥ " + NumberUtils.formatMoneyScale(0.00));

List<GoodsModel> goodsModel = CarUtrils.getGoodsList(goodShop, groupPosition);
 //判断是否最后一个
 if ((goodsModel.size() - 1) == childPosition) {
  goodsViewHolder.layout_item_foot.setVisibility(View.VISIBLE);
  /**
   * 统计操作<br>
   * 1.先清空全局计数器<br>
   * 2.遍历所有子元素，只要是被选中状态的，就进行相关的计算操作<br>
   * 3.给底部的textView进行数据填充
   */
  //1判断商品是否选中,再进行计算
  for (int j = 0; j < goodsModel.size(); j++) {
   GoodsModel model = goodsModel.get(j);
   if (model.isChoosed()) {
    totalCount += model.getSelectQty();
    totalPrice += TypeUtils.toDouble(NumberUtils.multiply(TypeUtils.toBigDecimal(NumberUtils.formatRounded(model.getPrice())), NumberUtils.toBigDecimal(model.getSelectQty())));
   }
  }

if (totalPrice != 0.00) {
   goodsViewHolder.tv_goods_number.setText(TypeUtils.toString(totalCount));
   goodsViewHolder.tv_goods_menoy.setText(NumberUtils.formatRounded(TypeUtils.toBigDecimal(totalPrice)));
   goodsViewHolder.tv_buys.setBackgroundColor(context.getResources().getColor(R.color.main_color));
   goodsViewHolder.tv_buys.setEnabled(true);
  } else {
   goodsViewHolder.tv_goods_number.setText(TypeUtils.toString(0));
   goodsViewHolder.tv_goods_menoy.setText("￥ " + NumberUtils.formatMoneyScale(0.00));
   goodsViewHolder.tv_buys.setBackgroundColor(context.getResources().getColor(R.color.resport_line));
   goodsViewHolder.tv_buys.setEnabled(false);
  }

} else {
  goodsViewHolder.layout_item_foot.setVisibility(View.GONE);
 }
 //设置基础数据
 if (goodsInfo.getImageSrc() != null) {
  Glide.with(context)
    .load(goodsInfo.getImageSrc())
    .centerCrop()
    .placeholder(R.mipmap.test2)
    .crossFade()
    .into(goodsViewHolder.ivAdapterListPic);
 }

goodsViewHolder.tvIntro.setText(goodsInfo.getName());
 goodsViewHolder.tvPrice.setText("￥ " + NumberUtils.formatRounded(goodsInfo.getPrice()));
 goodsViewHolder.tvBuyNum.setText("X " + NumberUtils.formatQty(goodsInfo.getQty()));
 //set Goods Check
 goodsViewHolder.checkBox.setChecked(goodsInfo.isChoosed());
 goodsViewHolder.tvNum.setText(TypeUtils.toString(goodsInfo.getSelectQty()));

//选中的状态下才能触发点击事件
 goodsViewHolder.tvAdd.setEnabled(true);
 goodsViewHolder.tvReduce.setEnabled(true);
 //加减
 final GoodsViewHolder finalGoodsViewHolder = goodsViewHolder;
 goodsViewHolder.tvAdd.setOnClickListener(new View.OnClickListener() {
  @Override
  public void onClick(View v) {
   modifyCountInterface.doIncrease(groupPosition, childPosition, finalGoodsViewHolder.tvNum, finalGoodsViewHolder.checkBox.isChecked());// 暴露增加接口

}
 });
 final GoodsViewHolder finalGoodsViewHolder1 = goodsViewHolder;
 goodsViewHolder.tvReduce.setOnClickListener(new View.OnClickListener() {
  @Override
  public void onClick(View v) {
   modifyCountInterface.doDecrease(groupPosition, childPosition, finalGoodsViewHolder1.tvNum, finalGoodsViewHolder1.checkBox.isChecked());// 暴露删减接口
  }
 });

//goods check state OnClick
 goodsViewHolder.checkBox.setOnClickListener(new View.OnClickListener() {
  @Override
  public void onClick(View v) {
   goodsInfo.setChoosed(((CheckBox) v).isChecked());
   ((CheckBox) v).setChecked(((CheckBox) v).isChecked());
   checkInterface.checkChild(groupPosition, childPosition, ((CheckBox) v).isChecked());
  }
 });
 //onClick to OrderDetailActivity
 final double finalTotalPrice = totalPrice;
 final int finalTotalCount = totalCount;
 goodsViewHolder.tv_buys.setOnClickListener(new View.OnClickListener() {
  @Override
  public void onClick(View v) {
   //check goods is not null
   //if not null can go other activity
   ShopCarModel shopCar = CarUtrils.getCheckShopCar(goodShop, groupPosition);
   if (shopCar != null && shopCar.getGoodsModel().size() > 0) {
    checkInterface.checkGoodsBuy(shopCar, finalTotalPrice, finalTotalCount);
   }
  }
 });
}

goodsViewHolder.laytou_car.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
  UIHelper.toShopCarGoodsDetailActivity(context, goodsInfo);
 }
});
return convertView;
}

以上代码的是先判断当前组是否为一个店铺中的最后一个，在最后一个元素中局部计算当前的Group的数据，根据数据来选择是否复位数据展示以及显示，把计算的数据展示出来，最后通过接口回调的方式跳转界面，把数据传到Activity中去。就这样子就处理完这个购物车的逻辑，以上可能不符合你的逻辑，但是你可以稍微修改就拿来使用。

Github地址: https://github.com/anhuifix/singleShopCar/tree/master