購物車項目，業務需要實現了一個購物車的項目，簡單的了解下實現邏輯：數據計算等是在Adapter中計算出來的，通過在Adapter中計算出來的數據就可以回調到Activity中進行訂單操作等功能業務邏輯，每一個店鋪產生的數據是走一條流程的，（業務需求：不是作為一個類似淘寶，京東的平臺數據又由平臺分發，所以我們實現的是一對一的客戶交易的交易流程)接著往下看：
1.界面使用到的控件
goodsAdapter = new GoodsCarAdapter(ShopCarAvtivity.this, result);lv_refresh.setAdapter(goodsAdapter);goodsAdapter.setCheckInterface(ShopCarAvtivity.this);// 關鍵步驟1,設置復選框接口goodsAdapter.setModifyCountInterface(ShopCarAvtivity.this);// 關鍵步驟2,設置數量增減接口for (int i = 0; i < goodsAdapter.getGroupCount(); i++) { lv_refresh.expandGroup(i);// 關鍵步驟3,初始化時，將ExpandableListView以展開的方式呈現}2.項目中使用到的數據接口
界面當中的復選框的接口回調
public interface CheckGoodsListener {/** * 組選框狀態改變觸發的事件 * * @param groupPosition 組元素位置 * @param isChecked 組元素選中與否 */void checkGroup(int groupPosition, boolean isChecked);/** * 子選框狀態改變時觸發的事件 * * @param groupPosition 組元素位置 * @param childPosition 子元素位置 * @param isChecked 子元素選中與否 */void checkChild(int groupPosition, int childPosition, boolean isChecked);/** * 購買 * @param groupPosition * @param childPosition * @param isChecked */void checkGoodsBuy(ShopCarModel shopCarModel, double totalMonery, int totalCount);} 商品增加和修改的接口
/** * 改變數量的接口 * Created by zhuangAH on 2016-11-7. */public interface ModifyCountListener { /** * 增加操作 * * @param groupPosition 組元素位置 * @param childPosition 子元素位置 * @param showCountView 用于展示變化后數量的View * @param isChecked 子元素選中與否 */ void doIncrease(int groupPosition, int childPosition, View showCountView, boolean isChecked); /** * 刪減操作 * * @param groupPosition 組元素位置 * @param childPosition 子元素位置 * @param showCountView 用于展示變化后數量的View * @param isChecked 子元素選中與否 */ void doDecrease(int groupPosition, int childPosition, View showCountView, boolean isChecked); /** * 刪除子item * * @param groupPosition * @param childPosition */ void childDelete(int groupPosition, int childPosition);}3.在Adapter中計算商品的金額數量
單個店鋪中有多個商品，所以這個店鋪的布局，包含選擇全組的按鈕，使用了接口的回調 checkInterface.checkGroup(groupPosition, ((CheckBox) v).isChecked());來判斷是否選中全組，在Activity中進行數據的便利是否選中商品之后再刷新數據。
@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中計算便利數據
/*** * 校對組元素 * * @param groupPosition 組元素位置 * @param isChecked 組元素選中與否 */ @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(); }在商品中計算數據結果：
@Overridepublic 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(); } //進行數據操作 final GoodsModel goodsInfo = (GoodsModel) getChild(groupPosition, childPosition); if (goodsInfo != null) { //數量初始化為0,金額初始化為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); //判斷是否最后一個 if ((goodsModel.size() - 1) == childPosition) { goodsViewHolder.layout_item_foot.setVisibility(View.VISIBLE); /** * 統計操作<br> * 1.先清空全局計數器<br> * 2.遍歷所有子元素，只要是被選中狀態的，就進行相關的計算操作<br> * 3.給底部的textView進行數據填充 */ //1判斷商品是否選中,再進行計算 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); } //設置基礎數據 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())); //選中的狀態下才能觸發點擊事件 goodsViewHolder.tvAdd.setEnabled(true); goodsViewHolder.tvReduce.setEnabled(true); //加減 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());// 暴露刪減接口 } }); //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;}以上代碼的是先判斷當前組是否為一個店鋪中的最后一個，在最后一個元素中局部計算當前的Group的數據，根據數據來選擇是否復位數據展示以及顯示，把計算的數據展示出來，最后通過接口回調的方式跳轉界面，把數據傳到Activity中去。就這樣子就處理完這個購物車的邏輯，以上可能不符合你的邏輯，但是你可以稍微修改就拿來使用。
Github地址: https://github.com/anhuifix/singleShopCar/tree/master
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