最近在做商城的项目，购物车的功能是核心，为了实现此功能，选用了GreenDao来实现数据的存储，当然在实际中，服务器和数据库之间数据的转换，才是完整的购物车功能。本篇文章只做GreenDao在购物车方面的使用介绍，关于GreenDao的配置，请参考https://github.com/greenrobot/greenDAO，下面附上效果图：
其实要做购物车，首先要明白购物车内部的产品关系，即店铺和产品的关系，很明显店铺和产品是一对多的关系，因此在设计数据库的时候就要使用GreenDao的一对多类型，下面附上具体代码：
1.商品表（需要注意的是，Generated内的hash值和变量的get/set方法是GreenDao自己生成的，切勿自己添加，否则，自己实践）
import org.greenrobot.greendao.annotation.Entity;
import org.greenrobot.greendao.annotation.Generated;
import org.greenrobot.greendao.annotation.Id;
@Entity
public class GoodsEntry {
private int goodsOldMoney;
private String goodsDes;
private String goodsImage;
private String goodsName;
@Id
private Long goodsId;
private Long shopId;
private int goodsBuyNum;
private int goodsMoney;
private String color;
private String size;
@Generated(hash = 414987192)
public GoodsEntry() {
}
@Generated(hash = 857959235)
public GoodsEntry(int goodsOldMoney, String goodsDes, String goodsImage, String goodsName, Long goodsId, Long shopId, int goodsBuyNum,
int goodsMoney, String color, String size) {
this.goodsOldMoney = goodsOldMoney;
this.goodsDes = goodsDes;
this.goodsImage = goodsImage;
this.goodsName = goodsName;
this.goodsId = goodsId;
this.shopId = shopId;
this.goodsBuyNum = goodsBuyNum;
this.goodsMoney = goodsMoney;
this.color = color;
this.size = size;
}
public int getGoodsOldMoney() {
return this.goodsOldMoney;
}
public void setGoodsOldMoney(int goodsOldMoney) {
this.goodsOldMoney = goodsOldMoney;
}
public String getGoodsDes() {
return this.goodsDes;
}
public void setGoodsDes(String goodsDes) {
this.goodsDes = goodsDes;
}
public String getGoodsImage() {
return this.goodsImage;
}
public void setGoodsImage(String goodsImage) {
this.goodsImage = goodsImage;
}
public String getGoodsName() {
return this.goodsName;
}
public void setGoodsName(String goodsName) {
this.goodsName = goodsName;
}
public Long getGoodsId() {
return this.goodsId;
}
public void setGoodsId(Long goodsId) {
this.goodsId = goodsId;
}
public Long getShopId() {
return this.shopId;
}
public void setShopId(Long shopId) {
this.shopId = shopId;
}
public int getGoodsBuyNum() {
return this.goodsBuyNum;
}
public void setGoodsBuyNum(int goodsBuyNum) {
this.goodsBuyNum = goodsBuyNum;
}
public int getGoodsMoney() {
return this.goodsMoney;
}
public void setGoodsMoney(int goodsMoney) {
this.goodsMoney = goodsMoney;
}
public String getColor() {
return this.color;
}
public void setColor(String color) {
this.color = color;
}
public String getSize() {
return this.size;
}
public void setSize(String size) {
this.size = size;
}2.店铺表（带有注释的和get/set方法都是GreenDao自己生成的，关键在于店铺ID属性，这是商品和店铺建立纽带的外键，GreenDao的 ToMany(referencedJoinProperty=“外键”)）是一对多关系的注解
import org.greenrobot.greendao.DaoException;
import org.greenrobot.greendao.annotation.Entity;
import org.greenrobot.greendao.annotation.Generated;
import org.greenrobot.greendao.annotation.Id;
import org.greenrobot.greendao.annotation.ToMany;
import java.util.List;
@Entity
public class GoodsDetailEntry {
@Id
private Long shopId;
private String shopName;
@ToMany(referencedJoinProperty = "shopId")
private List<GoodsEntry> list;
/** Used to resolve relations */
@Generated(hash = 2040040024)
private transient DaoSession daoSession;
/** Used for active entity operations. */
@Generated(hash = 706725451)
private transient GoodsDetailEntryDao myDao;
@Generated(hash = 181135608)
public GoodsDetailEntry(Long shopId, String shopName) {
this.shopId = shopId;
this.shopName = shopName;
}
@Generated(hash = 1925892336)
public GoodsDetailEntry() {
}
public Long getShopId() {
return this.shopId;
}
public void setShopId(Long shopId) {
this.shopId = shopId;
}
public String getShopName() {
return this.shopName;
}
public void setShopName(String shopName) {
this.shopName = shopName;
}
/**
* To-many relationship, resolved on first access (and after reset).
* Changes to to-many relations are not persisted, make changes to the target entity.
*/
@Generated(hash = 560962175)
public List<GoodsEntry> getList() {
if (list == null) {
final DaoSession daoSession = this.daoSession;
if (daoSession == null) {
throw new DaoException("Entity is detached from DAO context");
}
GoodsEntryDao targetDao = daoSession.getGoodsEntryDao();
List<GoodsEntry> listNew = targetDao
._queryGoodsDetailEntry_List(shopId);
synchronized (this) {
if (list == null) {
list = listNew;
}
}
}
return list;
}
/** Resets a to-many relationship, making the next get call to query for a fresh result. */
@Generated(hash = 589833612)
public synchronized void resetList() {
list = null;
}
/**
* Convenient call for {@link org.greenrobot.greendao.AbstractDao#delete(Object)}.
* Entity must attached to an entity context.
*/
@Generated(hash = 128553479)
public void delete() {
if (myDao == null) {
throw new DaoException("Entity is detached from DAO context");
}
myDao.delete(this);
}
/**
* Convenient call for {@link org.greenrobot.greendao.AbstractDao#refresh(Object)}.
* Entity must attached to an entity context.
*/
@Generated(hash = 1942392019)
public void refresh() {
if (myDao == null) {
throw new DaoException("Entity is detached from DAO context");
}
myDao.refresh(this);
}
/**
* Convenient call for {@link org.greenrobot.greendao.AbstractDao#update(Object)}.
* Entity must attached to an entity context.
*/
@Generated(hash = 713229351)
public void update() {
if (myDao == null) {
throw new DaoException("Entity is detached from DAO context");
}
myDao.update(this);
}
/** called by internal mechanisms, do not call yourself. */
@Generated(hash = 260075940)
public void __setDaoSession(DaoSession daoSession) {
this.daoSession = daoSession;
myDao = daoSession != null ? daoSession.getGoodsDetailEntryDao() : null;
}
}
3.购物车实现（请参考https://github.com/cmazxiaoma/taobao，开源的购物车项目，本篇文章就是在此基础上进行修改）
a.商品添加
GoodsDetailEntryDao goodsDetailEntryDao1 = BaseApplication.getInstances().getDaoSession().getGoodsDetailEntryDao();//获取商铺表
List<GoodsDetailEntry> goodsDetailEntries = goodsDetailEntryDao1.loadAll();//获取所有的店铺列表
GoodsEntryDao goodsEntryDao = BaseApplication.getInstances().getDaoSession().getGoodsEntryDao();//获取商品表
GoodsEntry goodsEntry = new GoodsEntry();//创建商品对象
goodsEntry.setGoodsName(bean.getGoodsName());//bean为作为传递的商品临时对象
goodsEntry.setGoodsId(bean.getId());
goodsEntry.setGoodsDes(bean.getGoodsDesc());
goodsEntry.setGoodsBuyNum(1);
goodsEntry.setShopId(bean.getShopId());
goodsEntry.setGoodsMoney(bean.getPrice());
goodsEntry.setGoodsOldMoney(bean.getOldPrice());
goodsEntry.setGoodsImage(bean.getImageId());
goodsEntry.setColor("蓝色");
goodsEntry.setSize("40");
GoodsDetailEntry goodsDetailEntry = new GoodsDetailEntry();//创建店铺对象
if (goodsDetailEntries.size()==0){//店铺列表为0说明购物车为空，直接插入商品和店铺
GoodsDetailEntry detatilEntry = new GoodsDetailEntry();
detatilEntry.setShopId(bean.getShopId());
detatilEntry.setShopName(bean.getShopName());
goodsEntryDao.insert(goodsEntry);
goodsDetailEntryDao1.insert(detatilEntry);
}else {
for (GoodsDetailEntry detailEntry:goodsDetailEntries) {
List<GoodsEntry> detailEntryList = detailEntry.getList();//获取当前店铺下的已加入购物车的所有商品
if (detailEntry.getShopId().equals(bean.getShopId())){//同一店铺下的处理
for (int i = 0; i <detailEntryList.size(); i++) {
GoodsEntry entry = detailEntryList.get(i);
if (entry.getGoodsId().equals(bean.getId())){//如果商品存在购物车，只需数量加1即可,更新商品表，更新店铺表
goodsEntry.setGoodsBuyNum(entry.getGoodsBuyNum()+1);
goodsEntryDao.update(goodsEntry);
goodsDetailEntry.setShopName(bean.getShopName());
goodsDetailEntry.setShopId(bean.getShopId());
goodsDetailEntryDao1.update(goodsDetailEntry);
}else {//如果商品在购物车不存在，插入商品表，更新店铺表，此处使用捕获异常来终止循环，尝试break无效
try {
goodsEntryDao.insert(goodsEntry);
goodsDetailEntry.setShopName(bean.getShopName());
goodsDetailEntry.setShopId(bean.getShopId());
goodsDetailEntryDao1.update(goodsDetailEntry);
}catch (Exception e){
e.printStackTrace();
}
}
}
}else {//不同店铺下的处理,插入商品表，插入店铺表，此处同上使用捕获异常终止循环
try {
goodsEntryDao.insert(goodsEntry);
goodsDetailEntry.setShopName(bean.getShopName());
goodsDetailEntry.setShopId(bean.getShopId());
goodsDetailEntryDao1.insert(goodsDetailEntry);
}catch (Exception e){
e.printStackTrace();
}
}
}
}b.获取购物车详情
/**
* 模拟数据<br>
* 遵循适配器的数据列表填充原则，组元素被放在一个list中，对应着组元素的下辖子元素被放在Map中
* 其Key是组元素的Id
*/
private void initData() {
mcontext = this;
groups = new ArrayList<StoreInfo>();
childs = new HashMap<String, List<GoodsInfo>>();
DaoSession daoSession = BaseApplication.getInstances().getDaoSession();
GoodsDetailEntryDao goodsDetailEntryDao = daoSession.getGoodsDetailEntryDao();
List<GoodsDetailEntry> goodsDetailEntries = goodsDetailEntryDao.loadAll();
for (int i = 0;i <goodsDetailEntries.size();i++) {
GoodsDetailEntry detailEntry = goodsDetailEntries.get(i);
groups.add(new StoreInfo(String.valueOf(detailEntry.getShopId()),detailEntry.getShopName()));
List<GoodsInfo> goods = new ArrayList<>();
List<GoodsEntry> goodsEntries = detailEntry.getList();
for (int j = 0; j <goodsEntries.size() ; j++) {
GoodsEntry entry = goodsEntries.get(j);
goods.add(new GoodsInfo(String.valueOf(entry.getGoodsId()),entry.getGoodsName(),entry.getGoodsDes(),entry.getGoodsMoney(),entry.getGoodsOldMoney(),entry.getColor(),entry.getSize(),entry.getGoodsImage(),entry.getGoodsBuyNum()));
}
childs.put(groups.get(i).getId(), goods);
}
}