Android开源：数据库ORM框架GreenDao封装工具类使用
Android开源：数据库ORM框架GreenDao封装工具类使用。
一、使用QureyBuilder实现表的增删改查
增删改查相当方便，完全的面向对象，不需要涉及到任何的sql语言。
1.查询
范例1：查询某个表是否包含某个id:
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publicbooleanisSaved(intID){
QueryBuilderqb=saveListDao.queryBuilder();
qb.where(Properties.Id.eq(ID));
qb.buildCount().count();
returnqb.buildCount().count()>0?true:false;
}
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/**通过图片id查找其目录id*/
publicintgetTypeId(intpicId)
{
QueryBuilderqb=photoGalleryDao.queryBuilder();
qb.where(Properties.Id.eq(picId));
if(qb.list().size()>0)
{
returnqb.list().get(0).getTypeId();
}else{
return-1;
}
}
Listjoes=userDao.queryBuilder()
where(Properties.FirstName.eq("Joe"))
orderAsc(Properties.LastName)
list();
范例5：多重条件查询
(1)获取id为cityId并且infotype为HBContant.CITYINFO_SL的数据集合：
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publicListgetSupportingList(intcityId){
QueryBuilderqb=cityInfoDao.queryBuilder();
qb.where(qb.and(Properties.CityId.eq(cityId),Properties.InfoType.eq(HBContant.CITYINFO_SL)));
qb.orderAsc(Properties.Id);//排序依据
returnqb.list();
}
(2)获取firstname为“Joe”并且出生于1970年10月以后的所有user集合:
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QueryBuilderqb=userDao.queryBuilder();
qb.where(Properties.FirstName.eq("Joe"),
qb.or(Properties.YearOfBirth.gt(1970),
qb.and(Properties.YearOfBirth.eq(1970),Properties.MonthOfBirth.ge(10))));
ListyoungJoes=qb.list();
picJsonDao.loadByRowId(picId);
publicvoidaddToPhotoTable(Photop){
photoDao.insert(p);
}
插入时需要new一个新的对象，范例如下:
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DevOpenHelperhelper=newDaoMaster.DevOpenHelper(this,"notes-db",null);
db=helper.getWritableDatabase();
daoMaster=newDaoMaster(db);
daoSession=daoMaster.newSession();
noteDao=daoSession.getNoteDao();
Notenote=newNote(null,noteText,comment,newDate());
noteDao.insert(note);
photoDao.insertOrReplace(photo);
photoDao.insertInTx(photo);
/**清空相册图片列表的数据*/
publicvoidclearPhoto(){
photoDao.deleteAll();
}
(2)删除某个对象
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publicvoiddeleteCityInfo(intcityId){
QueryBuilderqb=cityInfoDao.queryBuilder();
DeleteQuerybd=qb.where(Properties.CityId.eq(cityId)).buildDelete();
bd.executeDeleteWithoutDetachingEntities();
}
参考：https://github.com/greenrobot/greenDAO/issues/34
由上可见，使用greenDAO进行数据库的增删改查时及其方便，而且性能极佳。
(三)常用方法笔记
1.在Application实现得到DaoMaster和DaoSession的方法：
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privatestaticDaoMasterdaoMaster;
privatestaticDaoSessiondaoSession;
/**
*取得DaoMaster
*
*@paramcontext
*@return
*/
publicstaticDaoMastergetDaoMaster(Contextcontext)
{
if(daoMaster==null){
OpenHelperhelper=newDaoMaster.DevOpenHelper(context,ontant.DATABASE_NAME,null);
daoMaster=newDaoMaster(helper.getWritableDatabase());
}
returndaoMaster;
}
/**
*取得DaoSession
*
*@paramcontext
*@return
*/
publicstaticDaoSessiongetDaoSession(Contextcontext){
if(daoSession==null){
if(daoMaster==null){
daoMaster=getDaoMaster(context);
}
daoSession=daoMaster.newSession();
}
returndaoSession;
}
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publicclassDBHelper{
privatestaticContextmContext;
privatestaticDBHelperinstance;
privateCityInfoDBDaocityInfoDao;
privateDBHelper(){
}
publicstaticDBHelpergetInstance(Contextcontext){
if(instance==null){
instance=newDBHelper();
if(mContext==null){
mContext=context;
}
//数据库对象
DaoSessiondaoSession=HBApplication.getDaoSession(mContext);
instance.cityInfoDao=daoSession.getCityInfoDBDao();
}
returninstance;
}
/**添加数据*/
publicvoidaddToCityInfoTable(CityInfoitem){
cityInfoDao.insert(item);
}
/**查询*/
publicListgetCityInfoList(){
QueryBuilderqb=cityInfoDao.queryBuilder();
returnqb.list();
}
/**查询*/
publicListgetCityInfo(){
returncityInfoDao.loadAll();//查找图片相册
}
/**查询*/
publicbooleanisSaved(intId){
QueryBuilderqb=cityInfoDao.queryBuilder();
qb.where(Properties.Id.eq(Id));
qb.buildCount().count();
returnqb.buildCount().count()>0?true:false;//查找收藏表
}
/**删除*/
publicvoiddeleteCityInfoList(intId){
QueryBuilderqb=cityInfoDao.queryBuilder();
DeleteQuerybd=where(Properties.Id.eq(Id)).buildDelete();
bd.executeDeleteWithoutDetachingEntities();
}
/**删除*/
publicvoidclearCityInfo(){
cityInfoDao.deleteAll();
}
/**通过城市id查找其类型id*/
publicintgetTypeId(intcityId){
QueryBuilderqb=cityInfoDao.queryBuilder();
qb.where(Properties.Id.eq(cityId));
if(qb.list().size()>0){
returnqb.list().get(0).getTypeId();
}else{
return0;
}
}
/**多重查询*/
publicListgetIphRegionList(intcityId){
QueryBuilderqb=cityInfoDao.queryBuilder();
qb.where(qb.and(Properties.CityId.eq(cityId),perties.InfoType.eq(HBContant.CITYINFO_IR)));
qb.orderAsc(Properties.Id);//排序依据
returnqb.list();
}
}