Android開源:資料庫ORM框架GreenDao學習(三)封裝工具類使用
部落格轉載地址:http://www.it165.net/pro/html/201401/9026.html
上一篇中講解了基本的增刪改查,本篇繼續講解 QureyBuilder 使用,及工具類封裝使用
一、使用QureyBuilder
實現表的增刪改查
增刪改查相當方便,完全的面向物件,不需要涉及到任何的sql語言。
1.查詢
範例1:查詢某個表是否包含某個id:
public boolean isSaved(int ID){ QueryBuilder<SaveList> qb = saveListDao.queryBuilder(); qb.where(Properties.Id.eq(ID)); qb.buildCount().count(); return qb.buildCount().count() > 0 ? true : false; }
範例2:獲取整個表的資料集合,一句程式碼就搞定!
public List<PhotoGalleryDB> getPhotoGallery() { return photoGalleryDao.loadAll();// 獲取圖片相簿 }
範例3:通過一個欄位值查詢對應的另一個欄位值(為簡便直接使用下面方法,也許有更簡單的方法,尚未嘗試)
/** 通過圖片id查詢其目錄id */ public int getTypeId(int picId) { QueryBuilder<PhotoGalleryDB> qb = photoGalleryDao.queryBuilder(); qb.where(Properties.Id.eq(picId)); if (qb.list().size() > 0) { return qb.list().get(0).getTypeId(); }else{ return -1; } }
範例4:查詢所有第一姓名是“Joe”並且以lastname排序。
List joes = userDao.queryBuilder()
where(Properties.FirstName.eq("Joe"))
orderAsc(Properties.LastName)
list();
範例5:多重條件查詢
(1)獲取id為cityId並且infotype為HBContant.CITYINFO_SL的資料集合:
public List<CityInfoDB> getSupportingList(int cityId){ QueryBuilder<CityInfoDB> qb = cityInfoDao.queryBuilder(); qb.where(qb.and(Properties.CityId.eq(cityId),Properties.InfoType.eq(HBContant.CITYINFO_SL))); qb.orderAsc(Properties.Id);// 排序依據 return qb.list(); }
(2)獲取firstname為“Joe”並且出生於1970年10月以後的所有user集合:
QueryBuilder qb = userDao.queryBuilder();
qb.where(Properties.FirstName.eq("Joe"),
qb.or(Properties.YearOfBirth.gt(1970),
qb.and(Properties.YearOfBirth.eq(1970), Properties.MonthOfBirth.ge(10))));
List youngJoes = qb.list();
範例6:獲取某列物件
picJsonDao.loadByRowId(picId);
2.增添/插入、修改
插入資料更加簡單,也是隻要一句程式碼便能搞定!
public void addToPhotoTable(Photo p){
photoDao.insert(p);
}
插入時需要new一個新的物件,範例如下:
DevOpenHelper helper = new DaoMaster.DevOpenHelper(this, "notes-db", null);
db = helper.getWritableDatabase();
daoMaster = new DaoMaster(db);
daoSession = daoMaster.newSession();
noteDao = daoSession.getNoteDao();
Note note = new Note(null, noteText, comment, new Date());
noteDao.insert(note);
修改更新:
photoDao.insertOrReplace(photo);
photoDao.insertInTx(photo);
3.刪除:
(1)清空表格資料
/** 清空相簿圖片列表的資料 */
public void clearPhoto(){
photoDao.deleteAll();
}
(2)刪除某個物件
public void deleteCityInfo(int cityId){
QueryBuilder<DBCityInfo> qb = cityInfoDao.queryBuilder();
DeleteQuery<DBCityInfo> bd = qb.where(Properties.CityId.eq(cityId)).buildDelete();
bd.executeDeleteWithoutDetachingEntities();
}
參考:https://github.com/greenrobot/greenDAO/issues/34
由上可見,使用greenDAO進行資料庫的增刪改查時及其方便,而且效能極佳。
(三)常用方法筆記
1.在Application實現得到DaoMaster和DaoSession的方法:
private static DaoMaster daoMaster;
private static DaoSession daoSession;
/**
* 取得DaoMaster
*
* @param context
* @return
*/
public static DaoMaster getDaoMaster(Context context)
{
if (daoMaster == null){
OpenHelper helper = new DaoMaster.DevOpenHelper(context, ontant.DATABASE_NAME, null);
daoMaster = new DaoMaster(helper.getWritableDatabase());
}
return daoMaster;
}
/**
* 取得DaoSession
*
* @param context
* @return
*/
public static DaoSession getDaoSession(Context context){
if (daoSession == null){
if (daoMaster == null){
daoMaster = getDaoMaster(context);
}
daoSession = daoMaster.newSession();
}
return daoSession;
}
2.增刪改查工具類:
public class DBHelper{
private static Context mContext;
private static DBHelper instance;
private CityInfoDBDao cityInfoDao;
private DBHelper(){
}
public static DBHelper getInstance(Context context){
if (instance == null){
instance = new DBHelper();
if (mContext == null){
mContext = context;
}
// 資料庫物件
DaoSession daoSession = HBApplication.getDaoSession(mContext);
instance.cityInfoDao = daoSession.getCityInfoDBDao();
}
return instance;
}
/** 新增資料 */
public void addToCityInfoTable(CityInfo item){
cityInfoDao.insert(item);
}
/** 查詢 */
public List<EstateLoveListJson> getCityInfoList(){
QueryBuilder<CityInfo> qb = cityInfoDao.queryBuilder();
return qb.list();
}
/** 查詢 */
public List<CityInfo> getCityInfo(){
return cityInfoDao.loadAll();// 查詢圖片相簿
}
/** 查詢 */
public boolean isSaved(int Id){
QueryBuilder<CityInfo> qb = cityInfoDao.queryBuilder();
qb.where(Properties.Id.eq(Id));
qb.buildCount().count();
return qb.buildCount().count() > 0 ? true : false;// 查詢收藏表
}
/** 刪除 */
public void deleteCityInfoList(int Id){
QueryBuilder<CityInfo> qb = cityInfoDao.queryBuilder();
DeleteQuery<CityInfo> bd = where(Properties.Id.eq(Id)).buildDelete();
bd.executeDeleteWithoutDetachingEntities();
}
/** 刪除 */
public void clearCityInfo(){
cityInfoDao.deleteAll();
}
/** 通過城市id查詢其型別id */
public int getTypeId(int cityId){
QueryBuilder<CityInfo> qb = cityInfoDao.queryBuilder();
qb.where(Properties.Id.eq(cityId));
if (qb.list().size() > 0){
return qb.list().get(0).getTypeId();
}else{
return 0;
}
}
/** 多重查詢 */
public List<CityInfo> getIphRegionList(int cityId){
QueryBuilder<CityInfoDB> qb = cityInfoDao.queryBuilder();
qb.where(qb.and(Properties.CityId.eq(cityId), perties.InfoType.eq(HBContant.CITYINFO_IR)));
qb.orderAsc(Properties.Id);// 排序依據
return qb.list();
}
}
另外,還有多表關聯、惰性載入等功能,待後續研究。
參考資料:
1.https://github.com/greenrobot/greenDAO
2.http://greendao-orm.com/documentation/how-to-get-started/
3.http://blog.csdn.net/krislight/article/details/9391455