Single-instance database classes in Android projects to solve the locked

first, the database operation Packagecom.ping.db;ImportAndroid.content.Context;Importandroid.database.sqlite.SQLiteDatabase;Importandroid.database.sqlite.SQLiteDatabase.CursorFactory;ImportAndroid.database.sqlite.SQLiteOpenHelper;/*** @describe < database operations >*/ Public classSqlitetoolextendsSqliteopenhelper {Private Static FinalString db_name = "medicalscience.db";//Database file name Private Static Final intVERSION = 1;//Database Version    Public StaticSqlitetool newinstance (context context) {return NewSqlitetool (context, db_name,NULL, VERSION); } PrivateSqlitetool (context context, String name, Cursorfactory factory,intversion) {  Super(context, name, Factory, version);} @Override Public voidonCreate (Sqlitedatabase db) {Db.execsql (Dbtcollect.createtablesql ());//when you need to create a table, you can add a} @Override Public voidOnupgrade (Sqlitedatabase db,intOldversion,intNewVersion) {//called when the database version becomes largeronCreate (db);}} Second, the database management class Packagecom.ping.db;ImportJava.util.concurrent.atomic.AtomicInteger;ImportAndroid.annotation.SuppressLint;Importandroid.database.sqlite.SQLiteDatabase;ImportAndroid.os.Build;Importcom.ping.MyApplication;/*** @describe < database management Category >*/ Public classDBManager {PrivateAtomicinteger Dbopencount =NewAtomicinteger ();//counter Private StaticDBManager instance;Private StaticSqlitetool Sqllitetool;Privatesqlitedatabase database; Public Static synchronizedDBManager getinstance () {if(Instance = =NULL) {   synchronized(DBManager.class) {    if(Instance = =NULL) {instance=NewDBManager (); }   }  }  returninstance;} PrivateDBManager () {Sqllitetool=sqlitetool.newinstance (Myapplication.getinstance (). Getapplicationcontext ());} @SuppressLint ("Newapi")  Public synchronizedsqlitedatabase OpenDatabase () {if(Dbopencount.incrementandget () = = 1) {Database=sqllitetool.getwritabledatabase (); if(Build.VERSION.SDK_INT >= 11) {database.enablewriteaheadlogging ();//allow read and write simultaneous   }  }  returndatabase;}  Public synchronized voidcloseDatabase () {if(Dbopencount.decrementandget () = = 0) {database.close (); Database=NULL; }} III, data additions and deletions to search Packagecom.ping.db;Importjava.util.ArrayList;Importandroid.content.ContentValues;ImportAndroid.database.Cursor;Importandroid.database.sqlite.SQLiteDatabase;/*** @describe < database operations--operation of the collection table >*/ Public classDbtcollect { Public Static FinalString tname = "Tcollect"; //to create a statement for a table  Public StaticString Createtablesql () {return"CREATE TABLE IF not EXISTS" + Tname + "(Kid INTEGER PRIMARY KEY autoincrement, id text, title text)"; } //to delete a table statement  Public StaticString Deletetabelsql () {return"DROP TABLE IF EXISTS" +Tname;} //querying data for existence  Public Static Booleaniscollected (String id) {Booleaniscollected =false; Sqlitedatabase DB= Dbmanager.getinstance (). OpenDatabase ();//Get Sqlitedatabase ObjectString sql = "SELECT * from" + Tname + "WHERE id = '" + ID + "'"; Cursor Cursor= Db.rawquery (SQL,NULL); if(Cursor.getcount () > 0) {iscollected=true;  } cursor.close (); Dbmanager.getinstance (). CloseDatabase ();//Close  returniscollected;} //Delete Data  Public Static voidDeletecollect (String mid) {Sqlitedatabase db=dbmanager.getinstance (). OpenDatabase (); Db.delete (Tname,"id =?",Newstring[] {ID}); Dbmanager.getinstance (). CloseDatabase (); }     //Add Data  Public Static voidaddcollect (Object obj) {sqlitedatabase db=dbmanager.getinstance (). OpenDatabase (); Contentvalues CV=Newcontentvalues (); Cv.put ("id", obj.id); Cv.put ("Title", Obj.title); Db.insert (Tname,NULL, CV); Dbmanager.getinstance (). CloseDatabase (); } //Querying Data  Public StaticArraylist<object>Getallcollect () {Sqlitedatabase db=dbmanager.getinstance (). OpenDatabase (); Cursor Cursor= Db.query (Tname,NULL,NULL,NULL,NULL,NULL,NULL); ArrayList<Object> OBJS =NewArraylist<object>();  while(Cursor.movetonext ()) {Object obj=NewObject (); Obj.id= Cursor.getstring (Cursor.getcolumnindex ("id")); Obj.title= Cursor.getstring (Cursor.getcolumnindex ("title"));  Objs.add (obj);  } cursor.close ();  Dbmanager.getinstance (). CloseDatabase (); returnObjs;}}

Single-instance database classes in Android projects to solve the locked