Single-instance database classes in Android projects

First, the database operation

Package com.ping.db;

Import Android.content.Context;
Import Android.database.sqlite.SQLiteDatabase;
Import Android.database.sqlite.SQLiteDatabase.CursorFactory;
Import Android.database.sqlite.SQLiteOpenHelper;

/**
* @describe < database operations >
*/
public class Sqlitetool extends Sqliteopenhelper {
private static final String db_name = "medicalscience.db"; Database file name
private static final int version = 1;//database versions


public static Sqlitetool newinstance (context context) {
return new Sqlitetool (context, db_name, NULL, VERSION);
}

Private Sqlitetool (context context, String name, Cursorfactory factory, int version) {
Super (context, name, Factory, version);
}

@Override
public void OnCreate (Sqlitedatabase db) {
Db.execsql (Dbtcollect.createtablesql ());//When you need to create a table, you can add
}

@Override
public void Onupgrade (sqlitedatabase db, int oldversion, int newversion) {//called when the database version becomes larger
OnCreate (DB);
}
}

Second, the database management class

Package com.ping.db;

Import Java.util.concurrent.atomic.AtomicInteger;

Import Android.annotation.SuppressLint;
Import Android.database.sqlite.SQLiteDatabase;
Import Android.os.Build;

Import com.ping.MyApplication;

/**
* @describe < database management Category >
*/
public class DBManager {
Private Atomicinteger Dbopencount = new Atomicinteger ();//Counter
private static DBManager instance;
private static Sqlitetool Sqllitetool;
Private Sqlitedatabase database;

public static synchronized DBManager getinstance () {
if (instance = = null) {
Synchronized (Dbmanager.class) {
if (instance = = null) {
Instance = new DBManager ();
}
}
}
return instance;
}

Private DBManager () {
Sqllitetool = Sqlitetool.newinstance (Myapplication.getinstance (). Getapplicationcontext ());
}

@SuppressLint ("Newapi")
Public synchronized Sqlitedatabase OpenDatabase () {
if (dbopencount.incrementandget () = = 1) {
Database = Sqllitetool.getwritabledatabase ();
if (Build.VERSION.SDK_INT >= 11) {
Database.enablewriteaheadlogging ();//allow simultaneous reading and writing
}
}
return database;
}

Public synchronized void CloseDatabase () {
if (dbopencount.decrementandget () = = 0) {
Database.close ();
Database = null;
}
}
}

Third, data additions and deletions to check

Package com.ping.db;

Import java.util.ArrayList;

Import android.content.ContentValues;
Import Android.database.Cursor;
Import Android.database.sqlite.SQLiteDatabase;

/**
* @describe < Database operations--operation of the collection table >
*/
public class Dbtcollect {
public static final String tname = "Tcollect";

To create a statement for a table
public static String Createtablesql () {
Return "CREATE TABLE IF not EXISTS" + Tname + "(Kid INTEGER PRIMARY KEY autoincrement, id text, title text)";
}

To delete a table statement
public static String Deletetabelsql () {
Return "DROP TABLE IF EXISTS" + tname;
}

Querying data for existence
public static Boolean iscollected (String ID) {
Boolean iscollected = false;
Sqlitedatabase db = Dbmanager.getinstance (). OpenDatabase ();//Get Sqlitedatabase Object
String 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
return iscollected;
}

Delete data
public static void Deletecollect (String mid) {
Sqlitedatabase db = Dbmanager.getinstance (). OpenDatabase ();
Db.delete (tname, "id =?", new string[] {ID});
Dbmanager.getinstance (). CloseDatabase ();
}

Add data
public static void Addcollect (Object obj) {
Sqlitedatabase db = Dbmanager.getinstance (). OpenDatabase ();
Contentvalues CV = new Contentvalues ();
Cv.put ("id", obj.id);
Cv.put ("title", Obj.title);
Db.insert (tname, NULL, CV);
Dbmanager.getinstance (). CloseDatabase ();
}

Querying data
public static arraylist<object> Getallcollect () {
Sqlitedatabase db = Dbmanager.getinstance (). OpenDatabase ();
cursor cursor = db.query (tname, NULL, NULL, NULL, NULL, NULL, NULL);
arraylist<object> Objs = new arraylist<object> ();
while (Cursor.movetonext ()) {
Object obj = new Object ();
Obj.id = cursor.getstring (Cursor.getcolumnindex ("id"));
Obj.title = cursor.getstring (Cursor.getcolumnindex ("title"));
Objs.add (obj);
}
Cursor.close ();
Dbmanager.getinstance (). CloseDatabase ();
return OBJS;
}
}

Single-instance database classes in Android projects