Best practices for Android databases -

my android application needs local database. best manner this? class sub use, subclass, reimplement, etc. have found information on net still don't know best practices.

it's pretty broad question , depends little on level on experience , usage.

but common practice create own contentprovider abstract access database. way can use uri execute select/update/delete/insert queries.

for sqlite database itself, use sqliteopenhelper abstract creation , upgrading of sqlite database. allow upgrade database without user losing of data in easy manner.

i can attach piece of code used in 1 of older projects started. implementing whole thing may out of scope of single question/answer.

public class myserviceprovider extends contentprovider {     private sqlitedatabase db;      @override     public boolean oncreate() {         // initialize database , assign private variable         mydatabasehelper sqlhelper = new mydatabasehelper(getcontext());         db = sqlhelper.getreadabledatabase();          return (db == null)?false:true;     }      @override     cursor query (uri uri, string[] projection, string selection, string[] selectionargs, string sortorder) {         // handle query here, form it, checks , access db         db.query(....);     } }  class mydatabasehelper extends sqliteopenhelper {     private static final string log_tag = "myapptag";     private static final string db_name = "databasename";     private static final string table_name = "tablename";     private static final int database_version = 2;     public static myserviceprovider.content_uri = uri.parse("content://com.mycompany.myapp.myappservice/mytableoridentifier");      public mydatabasehelper(context context){         super(context, db_name, null, database_version);     }      @override     public void oncreate(sqlitedatabase db) {         string sql = "create table if not exists ....";         db.execsql(sql);     }     @override     public void onupgrade(sqlitedatabase db, int oldversion, int newversion) {         // here can perform updates when database structure changes         // begin transaction         db.begintransaction();          try {             if(oldversion<2){                 // upgrade database structure version 1 2                 string altertable = "alter ....";                  db.execsql(altertable);                 log.i(log_tag,"successfully upgraded version 2");             }             // allows upgrade version next              // recent 1 in multiple steps don't know if user has             // skipped of previous updates             if(oldversion<3){                 // upgrade database structure version 2 3                 string altertable = "alter ....";                  db.execsql(altertable);                 log.i(log_tag,"successfully upgraded version 3");             }              // when code executed, changes applied              // database             db.settransactionsuccessful();         } catch(exception ex){             ex.printstacktrace();         } {             // ends transaction             // if there error, database won't altered             db.endtransaction();         }     } } 

and can use cursors interact database.

contentresolver contentresolver = getcontentresolver(); ... cursor c = contentresolver.query(         // uri results in content://com.mycompany.myapp.myappservice/mytableoridentifier/someid         uri.withappendedpath(myserviceprovider.content_uri, someid),         new string[] {             // fields need!             "mydbfieldineed"         },         null, null, null); 

this return cursor can iterate through , results. how things in android implemented (i.e. obtaining address address book works via uri , cursor too).

edit: realized links hard see code highlights. here link of important classes need.

• contentprovider | android developers
• sqliteopenhelper | android developers
• cursor | android developers
• urimatcher | android developers

edit 2: if work multiple tables, urimatcher important source