Database Creation under Android

The databases used under Android are:SQLite, embedded lightweight

To create a SQLite database is generally to inherit the Sqliteopenhelper class.

The official documentation is this:

Since it is an abstract class that must be inherited with a class, there are two abstract methods OnCreate and Onupgrade must be implemented.

OnCreate method : is called when the database is first created (but is not called when created), especially for table structure initialization, requires SQL statement

Onupgrade Method : Database version number changes will be executed, especially for the table structure changes, after Android4.0 version can only increase or decrease, or there will be an exception

The following creates a Mysqliteopenhelper class to inherit from the Sqliteopenhelper class.

1  Public classMysqliteopenhelperextendsSqliteopenhelper {2 3      PublicMysqliteopenhelper (Context context) {4         //Context: Contexts Name: Database file names Factory: Used to create cursor objects, default NULL5         //version: The release number of the database, starting with 1, if a change occurs, the Onupgrade method calls6         Super(Context, "starry.db",NULL, 2);7     }8 @Override9      Public voidonCreate (Sqlitedatabase db) {Ten          OneDb.execsql ("CREATE table info (_id integer primary key autoincrement, name varchar (20))"); A     } - @Override -      Public voidOnupgrade (Sqlitedatabase db,intOldversion,intnewversion) { theDb.execsql ("ALTER TABLE info add phone varchar (11)"); -     } -  -}

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When you instantiate a mysqliteopenhelper in Mainactivity.java, you can initialize the database by running the Getreadabledatabase method.

1     New Mysqliteopenhelper (mcontext); 2     Mysqliteopenhelper.getreadabledatabase ();

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Database Creation under Android