The wording of the Android database upgrade

<span id="Label3"></p><p><p>Add the upgrade operation to the base class Table:</p></p><p><p></p></p><pre name="code" class="java">Public abstract class dbbasetable {private static final String TAG = "dbbasetable";/** * @return The DB table name */abstr Act String getName ();/** * creates the DB table according to the DB scheme * * @param db */abstract void OnCreate (sqlited Atabase db), void onupgrade (sqlitedatabase db, int oldversion, int newversion, String tempname) {//rename o LD table to temporary name<strong>dbutils.renametable (db, getName (), tempname);</strong>//create Clear Table According to the new scheme <strong> onCreate (db);</strong>//copy content of the matching Columns from the old table to the new one <strong> joincolumns (db, tempname, getName ());</strong> Delete old table <strong> dbutils.droptable (db, Tempname);</strong>//this is a few updates The contents of the table Inittablecontent (db); } void inittablecontent (sqlitedatabase db) {} void joincolumns (sqlitedatabase db, String tempName, String tableName) {<strong>dbutils.joincolumns (db, tempname, tableName);</strong>}} </pre><br><pre name="code" class="java">Final class Dbutils {private static final String TAG = "dbutils"; Private static Final Boolean DEBUG = false; private static final String sqlite_stmt_list_tables = "select name from sqlite_master WHERE type= ' table ' and name N OT like ' sqlite_% ' and ' name ' is not a like ' android% '; private static final String Sqlite_table_name_column = "NAME"; private static final String sqlite_stmt_template_list_columns = "select * from%s LIMIT 1"; private static final String sqlite_stmt_template_drop_table = "DROP TABLE IF EXISTS%s"; private static final String sqlite_stmt_template_rename_table = "ALTER TABLE%s RENAME to%s"; private static final String Sqlite_stmt_template_copy_columns = "INSERT into%s (%s) select%s from%s"; /** * @param db * @return Collection object containing table names in the database */static collection&lt ; string> listtables (sqlitedatabase db) {cursor cursor = db.rawquery (sqlite_stmt_list_tables, null); if (cursor = = NULL | |!cursor.movetofirst ()) {if (cursor! = Null) {cursor.close (); } return null; } int table_name_column = Cursor.getcolumnindex (sqlite_table_name_column); hashset<string> tables = new hashset<string> (cursor.getcount ()); Do {tables.add (cursor.getstring (table_name_column)); } while (cursor.movetonext ()); Cursor.close (); Return tables; }/** * @param db * @param table * @return List of column names in the DB table */public static list<string> listcolumns (sqlitedatabase db, String table) {cursor cursor = db.rawquery (string.forma T (sqlite_stmt_template_list_columns, table), null); if (cursor = = Null) {return null; } list<string> columns = arrays.aslist (cursor.getcolumnnames ()); Cursor.close (); Return columns; } /** * @param db * @param table */static void droptable (sqlitedatabase db, String table) {DB.E Xecsql (string.format (sqlite_stmt_template_drop_table, TABLE)); } static void Renametable (sqlitedatabase db, string oldname, string NewName) {db.execsql (string.format (SQLI te_stmt_template_rename_table, oldname, newName)); } static void Joincolumns (sqlitedatabase db, string oldtable, string Newtable) {//delete all re Cords in the new table before copying from the old table Db.delete (newtable, null, null); Find columns which exist in both tables arraylist<string> old_columns = new Arraylist<string> (listcol Umns (db, oldtable)); list<string> new_columns = ListColumns (db, newtable); Old_columns.retainall (new_columns); String common_columns = Textutils.join (",", old_columns); Copy records from old table to new table Example:<span style= "fOnt-family: Microsoft Jacob black; ><strong><span style= "font-size:10px;" >insert to Mytest1 (_id,account_id,test1,test3) SELECT _id,account_id,test1,test3 from Mytest1_temp_</span ></strong></span> db.execsql (string.format (sqlite_stmt_template_copy_columns, newtable, common_ columns, common_columns, oldtable)); }}</pre><br>Then overload the Onupgrade method in Dbhelper:<p><p></p></p><p><p></p></p><pre name="code" class="java"> @Override public void Onupgrade (sqlitedatabase db, int oldversion, int. Newversion) {//get table names in the O LD db collection<string> old_tables = Dbutils.listtables (db); if (old_tables = = NULL | | old_tables.size () = = 0) {onCreate (db); Return }//get table names in the new DB set<string> new_tables = DataBaseClass.sRCMDbTables.keySet () ; Try {db.begintransaction (); Remove old tables which is not in the new DB scheme hashset<string> obsolete_tables = new Hashset<s Tring> (); For (String table:old_tables) {if (!new_tables.contains (table)) {System.out.println ("= = = =dbhelp Onupgrade droptable table= "+table); Dbutils.droptable (db, table); Obsolete_tables.add (table); }} Old_tables.removeall (obsolete_tables);Create and upgrade new tables Dbbasetable table_descriptor; For (String table:new_tables) {table_descriptor = DataBaseClass.sRCMDbTables.get (table); Check If the new table exists in the old DB if (old_tables.contains (table)) { String temp_name = gettemptablename (table, old_tables, new_tables); System.out.println ("====dbhelp onupgrade temp_name =" +temp_name); Table_descriptor.onupgrade (db, oldversion, newversion, temp_name); } else {table_descriptor.oncreate (db); }} db.settransactionsuccessful (); } catch (throwable e) {throw new runtimeexception ("DB upgrade failed:" + e.getmessage ()); } finally {db.endtransaction (); } }</pre><br><br><p><p></p></p><p><p>The central idea is:</p></p><p><p>In contrast to the old and new database structure, if there is a table in the old table in the new database, then delete the old</p></p><p><p>Suppose there is a table update in the new Database. You need to update the structure of this table. and copy the data from the old Table.</p></p><p><p>(rename the old table to a name.) Copy the data from the named table to the new Table)</p></p><p><p>The code can be downloaded in http://download.csdn.net/detail/baidu_nod/7684479</p></p> <p style="font-size:12px;"><p style="font-size:12px;">Copyright Notice: This article blog original Article. blogs, without consent, may not be reproduced.</p></p> <p><p>The wording of the Android database upgrade</p></p></span>