SQLite Learning Notes

1: Create a Db.java that inherits from Sqliteopenhelper

Package Com.example.sqlite;import Android.content.context;import Android.database.sqlite.sqlitedatabase;import Android.database.sqlite.sqlitedatabase.cursorfactory;import Android.database.sqlite.sqliteopenhelper;public Class DB extends Sqliteopenhelper {private String sql = "CREATE TABLE person (" + "ID integer primary key autoincrement," + "NA  Me text, "+" Age integer) ";p ublic DB (context context, String name, cursorfactory factory,int version) {Super (context, name, Factory, version);} @Overridepublic void OnCreate (Sqlitedatabase db) {db.execsql (SQL);} @Overridepublic void Onupgrade (sqlitedatabase db, int oldversion, int newversion) {//TODO auto-generated method stub}}

Mainactivity.java

Package Com.example.sqlite;import Android.content.contentvalues;import Android.database.cursor;import Android.database.sqlite.sqlitedatabase;import Android.database.sqlite.sqliteopenhelper;import Android.os.Bundle; Import Android.support.v7.app.actionbaractivity;import Android.widget.textview;import Android.widget.Toast;public Class Mainactivity extends Actionbaractivity {private TextView text;p rivate sqlitedatabase database = null; @Overridepro tected void OnCreate (Bundle savedinstancestate) {super.oncreate (savedinstancestate); Setcontentview ( R.layout.activity_main); this.text = (TextView) Findviewbyid (R.id.text); Sqliteopenhelper helper = new DB (This, "test.db", NULL, 1);d atabase = Helper.getwritabledatabase ();//Start testing the written function//put five data first for (int i = 0; i<5; i++) {Contentvalues values = new Contentvalues (); Values.put ("name", "Insert Data"); Values.put ("Age", i+20 Insert ("person", values);}    Delete ("Delete from person where age>23"); Remove the cursor cursor = query ("SELECT * from person") that is greater than 23 years old;/showdata (cursor); Display data Contentvalues values = new Contentvalues (), Values.put ("name", "Test Update Method"), Values.put ("Age", 6666), Update ("  Person ", values," age= ", New string[]{" 21 "});    Set the full age of 21 to 6666showData (cursor), cursor.close ();d atabase.close (); }/* * @param tableName table name * @param values DataSet */private void Insert (String tablename,contentvalues values) {if (databas E! = null) {Database.insert (tableName, null, values);//Can of course be database.exesql (SQL statement execution)}else {Toast.maketext (this, " Database object has not been instantiated!! ", Toast.length_long). Show ();}} /* * Delete data based on SQL statement */private void Delete (String sql) {if (database! = null) {database.execsql (SQL);//Of course you can use Database.exesql (SQL statement execution)} else {Toast.maketext (this, "the database object has not been instantiated!! ", Toast.length_long). Show ();}} /* * Query statement that returns a cursor cursor */private cursor query (String SQL) {cursor cursor = database.rawquery (sql, NULL); return cursor; /* Change data */private void update (String table,contentvalues values,string whereclause,string[] whereargs) {if (Database! = N ull) {DATABASE.UPDATe (table, values, Whereclause, Whereargs);//can also be database.exesql (SQL statement execution)}else {Toast.maketext (this, "the database object has not been instantiated!! ", Toast.length_long). Show ();}} /* * Show all data */private void ShowData (cursor cursor) {while (Cursor.movetonext ()) {int nameColumn = Cursor.getcolumnindex ("N Ame "); int agecolumn = Cursor.getcolumnindex (" Age "); String name = cursor.getstring (nameColumn); int age = Cursor.getint (Agecolumn); This.text.append ("Name:" +name+ "Ages:" +age+ "\ n");} This.text.append ("All data query finished! ");}}

SQLite Learning Notes