android - Sqlite foreign key -


i have 4 tables namely driveover, tyres, error , vehicle in database. when insert data drive on table, drive on id referenced in table tyres drive_log. when try adding data database, drive_log remains null , number enter valid though not exist in drive_over. searched online solutions , read foreign keys have turned on off default. added onconfigure method in sqliteopenhelper class , when tried insert invalid data in drive_log foreign key constraint not fail. pragma foreign_key=0; returned when tried check if turned on via command line on sqlite guessing foreign keys constraint not being enabled. question is, how turn on foreign keys? 

import android.content.context; import android.database.sqlite.sqlitedatabase; import android.database.sqlite.sqliteopenhelper;  public class database extends sqliteopenhelper {    public static final string database_name = "allan303.db";   public static final int database_version = 1;    public static final string table_drive_over = "drive_over";   public static final string drive_over_id = "drive_over_id";   public static final string date = "date";   public static final string vechile_log = "vechile_log";   public static final string error_log = "error_log";    public static final string table_vechiles = "vechiles";   public static final string vechiles_id = "vechiles_id";   public static final string model = "model";   public static final string year = "year";   public static final string number_plate = "number_plate";    public static final string table_tyres = "tyres";   public static final string tyres_id = "tyres_id";   public static final string drive = "drive_log";   public static final string axle = "axle";   public static final string tyre = "tyre";   public static final string pressure = "pressure";   public static final string units = "units";    public static final string table_errors = "errors";   public static final string errors_id = "errors_id";   public static final string message = "message";     private static final string create_table_vechiles = "create table " +      table_vechiles + " ("+ vechiles_id + " integer primary key, "         + model + " text, " + year + " text, " + number_plate + " text " +   ");";     private static final string create_table_errors = "create table " + table_errors + " ("+ errors_id + " integer primary key, " +         message + " text " + ");";    private static final string create_table_drive_over = "create table " + table_drive_over+ " (" + drive_over_id + " integer primary key autoincrement, "         + date + " text, " + vechile_log+ " integer, " + error_log + " integer," + " foreign key ("+vechile_log+") references "+table_vechiles+"("+vechiles_id+"), "         + " foreign key ("+error_log+") references "+table_errors+"("+errors_id+"));";   private static final string create_table_tyres = "create table "         + table_tyres + " ("         + tyres_id + " integer primary key autoincrement, "         + drive + " integer, "         + axle + " integer, "         + tyre + " integer, "         + pressure + " integer, "         + units + " text, "         + " foreign key ("+drive+") references "+table_drive_over+"("+drive_over_id+"));";    private static database sinstance;   public static synchronized database getinstance(context context){     if(sinstance == null){         sinstance = new database(context.getapplicationcontext());     }     return sinstance; }    public database(context context){     super(context, database_name, null, database_version); }   @override  public void onconfigure(sqlitedatabase db){     super.onconfigure(db);     db.setforeignkeyconstraintsenabled(true); }     @override   public void oncreate(sqlitedatabase db){       db.execsql(create_table_drive_over);       db.execsql(create_table_vechiles);       db.execsql(create_table_tyres);       db.execsql(create_table_errors); }    @override   public void onupgrade(sqlitedatabase db, int oldversion, int newversion){     if(oldversion != newversion){         db.execsql("drop table if exists" + table_drive_over);         db.execsql("drop table if exists" + table_vechiles);         db.execsql("drop table if exists" + table_tyres);         db.execsql("drop table if exists" + table_errors);         oncreate(db);     }   } }

you miss space after each of drop table statements.
won't allow deleting existing tables, , tables won't recreated.

this

@override public void onupgrade(sqlitedatabase db, int oldversion, int newversion){     if(oldversion != newversion){         db.execsql("drop table if exists" + table_drive_over);         db.execsql("drop table if exists" + table_vechiles);         db.execsql("drop table if exists" + table_tyres);         db.execsql("drop table if exists" + table_errors);         oncreate(db);     } }

should be

@override public void onupgrade(sqlitedatabase db, int oldversion, int newversion){     if(oldversion != newversion){         db.execsql("drop table if exists " + table_drive_over);         db.execsql("drop table if exists " + table_vechiles);         db.execsql("drop table if exists " + table_tyres);         db.execsql("drop table if exists " + table_errors);         oncreate(db);     } }

also, in posted code, there's missing closing bracket (}), needed close containing class.

please note public static final int database_version = 1; must increased each time make strucural changes database (i.e.: adding column table).


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