Existing DB - SQLite / android - read from db -
i tried many times use existing data base sqlite in android app ! can create new db, here , wanna use existing 1 ! codes , there's no problems there , not error , doesnot work , 1 can me whith ?
databasehelper.java:
public class databasehelper extends sqliteopenhelper { private static string db_path = "/data/data/com.global.getrain/databases/"; private static string db_name = "bookdb"; private sqlitedatabase mydatabase; private context mycontext; public databasehelper(context context) { super(context, db_name, null, 1); this.mycontext = context; } public void createdatabase() throws ioexception{ boolean dbexist = checkdatabase(); if(dbexist){ }else{ this.getreadabledatabase(); try { copydatabase(); } catch (ioexception e) { throw new error("error copying database"); } } } public boolean checkdatabase(){ sqlitedatabase checkdb = null; try{ string mypath = db_path + db_name; checkdb = sqlitedatabase.opendatabase(mypath, null, sqlitedatabase.open_readonly); }catch(sqliteexception e){ } if(checkdb != null){ checkdb.close(); } return checkdb != null ? true : false; } private void copydatabase() throws ioexception{ //open local db input stream inputstream myinput = mycontext.getassets().open(db_name); // path created empty db string outfilename = db_path + db_name; //open empty db output stream outputstream myoutput = new fileoutputstream(outfilename); byte[] buffer = new byte[1024]; int length; while ((length = myinput.read(buffer))>0){ myoutput.write(buffer, 0, length); } //close streams myoutput.flush(); myoutput.close(); myinput.close(); } public void opendatabase() throws sqlexception{ //open database string mypath = db_path + db_name; mydatabase = sqlitedatabase.opendatabase(mypath, null, sqlitedatabase.open_readonly); } @override public synchronized void close() { if(mydatabase != null) mydatabase.close(); super.close(); } @override public void oncreate(sqlitedatabase db) { // sql statement create book table string create_book_table = "create table books ( " + "id integer primary key autoincrement, " + "title text, " + "author text )"; // create books table db.execsql(create_book_table); } @override public void onupgrade(sqlitedatabase db, int oldversion, int newversion) { // drop older books table if existed db.execsql("drop table if exists books"); // create fresh books table this.oncreate(db); } // books table name private static final string table_books = "books"; // books table columns names private static final string key_id = "id"; private static final string key_title = "title"; private static final string key_author = "author"; private static final string[] columns = { key_id, key_title, key_author }; public void addbook(book book) { log.d("addbook", book.tostring()); // 1. reference writable db sqlitedatabase db = this.getwritabledatabase(); // 2. create contentvalues add key "column"/value contentvalues values = new contentvalues(); values.put(key_title, book.gettitle()); // title values.put(key_author, book.getauthor()); // author // 3. insert db.insert(table_books, // table null, // nullcolumnhack values); // key/value -> keys = column names/ values = column // values // 4. close db.close(); } public book getbook(int id) { // 1. reference readable db sqlitedatabase db = this.getreadabledatabase(); // 2. build query cursor cursor = db.query(table_books, // a. table columns, // b. column names " id = ?", // c. selections new string[] { string.valueof(id) }, // d. selections args null, // e. group null, // f. having null, // g. order null); // h. limit // 3. if got results first 1 if (cursor != null) cursor.movetofirst(); // 4. build book object book book = new book(); book.setid(integer.parseint(cursor.getstring(0))); book.settitle(cursor.getstring(1)); book.setauthor(cursor.getstring(2)); log.d("getbook(" + id + ")", book.tostring()); // 5. return book return book; } // books public list<book> getallbooks() { list<book> books = new linkedlist<book>(); // 1. build query string query = "select * " + table_books; // 2. reference writable db sqlitedatabase db = this.getwritabledatabase(); cursor cursor = db.rawquery(query, null); // 3. go on each row, build book , add list book book = null; if (cursor.movetofirst()) { { book = new book(); book.setid(integer.parseint(cursor.getstring(0))); book.settitle(cursor.getstring(1)); book.setauthor(cursor.getstring(2)); // add book books books.add(book); } while (cursor.movetonext()); } log.d("getallbooks()", books.tostring()); // return books return books; } // updating single book public int updatebook(book book) { // 1. reference writable db sqlitedatabase db = this.getwritabledatabase(); // 2. create contentvalues add key "column"/value contentvalues values = new contentvalues(); values.put("title", book.gettitle()); // title values.put("author", book.getauthor()); // author // 3. updating row int = db.update(table_books, // table values, // column/value key_id + " = ?", // selections new string[] { string.valueof(book.getid()) }); // selection // args // 4. close db.close(); return i; } // deleting single book public void deletebook(book book) { // 1. reference writable db sqlitedatabase db = this.getwritabledatabase(); // 2. delete db.delete(table_books, key_id + " = ?", new string[] { string.valueof(book.getid()) }); // 3. close db.close(); log.d("deletebook", book.tostring()); } } mainactivity.java:
public class mainactivity extends activity { private listview obj; protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_main); databasehelper db = new databasehelper(this); db = new databasehelper(this); try { db.createdatabase(); } catch (ioexception ioe) { throw new error("unable create database"); } try { db.opendatabase(); } catch (sqlexception sqle) { throw sqle; } /* * db.addbook(new book("android application development cookbook", * "wei meng lee")); db.addbook(new book( * "android programming: big nerd ranch guide", * "bill phillips , brian hardy")); db.addbook(new book( * "learn android app development", "wallace jackson")); * * * // books list<book> list = db.getallbooks(); * * // delete 1 book db.deletebook(list.get(0)); * * // books db.getallbooks(); */ obj = (listview) findviewbyid(r.id.listview1); list<book> array_list = db.getallbooks(); arrayadapter<book> arrayadapter = new arrayadapter<book>(this, android.r.layout.simple_list_item_1, array_list); obj.setadapter(arrayadapter); db.close(); } ps : can publish book class if that's !
the issue in assets folder , must :
assets/databases/
i added databases folder work :d
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