java - Is this correct way to use Sqlite database in Android -
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i beginner android. start learning it. creating register form integrated sqlite database. throwing error when click register button. please me. correct ? wrong code. how can debug application in android. using gennymotion emulator.
this database helper class : databasehelper.java
public class databasehelper extends sqliteopenhelper { private static final int database_version = 1; private static final string database_name = "contacts.db"; private static final string table_name = "contacts"; private static final string column_id = "id"; private static final string column_name = "name"; private static final string column_password = "password"; sqlitedatabase db; private static final string table_create = "create table contacts (id integer primary key not null auto_increment,"+ "name text not null , password text not null);"; public databasehelper(context context){ super(context,database_name,null,database_version); } @override public void oncreate(sqlitedatabase db) { this.db = db; db.execsql(table_create); } @override public void onupgrade(sqlitedatabase db, int oldversion, int newversion) { string query = "drop table if exists "+table_name; db.execsql(query); this.oncreate(db); } public void insertcontact(contact c) { db = getwritabledatabase(); contentvalues values = new contentvalues(); values.put(column_name,c.getname()); values.put(column_password,c.getpassword()); db.insert(table_name, null, values); db.close(); } public string getusers() { string users = ""; db = this.getreadabledatabase(); string query = "select name,password "+table_name; cursor cursor = db.rawquery(query,null); if(cursor.movetofirst()) { do{ users = users + cursor.getstring(0)+":"+cursor.getstring(1)+" "; }while(cursor.movetonext()); } return users; } } this register activity.
public class registeractivity extends activity { databasehelper helper = new databasehelper(this); button registerbtn; @override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.register); registerbtn = (button)findviewbyid(r.id.btn_register); registerbtn.setonclicklistener(new view.onclicklistener() { @override public void onclick(view v) { registerbtnclick(v); } }); } public void registerbtnclick(view v) { string name = ((edittext)findviewbyid(r.id.tf_name_register)).gettext().tostring(); string password = ((edittext)findviewbyid(r.id.tf_password_register)).gettext().tostring(); string confirm_password = ((edittext)findviewbyid(r.id.tf_confirm_password_register)).gettext().tostring(); if(name.isempty()) { toast.maketext(getbasecontext(),"name should not empty",toast.length_long).show(); } else if(password.isempty()) { toast.maketext(getbasecontext(),"password required",toast.length_long).show(); } else if(!password.equals(confirm_password)) { toast.maketext(getbasecontext(),"password not match",toast.length_long).show(); } else{ //save database contact c = new contact(); c.setname(name); c.setpassword(password); helper.insertcontact(c); } } } please me when hit register button. throwing error. how can detect error , wrong code please ? start learning android.
here:
databasehelper helper = new databasehelper(this); this line causing issue because accessing activity context before creation of it.
use this or registeractivity.this inside other valid context.
declare helper @ class level , initialize inside oncreate method as:
databasehelper helper ;//>> declare here @override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.register); // initialize `helper` here helper = new databasehelper(this); .... }
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