I'm using SQLiteAssetHelper for importing ready databases into my app.
Now I want to release a 2nd version of my database, but when users update the app, the database in not updating. I see documentation and saw I must use setForcedUpgrade(), but i don't know where to use it, I'll appreciate if you guide me. :)
MyDatabase.java :
public class MyDatabase extends SQLiteAssetHelper {
private static final String DATABASE_NAME = "database.db";
private static final int DATABASE_VERSION = 2;
public MyDatabase(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}}
And I read database with these:
MyDatabase my;
SQLiteDatabase sq;
my = new MyDatabase(getApplicationContext());
sq = my.getWritableDatabase();
Thanks by the way.
For your example:
public class MyDatabase extends SQLiteAssetHelper {
private static final String DATABASE_NAME = "database.db";
private static final int DATABASE_VERSION = 2;
public MyDatabase(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
//FORCE UPGRADE BY DELETING OLD DATABASE
setForcedUpgrade(DATABASE_VERSION);
}}
In Android you should use SQLiteOpenHelper (http://developer.android.com/reference/android/database/sqlite/SQLiteOpenHelper.html). Inherid your own class and overwrite onCreate and onUpgrade.
Related
I have 2 classes which connect to a database. But with my current implementation I have to connect to 2 different databases.How can I fix this? If I use the same name for both databases it gives me an error
One class.....
public static final String DATABASE_NAME = "140398L.db";
Context context;
public PersistantAccountDAO(Context context) {
super(context, DATABASE_NAME, null, 1);
this.context = context;
}
Other class......
public class PersistantTransactionDAO extends SQLiteOpenHelper implements TransactionDAO {
public static final String DATABASE_NAME = "140398L";
public PersistantTransactionDAO(Context context) {
super(context, DATABASE_NAME, null, 1);
}
The DatabaseName is different, one class is 140398L.db and the other is 140398L
I must declare the following variable in a class extending Fragment:
public class CarrelloFragment extends Fragment {
DatabaseHelper sqLite=new DatabaseHelper(this); //here is the error
The constructor of DatabaseHelper class does not allow to do this with a fragment.
Here is the code of the constructor of DatabaseHelper class that extends SQLiteOpenHelper:
public class DatabaseHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "MySupermarket.db";
private static final int SCHEMA_VERSION = 2;
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, SCHEMA_VERSION);
}
Is there a way to declare a DatabaseHelper variable inside the fragment class?
try DatabaseHelper sqLite=new DatabaseHelper(getActivity());
I am trying to understand a class responsible to make a connection to a DB
the code is:
public class DBAdapter
{
final Context context;
DatabaseHelper DBHelper;
SQLiteDatabase db;
public DBAdapter(Context ctx)
{
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
//All the necessary method are implemented.
}
}
So to make a conection i should just"
DBAdapter db=new DBAdapter(this);
My question is what does this line this.context = ctx; does:
Why we can not omit that and simply :
public DBAdapter(Context ctx)
{
DBHelper = new DatabaseHelper(ctx);
}
Through this keyword you are specifying that the address or the reference of activity class which is coming to the DBAdapter method in ctx variable which is of Context type will be assigned to class level Context variable.
Though you can remove class level variable and this.context = ctx; line and simply write as you had specified
public DBAdapter(Context ctx)
{
DBHelper = new DatabaseHelper(ctx);
}
but if you want to use ctx (context reference) value to all over class it is advised to use class variable.
According to your class code. you does not required to assign context to another context variable . this is simplified code.
public class DBAdapter
{
DatabaseHelper DBHelper;
SQLiteDatabase db;
public DBAdapter(Context ctx)
{
DBHelper = new DatabaseHelper(ctx);
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
//All the necessary method are implemented.
}
}
To assign context to another variable is useful when you use context in some other methods as well. because the scope of the variable is limited to its method. you cannot use it outside of the constructor(according to your code)
If you're following the tutorial, they have a Context class variable because they reference it in the open method.
public DbAdapter(Context ctx)
{
this.mCtx = ctx;
mUsername = PreferenceManager.getDefaultSharedPreferences(ctx).getString(Preferences.USERNAME, "");
}
public DbAdapter open() throws SQLException
{
mDbHelper = new DatabaseHelper(mCtx);
mDb = mDbHelper.getWritableDatabase();
return this;
}
hello i am building a SQLite Db for my android application . this is the code :
package com.example.pap_e;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class FeedsDbAdapter {
private final Context mCtx;
private static final String DEBUG_TAG = "RSSDatabase";
private static final int DB_VERSION = 1;
private static final String DB_NAME = "rss_data";
public static String TABLE = "list";
public static final String ID = "_id";
public static final String RSS = "_rss";
public static final String TITLE = "_title";
public static final String PUBDATE = "_pubdate";
public static final String DESCRIPTION = "_description";
public static final String LINK = "_link";
private DatabaseHelper mDbHelper;
private SQLiteDatabase mDb;
private static class DatabaseHelper extends SQLiteOpenHelper{
DatabaseHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
}
#Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE_TABLE"+TABLE+"("+ID+ "integer PRIMARY KEY AUTOINCREMENT,"+RSS+"text NOT NULL,"
+TITLE+"text NOT NULL,"+PUBDATE+"text NOT NULL,"+DESCRIPTION+"text NOT NULL,"+LINK+"text NOT NULL"+")");
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE);
onCreate(db);}
}
public FeedsDbAdapter open() throws SQLException {
mDbHelper = new DatabaseHelper(mCtx);
mDb = mDbHelper.getWritableDatabase();
return this;
}
public void close() {
mDbHelper.close();
}
public boolean updateAnakoinosi(long rowId, String rss, String title,
String pubdate, String description, String link) {
ContentValues args = new ContentValues();
args.put(RSS, rss);
args.put(TITLE, title);
args.put(PUBDATE, pubdate);
args.put(DESCRIPTION, description);
args.put(LINK, link);
return mDb.update(TABLE, args, ID + "=" + rowId, null) > 0;}
public Cursor fetchAllAnakoinoseis() {
return mDb.query(TABLE, new String[] { ID, RSS, TITLE, PUBDATE,
DESCRIPTION,LINK }, null, null, null, null, null); }
}
The thing is that i get an error at public class FeedsDbAdapter that says:"The blank final field mCtx may not have been initialized" but i had it initialized using private final Context mCtx; Am i missing something here ? Thanks a lot in advance!
You didn't initialize the context yet. You have to initialize it inside FeedsDbAdapter constructor like :
public FeedsDbAdapter (Context context){
mCtx = context;
}
first declare FeedsDbAdapter constructor, because you use FeedsDbAdapter class through its constructor in other classes ans the other activity context will assign to this current context.
Change your code to :
private static class DatabaseHelper extends SQLiteOpenHelper{
DatabaseHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
mCtx = context;
}
This question of yours relates to java. This line private final Context mCtx; is just a declaration of field mCtx of type context. And as this field has been declared as final, It has to be iniliazed inside the constructor mCtx = context;. Even if mCtx is not declared as final, it has still to be initialized before being used.
Thats because your class is static... Remove static from your class and change your code to
DatabaseHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
mCtx = context;
}
Hey guys I already have a data in my database but I want to show it into spinner I'm really new to this problem, so would you guys help me to solve this problem,or I would prefer if you write the correct code for me :) Thanks in advance.
First this is my DB class
public class DBAdapter
{
public static final String UPDATEDATE = "UpdateDate";
//Declare fields in PersonInfo
public static final String ROWID = "_id";
public static final String PT_FNAME = "Username";
public static final String PT_COLORDEF = "ColorDeficiency";
private static final String DATABASE_CREATE =
"create table PersonInfo (_id integer primary key autoincrement, "
+ "Username text not null, ColorDeficiency text);";
private static final String DATABASE_NAME = "CAS_DB";
private static final String tbPerson = "PersonInfo";
private static final int DATABASE_VERSION = 1;
private final Context databaseContext;
private final Context context;
private DatabaseHelper DBHelper;
public SQLiteDatabase db;
public DBAdapter(Context ctx)
{
this.context = ctx;
DBHelper = new DatabaseHelper(context);
databaseContext = ctx;
}
//start database helper
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
#Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(DATABASE_CREATE);
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion,
int newVersion)
{
}
}
//---opens the database---
public DBAdapter open() throws SQLException
{
db = DBHelper.getWritableDatabase();
return this;
}
//---closes the database---
public void close()
{
DBHelper.close();
}
public Cursor all(Activity activity){
String[] from ={ROWID,PT_FNAME,PT_COLORDEF};
String order = PT_FNAME;
Cursor cursor =db.query(tbPerson, from, null, null, null, null, order);
activity.startManagingCursor(cursor);
return cursor;
}
In another class
private DBAdapter db;
private Spinner spinner;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.greeting);
initComponent();
db = new DBAdapter(this);
Cursor c = db.all(this);
SimpleCursorAdapter CursorAdapter = new SimpleCursorAdapter(
this,android.R.layout.simple_spinner_item,c,
new String[]{DBAdapter.PT_FNAME},new int[]{android.R.id.list});
CursorAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(CursorAdapter);
try changing
new int[]{android.R.id.list}
to
new int[]{android.R.layout.simple_spinner_item}