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How to get PRIMARY KEY ID of objects in DataBase -android sqlite 3

I want to get a primary key of a saved object in a table in database I wrote a class to handle my database I want to add a function to it for getting the Id (I tried to give id to objects manually it didn't go well so I prefer the primary key id)so how should this function look like?and also if u see a thing that needs changing in my code please let me know.
public class DataBaseHandler extends SQLiteOpenHelper {
private static int _ID =0;
private int ID =0;
private ArrayList<marker_model> markerList=new ArrayList<>();
public DataBaseHandler(Context context) {
super(context, Constans.TABLE_NAME, null, Constans.DATABASE_VERSION);
}
#Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE "+Constans.TABLE_NAME+
" ("+Constans.MARKER_ID+" INTEGER PRIMARY KEY, "+
Constans.MARKER_TITLE+" TEXT, " +Constans.MARKER_DESCRIPTION+" TEXT ,"+Constans.My_MARKER_ID+" INT );");
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS "+Constans.TABLE_NAME);
onCreate(db);
}
public void AddMarker(marker_model marker){
marker.set_Id(_ID);
SQLiteDatabase db=this.getWritableDatabase();
ContentValues values=new ContentValues();
values.put(Constans.MARKER_TITLE,marker.getTitle());
values.put(Constans.My_MARKER_ID,marker.get_Id());
values.put(Constans.MARKER_DESCRIPTION,marker.getDescription());
db.insert(Constans.TABLE_NAME,null,values);
db.close();
Log.d(TAG, "AddMarker: Successfully added to DB");
_ID++;
}
public ArrayList<marker_model> getMarkers(){
markerList.clear();
SQLiteDatabase db =getReadableDatabase();
Cursor cursor=db.query(Constans.TABLE_NAME
,new String[]{Constans.My_MARKER_ID,Constans.MARKER_TITLE,
Constans.MARKER_DESCRIPTION},null,null,null,null,null);
if (cursor.moveToFirst()){
do {
ID=0;
marker_model model=new marker_model();
model.set_Id(_ID);
model.setDescription(cursor.getString(cursor.getColumnIndex(Constans.MARKER_DESCRIPTION)));
model.setTitle(cursor.getString(cursor.getColumnIndex(Constans.MARKER_TITLE)));
markerList.add(model);
ID++;
}while(cursor.moveToNext());
}
cursor.close();
db.close();
return markerList;
}
public int getMarkerPrimaryId(Marker marker){
}
}

Assuming that you want to get the _id (the primary key) from the database and that marker is an instance of a marker_model object AND that
marker_model has methods getTitle and getDescription that return a string with the respective values, then something along the lines of the following would work.
public long getMarkerPrimaryId(Marker marker){
long rv = 0;
SQLiteDatabase db = getReadableDatabase();
String[] columns = new String[]{Constans.My_MARKER_ID};
String whereclause = Constans.MARKER_TITLE + "=?" +
Constans.MARKER_DESCRIPTION + "=?";
String[] whereargs = new String[]{
marker.getTitile,
marker.getDescription
}
Cursor cursor = db.query(Constans.TABLE_NAME,
columns,
whereclause,
whereargs,
null,null,null);
if (cursor.getCount() > 0) {
cursor.moveToFirst();
rv = cursor.getLong(cursor.getColumnIndex(Constans.My_MARKER_ID);
}
cursor.close;
db.close;
return rv;
}
However, if your issue is that getMarkers is not setting the Id member appropriately (i.e. to match the id in the database), then changing model.set_Id(_ID);
to
model.set_Id(cursor.getLong(cursor.getColumnIndex(Constans.My_MARKER_ID));
would suffice.
If your expectation is that an automatically generated incrementing _id is to be used the addMarker is a little flawed. Simply by removing the line values.put(Constans.My_MARKER_ID,marker.get_Id()); will result in _id being automatically generated (which how _id's tend to be used).
The following (BACKGROUND paragraph mostly) explains much about automatically generated unique identifiers (even though it is about AUTOINCREMENT you likely DO NOT want to code AUTOINCREMENT).
Id suggest that rather than :-
if (cursor.moveToFirst()){
do {
...
}while(cursor.moveToNext());
using :-
while (cursor.moveToNext() {
....
}
is simpler (a cursor, when created, will be positioned to before the first row (moveToPosition(-1) has the same effect) , moveToNext() will move to the first row the first time, if there are no rows the loop will not be entered (you may wish to consider this and the state of returned markerlist)).
Note! the above has been written without testing, so there may be the odd mistake.

Database in android studio [closed]

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I'm a windows phone developer and newly I started developing android apps using android studio.
I need to create a database and store in it values and retrieve the updated values on screen, so I need help in:
Creating the database.
How to show values from the database on screen?

to create database , you need to extend SQLiteOpenHelper and need a constructor that takes Context.
lets say you name this class DBOperator. The table creation process will look something like this ,
public class DbOperator extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "DB_NAME";
protected static final String FIRST_TABLE_NAME = "FIRST_TABLE";
protected static final String SECOND_TABLE_NAME = "SECOND_TABLE";
public static final String CREATE_FIRST_TABLE = "create table if not exists "
+ FIRST_TABLE_NAME
+ " ( _id integer primary key autoincrement, COL1 TEXT NOT NULL, COL2 TEXT NOT NULL,COL3 TEXT, COL4 int, COL5 TEXT,"
+ "COL6 TEXT,COL7 REAL, COL8 INTEGER,COL9 TEXT not null);";
public static final String CREATE_SECOND_TABLE = "create table if not exists "
+ SECOND_TABLE_NAME+.........
public DbOperator(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
#Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_SFIRST_TABLE);
db.execSQL(CREATE_SECOND_TABLE);
//db.close();
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
//THIS WILL BE EXECUTED WHEN YOU UPDATED VERSION OF DATABASE_VERSION
//YOUR DROP AND CREATE QUERIES
}
}
Now your data manipulation class ( add, delete , update ) will look something like this ,
public class FirstTableDML extends DbOperator {
public FirstTableDML(Context context) {
super(context);
}
private static final String COL_ID = "_id";
private static final String COL1 = "COL1";
private static final String COL2 = "COL2";
........
.......
public void deleteFirstTableDataList(List<FirstTableData> firstTableDataList) {
for (FirstTableData data : firstTableDataList)
deleteFirstTableDetailData(data);
}
public void deleteFirstTableDetailData(FirstTableData item) {
SQLiteDatabase db = this.getWritableDatabase();
db.delete(FIRST_TABLE_NAME, item.getId() + "=" + COL_ID, null);
db.close();
}
/**this method retrieves all the records from table and returns them as list of
FirstTableData types. Now you use this list to display detail on your screen as per your
requirements.
*/
public List< FirstTableData > getFirstTableDataList() {
List< FirstTableData > firstTableDataList = new ArrayList< FirstTableData >();
String refQuery = "Select * From " + FIRST_TABLE_NAME;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(refQuery, null);
try {
if (cursor.moveToFirst()) {
do {
FirstTableData itemData = new FirstTableData();
itemData.setId(cursor.getInt(0));
itemData.setCol1(cursor.getString(1));
itemData.setCol2(cursor.getInt(2));
.....
.....
firstTableDataList.add(itemData);
} while (cursor.moveToNext());
}
} finally {
db.close();
}
Collections.sort(itemDataList);
return itemDataList;
}
public int addFirstTableData(FirstTableData data) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(COL1, data.getCol1());
values.put(COL2, data.getCol2());
.....
.....
long x=db.insert(FIRST_TABLE_NAME, null, values);
db.close();
return (int)x;
}
public void updateItemDetailData(FirstTableData data) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(COL1, data.getCol1());
values.put(COL2, data.getCol2());
values.put(COL3, data.getCol3());
.....
.....
db.update(FIRST_TABLE_NAME, values, COL_ID + "=" + data.getId(), null);
db.close();
}
}
P.S : *Data class are POJO data class representing the corresponding table.
Since you said you are not totally new to these, I have not provided any helper comments as most of the method names are self explanatory.
Hope it helps you to get started.

To creating a database for Android application, there are 2 ways:
Create database and tables using Code
Use existing database
1) Create database and tables using Code
In this scenario, you have to write a class and code to create database and tables for it. You have to use different classes and interfaces like SQLiteOpenHelper, SQLiteDatabase, etc. Check answer posted by Jimmy above.
2) Use existing database
In this scenario, you can use your existing sqlite database inside your android application. You have to place database file inside assets folder and write a code to copy that existing database on to either internal or external storage.
Regarding best scenario, I would say it's depend on the application functionality and nature, if your database is small then you should go with 1st scenario and if your database is large with many tables then you should go with 2nd scenario because you would be creating database using any GUI based SQLite browser and which would help you to make less mistakes. (When I say less mistakes using GUI, believe me there are chances of creating tables by code).
How to show values from the database on screen?
For that you have to write a SQL query which gives you Cursor in return which is a set of resultant data, so you have to iterate through the cursor data and prepare a set of data in terms of ArrayList or Array or HashMap.
You can display this set of data in ListView or GridView.
P.S. I am not posting links to any tutorials or examples as there are plenty of information/examples available on web, so suggesting you to search around the given points.

A good way to start is to read about Storage Options on the official Android documentation website: http://developer.android.com/guide/topics/data/data-storage.html

Check for the existence of database in Android [duplicate]

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
How to check existing database before creating new database on Android 2.2?
I have an app which check the existence of database in the start up. If not exits create a new one and if there then access the database. Can you please tell me how to check the existence of db(SQlite)?

Android helps a lot developpers to manage a database.
You should have a class like this (a single table with only 1 column) :
public class MyDBOpenHelper extends SQLiteOpenHelper {
private static final String queryCreationBdd = "CREATE TABLE partie (id INTEGER PRIMARY KEY)";
public MyDBOpenHelper(Context context, String name, CursorFactory factory, int version)
{
super(context, name, factory, version);
}
#Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(queryCreationBdd);
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
db.execSQL("DROP TABLE partie;");
db.execSQL("DELETE FROM sqlite_sequence"); //table which contains the next incremented key value
onCreate(db);
}
}
Then you simply do this :
MyDBOpenHelper databaseHelper = new MyDBOpenHelper(context, "dbname.db", null, 1);
SQLiteDatabase bdd = databaseHelper .getWritableDatabase();
If necessary, Android will create the database (call the onCreate method) or give you the one that already exists. The fourth parameter is the version of the database. If the currently created database is not the latest version, onUpgrade will be called.
EDIT : The database path will be something like this :
/data/data/fr.mathis.application/databases/dbname.db

Take a look at query-if-android-database-exists
Open your database in try block with path of the databse like:
try{
SQLiteDatabase dbe = SQLiteDatabase.openDatabase("/data/data/bangla.rana.fahim/databases/dictionary", null,0);
Log.d("opendb","EXIST");
dbe.close();
}
if an exception occurs then database doesn't exist so create it:
catch(SQLiteException e){
Log.d("opendb","NOT EXIST");
SQLiteDatabase db = openOrCreateDatabase("dictionary", MODE_PRIVATE, null);
db.execSQL("CREATE TABLE IF NOT EXISTS LIST(wlist varchar);");
db.execSQL("INSERT INTO LIST VALUES('খবর');");
db.execSQL("INSERT INTO LIST VALUES('কবর');"); //whatever you want
db.close();
}
that's it you are done :)

I use a boolean flag which is set to true when onCreate of SQLiteOpenHelper is invoked. You can find my full code here

Storing application database schema

In example apps database is in most cases single table, so db schema is stored in static variable.
Storing large schema in seperate file is more friendly for me.
How can I do that? I thought about using resources (R.strings.db_schema) but probably there is a better way.
Could somebody give me any advice?

You could put the schema data in a raw file under res/raw. Then you can just load and parse that file the first time.

The way I do is to have a class per table, named after the table with "Table" suffix (e.g. PlayerTable or EventTable).
These classes contain all the static variable for the table name and all the field names, and they also contain two static methods:
public static void onCreate(SQLiteDatabase database)
public static void onUpgrade(SQLiteDatabase database, int oldVersion, int newVersion)
So that my SQLiteOpenHelper can just call all of them, without having hundreds of static variables with all the fields and create queries. E.g:
#Override
public void onCreate(SQLiteDatabase database) {
PlayerTable.onCreate(database);
EventTables.onCreate(database);
..... any other table you have .....
}
This class is then injected into all my data access objects (select / update / insert queries). For them I have dedicated classes that contain all my methods, by functionality (e.g. EventHandlingDAO for all the queries that deal with event handling).
And finally, theses DAO are injected into the activities that need them, when needed.
EDIT: A few more details about my code:
My main objects are the DAO (data access objects), in which I have methods like:
// in EventHandlingDAO:
public void addEvent(Event event) {
SQLiteDatabase database = databaseHelper.getWritableDatabase();
try {
database.execSQL("INSERT INTO " + EventTable.EVENT_TABLE_NAME + " (...."); // list of fields and values
} finally {
database.close();
}
}
public List<Event> getAllEvents() {
final List<Event> result = new ArrayList<Event>();
SQLiteDatabase database = databaseHelper.getReadableDatabase();
try {
final Cursor cursor = database.rawQuery("SELECT " + EventTable.KEY_NAME + ", " + EventTable.KEY_DATE_AS_STRING + " FROM " + EventTable.TABLE_NAME, null);
cursor.moveToFirst();
// ... rest of the logic, that iterates over the cursor, creates Event objects from the cursor columns and add them to the result list
return result;
} finally {
database.close();
}
}
So in that DAO, I have my databaseHelper object, which instanciates my class that extends SQLiteOpenHelper with the methods I talked about above.
And of course, I have interfaces to all my DAO, so that I can inject a Stub or mocked implementation in my tests (or experiment with different implementations if I want to try another solution based on SharedPreference for example)
And the code for my PlayerTable table:
public static void onCreate(SQLiteDatabase database) {
database.execSQL(TABLE_CREATE); // TABLE_CREATE is my "CREATE TABLE..." query
}
public static void onUpgrade(SQLiteDatabase database, int oldVersion, int newVersion) {
// A bit blunt, that destroys the data unfortunately, I'll think about doing something more clever later ;)
database.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(database);
}

Select data from SQLite into ListArrays

I've been racking my brain on this for days and I just can't wrap my head around using SQLite databases in Android/Java. I'm trying to select two rows from a SQLite database into a ListArray (or two, one for each row. Not sure if that would be better or worse) and I just don't understand how to do it. I've tried various database manager classes that I've found but none of them do what I need and it seems that I should be able to do this simple task without the extra features I've seen in other database managers. Is there any simple way to JUST query some data from an existing SQLite database and get it into a ListArray so that I can work with it? I realize I need to copy the database from assets into the Android database path and I can handle that part. I also need to be able to modify one of the columns per row. I don't need to create databases or tables or rows. I implore someone to help me with this as I consider any code I've written (copied from the internet) to be completely useless.

You can create a method like this :
private List<MyItem> getAllItems()
List<MyItem> itemsList = new ArrayList<MyItem>();
Cursor cursor = null;
try {
//get all rows
cursor = mDatabase.query(MY_TABLE, null, null, null, null,
null, null);
if (cursor.moveToFirst()) {
do {
MyItem c = new MyItem();
c.setId(cursor.getInt(ID_COLUMN));
c.setName(cursor.getString(NAME_COLUMN));
itemsList.add(c);
} while (cursor.moveToNext());
}
} catch (SQLiteException e) {
e.printStackTrace();
} finally {
cursor.close();
}
return itemsList;
}
This will be inside your class let say MyDatabaseHelper where you will also have to declare a :
private static class DatabaseHelper extends SQLiteOpenHelper{
private final static String DATABASE_CREATE="create table " + MY_TABLE + " (id integer primary key, country string);";
public DatabaseHelper(Context context,String name, CursorFactory factory, int version){
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){
Log.w(TAG, "Upgrading database from version " + oldVersion
+ " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS "+ MY_TABLE);
onCreate(db);
}
}
used to open() and close() the database.