Develop Reference

How to display data from a database in a table?

I'm new to Android Studio and can't seem to find what I'm asking for.
I want to have a database that stores the data of a few people, e.g.
Steve Hardy, 16 Somewhere Land, Colorado, U.S.A.
I would like this to have headings (Name, Address, City, Country).
I'm just struggling with how to format a table like this and how I would link a database to this.

In android, mostly use sqlite databases. I can give you 3 simple functions I use to create database and table, insert data to table, & to read database values. If there is any unclear thing or you want any clarification, ask. I can help you.
public class MainActivity extends AppCompatActivity {
//Assign below 3 variables as global variables where class start.
SQLiteDatabase db; //Assign as a global variable
String DBName = "MyDB"; //Assign as a global variable
String TableName = "PeopleData"; //Assign as a global variable
//Call 3 function inside oncreate method.
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
createDB_Table(); //calling 3 functions.
InsertDataToDB();
ReadDBData();
}
public void createDB_Table(){ //This function use to create database, table & columns.
db = this.openOrCreateDatabase(DBName, MODE_PRIVATE, null);
db.execSQL("CREATE TABLE IF NOT EXISTS " + TableName + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, Name TEXT, Address TEXT, City TEXT, Country TEXT);");
db.close();
}
public void InsertDataToDB(){ //This function use to inset values to database.
db = this.openOrCreateDatabase(DBName, MODE_PRIVATE, null);
ContentValues cv = new ContentValues();
cv.put("Name","Steve Hardy");
cv.put("Address","16 Somewhere Land");
cv.put("City","Colorado");
cv.put("Country","USA");
db.insert(TableName, null, cv);
db.close();
}
public void ReadDBData() { //This function use to read data from database.
db = this.openOrCreateDatabase(DBName, MODE_PRIVATE, null);
Cursor cursor = db.rawQuery("SELECT * FROM " + TableName, null);
if (cursor.getCount() > 0) { //check cursor is not empty.
cursor.moveToFirst();
String DName = cursor.getString(cursor.getColumnIndex("Name"));
String DAddress = cursor.getString(cursor.getColumnIndex("Address"));
String DCity = cursor.getString(cursor.getColumnIndex("City"));
String DCountry = cursor.getString(cursor.getColumnIndex("Country"));
//Got the values from database. Then you can set those values to text view or something you use.
}
cursor.close();
db.close();
}
}

E/SQLiteLog﹕ (1) near "Table": syntax error

I'm trying to start with SQLite in android but I have some problems..
I took the code from a tutorial which was written in 2012, but it's not working for me now and shows me this error:
E/SQLiteLog﹕ (1) near "Table": syntax error
The problem is with creating/opening the Database.
package db.com.example.kids1.databasetest;
import android.app.ListActivity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
import org.w3c.dom.Text;
import java.io.IOException;
import java.util.ArrayList;
public class MainActivity extends ListActivity{
private final String DB_NAME = "Database";
private final String TABLE_NAME = "Table";
SQLiteDatabase DB = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ArrayList<String> results = new ArrayList<>();
String[] res = {"Red", "Green", "Text"};
try {
DB = this.openOrCreateDatabase(DB_NAME, MODE_PRIVATE, null);
DB.execSQL("CREATE TABLE IF NOT EXISTS " +
TABLE_NAME +
"(Name VARCHAR, Street VARCHAR, Block INT, City VARCHAR, Tel VARCHAR);");
mFillDbsTable();
Cursor c = DB.rawQuery("SELECT Name, Street, Block, City, Tel FROM " +
TABLE_NAME +
" where Blcok == 9 LIMIT 5", null);
if (c!=null){
if (c.moveToFirst()) {
do {
String name = c.getString(c.getColumnIndex("Name"));
String street = c.getString(c.getColumnIndex("Street"));
int block = c.getInt(c.getColumnIndex("Block"));
String city = c.getString(c.getColumnIndex("City"));
String tel = c.getString(c.getColumnIndex("Tel"));
results.add(name + "," + street + "," + block + "," + city + "," + tel);
} while (c.moveToNext());
}
}
ListView list = (ListView)findViewById(android.R.id.list);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, res);
list.setAdapter(adapter);
} catch (SQLiteException se){
Log.e(getClass().getSimpleName(), "Create/Open Database Problem.");
}
}
private void mFillDbsTable(){
try {
DB.execSQL("INSERT INTO " +
TABLE_NAME +
" Values('Noam', 'Shkolnik', 9, 'Rehovot', '054-4900807');");
DB.execSQL("INSERT INTO " +
TABLE_NAME +
" Values('Eyal', 'Shkolnik', 9, 'Rehovot', '055-4488779');");
DB.execSQL("INSERT INTO " +
TABLE_NAME +
" Values('Yehontan', 'Shkolnik', 9, 'Rehovot', '058-7789547');");
} catch (SQLiteException se) {
Log.e(getClass().getSimpleName(), "Could not create records.");
}
}
}

private final String TABLE_NAME = "Table"
You can't create a table named Table, because it's a reserved keyword.
You better create a table named MyTable (or _Table or better give a more talkative name, such as Persons - note the s for plurals).
So:
private final String TABLE_NAME = "MyTable"
For your reference: https://sqlite.org/lang_keywords.html
You could (but it's not recommended) use reserved keywords, but then you have to use special delimiters everytime you refer to that table.
Something like
private final String TABLE_NAME = "[Table]"
And there's also another (double) error in your query:
" where Blcok == 9 LIMIT 5"
Should be
" where Block = 9 LIMIT 5"

Try VARCHAR(100) and remove the trailing ;

You got couple of errors. First, do not name your table Table. Table is reserved word (see docs) and cannot be used directly. It's basically not recommended to use reserved words, so I suggest you change your table name, yet if you insist of using it, you need to quote it first:
If you want to use a keyword as a name, you need to quote it. There are four ways of quoting keywords in SQLite:
'keyword' A keyword in single quotes is a string literal.
"keyword" A keyword in double-quotes is an identifier.
[keyword] A
keyword enclosed in square brackets is an identifier. This is not
standard SQL. This quoting mechanism is used by MS Access and SQL
Server and is included in SQLite for compatibility.
keyword A
keyword enclosed in grave accents (ASCII code 96) is an identifier.
This is not standard SQL. This quoting mechanism is used by MySQL and
is included in SQLite for compatibility.
BTW: your further select query will fail too due to typo in where clause:
where Blcok == 9

Why am I not able to fetch the code from the DataBase?

I'm unable to fetch the data although I'm able to add data. I have two questions here: What is the purpose of the primary key and how can I implement it? In my code, if I give the same values multiple times then it also gets accepted.
//Check this statement
db.execSQL("create table mtable (_Id Integer auto_increment, name Text Primary key , mail Text)");
Now,my 2nd major problem..
Why am I not able to fetch the data from the database ?
My two java classes are as follows:
MainActivity.java
package com.apna.mydatabase;
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class MainActivity extends Activity implements OnClickListener {
Button save,fetch,update,Delete;
EditText edtname,edtmail,afetch;
MySqlOpenHelper ab,db;
SQLiteDatabase sql,sql1;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
edtname=(EditText) findViewById(R.id.editText1);
edtmail=(EditText)findViewById(R.id.editText2);
afetch=(EditText) findViewById(R.id.editText3);
save=(Button) findViewById(R.id.button1);
fetch=(Button) findViewById(R.id.button2);
update=(Button) findViewById(R.id.button3);
Delete=(Button)findViewById(R.id.button4);
save.setOnClickListener(this);
fetch.setOnClickListener(this);
ab=new MySqlOpenHelper(MainActivity.this);
sql=ab.getWritableDatabase();
}
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch(v.getId())
{
case R.id.button1:
ContentValues cv=new ContentValues();
cv.put("name", edtname.getText().toString());
cv.put("mail",edtmail.getText().toString());
long result=sql.insert("mtable", "nullCo", cv);
if (result>0)
{
Toast.makeText(MainActivity.this, "Saved at"+result, 5000).show();
edtname.setText(" ");
edtmail.setText(" ");
}
else
{
Toast.makeText(MainActivity.this, "Not Saved"+result, 5000).show();
}
break;
case R.id.button2:
db= new MySqlOpenHelper(MainActivity.this);
sql1=db.getReadableDatabase();
String a=afetch.getText().toString();
Cursor c=sql1.rawQuery("Select * from mtable where _id ="+a,null );
String str=null,str1=null;
if(c.getCount()>0)
{
while(c.moveToNext())
{
str=c.getString(c.getColumnIndex("name"));
str1=c.getString(c.getColumnIndex("mail"));
}
edtname.setText(str);
edtmail.setText(str1);
}
else
{
Toast.makeText(MainActivity.this,"Invalid record",5000 ).show();
}
}
}
}
MySqlOpenHelper.java
package com.apna.mydatabase;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
public class MySqlOpenHelper extends SQLiteOpenHelper {
public MySqlOpenHelper(Context context)
{
super(context, "Mynew", null,1);
}
#Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL("create table mtable (_Id Integer auto_increment, name Text Primary key , mail Text)");
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
}
It would be my pleasure to get the required results.

what the purpose of primary key
A primary key is a special relational database table column (or combination of columns) designated to uniquely identify all table records.
A primary key’s main features are:
It must contain a unique value for each row of data.
It cannot contain null values.
See reference.
how to implement it
Primary Key can also be a composite key meaning two columns say in your case _Id and name could both be primary key. Satisfying the above conditions.
EDIT:
It is not advisable to have only name as the primary key since names can recur and defeat the purpose of the primary key. For a composite key you could :
db.execSQL("create table mtable (_Id Integer auto_increment, name Text not null,primary key (_Id,name) , mail Text)")
Simply put I have achieved it as:
create table mtable (_Id Integer identity, name varchar not null,primary key (_Id,name) , mail Text)
For example:
If you enter name say Anand and insert the record. Say another person is name Anand you insert it again it would defeat the purpose of the primary key as in relational databases it is meant to uniquely identify a record which in this case won't happen.
if i give same values multiple times then it also accept it
You can insert multiple values having the same primary key because you haven't specified your primary key to be unique or identity as in :
db.execSQL("create table mtable (_Id Integer auto_increment, name Text Primary key , mail Text)");
Why am I not able to fetch the data from the database ?
Your code seems to be fine. Debug it and see if the cursor contains anything and is not null. You could check first:
if (cursor != null) {
//move cursor to first row
if (cursor.moveToFirst()) {
do {
// Get version from Cursor
String name = cursor.getString(cursor.getColumnIndex("name"));
//more code
// move to next row
} while (cursor.moveToNext());
}
}
Update:
If you try to reinsert a row with the same primary key you would get the error that primary key should be unique and the primary key includes in itself the not null and unique traits so no need to specify these with it.

How to select the remaining rows after selected some in Android SQLite?

I have a task in which i have to display the rows selected using a query in one tab and the remaining rows in another tab. I have displayed the selected rows using SimpleCursorAdapter. When i tried to display the remaining rows in next tab it throws error. I have tried NOT IN but it also doesn't work. I have tried NOT EXISTS also it shows all rows. Anyone who can answer please help. I have posted my code here. Thanks in advance.
This is the activity of first tab which displays selected rows
public class OnlineDevices extends Activity {
ListView listOnline;
DatabaseHelper databaseHelper;
String count;
int conut;
TextView tvOnlineCount;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_online_devices);
listOnline=(ListView)findViewById(R.id.listView3);
tvOnlineCount = (TextView) findViewById(R.id.textView59);
databaseHelper=new DatabaseHelper(this);
SQLiteDatabase db=databaseHelper.getReadableDatabase();
String date= DateFormat.getDateInstance().format(new Date());
String statusQuery="select rowid _id, deviceContact from statusTable where sentTime='"+date+"'";
Cursor cursor1=db.rawQuery(statusQuery,null);
if (cursor1.getCount()>0){
while (cursor1.moveToNext()){
String deviceNo=cursor1.getString(cursor1.getColumnIndex("deviceContact"));
String device=deviceNo.substring(2, 12);
String query="select rowid _id, userName, uSerialNo from bikeTable where uContactNo='"+device+"' AND userName IS NOT NULL";
Cursor cursor2=db.rawQuery(query, null);
SimpleCursorAdapter adapter=new SimpleCursorAdapter(this,R.layout.status_item,cursor2,new String[]{"userName","uSerialNo"},new int[]{R.id.textView51,R.id.textView52});
listOnline.setAdapter(adapter);
}
}
try {
conut = listOnline.getAdapter().getCount();
count = String.valueOf(conut);
tvOnlineCount.setText(count);
}catch (Exception e){
e.printStackTrace();
int i=0;
Toast.makeText(OnlineDevices.this,"No device is active",Toast.LENGTH_SHORT).show();
tvOnlineCount.setText(String.valueOf(i));
}
}
}
Activity for second tab which display the remaining rows are
public class OfflineDevices extends Activity {
ListView listOffline;
DatabaseHelper databaseHelper;
String deviceContact;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_offline_devices);
listOffline=(ListView)findViewById(R.id.listView4);
databaseHelper=new DatabaseHelper(this);
SQLiteDatabase db=databaseHelper.getReadableDatabase();
String date= DateFormat.getDateInstance().format(new Date());
String query="select rowid _id, deviceContact from statusTable where sentTime='"+date+"'";
Cursor cursor1=db.rawQuery(query,null);
if (cursor1.getCount()>0){
while (cursor1.moveToNext()) {
deviceContact = cursor1.getString(cursor1.getColumnIndex("deviceContact"));
}
String device=deviceContact.substring(2, 12);
String query2="select rowid _id, userName, uSerialNo from bikeTable where userName IS NOT NULL AND uContactNo='"+device+"'";
Cursor cursor3=db.rawQuery(query2,null);
String query1="select rowid _id,*from bikeTable where userName IS NOT NULL NOT IN('"+query2+"')";
Cursor cursor2=db.rawQuery(query1,null);
SimpleCursorAdapter adapter=new SimpleCursorAdapter(this,R.layout.status_item,cursor2,new String[]{"userName","uSerialNo"},new int[]{R.id.textView51,R.id.textView52});
listOffline.setAdapter(adapter);
}
}
}

You have syntax errors in your query. In theory the following should work:
String query2 = "SELECT userName FROM bikeTable WHERE userName IS NOT NULL "
+ "AND uContactNo = '" + device + "'";
String query1 = "SELECT * FROM bikeTable WHERE userName IS NOT NULL "
+ "AND userName NOT IN(" + query2 + ")";
Here are the differences:
Your original code has single quotes around query2 inside the parentheses. This makes SQLite treat it as a string literal instead of an inner query.
Since query2 is being used in a NOT IN expression, it needs to
have a single result column, and it seems like userName is the one
you are interested in.
I advise spending some time going through the SQLite language pages. I'm fairly certain you can actually get the results you want using a single query that has a JOIN instead of making one query, checking the result, then making another query.
As an aside, it's considered best practice in Android to load data from a database on a background thread. Typically this is done with the Loader framework. You should also be closing cursors when you are finished with them (not the ones you give to the adapters, but the ones you use just to check for an online device).

SQLite database in Android, causes application crash

I'm testing SQLite database in android for the first time.
My program stops as I open it, and i cannot check it, i was wondering if there is a mistake in my code, or database connection,
any help will be appreciated :)
this is my Main.java file:
package de.blattsoft.SQLite;
import android.os.Bundle;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import android.view.Menu;
public class Main extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
SQLiteDatabase db = openOrCreateDatabase("MyDB", MODE_PRIVATE, null);
Cursor c = db.rawQuery("SELECT * FROM MyTable", null);
c.moveToFirst();
Log.d("Ali", c.getString(c.getColumnIndex("FirstName")));
db.close();
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
Note: I have asked this question many times ago, and I have written the full answer of how to implement databases in Android in the answers bellow.

First of all you need to create a database, then insert some data in it an then try to display.
What you are doing is ,if database is not there then create and select the column and display. It will obviously fail and your app crash.
Do something like
public void onCreate(SQLiteDatabase db) {
/*CREATE LOGIN TABLE*/
String CREATE_TABLE = "CREATE TABLE " + TABLE_NAME + "("
+ KEY_ID + " INTEGER PRIMARY KEY,"
+ KEY_NAME + " TEXT," + ")";
db.execSQL(CREATE_LOGIN_TABLE);
}
Then do this ,
public void addMessage(String id, String name){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_ID, id); //
values.put(KEY_NAME, name);
db.insert(TABLE_NAME, null, values);
db.close(); // Closing database connection
}
Then you can display ,

You haven't created the database. And inserting or fetching values from the structure which doesn't exist will lead to crash your app. It's like climbing a building which doesn't exist.
So, first create the database then do rest of the things.
For better understanding follow the you tube video tutorial of Slidenerd. They have sequentially explained all the things for beginners here.
Hope it will help.

I have asked this question many times ago when I was an Android noob! :D
right now this is the way I recommend you to use android sqlite database using helper classes.
as an overview, we need to create two classes, DatabaseHelper class
and DataSource class.
What we need to create:
The DatabaseHelper class must extend SQLiteOpenHelper which is a built-in Android class from android.database.sqlite package and its purpose is to manage database creation and version management.
The DataSource class uses our helper class to implement methods which you need for your application.
For Example, we're going to create a database which has one table called users, and the table has 2 columns: id and name;
The id is going to be used as the primary key.
So, let's create the helper class:
DatabaseHelper.java:
package com.mpandg.android.dbtest;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class DatabaseHelper extends SQLiteOpenHelper {
// this tag is used for logging purposes.
public static final String TAG = "database";
// database version.
public static final int DATABASE_VERSION = 1;
// database file name.
public static final String DATABASE_NAME = "database.db";
// table details:
public static final String TABLE_USERS = "users";
public static final String USERS_COLUMN_ID = "id";
public static final String USERS_COLUMN_NAME = "name";
// query of creating users table.
public static final String CREATE_USERS_TABLE =
"CREATE TABLE " + TABLE_USERS + " (" +
USERS_COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
USERS_COLUMN_NAME + " TEXT" + ")";
// query string of deleting users table.
public static final String DELETE_TABLES =
"DROP TABLE IF EXISTS " + TABLE_USERS + ";";
// constructor method which takes the context and passes it
// to appropriate super method with other database details
// which creates the database.
public DatabaseHelper(Context context) {
// creates the database using given information.
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
#Override
public void onCreate(SQLiteDatabase db) {
// this line executes the query we made earlier
// to create the users table.
db.execSQL(CREATE_USERS_TABLE);
// log the table creation for debugging.
Log.i(TAG, TABLE_USERS + " has been created.");
}
// whenever you give a new update for your application,
// if you change the version of the database, this method
// will be called, you can do your own complicated operations
// on your tables if you need, but right now, I just delete
// the old table and I make an explicit call to onCreate
// method to create the tables again.
// but never forget that you should never make explicit
// calls to onCreate method, but this is an exception here.
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// execute the delete query we made earlier.
db.execSQL(DELETE_TABLES);
// explicit call to onCreate. (read the comment above method)
onCreate(db);
}
}
As you see, we have actually created a subclass of SQLiteOpenHelper and we have implemented onCreate(SQLiteDatabase) and onUpgrade(SQLiteDatabase, int, int) methods, and the helper class we created, takes care of opening the database if it exists, creating it if it does not exist and upgrading it if it's necessary.
Now it's time to use the helper class we created and write our methods to use the database in DataSource class.
We will create a database object and we will instantiate it using the methods in our helper class, and we create methods to insert, select and delete.
So, Let's create DataSource.java:
package com.mpandg.android.dbtest;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import java.util.ArrayList;
import java.util.List;
public class DataSource {
// create an instance of SQLiteOpenHelper
// but we're going to instantiate it using
// the helper class we created earlier.
SQLiteOpenHelper dbHelper;
// the main database object which will be
// instantiated using the helper class methods.
SQLiteDatabase dataBase;
private final String TAG = "dataSource";
// an string array holding our table's column names
// which is going to be used by database methods.
public static final String[] usersTableColumns = {
DatabaseHelper.USERS_COLUMN_ID,
DatabaseHelper.USERS_COLUMN_NAME
};
// constructor which receives the activity context.
public DataSource(Context context){
// instantiate the dbHelper object using our DatabaseHelper class.
dbHelper = new DatabaseHelper(context);
}
public void open(){
// opening the database or
// creating the table structures for the first time.
// the helper class knows when to open or create the database.
dataBase = dbHelper.getWritableDatabase();
// log the event for debugging purposes.
Log.i(TAG, "database opened");
}
public boolean isOpen () {
// check if the database is already open.
return dataBase.isOpen();
}
public void close(){
// close the database.
dataBase.close();
// log the event for debugging purposes.
Log.i(TAG, "database closed");
}
// insert a name record into database .
public void insertName (String name) {
// ContentValues implements a map interface.
ContentValues values = new ContentValues();
// put the data you want to insert into database.
values.put(DatabaseHelper.USERS_COLUMN_NAME, name);
// passing the string array which we created earlier
// and the contentValues which includes the values
// into the insert method, inserts the values corresponding
// to column names and returns the id of the inserted row.
long insertId = dataBase.insert(DatabaseHelper.TABLE_USERS , null, values);
// log the insert id for debugging purposes.
Log.i(TAG, "added name id:" + insertId);
}
// returns a list of string
// containing the names saved in the database.
public List<String> getNames (){
List<String> names;
// creating the cursor to retrieve data.
// cursor will contain the data when the
// query is executed.
Cursor cursor = dataBase.query(DatabaseHelper.TABLE_USERS, usersTableColumns,
null, null, null, null, null);
// log the number of returned rows for debug.
Log.i(TAG, "returned: " + cursor.getCount() + " name rows .");
// check if the cursor is not null.
if(cursor.getCount()>0){
// instantiate the list.
names = new ArrayList<>();
// cursor starts from -1 index, so we should call
// moveToNext method to iterate over the data it contains.
while (cursor.moveToNext()) {
// read the string in the cursor row using the index which is the column name.
String name = cursor.getString(cursor.getColumnIndex(DatabaseHelper.USERS_COLUMN_NAME));
// log the retrieved name.
Log.i(TAG, "name retrieved:" + name);
// now add the retrieved name into the list.
names.add(name);
}
// now we have the names in our string list
return names;
} else {
// if the cursor was empty, it means that
// there was no name found in the table,
// so return null.
return null;
}
}
// returns a name corresponding to given id.
public String findNameById (long id){
String name;
// the where clause which is our condition.
String whereClause = DatabaseHelper.USERS_COLUMN_ID + " = ?";
// the arguments passed to
// the where clause. (here is only one argument)
String[] whereArgs = {id+""};
// creating the cursor to retrieve data.
// cursor will contain the data when the
// query is executed.
Cursor cursor = dataBase.query(DatabaseHelper.TABLE_USERS, usersTableColumns,
whereClause, whereArgs, null, null, null);
// log the number of returned rows for debug.
// (logically it should return one row here)
Log.i(TAG, "returned: " + cursor.getCount() + " name rows .");
// check if the cursor is not null.
if(cursor.getCount()>0){
// cursor starts from -1 index, so we should call
// moveToNext method to iterate over the data it contains.
cursor.moveToNext();
// read the string in the cursor row using the index which is the column name.
name = cursor.getString(cursor.getColumnIndex(DatabaseHelper.USERS_COLUMN_NAME));
// log the retrieved name.
Log.i(TAG, "name retrieved:" + name);
return name;
} else {
// if the cursor was empty, it means that
// there was no name found with given id,
// so return null.
return null;
}
}
// delete a name from the table.
public void deleteName (String name) {
// where statement of our delete method.
String whereClause = DatabaseHelper.USERS_COLUMN_NAME + "=" + "?";
// the arguments passed to
// the where clause. (here is only one argument)
String[] whereArgs = {name};
// execute the delete query with delete method.
int deleteId = dataBase.delete(DatabaseHelper.TABLE_USERS , whereClause, whereArgs);
// log the id of the deleted row.
Log.i(TAG, "deleted name id:" + deleteId);
}
}
Now that we have done writing the necessary classes to create and use our database in an appropriate way, it's time to use the methods we wrote in our DataSource class.
All you have to do, is to create an object of DataSource class in your activity and use the methods in it.
when you are intending to use the database, you should open it, you can simply do it by the open() method we wrote in our DataSource class, and after you are done, you must close it to avoid leaks; you can close it using the close() method in 'DataSource` class.
For example, you have some users and you want to add them in the database:
// create the dataSource object
// "this" refers to the activity.
DataSource dataSource = new DataSource(this);
// open the dataBase
dataSource.open();
// insert the names.
dataSource.insertName("Amy");
dataSource.insertName("Johnny");
dataSource.insertName("Abbey");
dataSource.insertName("Miley");
// close the database.
dataSource.close();
Or you want to log all the users in the database:
//TAG for debug logs.
String TAG = "db log";
// create the dataSource object
// "this" refers to the activity.
DataSource dataSource = new DataSource(this);
// open the dataBase
dataSource.open();
// get the names.
List<String> names = dataSource.getNames();
// log all the names in the list.
for (String name: names) {
Log.i(TAG, "retrieved name:" + name);
}
// close the database.
dataSource.close();
Or you want to find a name by its id:
//TAG for debug logs.
String TAG = "db log";
// create the dataSource object
// "this" refers to the activity.
DataSource dataSource = new DataSource(this);
// open the dataBase
dataSource.open();
// find the name by id.
String name = dataSource.findNameById(1);
// log the retrieved name wit id:1.
Log.i(TAG, "retrieved name:" + name);
// close the database.
dataSource.close();
Finally if you want to delete a name:
// create the dataSource object
// "this" refers to the activity.
DataSource dataSource = new DataSource(this);
// open the dataBase
dataSource.open();
// delete the given name
dataSource.deleteName("Amy");
// close the database.
dataSource.close();
That's it.
This is a basic structure for creating databases in Android, as you can see, you can add other tables and columns, easily by adding your own code to the helper class and your own methods to use them in the DataSource class.

Try this
package ir.itstuff.SQLite;
import android.os.Bundle;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import android.view.Menu;
public class Main extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
(EditText) fName = (EditText)findViewById(R.id.editText1);
(EditText) sName = (EditText)findViewById(R.id.editText2);
(Button) save = (Button)findViewById(R.id.button1);
SQLiteDatabase db = openOrCreateDatabase("MyDB", MODE_PRIVATE, null);
db.execSQL("CREATE TABLE IF NOT EXISTS MyTable(id INTEGER PRIMARY KEY AUTOINCREMENT, FirstName varchar,SecondName varchar);")
//Inserting data from inputs
save.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
String first_name = fName.getText().toString();
String second_name = sName.getText().toString();
String insert_data="INSERT INTO MyTable (FirstName,SecondName) VALUES " + "('" + first_name + "'," + "'" + second_name + "'" + ")";
shoppingListDB.execSQL(insert_data);
Toast.makeText(getBaseContext(), "Data Inserted", Toast.LENGTH_LONG).show();
Cursor cr=shoppingListDB.rawQuery("SELECT * FROM MyTable;", null);
if (cr.moveToFirst()){
do{
String name = cr.getString(cr.getColumnIndex("FirstName"));
}
while (cr.moveToNext());
Toast.makeText(getBaseContext(), name, Toast.LENGTH_LONG).show;
}
cr.close();
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}