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Unable to delete data from SQLite

I am having issues when trying to clear the entries from a Arraylist in Android studio, not matter what code I try the app either does nothing or as with the code below crashes. I'm pulling my hair out with this as in my mind it should work.
I have also tried (not included in the code):
odb.rawquery(" delete from DATABASE_TABLE") //from memory so may not be 100%
This crashed the app and it would not reload, I'm assuming that it was successful in removing the table and not re-creating it?
It will be running on KitKat
Have I missed anything?
This is the last thing I need to make it work so any help or suggestions would be great!
TIA
Main
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleAdapter;
public class MainActivity extends Activity {
private ListView list_lv;
private EditText col2_ed;
private Button sub_btn;
Button del_btn;
private DBclass db;
private ArrayList<String> collist_2;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
collist_2 = new ArrayList<String>();
items();
getData();
DeleteData();
}
private void items() {
sub_btn = (Button) findViewById(R.id.submit_btn);
del_btn = (Button) findViewById(R.id.delete_btn);
col2_ed = (EditText) findViewById(R.id.ed2);
list_lv = (ListView) findViewById(R.id.dblist);
sub_btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
submitData();
}
});
}
public void DeleteData(){
del_btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
db.deleteData();
}
});
}
protected void submitData() {
String b = col2_ed.getText().toString();
db = new DBclass(this);
long num;
db.open();
num = db.insertmaster(b);
db.close();
getData();
}
public void getData() {
collist_2.clear();
db = new DBclass(this);
try {
db.open();
Cursor cur = db.getAllTitles();
while (cur.moveToNext()) {
String valueofcol2 = cur.getString(2);
collist_2.add(valueofcol2);
}
}
finally {
db.close();
}
printList();
setDataIntoList();
}
private void printList() {
for (int i = 0; i < collist_2.size(); i++) {
}
}
private void setDataIntoList() {
// create the list item mapping
String[] from = new String[] { "col_2" };
int[] to = new int[] { R.id.col2tv };
// prepare the list of all records
List<HashMap<String, String>> fillMaps = new ArrayList<HashMap<String, String>>();
for (int i = 0; i < collist_2.size(); i++) {
HashMap<String, String> map = new HashMap<String, String>();
map.put("col_2", collist_2.get(i));
fillMaps.add(map);
}
// fill in the grid_item layout
SimpleAdapter adapter = new SimpleAdapter(this, fillMaps,
R.layout.custom, from, to);
list_lv.setAdapter(adapter);
}
}
DBclass
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;
import android.util.Log;
public class DBclass {
public String KEY_ROWID = "_id";
public String KEY_COL2 = "col2";
private String DATABASE_NAME = "mydb";
private String DATABASE_TABLE = "mytable";
private int DATABASE_VERSION = 1;
private Context ourContext;
private DbHelper dbh;
private SQLiteDatabase odb;
private String USER_MASTER_CREATE =
"CREATE TABLE IF NOT EXISTS " + DATABASE_TABLE+ "("
+ KEY_ROWID + " INTEGER PRIMARY KEY AUTOINCREMENT," + KEY_COL2 + " VARCHAR(15) )";
private class DbHelper extends SQLiteOpenHelper {
public DbHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
#Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(USER_MASTER_CREATE);
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// if DATABASE VERSION changes
// Drop old tables and call super.onCreate()999
}
}
public DBclass(Context c) {
ourContext = c;
dbh = new DbHelper(ourContext);
}
public DBclass open() throws SQLException {
odb = dbh.getWritableDatabase();
return this;
}
public void close() {
dbh.close();
}
public long insertmaster(String col2) throws SQLException{
ContentValues IV = new ContentValues();
IV.put(KEY_COL2, col2);
return odb.insert(DATABASE_TABLE, null, IV);
// returns a number >0 if inserting data is successful
}
public void updateRow(long rowID, String col2) {
ContentValues values = new ContentValues();
values.put(KEY_COL2, col2);
odb.update(DATABASE_TABLE, values, KEY_ROWID + "=" + rowID, null);
}
public void deleteData(){
odb.delete(DATABASE_TABLE, null,null);
}
public Cursor getAllTitles() {
// using simple SQL query
return odb.rawQuery("select * from " + DATABASE_TABLE, null);
}
public Cursor getallCols(String id) throws SQLException {
Cursor mCursor = odb.query(DATABASE_TABLE, new String[] { KEY_COL2 }, null, null, null, null, null);
Log.e("getallcols zmv", "opening successfull");
return mCursor;
}
public Cursor getColsById(String id) throws SQLException {
Cursor mCursor = odb.query(DATABASE_TABLE, new String[] { KEY_COL2 }, KEY_ROWID + " = " + id, null, null, null, null);
Log.e("getallcols zmv", "opening successfull");
return mCursor;
}
}

I think you're not opening the database before trying to delete.
public void DeleteData(){
del_btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
//Try adding these lines
try {
db = new DBclass(this);
db.open();
db.deleteData();
}catch(Exception e){
e.print
}finally{
db.close();
}
}
});
}

Add this in DBclass will delete all data from the particular table
public void deleteAll(){
SQLiteDatabase db = this.getWritableDatabase();
String deleteStmt="DELETE FROM "+TABLE_NAME;
db.execSQL(deleteStmt);
db.close();
}
Deleting a single row or single item (where item is the model class or you can pass the keyId/primarykey )
// Deleting single Item
public void deleteItem(Item item) {
SQLiteDatabase db = this.getWritableDatabase();
db.delete(TABLE_NAME, KEY_ID + " = ?",
new String[] { String.valueOf(item.getKeyId()) });
db.close();
}
Also please refer the below link :
https://www.androidhive.info/2013/09/android-sqlite-database-with-multiple-tables/

Android Studio project

Hi i am doing an andorid studio project, when I am adding my data the application and then trying to view the data im getting an Error saying "Error, Nothing Found". I made up a SQLite Database and hope someone can help me find the error.
package ie.wit.andrew.drivingschool;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DatabaseHelper extends SQLiteOpenHelper {
public static final String DATABASE_NAME = "Driver.db";
public static final String TABLE_NAME = "driver_table";
public static final String COL_1 = "ID";
public static final String COL_2 = "NAME";
public static final String COL_3 = "DATE OF BIRTH";
public static final String COL_4 = "LOGBOOK NUMBER"; //Making up my
//database of the
//information I will
//be entering into my
//application
public static final String COL_5 = "LESSON NUMBER";
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, 1); //when this constructor is
//called your Database has been
//created
}
#Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table " + TABLE_NAME + " (ID INTEGER PRIMARY KEY
AUTOINCREMENT,NAME TEXT,DATE OF BIRTH TEXT, LOGBOOK NUMBER TEXT, LESSON
NUMBER INTEGER)");
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
onCreate(db);
}
public boolean insertData(String name, String dateofbirth, String
logbooknumber, String lessonnumber) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put(COL_2,name);
contentValues.put(COL_3,dateofbirth);
contentValues.put(COL_4,logbooknumber);
contentValues.put(COL_5,lessonnumber);
long result = db.insert(TABLE_NAME,null,contentValues); //This method
//returns -1
if (result == -1)
return false;
else
return true;
}
public Cursor getAllData() {
SQLiteDatabase db = this.getWritableDatabase();
Cursor res = db.rawQuery("select * from "+ TABLE_NAME,null);
return res;
}
}
package ie.wit.andrew.drivingschool;
import android.database.Cursor;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class DrivingSchool extends AppCompatActivity {
DatabaseHelper myDb;
EditText editName,editDateofBirth,editLogbookNumber,editLessonNumber;
Button btnAddData;
Button btnviewAll;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_driving_school);
myDb = new DatabaseHelper(this);
editName = (EditText)findViewById(R.id.editText_name);
editDateofBirth = (EditText)findViewById(R.id.editText_dateofbirth);
editLogbookNumber = (EditText)findViewById(R.id.editText_logbooknumber);
editLessonNumber = (EditText)findViewById(R.id.editText_lessonNumber);
btnAddData = (Button)findViewById(R.id.button_add);
btnviewAll = (Button)findViewById(R.id.button_viewAll);
AddData();
viewAll();
}
public void AddData() {
btnAddData.setOnClickListener(
new View.OnClickListener() {
#Override
public void onClick(View v) {
boolean isInserted =
myDb.insertData(editName.getText().toString(),
editDateofBirth.getText().toString(),
editLogbookNumber.getText().toString(),
editLessonNumber.getText().toString());
if(isInserted = true)
Toast.makeText(DrivingSchool.this,"Data
Inserted",Toast.LENGTH_LONG).show();
else
Toast.makeText(DrivingSchool.this,"Data not
Inserted", Toast.LENGTH_LONG).show();
}
}
);
}
public void viewAll() {
btnviewAll.setOnClickListener(
new View.OnClickListener() {
#Override
public void onClick(View v){
Cursor res = myDb.getAllData();
if(res.getCount() == 0) {
//Show Message
showMessage("Error", "Nothing found");
return;
}
StringBuffer buffer = new StringBuffer();
while(res.moveToNext()) {
buffer.append("ID : "+ res.getString(0)+"\n");
buffer.append("NAME : "+ res.getString(1)+"\n");
buffer.append("DATE OF BIRTH : "+
res.getString(2)+"\n");
buffer.append("LOGBOOK NUMBER : "+
res.getString(3)+"\n\n");;
}
//showdata
showMessage("Data",buffer.toString());
}
}
);
}
public void showMessage(String title,String Message){
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setCancelable(true);
builder.setTitle(title);
builder.setMessage(Message);
builder.show();
}
}

Try removing space from your column name's

you are providing wrong column name that's why your database is not creating, please check this link for complete guide for creating and using database in Android application
http://www.androidhive.info/2011/11/android-sqlite-database-tutorial/

Accessing Methods from Another Class Android

I am creating an android application that will be using a SQLite database. I have created a separate class called DBAdapter that holds all the methods relating to the database.
My issue comes when I try to access these methods from the main activity. I am still learning but I would normally instantiate the DBAdapter class and then I would be able to reference the methods. However the approach I am taking isnt working. Below is the single line of how I am trying to instantiate the class and under that is the rest of the class.
The error I am getting is cannot resolve method 'open()'
Instantiate Line and method
DBAdapter db = new DBAdapter(this);
db.open();
Main Class
import android.app.Dialog;
import android.content.Context;
import android.content.SharedPreferences;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.ContentFrameLayout;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
final Context context = this;
private FloatingActionButton fab;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
DBAdapter db = new DBAdapter(this);
db.open();
fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
final Dialog dialog = new Dialog(context);
dialog.setContentView(R.layout.dialog_box);
dialog.setTitle("Add new Location!");
dialog.show();
final EditText NameEdit = (EditText) findViewById(R.id.NameInput);
final EditText LatEdit = (EditText) findViewById(R.id.LatInput);
final EditText LongEdit = (EditText) findViewById(R.id.LongInput);
final EditText PhoneEdit = (EditText) findViewById(R.id.PhoneInput);
final Button OkButton = (Button) dialog.findViewById(R.id.dialogButtonOK);
final Button CancelButton = (Button) dialog.findViewById(R.id.dialogButtonCancel);
OkButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
String RealName = NameEdit.getText().toString();
String Lat = LatEdit.getText().toString();
Float realLat = Float.parseFloat(Lat);
String Long = LongEdit.getText().toString();
Float realLong = Float.parseFloat(Long);
String Phone = PhoneEdit.getText().toString();
Double realPhone = Double.parseDouble(Phone);
//Use above to create a new Geofence
}
});
CancelButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
dialog.dismiss();
}
});
}
});
}
}
DBAdpater Class
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;
import android.util.Log;
/**
* Created by Rory on 09/09/2016.
*/
public class DBAdapter {
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
//Database Version & name
private static final String DATABASE_NAME = "OpenSesame";
private static final int DATABASE_VERSION = 1;
private static final String TAG = "DBMain";
private static final String GEOTABLE = "geoTable";
private static final String KEY_ID = "_id";
private static final String KEY_NAME = "name";
private static final String KEY_LAT = "lat";
private static final String KEY_LONG = "long";
private static final String KEY_RADIUS = "radius";
private static final String KEY_PHONE = "phone";
private static final String CREATE_GEO_TABLE = "CREATE TABLE "
+ GEOTABLE + "("
+ KEY_ID + " INTEGER PRIMARY KEY AUTO INCREMENT,"
+ KEY_NAME + " TEXT,"
+ KEY_LAT + " FLOAT,"
+ KEY_LONG + " FLOAT,"
+ KEY_RADIUS + " INTEGER,"
+ KEY_PHONE + " INTEGER" + ")";
public DBAdapter(Context ctx) {
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
private class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
/**
* Method to create each of the tables defined above
* #param db
*/
#Override
public void onCreate(SQLiteDatabase db)
{
try {
db.execSQL(CREATE_GEO_TABLE);
} catch (SQLException e) {
e.printStackTrace();
}
}
/**
* Method for updating the database
* #param db
* #param newVersion
* #param oldVersion
*/
#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 contacts");
onCreate(db);
}
public DatabaseHelper open() throws SQLException
{
db = DBHelper.getWritableDatabase();
return this;
}
public void close() {
DBHelper.close();
}
public Cursor DeleteGeo(String name) {
return db.rawQuery("delete from geoTable where name = " + name, null);
}
public long AddGeo(String name, float lat, float lon, double phone, int radius) {
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_NAME, name);
initialValues.put(KEY_LAT, lat);
initialValues.put(KEY_LONG, lon);
initialValues.put(KEY_PHONE, phone);
initialValues.put(KEY_RADIUS, radius);
return db.insert(GEOTABLE, null, initialValues);
}
public Cursor GetAllGeos() {
return db.rawQuery("select * from geoTable order by name ASC", null);
}
}
}

Your DBAdapter class does not have the open() method. It is the private inner class DatabaseHelper that has that method. You have two options to expose open() to be able to call it the way you are expecting.
Option 1: add an open() method to DBAdapter that calls DatabaseHelper's open() method
public void open() {
DBHelper.open();
}
Option 2: remove DatabaseHelper entirely, and have DBAdapter extends SQLiteOpenHelper instead
public class DBAdapter extends SQLiteOpenHelper {
...
public DBAdapter(Context ctx) {
this.context = ctx;
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
// add all the code from inside DatabaseHelper below
/**
* Method to create each of the tables defined above
* #param db
*/
#Override
public void onCreate(SQLiteDatabase db)
{
try {
db.execSQL(CREATE_GEO_TABLE);
} catch (SQLException e) {
e.printStackTrace();
}
}
// you will have to change this method to work
public DBAdapter open() throws SQLException
{
db = getWritableDatabase();
return this;
}
...
}

Cant validate Login on Android app using a SQLite db

I am having a problem validating my login for my android app. I have 2 fields that require user to enter email and password, if both exist in db then they will be taken to mainscreen (log in successful) if incorrect error will appear. I have tried everything but still doesnt work! Please help I have posted my code below.
package com.example.finalproject;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class LoginActivity extends Activity implements OnClickListener{
EditText mEmailAdd;
EditText mPassword;
private SQLiteAdapter mydb = null;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.login_activity);
//addListenerOnButton();
}
public void onCreateMainscreen(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.screenmain_activity);
Button mNewUser = (Button)findViewById(R.id.btnLogMain);
mNewUser.setOnClickListener(this);
}
public void onClick(View v) {
switch(v.getId()){
case R.id.btnLogMain:
mEmailAdd = (EditText)findViewById(R.id.email);
mPassword = (EditText)findViewById(R.id.password);
String uname = mEmailAdd.getText().toString();
String pass = mPassword.getText().toString();
if(uname.equals("") || uname == null){
Toast.makeText(getApplicationContext(), "email Empty", Toast.LENGTH_SHORT).show();
}else if(pass.equals("") || pass == null){
Toast.makeText(getApplicationContext(), "Password Empty", Toast.LENGTH_SHORT).show();
}else{
boolean validLogin = validateLogin(uname, pass, LoginActivity.this);
if(validLogin){
System.out.println("In Valid");
Intent i = new Intent(LoginActivity.this, MainMenuActivity.class);
startActivity(i);
finish();
}
}
break;
}
}
// #SuppressWarnings("deprecation")
public boolean validateLogin(String uemail, String pass, Context context) {
mydb = new SQLiteAdapter(this);
SQLiteAdapter db = mydb.openToWrite();
//SELECT
String[] columns = {"_id"};
//WHERE clause
String selection = "email=? AND password=?";
//WHERE clause arguments
String[] selectionArgs = {uemail,pass};
Cursor cursor = null;
try{
//SELECT _id FROM login WHERE email=uemail AND password=pass
cursor = db.query(SQLiteAdapter.MYDATABASE_TABLE, columns, selection, selectionArgs, null, null, null);
// startManagingCursor(cursor);
}catch(Exception e){
e.printStackTrace();
}
int numberOfRows = cursor.getCount();
if(numberOfRows <= 0){
Toast.makeText(getApplicationContext(), "Failed..\nTry Again", Toast.LENGTH_SHORT).show();
return false;
}
return true;
}
public void onDestroy(){
super.onDestroy();
mydb.close();
}
}
DATABASE CLASS
package com.example.finalproject;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
public class SQLiteAdapter {
public static final String MYDATABASE_NAME = "MY_PROJECT_DATABASE";
public static final String MYDATABASE_TABLE = "MY_USERS_TABLE";
public static final int MYDATABASE_VERSION = 1;
public static final String KEY_ID = "_id";
public static final String KEY_NAME = "name";
public static final String KEY_EMAIL = "email";
public static final String KEY_PASSWORD = "password";
//create table MY_DATABASE (ID integer primary key, Content text not null);
private static final String SCRIPT_CREATE_DATABASE =
"create table " + MYDATABASE_TABLE + " ("
+ KEY_ID + " integer primary key autoincrement, "
+ KEY_NAME + " text not null, "
+ KEY_EMAIL + " text not null, "
+ KEY_PASSWORD + " text not null);";
private SQLiteHelper sqLiteHelper;
private SQLiteDatabase sqLiteDatabase;
private Context context;
public SQLiteAdapter(Context c){
context = c;
}
public SQLiteAdapter openToRead() throws android.database.SQLException {
sqLiteHelper = new SQLiteHelper(context, MYDATABASE_NAME, null, MYDATABASE_VERSION);
sqLiteDatabase = sqLiteHelper.getReadableDatabase();
return this;
}
public SQLiteAdapter openToWrite() throws android.database.SQLException {
sqLiteHelper = new SQLiteHelper(context, MYDATABASE_NAME, null, MYDATABASE_VERSION);
sqLiteDatabase = sqLiteHelper.getWritableDatabase();
return this;
}
public void close(){
sqLiteHelper.close();
}
public long insert(String name, String email, String password){
ContentValues contentValues = new ContentValues();
contentValues.put(KEY_NAME, name);
contentValues.put(KEY_EMAIL, email);
contentValues.put(KEY_PASSWORD, password);
return sqLiteDatabase.insert(MYDATABASE_TABLE, null, contentValues);
}
public int deleteAll(){
return sqLiteDatabase.delete(MYDATABASE_TABLE, null, null);
}
public Cursor queueAll(){
String[] columns = new String[]{KEY_ID, KEY_NAME, KEY_EMAIL,KEY_PASSWORD};
Cursor cursor = sqLiteDatabase.query(MYDATABASE_TABLE, columns,
null, null, null, null, null);
return cursor;
}
public class SQLiteHelper extends SQLiteOpenHelper {
public SQLiteHelper(Context context, String name,
CursorFactory factory, int version) {
super(context, name, factory, version);
}
#Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL(SCRIPT_CREATE_DATABASE);
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
}
}

not your error, but change
if(uname.equals("") || uname == null){ // throws nullpointerexception if uname == null
to
if(uname == null || uname.length() == 0 ){ // throws no exception and also checks the " "

Not sure if this was just a copy-paste error but the code as provided not only doesn't compile, but never sets up the click listener for the login button either. Here's what I modified to make it both compile and query the database.
In SQLiteAdapter:
public SQLiteDatabase openToWrite() throws android.database.SQLException {
sqLiteHelper = new SQLiteHelper(context, MYDATABASE_NAME, null,
MYDATABASE_VERSION);
sqLiteDatabase = sqLiteHelper.getWritableDatabase();
return sqLiteDatabase;
}
In LoginActivity:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.login_activity);
//addListenerOnButton();
Button mNewUser = (Button)findViewById(R.id.btnLogMain);
mNewUser.setOnClickListener(this);
}
public void onCreateMainscreen(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.screenmain_activity);
Button mNewUser = (Button)findViewById(R.id.btnLogMain);
mNewUser.setOnClickListener(this);
}
public boolean validateLogin(String uemail, String pass, Context context) {
mydb = new SQLiteAdapter(this);
SQLiteDatabase db = mydb.openToWrite();
//SELECT
String[] columns = {"_id"};
//WHERE clause
String selection = "email=? AND password=?";
//WHERE clause arguments
String[] selectionArgs = {uemail,pass};
Cursor cursor = null;
try{
//SELECT _id FROM login WHERE email=uemail AND password=pass
cursor = db.query(SQLiteAdapter.MYDATABASE_TABLE, columns, selection, selectionArgs, null, null, null);
// startManagingCursor(cursor);
}catch(Exception e){
e.printStackTrace();
}
int numberOfRows = cursor.getCount();
if(numberOfRows <= 0){
Toast.makeText(getApplicationContext(), "Failed..\nTry Again", Toast.LENGTH_SHORT).show();
return false;
}
return true;
}
Note also that this code will never insert anything into the database, either. I assume this will be done elsewhere. Further there are many naming convention and general good practices being broken here.
A few issues:
Never do database work on the main thread.
Variables prefixed with 'm' indicate they are member variables of the class.
Be sure to use the #Override notation when appropriate.

Error on Android's rawQuery()

i got nullPointerException when trying to fetch some data from database with rawQuery.
Here's an error:
03-11 18:09:01.522: E/AndroidRuntime(2057): Uncaught handler: thread
main exiting due to uncaught exception 03-11 18:09:01.532:
E/AndroidRuntime(2057): java.lang.NullPointerException 03-11
18:09:01.532: E/AndroidRuntime(2057): at
com.math.scan.FormulaModel.setFormulaList(FormulaModel.java:27)
Look at my code:
DbHelper
package com.math.scan;
import java.io.IOException;
import java.io.InputStream;
import java.util.Scanner;
import android.content.Context;
import android.content.res.AssetManager;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class DbHelper extends SQLiteOpenHelper{
public static final String TABLE_NAME = "formulas";
public static final String COLUMN_ID = "_id";
public static final String COLUMN_UNKNOWN = "unknown";
public static final String COLUMN_FORMULA = "formula";
public static final String COLUMN_CTG = "ctg";
private static final String DB_NAME = "formulas.db";
private static int DB_VERSION = 1;
private static final String DB_CREATE = "CREATE TABLE "+TABLE_NAME+
"("+COLUMN_ID+" integer primary key autoincrement,"
+COLUMN_UNKNOWN+" text not null,"
+COLUMN_FORMULA+" text not null,"
+COLUMN_CTG+" text not null );";
public Context mCtx;
public DbHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
this.mCtx = context;
}
#Override
public void onCreate(SQLiteDatabase database) {
database.execSQL(DB_CREATE);
// reading formulas
AssetManager asset = mCtx.getAssets();
try {
InputStream input = asset.open("formulas");
int size = input.available();
byte[] buffer = new byte[size];
input.read(buffer);
input.close();
String content = new String(buffer);
Scanner scan = new Scanner(content);
String current;
String[] f = new String[2];
String[] formula = new String[2];
while(scan.hasNextLine()) {
current = scan.nextLine();
// get category
f = current.split("!!");
formula = f[1].split(" = ");
database.execSQL("INSERT INTO `formulas` VALUES (NULL, '"+formula[0]+"', '"+formula[1]+"', '"+f[0]+"');");
Log.d("DB", "INSERT INTO `formulas` VALUES (NULL, '"+formula[0]+"', '"+formula[1]+"', '"+f[0]+"');");
}
} catch (IOException e) {
e.printStackTrace();
}
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.w(DbHelper.class.getName(),
"Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(db);
}
}
FormulaModel
package com.math.scan;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
public class FormulaModel {
private SQLiteDatabase database;
private DbHelper dbHelper;
public FormulaModel(Context context) {
dbHelper = new DbHelper(context);
}
public void open() throws SQLException {
dbHelper.getWritableDatabase();
}
public void close() {
dbHelper.close();
}
public void setFormulaList(String ctg) {
open();
// app stops working here
Cursor cursor = database.rawQuery("SELECT unknown, formula FROM formulas WHERE ctg = '"+ctg+"'", null);
int results = cursor.getCount();
cursor.moveToFirst();
Global.FormuleResult = new String[results];
Global.FormuleTable = new String[results];
for(int i = 0; i < results; i++) {
Global.FormuleTable[i] = cursor.getString(1);
Global.FormuleResult[i] = cursor.getString(0);
}
close();
}
}
This is activity, where I call setFormulaList() method in FormulaModel class.
package com.math.scan;
import net.sourceforge.jeval.EvaluationException;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class ProblemActivity extends Activity {
private EditText prob;
private Button solve;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.problem);
// text field
prob = (EditText) findViewById(R.id.problem);
// confirm btn
solve = (Button) findViewById(R.id.solve);
// check if confirm button was pressed
solve.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// get text from the field
String problem = prob.getText().toString();
// check if expression is not empty
if(problem.length() == 0) {
// string is empty!
Toast.makeText(ProblemActivity.this, getString(R.string.empty_field), Toast.LENGTH_SHORT).show();
} else {
FormulaModel f = new FormulaModel(ProblemActivity.this);
f.setFormulaList("mech");
pears.doMagic(problem);
try {
String str = Global.eval.getVariableValue(Global.UNKNOWN);
TextView answ = (TextView) findViewById(R.id.answer);
answ.setText(getString(R.string.prob_answ) + str);
} catch (EvaluationException e) {
Toast.makeText(ProblemActivity.this, getString(R.string.prob_error), Toast.LENGTH_SHORT).show();
}
}
}
});
}
}
I can't figure out what is wrong here.
Any ideas?

You have to set your database variable in open():
database = dbHelper.getWritableDatabase();