Good afternoon,
I am trying to create a database for a monthly assessment form as part of my, it will be the second table of my application first being login details.
I followed the same format but am getting "NO SUCH TABLE" followed by my variable name.
I was hoping this issue had been seen before and how it could be eradicated.
Uninstall the old application on your phone completely and run your project again. This error is happening because the onCreate() method of the SQLiteOpenHelper derived class is called only once. For it to be called again, either you derive another custom class from SQLiteOpenHelper and define your second table there, or you uninstall the old APK and re-run the project from the IDE. When you run it again, both tables will be created.
Make database like this :
public class Data_Base extends SQLiteOpenHelper {
public static final String dbname = "suri29";
public static final Integer dbversion = 1;
public static final String dbtable = "user";
public static final String name = "username";
public static final String column_id = "_id";
public Data_Base(Context context) {
super(context, dbname, null, dbversion);
// TODO Auto-generated constructor stub
}
#Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL("create table " + dbtable + " (" + column_id
+ " integer primary key autoincrement, username text not null)");
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVesion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("drop table if exists " + dbtable);
onCreate(db);
}
Without digging deeper into you code, I have some advices for you that going to make you avoid tons of mistakes:
1)Use SQLite Database Helper for creating, inserting, deleting you data from the database...Follow this tutorial
2)Rewriting your columns name in each query is a very bad practice. Initialize them at the beginning of your class as final static string and use this variable whenever you need it.
private final static String COL_COMMENTS = "COMMENTS";
3)Try and catch all your database transactions with logging to avoid crashes.
try{
//Database transaction
}
catch(Exception e){
e.printstacktrace();
}
4)Uninstall the application and install it again after adding any new table.
Related
public class ProjectConstants {
public static final String myDbName = "ContactsDatabase.db";
public static final String myTableName = "ContactDetails";
// public static final String myTableName = "ContactDetails1";
public static final String nameColumn = "ContactName";
public static final String numberColumn = "ContactNumber";
}
First I create a contact application with Table Name : ContactDetails
Then I do all the adding, editing and deleting operations over that database table. Say I have 15 contact details in that database table named ContactDetails.
Now in the above code snippet I make 2 changes:
I comment this line
//public static final String myTableName = "ContactDetails";
And I uncomment this line
public static final String myTableName = "ContactDetails1";
Now if I run the code, the App crashes.
My learning from Stack Overflow has crudely taught me 2 things to ponder
1.
Remember to uninstall and then reinstall your app so the onCreate
method is called again and the database recreated.
2.
If the database is created for the first time, the onCreate method is
called in the helper class, otherwise onUpgrade is called.
My subclass that extends SQLiteOpenHelper class looks like this,
public class DBHelper extends SQLiteOpenHelper {
private static final String TEXT_TYPE = " TEXT";
private static final String COMMA_SEP = ",";
private static final String SQLCreateEntries =
"CREATE TABLE " + ProjectConstants.myTableName + " (" +
ProjectConstants.nameColumn + TEXT_TYPE + COMMA_SEP +
ProjectConstants.numberColumn + TEXT_TYPE + " )";
private static final String SQLDeleteEntries = "DROP TABLE IF EXISTS " + ProjectConstants.myTableName;
public DBHelper(Context context) {
super(context, String.valueOf(name), null, version);
}
#Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
sqLiteDatabase.execSQL(SQLCreateEntries);
}
#Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
sqLiteDatabase.execSQL(SQLDeleteEntries);
onCreate(sqLiteDatabase);
}
Now if I follow the instruction in the 1st quote block by uninstalling and reinstalling the application every time I mess with the database, the app never crashes.
But if I revert back to the original database,(then I do this uninstalling and reinstalling the application) obviously my data in the database do not exist anymore.
As mentioned above my Database table named "ContactDetails" which held 15 contacts will no more have that data now.
But I want that 15 contacts to stay intact inside my database Table "ContactDetails".
Is there anyway to make changes to the database without having to uninstalling-reinstalling apk and without losing the previous data ?
You have write SQL Commands and execute block of SQL commands with different version of code on OnUpgrade() of Helper class as follows:
#Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
sqLiteDatabase.execSQL(SQLDeleteEntries);
onCreate(sqLiteDatabase);
switch(i){
case 1:
<commands for version 1>
break;
case 2:
<commands for version 2>
break;
}
You can write the swich cases as per version of applications. you can write different block of SQL commands as you want to execute on different version of applications.
I am trying to implement an Android application that uses SQLite as its data store. I am using ActiveAndroid. I have a model called Item, and I create items in the following way, calling this from the Activity's onCreate method:
Item item = new Item();
item.name = "test item";
item.save();
After launching my app, I then go to the Android Device Monitor to have access to the database files. And what I see are 2 databases in the filesystem of my app: Application.db and todoListDatabase:
Both of these databases contain a table called items, but only Application.db's version of the items table actually contains the new item records I created. Is that correct?
If this is correct, then what is the point of todoListDatabase?
Edit
Here are the relevant files I have:
My SQLite Helper class:
public class ItemDatabaseHelper extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 2;
private static final String DATABASE_NAME = "todoListDatabase";
private static final String ITEMS = "items";
private static final String KEY_ID = "id";
private static final String KEY_BODY = "name";
public ItemDatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
#Override
public void onCreate(SQLiteDatabase db) {
String CREATE_TODO_TABLE = "CREATE TABLE " + ITEMS + "("
+ KEY_ID + " INTEGER PRIMARY KEY," + KEY_BODY + " TEXT" + ")";
db.execSQL(CREATE_TODO_TABLE);
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
if (newVersion == 2) {
db.execSQL("DROP TABLE IF EXISTS " + ITEMS);
onCreate(db);
}
}
}
My Item class:
#Table (name = "Items")
public class Item extends Model {
#Column(name = "name")
public String name;
public Item() {
super();
}
public Item(String name){
super();
this.name = name;
}
}
There's just not enough information in this question, to allow it to be answered. SQLite Databases don't just appear. You have to create them. Typically, you do that with a SQLiteOpenHelper.
Unless you do something odd, your database will be in the directory:
/data/data/<your application's package name>/databases
For example, a database for the Google mail application might be:
/data/data/com.google.android.gm/databases/mail.db
Because I was using ActiveAndroid, creating a SQLiteOpenHelper was doing double work. That's why I was seeing 2 databases. To fix this, I deleted the ItemDatabaseHelper class. Then, when I go to the Android Device Monitor to see the database files, I see that Application.db is the only database there, and it has the items I created in it.
I have a simple game where users guess words. Now, I'm thinking using database to store these words to be guessed.
My problem is the tutorials that are available in the web show how to create a database and save user inputs to that database. They create, for example, a DBHelper.java in src, extends it to SQLiteOpenHelper, override the methods. Back to a specific activity, create an instance of DBHelper, then create the db, open the writable, insert user inputs, close db.
But what I think I only need to do is create a database, insert words in it, then make my app retrieve words from this database.
Am i just wondering if what i'm planning to do is right:
1. create a DBHelper.java in src, extends the class to SQLiteOpenHelper
2. define needed Strings like name of database etc.
3. Create a constructor and override the onCreate and onUpgrade methods
4. CREATE A LOADWORDS METHOD this is where i will insert my words to the database.
5. on my main activity(the first screen on my app) I will create an instance of DBHelper and call the onCreate and loadWords method.
// you would want an onCreate and onUpgrade method for best practices,, here's a partial look of what you want...
public class DBManager extends SQLiteOpenHelper
{
static final String TAG = "DBManager";
static final String DB_NAME = "words.db";
static final int DB_VERSION = 1;
static final String TABLE = "words_table";
static final String C_ID = "id";
static final String C_WORD = "word";
public DBManager(Context context)
{
super(context, DB_NAME, null, DB_VERSION);
}
#Override
public void onCreate(SQLiteDatabase db)
{
String sql = "CREATE TABLE " + TABLE + " ("
+ C_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ C_WORD + " TEXT)";
db.execSQL(sql);
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
db.execSQL("DROP TABLE IF EXISTS " + TABLE);
onCreate(db);
}
//**** Code Insert Word and Retrieve Word Methods *****//
//**** End Code Insert Word and Retrieve Word Methods *****//
}
I want to use a SQLite database within my application. I have created a class which extends SQLiteOpenHelper. When I first wrote the code the database appeared in /data/data/(package)/database. The package name was my reverse domain + /mobile/app. I then created a separate package within my project reverse domain + /mobile/data and moved my Database class into it.
/data/data/(original package)/database existed until I reloaded(to not use the snapshot) my emulator.
since then:
/data/data/(original package)/ is created but with no database directory, /data/data/(data package)/ is not created on the file system. I have tried:
moving my database class back to the original package
creating a new version of the emulator
uninstalling the app within the emulator and then re-installing it.
increasing the database version variable
commenting our code associated with the database class in other parts of my app.
Here is my db class code.
public class BusinessOpsDatabase extends SQLiteOpenHelper {
private static final String TAG = "BusinessOpsDatabase";
private static final int DB_VERSION = 1;
private static final String DB_NAME = "bss_business_ops";
// country table variables
public static final String TABLE_COUNTRY = "country";
public static final String ID = "_ID";
public static final String COL_COUNTRY_NAME = "country_name";
private static final String CREATE_TABLE_COUNTRY = "create table "
+ TABLE_COUNTRY + " (" + ID
+ " integer primary key autoincrement, " + COL_COUNTRY_NAME
+ " text not null);";
private static final String COUNTRY_SCHEMA = CREATE_TABLE_COUNTRY;
public BusinessOpsDatabase(Context context) {
super(context, DB_NAME, null, DB_VERSION);
}
#Override
public void onCreate(SQLiteDatabase db) {
// create tables
db.execSQL(COUNTRY_SCHEMA);
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// drop country
Log.w(TAG, "Upgrading database. Existing contents will be lost. ["
+ oldVersion + "]->[" + newVersion + "]");
db.execSQL("DROP TABLE IF EXISTS " + TABLE_COUNTRY);
// create tables
onCreate(db);
}
}
http://www.techotopia.com/index.php/An_Android_SQLite_Database_Tutorial
Use above link to learn . you may solve all your problems regarding sqlite
I managed to resolve the problem by adding the following code to the database constructor.
SQLiteDatabase db = getWritableDatabase();
I made two classes, the main class that extends Activity and the Database class that holds the database and it's methods. parts of the code from the database class are shown below.
the SQLiteOpenHelper class is a nested class inside the database class. I took it from an example I found on the internet. inside of this nested class is the method,
db.execSQL(SCRIPT_CREATE_DATABASE);
how do I create a new database? If I instantiate the Database class from the Main class like this:
Database db = new Database(this);
does that instantiation automatically instantiate the nested SQLiteOpenHelper class too? so i don't have to explicitly do that.
however for this example of how to create a database, i am confused. if every time I instantiate a new instance calling the addNewRow() method like this:
public void addNewRow(String label, int price){
Database db = new Database(context);
db.openToWrite();
db.insertNewRow(checkBoxStatus, label, price);
db.close();
}
then a new database is created on the "new Database(context)" call, and next I add the info to enter into the columns. and finally call db.close(), however every time i call the addNewRow method shown above, it will instantiate a new database and that also instantiates SQLiteOpenhelper class so a new database is created. that means the last database has been overwritten, and my last row added has been lost, is this correct?
how do i use this Database class to create a Database only once and then read and write things from it with multiple calls like this?
Database db = new Database(context);
db.openToWrite(); or db.openToRead();
// read or update or create new row in database
db.close();
the database class:
public class Database {
public static final String MYDATABASE_NAME = "my_database";
public static final String MYDATABASE_TABLE = "my_table";
public static final int MYDATABASE_VERSION = 1;
public static final String KEY_CHECKBOX_STATUS = "check_box_status";
public static final String KEY_CHECKBOX_LABEL = "check_box_label";
public static final String KEY_PRICE = "price";
//create table MY_DATABASE (ID integer primary key, Content text not null);
private static final String SCRIPT_CREATE_DATABASE =
"CREATE TABLE " + MYDATABASE_TABLE + " (" + "ID INTEGER PRIMARY KEY AUTOINCREMENT, " +
"KEY_CHECKBOX_STATUS INTEGER, " + "KEY_CHECKBOX_LABEL TEXT, " + " KEY_PRICE INTEGER" + ");";
SQLiteDatabase sqLiteDatabase;
SQLiteHelper sqLiteHelper;
Context context;
public Database(Context c){
context = c;
}
// after this all the rest of the methods for get and set of database values
code for the SQLiteOpenHelper class, nested inside of the Database Class:
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
}
}
Yes, every time you instantiate a Database class a SQLiteHelper is instantiate. But the SQLiteHelper onCreate is only called if the database does not exist. You can test this by adding a new column to one of the table and then try to insert a row having value in this column then your app will crash. The error would be "no such column". You then need to clear your data or change the version of your database or uninstall your app to have your change table to be recreated.
Whenever you want to just open your database, you need to use this:
myDatabase = myOpenHelper.getWritableDatabase();
This won't create a new database. It would just return the instance of existing database on which you can do Read/Write operations.
Refer this to get a firm idea of how creating database works in Sqlite. Hope it helps.
private static final String SCRIPT_CREATE_DATABASE =
"CREATE TABLE IF NOT EXISTS " + MYDATABASE_TABLE + " (" + "ID INTEGER PRIMARY KEY AUTOINCREMENT, " +
"KEY_CHECKBOX_STATUS INTEGER, " + "KEY_CHECKBOX_LABEL TEXT, " + " KEY_PRICE INTEGER" + ");";
Use this query while creating the table. It will create the Table if it doesn't exist.