Cosc 5/4730

Android and BlackberrySQLite

SQLite

• For the sql language syntax , please see SQlite documentation– http://www.sqlite.org

• Both Android and Blackberry implement the SQLite package– But very differently.

BLACKBERRYSQLite

Blackberry SQLite

• net.rim.device.api.database.*– accessible only by signed applications• For the purposes of the class, you don’t need a signing

keys. But if you plan to use an on the phone.» Category: Signed: This element is only accessible by

signed applications. If you intend to use this element, please visit http://www.blackberry.com/go/codesigning to obtain a set of code signing keys. Code signing is only required for applications running on BlackBerry smartphones

– development on BlackBerry Smartphone Simulators can occur without code signing.

SQLite Database files

• Each SQLite® database is stored in a single file.– If you only specify the database name as the

parameter value to DatabaseFactory.create() , the database file is created on the SD card of the device.

– The default location for the database file is /SDCard/databases/<application_name>/ . The name of the application that creates the database is included in the path to avoid name collisions.

Opening/create a DB

• Uses DatabaseFactory– open() //opens db, throws exception if fails– create() //creates db, but if fails throws exception– examples:Database d;

//using default location on the SDcardd = DatabaseFactory.create("myDB.db");d = DatabaseFactory.open("myDB.db");

Opening/create a DB

• Throws the following exceptions • DatabasePathException– Bad path or SDCard not there.• OS 5 Storm and Bold and 6+ can use internal

• ControlledAccessException– on access restriction

• DatabaseIOException– Can’t open it generally.

Statement interface

1. Creation: Statement = Database.createStatement(String)

2. Preparation: via Statement.prepare()3. Bind: of any formal parameters in the statement to

actuals via Statement.bind(int, int) and associated methods, starting from 1 for the first formal.

4. Query Execution: via Statement.getCursor(), which returns a Cursor

5. Update Execution: via Statement.execute()

Statements and cursor

• Use the statement, we then use SQLite sql statements to work on the database.

• For select statements, it returns a cursor• From the cursors, we get Row object for each

row of data selected.

example• Create Db and add a datad = DatabaseFactory.create("myDB.db");Statement st;st = d.createStatement( "CREATE TABLE 'HighScore' ('Name' TEXT, 'Score' INTEGER )" );st.prepare();st.execute();st.close();//add some datast = d.createStatement("INSERT INTO HighScore(Name,Score) VALUES ('Jim',3012)");st.prepare();st.execute();st.close();

Example (2)• Read back the datast = d.createStatement("SELECT Name,Score FROM HighScore");st.prepare();net.rim.device.api.database.Cursor c = st.getCursor();

Row r;while(c.next()) {

r = c.getRow();System.out.println("Row "+i+ "is "+r.getString(0)+"

"+r.getInteger(1));}c.close();st.close()

Where 0 is Name and 1 is Score column.

Closing the database

• Don’t forget to close the database when you are done.

try {d.close(); //where d is the database.

} catch (DatabaseIOException e) {//for some reason the db can’t be closed.

}

finally

• Don’t forgot to close everything– Cursor, statements and database– It releases all the resources that they are holding.

• Some more code samples on-line :– http://

docs.blackberry.com/en/developers/deliverables/8682/Create_a_SQLite_database_761831_11.jsp

A Note

• There is a RecordStore that can be used instead of SQLite– works on the rest of the phones

– Also, not a signed API either.

ANDROIDSQLite

SQLite and Android

• The similarity ends at the name between blackberry and android.– It SQLite, but handled very differently.

• Package– android.database.sqlite

• Normally the SQLite is implemented in a separate class from the Activity class.

SQL language

• Android sqlite uses sql, but the methods may break up the statement– example String WhereClause and String[] WhereArgs

• sql and android query examples– select Name, Score from HighScore where name=‘jim’;

• db.query(true, DATABASE_TABLE, new String[] {KEY_NAME, KEY_SCORE, }, KEY_NAME + "=\'" + VarName+"\'",, null, null, null, null, null);– NOTE the single quotes, which are required for any Text (android term), varchar,

or string fields in the table

– Select Name,Score from HighScore;• db.query(true, DATABASE_TABLE, new String[] {KEY_NAME,

KEY_SCORE}, null, null, null, null, null, null);– The red null so there is no WHERE CLAUSE.

DB class

• First you need to create a class to handle the database.– In my case,

DBAdapter. I'm also using a number of constants to simplify typing errors• let the compiler find

my typing errors.

public class DBAdapter {

public static final String KEY_NAME = "Name";public static final String KEY_SCORE = "Score";private static final String TAG = "DBAdapter";

private static final String DATABASE_NAME = "myDB";private static final String DATABASE_TABLE = "HighScore";private static final int DATABASE_VERSION = 1;

private static final String DATABASE_CREATE ="CREATE TABLE HighScore (Name TEXT, Score INTEGER );";

private final Context context;private DatabaseHelper DBHelper;private SQLiteDatabase db;

public DBAdapter(Context ctx) {this.context = ctx;DBHelper = new DatabaseHelper(context);

}

Extend SQLiteOpenHelper

• A helper class to manage database creation and version management. – You create a subclass implementing

onCreate(SQLiteDatabase), onUpgrade(SQLiteDatabase, int, int) and optionally onOpen(SQLiteDatabase)

– This class takes care of opening the database if it exists, creating it if it does not, and upgrading it as necessary.

– Transactions are used to make sure the database is always in a sensible state.

DB class (2)• subclass in DBAdapterprivate static class DatabaseHelper extends SQLiteOpenHelper {

DatabaseHelper(Context context) {super(context, DATABASE_NAME, null, DATABASE_VERSION);

}@Overridepublic void onCreate(SQLiteDatabase db) {

//only called when the database is created! db.execSQL(DATABASE_CREATE);

}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);onCreate(db);

}}

Now our stuff• Add a few classes in DBAdapter to do the heavy lifting.// ---opens the database---public DBAdapter open() throws SQLException {

db = DBHelper.getWritableDatabase();return this;

}

// ---closes the database---public void close() {

DBHelper.close();db.close();

}

SQLiteDatabase methods

• Some of the common methods– void execSQL(String sql)

• Execute a single SQL statement that is not a query.

– long insert(String table, String nullColumnHack, ContentValues values)• method for inserting a row into the database.

– long insertOrThrow(String table, String nullColumnHack, ContentValues values)• method for inserting a row into the database or throws a SQLException

– Cursor query(String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy)• Query the given table, returning a Cursor over the result set.• There are several query methods that can be used.

SQLiteDatabase methods (2)

– int delete(String table, String whereClause, String[] whereArgs)• method for deleting rows in the database.

– public Cursor rawQuery (String sql, String[] selectionArgs)• Runs the provided SQL and returns a Cursor over the result

set.• Sql is the SQL query. The SQL string must not be ; terminated• selectionArgs You may include ?s in where clause in the

query, which will be replaced by the values from selectionArgs. The values will be bound as Strings.– Maybe null.

Now our stuff (2)// ---insert into the database---public long insertName(String name, Integer value) {

ContentValues initialValues = new ContentValues(); initialValues.put(KEY_NAME, name); initialValues.put(KEY_SCORE, value); return db.insert(DATABASE_TABLE, null, initialValues); }

// ---retrieves all rows---public Cursor getNames() { Cursor c = db.query(DATABASE_TABLE, new String[] {KEY_NAME, KEY_SCORE},

null, null, null, null, KEY_NAME);if (c != null ) //make sure db is not empty! c.moveToFirst(); return c;

}

Now our stuff (3)public Cursor getRow(long rowId) throws SQLException {

Cursor mCursor = db.query(true, DATABASE_TABLE, new String[] { KEY_ROWID, KEY_NAME, KEY_IP, KEY_OWNER }, KEY_ROWID + "="+ rowId, null, null, null, null, null);if (mCursor != null) {

mCursor.moveToFirst();}return mCursor;

}

// ---updates a row---public boolean updateRow(String name, int score) { ContentValues args = new ContentValues(); args.put(KEY_SCORE, score);

//returns true if one or more updates happened, otherwise false. return db.update(DATABASE_TABLE, args, KEY_NAME + "= \'" + name+"\'", null) > 0;}

Now our stuff (4)

// ---deletes a particular row---public boolean deleteRow(long rowId) {

return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;

}

//Delete all rows with namepublic boolean deleteName(String name) {

return db.delete(DATABASE_TABLE, KEY_NAME + "= \'" + name+"\'", null) > 0;

}

The Activity class.

• create an activity class and addDBAdatper db = new DBAdapter(this);• Access and use the DB. db.open();id = db.insertName("Jim", 3012);• note if (id == -1) then it failed to insert//whatever else you want to do.db.close();

Cursor notes

• The queries all return Cursor, so you need to pull the information out of it.– In my example, there are 2 columns in the db (and

both are requested)

Cursor c = db.getNames(); String str = “Name: " + c.getString(0); //name

str += " Score:" + c.getInt(1); //score

Cursor notes (2)• The Score column is actually an integer, so I could use .getInt(1) as

well.• Cursor has a number of useful methods• double getDouble(int columnIndex), float getFloat(int columnIndex),

int getInt(int columnIndex), long getLong(int columnIndex), short getShort(int columnIndex), String getString(int columnIndex)

• String[] getColumnNames()– Returns a string array holding the names of all of the columns in the result

set in the order in which they were listed in the result.• int getCount()

– Returns the numbers of rows in the cursor.• int getColumnCount()

– Return total number of columns

Example with Cursor

public void delRowbyName(String name) {db.open();Cursor c = db.getNames();

for(c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) { //0 name, 1 score label1.setText(c.getString(0) + " " + c.getInt(1)); }

db.close();}

Debugging a "stopped unexpectedly"

• bring up the ddms – ddms.bat or eclipse

ddms– There will you give a way

to debug your app, including what caused

– Check the log for Errors (in red)

debugging the database

• The system stores databases in the /data/data/package_name/databases folder by default.

• In a command line using the adb (Android Debug Bridge - found in the android sdk tools library) you can access the databases on a running emulator like below– adb -s emulator-5554 shell

• assuming 5554 is your emulator

– sqlite3 /data/data/package_name/databases/database_name• After this you can type normal SQL commands to test the

content. For example:– SELECT * FROM table_name;

• The output format is pretty ugly, but workable .

References

• Creating an using Databases with android– http://www.devx.com/wireless/Article/40842

• Android Tutorials– http://www.helloandroid.com/tutorials– http://www.helloandroid.com/ Some good general

help• Android developer site– http://developer.android.com/intl/zh-CN/reference/

android/database/sqlite/package-summary.html

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