SQLiteAndroid Application Development

By creating the SQLiteScores app, you will gain experience with ... Writing a DatabaseAdapter Extending the DatabaseOpenHelper class Cursors and CursorAdapters ContentValues CRUD

https://github.com/AndroidCourseMaterial/SQLiteScoreshttps://github.com/AndroidCourseMaterial/SQLiteScores_Solution

SQLite is a relational database system

Stores data in tables.

Visual representation of a SQLite table:

The right way to do data storage on mobile devices!For media, just stores URI's of the files

_id name score

0 Dave 95

1 Jimmy 100

2 Dr. B 75

3 Stokes 98

Main concepts: ContentValues and Cursors

ContentValues: a single row in a Table. Maps column names to values.put(key, value)

Cursor: a pointer to a result set returned by a QueryIs iterable: while (cursor.moveToNext()) {...}

_id name score

0 Dave 67

1 Jimmy 100

2 Dr. B 95

3 Stokes 98

ContentValues

Main concepts: ContentValues and Cursors

ContentValues: a single row in a Table. Maps column names to values

Cursor: a pointer to a result set returned by a QueryIs iterable: while (cursor.moveToNext()) {...}Also: .moveToFirst, .getColumnIndex, .getString, ...

_id name score

0 Dave 67

1 Jimmy 100

2 Dr. B 95

3 Stokes 98

Cursor on query, Get all entries with score > 80

Download or git clone the starting code

SQLiteScoreshttps://github.com/AndroidCourseMaterial/SQLiteScores

I recommend changing the SDK to 4.0+ and making sure the Java compiler compliance level is 1.6:

Right-click project > Properties > Android | Java CompilerChange the version in the Manifest to SDK 11+You may also need to clean and rebuild the projectRun it to see what you have!

Github download instructions

Add some names and scores, then edit and delete scoresGood... Menu, dialogs, and view adapter work

Bad... Old-style dialogsNo storage

Score.java

Basic Java model object

Variable Type DescriptionmName String Stores the name of a personmScore int Stores the score that person got

SQLiteScoreAdapter.java

Placeholder to interact with SQLite database SQLiteOpenHelper subclass to open/close database CRUD convenience methods for Scores

Create: Add a score to the SQLite database Read: Get a score from the SQLite database Update: Edit a score in the SQLite database Delete: Remove a score from the SQLite database

Currently holds just a few basic constants.

Score Instance

SQLite Table Row

ScoresListActivity.java

ListActivity ListView + ArrayAdapter + ArrayList

OnItemClick listener to Edit a score Options menu

Add score Context menu

Delete scoreEdit score

CRUD stubs (to be replaced) Dialog

Add a new scoreUpdate an existing score

Take a step of faith: remove the arrays

Delete or comment out the array and adapter:// private ArrayList mScores = new ArrayList();// private ArrayAdapter mScoreAdapter;

Comment out the CRUD until it compiles again. For example:private void addScore(Score s) {

// mScores.add(s);// Collections.sort(mScores);// mScoreAdapter.notifyDataSetChanged();

}

private Score getScore(long id) {// return mScores.get((int) id);return null ;

} Now it's REALLY broken!

We need some boilerplate code in two classes to set up the database

ScoreListActivityCRUD, keys

ScoreDataAdapter create, upgrade, returns database

SQLiteOpenHelper subclass SQLiteDatabase

Add instance variables to prepare for the database

Code from the top down: call some methods you'll write next

Stub in methods in ScoreDataAdapter.java

public ScoreDataAdapter(Context context) {// Create a SQLiteOpenHelper

}

public void open() {// Open the database

}

public void close() {// Close the database

}

Member variables

private SQLiteOpenHelper mOpenHelper; private SQLiteDatabase mDb;

SQLiteOpenHelper - Opening a SQLite database involves a lot of steps that are always the same (mostly the same). So Android has a class that does all the identical work. You will need to customize it for your needs.

SQLiteDatabase - The actual database: SQLite table(s)

Create a nested class: ScoreDbHelper

Define the adapter functions in terms of the database and helper

They don't do much until you finish the ScoreDbHelper inner class

Defining your columns

_id is always recommendedname and score

_id name score

0 Dave 67

1 Jimmy 100

2 Dr. B 95

3 Stokes 98

Add a member variable in the Score

public class Score implements Comparable{

private String mName;

private int mScore;

private long mId;

public long getId() { return mId; }

public void setId(int id) { mId = id; }

public String getName() { return mName; }

public void setName(String name) { mName = name; }

public int getScore() { return mScore; }

public void setScore(int score) { mScore = score; }

public int compareTo(Score other) { return other.getScore() - getScore(); }

public String toString() { return getName() + " " + getScore(); }

}

Create SQLiteScoreAdapter constants for each table column

Add below the DATABASE_VERSION constant.

Here are the only SQL statements you'll write

Use these when you create and upgrade (delete and re-create) your database in the helper

Execute the SQL in the helper's onCreate and onUpgrade methods

@Override

public void onCreate(SQLiteDatabase db) {db.execSQL(CREATE_STATEMENT);

}

@Override

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

Log.d(TAG, "Updating from version " + oldVersion + " to " + newVersion + ", which will destroy old table(s).");

db.execSQL(DROP_STATEMENT);onCreate(db);

}

Backing up the CRUD methods

Time for the Magic

// Convert from score object to a table rowprivate ContentValues getContentValuesFromScore(Score score) {

ContentValues rowValues = new ContentValues();rowValues.put(KEY_NAME, score.getName());rowValues.put(KEY_SCORE, score.getScore());return rowValues;

}

/**

* Add score to the table. If is successful,

* return the new id for that Score, otherwise return -1.

*

* @param score

* @return id of the inserted row or -1 if failed

*/public long addScore(Score score) {

ContentValues rowValues = getContentValuesFromScore(score);return mDb.insert(TABLE_NAME, null, rowValues);

}

Adding a row, returning it with id

These go into the ScoreDataAdapter class below the open() and close() methods

Rewrite CRUD's addScore to use the dbAdapter

private void addScore(Score s) {// mScores.add(s);// Collections.sort(mScores);// mScoreAdapter.notifyDataSetChanged();mScoreDataAdapter.addScore(s);

}

Adding is now ready! But we need to see the data.

We need to read all data in the table to update our view

Back in the ScoreDataAdapter

public Cursor getScoresCursor() {String[] projection = new String[] { KEY_ID, KEY_NAME, KEY_SCORE };return mDb.query( TABLE_NAME, projection, null, null, null, null, KEY_SCORE + " DESC");

}query(tableName, list of columns, where clause, where params for wildcards,group by, having, order, max rows)

The order of the cursor is setup as scores in decreasing order

Replace the ArrayAdapter with a SimpleCursorAdapter in the ListActivity

@Override

public void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout. scores_list_activity);

mScoreDataAdapter = new SQLiteScoreAdapter(this);mScoreDataAdapter.open();

int viewResourceId = R.layout.score_list_item;

Cursor cursor = mScoreDataAdapter.getScoresCursor();String[] fromColumns = new String[] { ScoreDataAdapter.KEY_NAME,

ScoreDataAdapter.KEY_SCORE };int[] toTextViews = new int[] { R.id.textViewName, R.id.textViewScore};

mCursorAdapter = new SimpleCursorAdapter(this, viewResourceId, cursor, fromColumns, toTextViews, 0);

setListAdapter(mCursorAdapter);registerForContextMenu(getListView());

}

We can see stuff!

And the values persist!Hit home and then come back (or rotate)

To get an immediate result when you add, you need to reload the cursorprivate void addScore(Score s) {

// mScores.add(s);// Collections.sort(mScores);// mScoreAdapter.notifyDataSetChanged();mScoreDataAdapter.addScore(s);Cursor cursor = mScoreDataAdapter.getScoresCursor();mCursorAdapter.changeCursor(cursor);

}

Adding the remaining CRUD

CRUD ScoresListActivity ScoreDataAdapter

Create addScore (done) addScore (done)

Read getScore getScoresCursor (done)getScore

Update editScore updateScore

Delete removeScore removeScore

Updating the fields in the dialog edits

Adding new scores works. What about editing an existing score? First we just need to autofill the dialog with getS

ScoreDataAdapter: Get a single row in the table

public Score getScore(long id) {

// Getting a cursor for the specific idString[] projection = new String[] { KEY_ID, KEY_NAME, KEY_SCORE };String selection = KEY_ID + "=" + id;Cursor c = mDb.query(true, TABLE_NAME, projection, selection,

null,null,null,null,null);

// Using the cursor to get values from the tableif(c != null && c.moveToFirst()) {

Score s = new Score();int idColumn = c.getColumnIndexOrThrow(KEY_ID);int nameColumn = c.getColumnIndexOrThrow(KEY_NAME);int scoreColumn = c.getColumnIndexOrThrow(KEY_SCORE);s.setID(c.getInt(idColumn));s.setName(c.getString(nameColumn));s.setScore(c.getInt(scoreColumn));return s;

}return null;

}

Get a distinct Cursor (one value)

ScoresListActivity

private Score getScore(long id) {// return mScores.get((int) id);return mScoreDataAdapter.getScore(id);

}

Now the edit dialog box should auto fill correctly. It just won't update the table. :)

ScoreDataAdapter updateScore

public void updateScore(Score score) {ContentValues rowValues = getContentValuesFromScore(score);

String whereClause = KEY_ID + "=" + score.getID();mDb.update(TABLE_NAME, rowValues, whereClause, null);

}

ScoresListActivity

private void editScore(Score s) {if (mSelectedId == NO_ID_SELECTED) {

Log.e(TAG, "Attempt to update with no score selected.");}

s.setID((int) mSelectedId);mScoreDataAdapter.updateScore(s);Cursor cursor = mScoreDataAdapter.getScoresCursor();mCursorAdapter.changeCursor(cursor);

}

Edits done, only delete remains

Edits should actually update the database now

ScoreDataAdapter removeScore

public boolean removeScore(long id) {return mDb.delete(TABLE_NAME, KEY_ID + "=" + id, null) > 0;

}

public boolean removeScore(Score s) {return removeScore(s.getID());

}

ScoresListActivity

private void removeScore(long id) {// mScores.remove((int)id);// Collections.sort(mScores);// mScoreAdapter.notifyDataSetChanged();

mScoreDataAdapter.removeScore(id);Cursor cursor = mScoreDataAdapter.getScoresCursor();mCursorAdapter.changeCursor(cursor);

}

Delete. That's all four CRUD methods

Long press a row then select Delete

SQLiteScores

Subtle but HUGE

It might not have felt like a huge difference from the starting app to the end, but we assure you it was.

Data Persistence is an invaluable skill in your bag of tricks

But there is more! Content Providers are an interface that ......lets you share your data with other apps...allows you to use data from other apps

Contacts, media, calendars, 3rd party apps

SQL Editors (require root access)

Copy database from rooted phone to laptop to view:SQLite Browser Database (free)

http://sourceforge.net/projects/sqlitebrowser/

View directly on phone:SQLite Editor by Speed Software ($2.99)

https://play.google.com/store/apps/details?id=com.speedsoftware.sqleditor&hl=en

Worth every penny if your phone is rooted