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Better Data Persistence on Android

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Whether you’re an experienced Android developer, or you’re just getting started, you will need to think about storing data on the device. Android offers several options including relational data storage on a SQLite Database, but the APIs and examples provided by Google look like the state-of-the-art JDBC programming you did back in 1995! In this talk, you’ll learn how to use RealmDB, an elegant Object Relational database alternative to SQLite, to make database development on Android fun, easy, and testable.

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Better Data Persistence on Android

  1. 1. Better Data Persistence on Android Eric Maxwell Credible Software
  2. 2. What to Expect • Android Storage Options • Focus on SQLite / Database Storage • Make it better using the Realm Mobile Database
  3. 3. Android Storage Options • Shared Preferences
  4. 4. Android Storage Options • Shared Preferences • Disk Storage • Internal • External
  5. 5. Android Storage Options • Shared Preferences • Disk Storage • Internal • External • Relational Database w/ SQLite
  6. 6. SQLite • Relational Database on the device • android.database.sqlite.SQLiteDatabase • Perform insert, query, update, delete, begin/end transaction • android.database.sqlite.SQLiteOpenHelper • Handle Create, Upgrade events
  7. 7. Nae Nae Assistant App • List of Nae Nae Lyrics • Add New • Delete • Persistent across launches
  8. 8. View Layout <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 android:orientation="vertical" >
 
 <GridLayout
 android:id="@+id/lyricButtons"
 android:layout_width="fill_parent"
 android:layout_height="wrap_content"
 android:padding="10dp">
 
 <Button
 android:id="@+id/watch_me"
 android:text="@string/lyric_watch_me"
 android:onClick="add"/>
 
 <Button
 android:id="@+id/whip"
 android:text="@string/lyric_whip"
 android:onClick="add"/>
 
 <Button
 android:id="@+id/nea"
 android:text="@string/lyric_nea"
 android:onClick="add"/>
 
 <Button
 android:id="@+id/bop"
 android:text="@string/lyric_bop"
 android:onClick="add"/>
 
 </GridLayout>
 
 <ListView
 android:id="@android:id/list"
 android:layout_width="fill_parent"
 android:layout_height="wrap_content"
 android:text="@string/hello_world" />
 
 </LinearLayout>
  9. 9. Simple Data Object public class Lyric { 
 private long id;
 private String lyricText;
 
 // Getters / Setters...
 
 // Will be used by the ArrayAdapter in the ListView
 @Override
 public String toString() {
 return lyricText;
 }
 }
  10. 10. Activity - Lifecycle Events public class NaeNaeActivity extends ListActivity {
 
 private LyricDataSource datasource;
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_naenae);
 
 datasource = new LyricDataSource(this);
 datasource.open();
 
 List<Lyric> values = datasource.getAllLyrics();
 
 // Use the SimpleCursorAdapter to show the
 // elements in a ListView
 ArrayAdapter<Lyric> adapter = new ArrayAdapter<Lyric>(this,
 android.R.layout.simple_list_item_1, values);
 setListAdapter(adapter); 
 }
 
 @Override
 protected void onResume() {
 super.onResume();
 datasource.open();
 }
 
 @Override
 protected void onPause() {
 super.onPause();
 datasource.close();
 } ... } The datasource gets initialized and opened on create and is then used to get all of the lyrics and placed into an array adapter. The datasource is opened and closed on resume and stop.
  11. 11. Activity - Events Add/Remove public void add(View view) {
 String lyricText = ((Button) view).getText().toString();
 if (!TextUtils.isEmpty(lyricText)) {
 ArrayAdapter<Lyric> adapter = getListAdapter();
 Lyric lyric = null;
 lyric = datasource.createLyric(lyricText);
 adapter.add(lyric);
 }
 }
 
 public void delete (int position) {
 if (getListAdapter().getCount() > 0) {
 ArrayAdapter<Lyric> adapter = getListAdapter();
 Lyric lyric = adapter.getItem(position);
 datasource.deleteLyric(lyric);
 adapter.remove(lyric);
 }
 } 
 
 @Override
 @SuppressWarnings("unchecked")
 public ArrayAdapter<Lyric> getListAdapter() {
 return (ArrayAdapter<Lyric>) super.getListAdapter();
 } 
 Add Remove
  12. 12. Custom SQLiteOpenHelper public class MySQLiteHelper extends SQLiteOpenHelper {
 
 public static final String TABLE_LYRICS = "lyrics";
 public static final String COLUMN_ID = "_id";
 public static final String COLUMN_LYRIC = "lyric";
 
 private static final String DATABASE_NAME = "lyric.db";
 private static final int DATABASE_VERSION = 1;
 
 // Database creation sql statement
 private static final String DATABASE_CREATE = "create table "
 + TABLE_LYRICS + "( " + COLUMN_ID
 + " integer primary key autoincrement, " + COLUMN_LYRIC
 + " text not null);";
 
 public MySQLiteHelper(Context context) {
 super(context, DATABASE_NAME, null, DATABASE_VERSION);
 }
 
 @Override
 public void onCreate(SQLiteDatabase database) {
 database.execSQL(DATABASE_CREATE);
 }
 
 @Override
 public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
 Log.w(MySQLiteHelper.class.getName(),
 "Upgrading database from version " + oldVersion + " to "
 + newVersion + ", which will destroy all old data");
 db.execSQL("DROP TABLE IF EXISTS " + TABLE_LYRICS);
 onCreate(db);
 }
 
 }
  13. 13. Lyric Datasource public class LyricDataSource {
 
 // Database fields
 private SQLiteDatabase database;
 private MySQLiteHelper dbHelper;
 private String[] allColumns = { MySQLiteHelper.COLUMN_ID,
 MySQLiteHelper.COLUMN_LYRIC};
 
 public LyricDataSource(Context context) {
 dbHelper = new MySQLiteHelper(context);
 }
 
 public void open() throws SQLException {
 database = dbHelper.getWritableDatabase();
 }
 
 public void close() {
 dbHelper.close();
 } public List<Lyric> getAllLyrics() {
 List<Lyric> lyrics = new ArrayList<Lyric>();
 
 Cursor cursor = database.query(MySQLiteHelper.TABLE_LYRICS,
 allColumns, null, null, null, null, MySQLiteHelper.COLUMN_ID);
 cursor.moveToFirst();
 while (!cursor.isAfterLast()) {
 Lyric lyric = cursorToLyric(cursor);
 lyrics.add(lyric);
 cursor.moveToNext();
 }
 // Make sure to close the cursor
 cursor.close();
 return lyrics;
 } public Lyric createLyric(String lyric) {
 ContentValues values = new ContentValues();
 values.put(MySQLiteHelper.COLUMN_LYRIC, lyric);
 long insertId = database.insert(MySQLiteHelper.TABLE_LYRICS, null,
 values);
 Cursor cursor = database.query(MySQLiteHelper.TABLE_LYRICS,
 allColumns, MySQLiteHelper.COLUMN_ID + " = " + insertId, null,
 null, null, null);
 cursor.moveToFirst();
 Lyric newLyric = cursorToLyric(cursor);
 cursor.close();
 return newLyric;
 }
 
 public void deleteLyric(Lyric lyric) {
 long id = lyric.getId();
 database.delete(MySQLiteHelper.TABLE_LYRICS, MySQLiteHelper.COLUMN_ID
 + " = " + id, null);
 }
 
 public Lyric getLyricByValue(String lyricText) {
 Lyric lyric = null;
 Cursor cursor = database.query(MySQLiteHelper.TABLE_LYRICS,
 allColumns, MySQLiteHelper.COLUMN_LYRIC + " = '" + lyricText + "'" , null, null, null, null);
 cursor.moveToFirst();
 if (!cursor.isAfterLast()) {
 lyric = cursorToLyric(cursor);
 }
 // Make sure to close the cursor
 cursor.close();
 return lyric;
 } 
 private Lyric cursorToLyric(Cursor cursor) {
 Lyric lyric = new Lyric();
 lyric.setId(cursor.getLong(0));
 lyric.setLyricText(cursor.getString(1));
 return lyric;
 }
  14. 14. Using SQLite Pros • No additional dependencies • Built in programatic transaction management • Built in creation and upgrade event handling
  15. 15. What happens when you add a couple fields? public class MySQLiteHelper extends SQLiteOpenHelper {
 
 public static final String TABLE_LYRICS = "lyrics";
 public static final String COLUMN_ID = "_id";
 public static final String COLUMN_LYRIC = "lyric";
 
 private static final String DATABASE_NAME = "lyric.db";
 private static final int DATABASE_VERSION = 1;
 
 // Database creation sql statement
 private static final String DATABASE_CREATE = "create table "
 + TABLE_LYRICS + "( " + COLUMN_ID
 + " integer primary key autoincrement, " + COLUMN_LYRIC
 + " text not null);";
 
 public MySQLiteHelper(Context context) {
 super(context, DATABASE_NAME, null, DATABASE_VERSION);
 }
 
 @Override
 public void onCreate(SQLiteDatabase database) {
 database.execSQL(DATABASE_CREATE);
 }
 
 @Override
 public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
 Log.w(MySQLiteHelper.class.getName(),
 "Upgrading database from version " + oldVersion + " to "
 + newVersion + ", which will destroy all old data");
 db.execSQL("DROP TABLE IF EXISTS " + TABLE_LYRICS);
 onCreate(db);
 }
 
 }
  16. 16. Update the data model public class Lyric {
 private long id;
 private String lyricText; private String source; private boolean isChorus;
 
 public long getId() {
 return id;
 }
 
 public void setId(long id) {
 this.id = id;
 }
 
 public String getLyricText() {
 return lyricText;
 }
 
 public void setLyricText(String lyricText) {
 this.lyricText = lyricText;
 } // Additional Getter/Setters
 
 // Will be used by the ArrayAdapter in the ListView
 @Override
 public String toString() {
 return lyricText;
 }
 }
  17. 17. Update the Datasource public class LyricDataSource {
 
 // Database fields
 private SQLiteDatabase database;
 private MySQLiteHelper dbHelper;
 private String[] allColumns = { MySQLiteHelper.COLUMN_ID,
 MySQLiteHelper.COLUMN_LYRIC, MySQLiteHelper.COLUMN_SOURCE, MySQLiteHelper.COLUMN_CHORUS};
 
 public LyricDataSource(Context context) {
 dbHelper = new MySQLiteHelper(context);
 }
 
 public void open() throws SQLException {
 database = dbHelper.getWritableDatabase();
 }
 
 public void close() {
 dbHelper.close();
 } public List<Lyric> getAllLyrics() {
 List<Lyric> lyrics = new ArrayList<Lyric>();
 
 Cursor cursor = database.query(MySQLiteHelper.TABLE_LYRICS,
 allColumns, null, null, null, null, MySQLiteHelper.COLUMN_ID);
 cursor.moveToFirst();
 while (!cursor.isAfterLast()) {
 Lyric lyric = cursorToLyric(cursor);
 lyrics.add(lyric);
 cursor.moveToNext();
 }
 // Make sure to close the cursor
 cursor.close();
 return lyrics;
 } public Lyric createLyric(String lyric) {
 ContentValues values = new ContentValues();
 values.put(MySQLiteHelper.COLUMN_LYRIC, lyric);
 values.put(MySQLiteHelper.COLUMN_CHORUS, isChorus ? 1 : 0);
 values.put(MySQLiteHelper.COLUMN_SOURCE, source);
 long insertId = database.insert(MySQLiteHelper.TABLE_LYRICS, null,
 values);
 Cursor cursor = database.query(MySQLiteHelper.TABLE_LYRICS,
 allColumns, MySQLiteHelper.COLUMN_ID + " = " + insertId, null,
 null, null, null);
 cursor.moveToFirst();
 Lyric newLyric = cursorToLyric(cursor);
 cursor.close();
 return newLyric;
 }
 
 public void deleteLyric(Lyric lyric) {
 long id = lyric.getId();
 database.delete(MySQLiteHelper.TABLE_LYRICS, MySQLiteHelper.COLUMN_ID
 + " = " + id, null);
 }
 
 public Lyric getLyricByValue(String lyricText) {
 Lyric lyric = null;
 Cursor cursor = database.query(MySQLiteHelper.TABLE_LYRICS,
 allColumns, MySQLiteHelper.COLUMN_LYRIC + " = '" + lyricText + "'" , null, null, null, null);
 cursor.moveToFirst();
 if (!cursor.isAfterLast()) {
 lyric = cursorToLyric(cursor);
 }
 // Make sure to close the cursor
 cursor.close();
 return lyric;
 } 
 private Lyric cursorToLyric(Cursor cursor) {
 Lyric lyric = new Lyric();
 lyric.setId(cursor.getLong(0));
 lyric.setLyricText(cursor.getString(1)); lyric.setChorus(cursor.getInt(2) == 1);
 lyric.setSource(cursor.getString(3));
 return lyric;
 }
  18. 18. Add the columns to our SQLiteOpenHelper public class MySQLiteHelper extends SQLiteOpenHelper {
 
 private static final String DATABASE_NAME = "lyric.db";
 private static final int DATABASE_VERSION = 1;
 public static final String COLUMN_ID = "_id";
 
 public static final String TABLE_LYRICS = "lyrics";
 public static final String COLUMN_LYRIC = "lyric";
 public static final String COLUMN_SOURCE = "source";
 
 public static final String COLUMN_CHORUS = "isChorus";
 
 
 // Database creation sql statement
 private static final String DATABASE_CREATE =
 
 "create table "
 + TABLE_LYRICS + "( " + COLUMN_ID
 + " integer primary key autoincrement, “ + COLUMN_LYRIC + " text not null, "
 + COLUMN_CHORUS + " text, "
 + COLUMN_SOURCE + " integer, "
 + " ); "
 ;
 
 ...
 
 }
  19. 19. How about a second table public class MySQLiteHelper extends SQLiteOpenHelper {
 
 private static final String DATABASE_NAME = "lyric.db";
 private static final int DATABASE_VERSION = 1;
 public static final String COLUMN_ID = "_id";
 
 public static final String TABLE_LYRICS = "lyrics";
 public static final String COLUMN_LYRIC = "lyric";
 public static final String COLUMN_SOURCE = "source";
 public static final String COLUMN_CHORUS = "isChorus";
 
 public static final String TABLE_ARTISTS = "artists";
 public static final String COLUMN_ARTIST_NAME = "name";
 public static final String COLUMN_ARTIST_LABEL = "label";
 
 // Database creation sql statement
 private static final String DATABASE_CREATE =
 
 "create table "
 + TABLE_LYRICS + "( " + COLUMN_ID + " integer primary key autoincrement, "
 + COLUMN_LYRIC + " text not null, "
 + COLUMN_CHORUS + " text, "
 + COLUMN_SOURCE + " integer "
 + " ); "
 +
 "create table "
 + TABLE_ARTISTS + "( " + COLUMN_ID + " integer primary key autoincrement, "
 + COLUMN_ARTIST_NAME + " text not null, "
 + COLUMN_ARTIST_LABEL + " text "
 + " ); "
 ; 
 
 ...
 
 }
  20. 20. Or a many to many relationship public class MySQLiteHelper extends SQLiteOpenHelper {
 
 private static final String DATABASE_NAME = "lyric.db";
 private static final int DATABASE_VERSION = 1;
 public static final String COLUMN_ID = "_id";
 
 public static final String TABLE_LYRICS = "lyrics";
 public static final String COLUMN_LYRIC = "lyric";
 public static final String COLUMN_SOURCE = "source";
 public static final String COLUMN_CHORUS = "isChorus";
 
 public static final String TABLE_ARTISTS = "artists";
 public static final String COLUMN_ARTIST_NAME = "name";
 public static final String COLUMN_ARTIST_LABEL = “label"; public static final String TABLE_LYRIC_ARTIST = "lyric_artist";
 public static final String COLUMN_LYRIC_ID = "lyric_id";
 public static final String COLUMN_ARTIST_ID = "artist_id";
 
 
 // Database creation sql statement
 private static final String DATABASE_CREATE =
 
 "create table "
 + TABLE_LYRICS + "( " + COLUMN_ID + " integer primary key autoincrement, "
 + COLUMN_LYRIC + " text not null, "
 + COLUMN_CHORUS + " text, "
 + COLUMN_SOURCE + " integer "
 + " ); "
 +
 "create table "
 + TABLE_ARTISTS + "( " + COLUMN_ID + " integer primary key autoincrement, "
 + COLUMN_ARTIST_NAME + " text not null, "
 + COLUMN_ARTIST_LABEL + " text "
 + " ); “ +
 "create table "
 + TABLE_LYRIC_ARTIST + "( "
 + COLUMN_LYRIC_ID + " integer, "
 + COLUMN_ARTIST_ID + " integer, "
 + " FOREIGN KEY(" + COLUMN_ARTIST_ID + ") REFERENCES " + TABLE_ARTISTS + "(" + COLUMN_ID + "), "
 + " FOREIGN KEY(" + COLUMN_LYRIC_ID + ") REFERENCES " + TABLE_LYRICS + "(" + COLUMN_ID + ") "
 + " ); "
 ; 
 
 ...
 
 }
  21. 21. Using SQLite Cons • Queries / Updates are very tedious • Changes become cumbersome • Relationships between an object graph must be manually managed
  22. 22. Realm Mobile Database Replacement
  23. 23. About Realm • Realm is a Mobile Database: • A replacement for Core Data or SQLite • Feels like an Object Relational Mapping tool • Free & Open Source Apache 2.0 • Comparable Performance to SQLite
  24. 24. Fast Queries https://realm.io/news/introducing-realm/
  25. 25. Faster Counts https://realm.io/news/introducing-realm/
  26. 26. Slower Inserts https://realm.io/news/introducing-realm/
  27. 27. How it works
  28. 28. Realm Objects Look like Regular Objects… public class Dog extends RealmObject {
 
 private String name;
 private int age;
 @ignored private int dontPersistMe;
 
 // + Standard setters and getters here
 
 }
 
 @RealmClass public class Person implements RealmModel {
 
 private String name;
 private RealmList<Dog> dogs;
 
 }
 

  29. 29. Easy to add / relate objects try(Realm realm = Realm.getInstance(this.getContext())) {
 
 realm.beginTransaction();
 
 Dog dog = realm.createObject(Dog.class);
 dog.setName("Rex");
 dog.setAge(3);
 
 Person person = realm.createObject(Person.class);
 person.setName("Tim");
 person.getDogs().add(dog);
 
 realm.commitTransaction();
 }
  30. 30. Updates must be wrapped in transactions try(Realm realm = Realm.getInstance(this.getContext())) {
 
 realm.beginTransaction();
 
 Dog dog = realm.createObject(Dog.class);
 dog.setName("Rex");
 dog.setAge(3);
 
 Person person = realm.createObject(Person.class);
 person.setName("Tim");
 person.getDogs().add(dog);
 
 realm.commitTransaction();
 }
  31. 31. Updates must be wrapped in transactions try(Realm realm = Realm.getInstance(this.getContext())) {
 
 realm.beginTransaction();
 
 Dog dog = realm.createObject(Dog.class);
 dog.setName("Rex");
 dog.setAge(3);
 
 Person person = realm.createObject(Person.class);
 person.setName("Tim");
 person.getDogs().add(dog);
 
 realm.commitTransaction();
 } If an exception occurs, you must catch it and rollback with realm.cancelTransaction( );
  32. 32. 1 to Many try(Realm realm = Realm.getInstance(this.getContext())) {
 
 realm.beginTransaction();
 
 Dog dog = realm.createObject(Dog.class);
 dog.setName("Rex");
 dog.setAge(3);
 
 Person person = realm.createObject(Person.class);
 person.setName("Tim");
 person.getDogs().add(dog);
 
 realm.commitTransaction();
 } 1 to Many
  33. 33. Many to Many try(Realm realm = Realm.getInstance(this.getContext())) {
 
 realm.beginTransaction();
 
 Dog rex = realm.createObject(Dog.class);
 rex.setName("Rex");
 rex.setAge(3);
 
 Dog spot = realm.createObject(Dog.class);
 spot.setName("Spot");
 spot.setAge(4);
 Person tim = realm.createObject(Person.class);
 tim.setName(“Tim"); tim.getDogs().addAll(Arrays.asList(spot, rex)); Person mary = realm.createObject(Person.class);
 mary.setName("Mary");
 mary.getDogs().addAll(Arrays.asList(spot, rex));
 rex.getOwners().addAll(Arrays.asList(tim, mary)); spot.getOwners().addAll(Arrays.asList(tim, mary)); 
 realm.commitTransaction();
 } Many to Many
  34. 34. Querying // Queries uses Builder pattern to build up the query conditions // For this example, assume Dog has a property “Person owner”
 RealmResults<Dog> results = realm.where(Dog.class)
 .greaterThan("age", 8) .equalTo("owner.name", "Tim") .findAll(); // Queries are chainable
 RealmResults<Dog> allRex = results.where() .contains("name", "rex")
 .findAll(); // Or they can be combined
 RealmResults<Dog> result2 = realm.where(Dog.class) .greaterThan("age", 8) .equalTo(“owner.name", "Tim") .contains("name", "rex") .findAll();
  35. 35. More Queries // Logical Query Grouping boolean checkCase = false; RealmResults<Dog> r = realm.where(Dog.class) .greaterThan("age", 8) //implicit AND .beginGroup() .equalTo("name", “CuJo”, checkCase) .or() .contains("name", "rex") .endGroup() .findAll(); // Sorting RealmResults<Dog> result = r.where(Dog.class).findAll();
 result.sort("age"); // Sort ascending
 result.sort("age", RealmResults.SORT_ORDER_DESCENDING);
 // Result Aggregation long sum = result.sum("age").longValue();
 long min = result.min("age").longValue();
 long max = result.max("age").longValue();
 double average = result.average("age");
 long matches = result.size();
  36. 36. Query Conditions • between, greaterThan, lessThan, 
 greaterThanOrEqualTo & lessThanOrEqualTo • equalTo, notEqualTo, in, not & distinct • contains, beginsWith & endsWith • isNull & isNotNull • isEmpty & isNotEmpty
  37. 37. Realm Object Field Types • Java primitives • Wrapper types • byte[] for blob • Realm Object • RealmList<? extends RealmObject>
  38. 38. Realm Annotations • @Required - Not Null • @Ignore - Transient • @PrimaryKey - string or integer (short, int or long) • @Index - Implicitly set by Primary Key
  39. 39. Integrating Realm
  40. 40. Realm Installation 1. Add a classpath dependency to the project level build.grade file
 
 buildscript { repositories { jcenter() } dependencies { classpath "io.realm:realm-gradle-plugin:2.1.1" } }
 2. Apply the realm-android plugin at the app module level build.grade file apply plugin: 'realm-android'
  41. 41. Custom SQLiteOpenHelper Goes Away! public class MySQLiteHelper extends SQLiteOpenHelper {
 
 public static final String TABLE_LYRICS = "lyrics";
 public static final String COLUMN_ID = "_id";
 public static final String COLUMN_LYRIC = "lyric";
 
 private static final String DATABASE_NAME = "lyric.db";
 private static final int DATABASE_VERSION = 1;
 
 // Database creation sql statement
 private static final String DATABASE_CREATE = "create table "
 + TABLE_LYRICS + "( " + COLUMN_ID
 + " integer primary key autoincrement, " + COLUMN_LYRIC
 + " text not null);";
 
 public MySQLiteHelper(Context context) {
 super(context, DATABASE_NAME, null, DATABASE_VERSION);
 }
 
 @Override
 public void onCreate(SQLiteDatabase database) {
 database.execSQL(DATABASE_CREATE);
 }
 
 @Override
 public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
 Log.w(MySQLiteHelper.class.getName(),
 "Upgrading database from version " + oldVersion + " to "
 + newVersion + ", which will destroy all old data");
 db.execSQL("DROP TABLE IF EXISTS " + TABLE_LYRICS);
 onCreate(db);
 }
 
 }
  42. 42. public class Lyric extends RealmObject {
 
 private int sortKey; @PrimaryKey private String id;
 @Required private String lyricText;
 
 
 // Getters / Setters...
 
 // Will be used by the ArrayAdapter in the ListView
 @Override
 public String toString() {
 return lyricText;
 }
 } Simple Data Object - Still Simple RealmObject and Annotations
  43. 43. Lyric Datasource public class LyricDataSource {
 
 // Database fields
 private SQLiteDatabase database;
 private MySQLiteHelper dbHelper;
 private String[] allColumns = { MySQLiteHelper.COLUMN_ID,
 MySQLiteHelper.COLUMN_LYRIC};
 
 public LyricDataSource(Context context) {
 dbHelper = new MySQLiteHelper(context);
 }
 
 public void open() throws SQLException {
 database = dbHelper.getWritableDatabase();
 }
 
 public void close() {
 dbHelper.close();
 } public List<Lyric> getAllLyrics() {
 List<Lyric> lyrics = new ArrayList<Lyric>();
 
 Cursor cursor = database.query(MySQLiteHelper.TABLE_LYRICS,
 allColumns, null, null, null, null, MySQLiteHelper.COLUMN_ID);
 cursor.moveToFirst();
 while (!cursor.isAfterLast()) {
 Lyric lyric = cursorToLyric(cursor);
 lyrics.add(lyric);
 cursor.moveToNext();
 }
 // Make sure to close the cursor
 cursor.close();
 return lyrics;
 } public Lyric createLyric(String lyric) {
 ContentValues values = new ContentValues();
 values.put(MySQLiteHelper.COLUMN_LYRIC, lyric);
 long insertId = database.insert(MySQLiteHelper.TABLE_LYRICS, null,
 values);
 Cursor cursor = database.query(MySQLiteHelper.TABLE_LYRICS,
 allColumns, MySQLiteHelper.COLUMN_ID + " = " + insertId, null,
 null, null, null);
 cursor.moveToFirst();
 Lyric newLyric = cursorToLyric(cursor);
 cursor.close();
 return newLyric;
 }
 
 public void deleteLyric(Lyric lyric) {
 long id = lyric.getId();
 System.out.println("Lyric deleted with id: " + id);
 database.delete(MySQLiteHelper.TABLE_LYRICS, MySQLiteHelper.COLUMN_ID
 + " = " + id, null);
 }
 
 public Lyric getLyricByValue(String lyricText) {
 Lyric lyric = null;
 Cursor cursor = database.query(MySQLiteHelper.TABLE_LYRICS,
 allColumns, MySQLiteHelper.COLUMN_LYRIC + " = '" + lyricText + "'" , null, null, null, null);
 cursor.moveToFirst();
 if (!cursor.isAfterLast()) {
 lyric = cursorToLyric(cursor);
 }
 // Make sure to close the cursor
 cursor.close();
 return lyric;
 } 
 private Lyric cursorToLyric(Cursor cursor) {
 Lyric lyric = new Lyric();
 lyric.setId(cursor.getLong(0));
 lyric.setLyricText(cursor.getString(1));
 return lyric;
 }
  44. 44. Lyric Datasource private Realm r;
 
 public LyricDataSource(Realm realm) {
 r = realm;
 } 
 public void deleteAllLyrics() {
 r.executeTransaction(new Realm.Transaction() {
 @Override
 public void execute(Realm realm) {
 realm.delete(Lyric.class);
 }
 });
 }
 
 public Lyric getLyricByValue(String lyricText) {
 return r.where(Lyric.class) .equalTo("lyricText", lyricText) .findFirst();
 }
 
 public List<Lyric> getAllLyrics() {
 return r.where(Lyric.class) .findAllSorted("sortKey"); 
 } public Lyric createLyric(String lyricString) {
 final Lyric lyric = new Lyric();
 lyric.setId(UUID.randomUUID().toString());
 lyric.setLyricText(lyricString); lyric.setSortKey(System.currentTimeMillis()); 
 r.executeTransaction(new Realm.Transaction() {
 @Override
 public void execute(Realm realm) {
 lyric = realm.copyToRealm(lyric);
 }
 });
 return lyric;
 }
 
 public void deleteLyric(Lyric lyric) {
 r.executeTransaction(new Realm.Transaction() {
 @Override
 public void execute(Realm realm) {
 realm.where(Lyric.class)
 .equalTo("id", lyric.getId())
 .findAll()
 .deleteAllFromRealm();
 }
 });
 }
  45. 45. Application / Activity - Lifecycle Events public class TestDatabaseActivity extends ListActivity {
 
 private LyricDataSource datasource; private Realm realm; 
 @Override
 public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.main);
 realm = Realm.getDefaultInstance();
 datasource = new LyricDataSource(realm);
 
 List<Lyric> values = datasource.getAllLyrics();
 
 // Use the SimpleCursorAdapter to show the
 // elements in a ListView
 ArrayAdapter<Lyric> adapter = new ArrayAdapter<Lyric>(this,
 android.R.layout.simple_list_item_1, values);
 setListAdapter(adapter);
 }
 
 @Override
 protected void onDestroy() {
 super.onDestory();
 realm.close();
 }
 ... } public class NaeNaeApplication extends Application {
 
 @Override
 public void onCreate() {
 super.onCreate();
 Realm.init(this); RealmConfiguration realmConfiguration =
 new RealmConfiguration.Builder()
 .deleteRealmIfMigrationNeeded()
 .build();
 Realm.setDefaultConfiguration(realmConfiguration);
 }
 
 }
  46. 46. Application / Activity - Lifecycle Events public class TestDatabaseActivity extends ListActivity {
 
 private LyricDataSource datasource; private Realm realm; 
 @Override
 public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.main);
 realm = Realm.getDefaultInstance();
 datasource = new LyricDataSource(realm);
 
 List<Lyric> values = datasource.getAllLyrics();
 
 // Use the SimpleCursorAdapter to show the
 // elements in a ListView
 ArrayAdapter<Lyric> adapter = new ArrayAdapter<Lyric>(this,
 android.R.layout.simple_list_item_1, values);
 setListAdapter(adapter);
 }
 
 @Override
 protected void onDestroy() {
 super.onDestory();
 realm.close();
 }
 ... } Keep reference Get new instance of realm datasource on create and pass to the datasource to use. 1 public class NaeNaeApplication extends Application {
 
 @Override
 public void onCreate() {
 super.onCreate();
 Realm.init(this); RealmConfiguration realmConfiguration =
 new RealmConfiguration.Builder()
 .deleteRealmIfMigrationNeeded()
 .build();
 Realm.setDefaultConfiguration(realmConfiguration);
 }
 
 }
  47. 47. Application / Activity - Lifecycle Events public class TestDatabaseActivity extends ListActivity {
 
 private LyricDataSource datasource; private Realm realm; 
 @Override
 public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.main);
 realm = Realm.getDefaultInstance();
 datasource = new LyricDataSource(realm);
 
 List<Lyric> values = datasource.getAllLyrics();
 
 // Use the SimpleCursorAdapter to show the
 // elements in a ListView
 ArrayAdapter<Lyric> adapter = new ArrayAdapter<Lyric>(this,
 android.R.layout.simple_list_item_1, values);
 setListAdapter(adapter);
 }
 
 @Override
 protected void onDestroy() {
 super.onDestory();
 realm.close();
 }
 ... } Keep reference Get new instance of realm datasource on create and pass to the datasource to use. For getDefaultInstance to work, we must set the default configuration once 1 2 public class NaeNaeApplication extends Application {
 
 @Override
 public void onCreate() {
 super.onCreate();
 Realm.init(this); RealmConfiguration realmConfiguration =
 new RealmConfiguration.Builder()
 .deleteRealmIfMigrationNeeded()
 .build();
 Realm.setDefaultConfiguration(realmConfiguration);
 }
 
 }
  48. 48. Application / Activity - Lifecycle Events public class TestDatabaseActivity extends ListActivity {
 
 private LyricDataSource datasource; private Realm realm; 
 @Override
 public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.main);
 realm = Realm.getDefaultInstance();
 datasource = new LyricDataSource(realm);
 
 List<Lyric> values = datasource.getAllLyrics();
 
 // Use the SimpleCursorAdapter to show the
 // elements in a ListView
 ArrayAdapter<Lyric> adapter = new ArrayAdapter<Lyric>(this,
 android.R.layout.simple_list_item_1, values);
 setListAdapter(adapter);
 }
 
 @Override
 protected void onDestroy() {
 super.onDestory();
 realm.close();
 }
 ... } Close on destroy Keep reference Get new instance of realm datasource on create and pass to the datasource to use. For getDefaultInstance to work, we must set the default configuration once 1 2 3 public class NaeNaeApplication extends Application {
 
 @Override
 public void onCreate() {
 super.onCreate();
 Realm.init(this); RealmConfiguration realmConfiguration =
 new RealmConfiguration.Builder()
 .deleteRealmIfMigrationNeeded()
 .build();
 Realm.setDefaultConfiguration(realmConfiguration);
 }
 
 }
  49. 49. Checkpoint • Remove SQLite DataHelper • Made our datasource code easier to read • Reduced Code: SQLite Realm Lyric 28 40 Activity 77 72 DataSource 92 61 MySQLiteHelper 41 0 Application 0 21 Total 238 194
  50. 50. Additional Realm Features
  51. 51. Change Listeners public class MyActivity extends Activity {
 private Realm realm;
 private RealmChangeListener<RealmResults<Lyric>> listener;
 private RealmResults<Lyric> lyrics;
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 realm = Realm.getDefaultInstance();
 lyrics = realm.where(Lyric.class).contains("lyricText", "Bop").findAll();
 listener = new RealmChangeListener<RealmResults<Lyric>>() {
 @Override
 public void onChange(RealmResults<Lyric> updatedResults) {
 // Do something with the updated results, actually the results here
 // match the ones stored as a reference in this activity.
 }
 };
 lyrics.addChangeListener(listener);
 }
 
 @Override
 protected void onDestroy() {
 super.onDestroy();
 realm.removeAllChangeListeners();
 realm.close();
 } }
  52. 52. Async Operations // Async with Callback private RealmChangeListener callback = new RealmChangeListener() {
 @Override
 public void onChange() { // called once the query complete and on every update
 // use the result
 }
 };
 public void onStart() {
 try(Realm r = Realm.getInstance(context)) {
 RealmResults<Lyric> result = r.where(Lyric.class).findAllAsync();
 result.addChangeListener(callback);
 }
 } // Or you can block (be careful) while (!result.isLoaded()) {
 // Results are now available
 } // Or to block until async results are loaded result.load()
  53. 53. Transaction Blocks & Async Transactions // Transaction will be committed after block unless exception occurs. realm.executeTransaction(new Realm.Transaction() {
 @Override
 public void execute(Realm realm) {
 Lyric user = realm.createObject(Lyric.class);
 user.setId(UUID.randomUUID().toString());
 user.setLyricText("Let's get it started!");
 }
 });
 // Asynchronous Transaction realm.executeTransactionAsync(new Realm.Transaction() {
 @Override
 public void execute(Realm bgRealm) {
 Lyric user = bgRealm.createObject(Lyric.class);
 
 user.setId(UUID.randomUUID().toString());
 
 user.setLyricText("Let's get it started in here");
 
 }
 }, new Realm.Transaction.OnSuccess() {
 @Override
 public void onSuccess() {
 // Do something on the thread you were on.
 }
 }, new Realm.Transaction.OnError() {
 @Override
 public void onError(Throwable error) {
 // Transaction failed and was automatically canceled.
 // Do something on the thread you were on.
 }
 });
  54. 54. Insert JSON Directly // Insert from a string
 r.beginTransaction();
 r.createObjectFromJson(Lyric.class,
 "{ lyricText: "Bidi-bidi-bop", " +
 "id: "864dee8a-d9ac-4e5a-a843-e051ad2d6e8a" }");
 r.commitTransaction();
 
 // Insert multiple items using a InputStream
 InputStream is = new FileInputStream(new File("path_to_file"));
 r.beginTransaction();
 try {
 r.createAllFromJson(Lyric.class, is);
 r.commitTransaction();
 } catch (IOException e) {
 r.cancelTransaction();
 }
  55. 55. ListAdapter & Recycler Adapters dependencies { compile ‘io.realm:android-adapters:1.4.0' }
  56. 56. ListAdapter & Recycler Adapters dependencies { compile ‘io.realm:android-adapters:1.4.0' } public class MyAdapter extends RealmBaseAdapter<Lyric> implements ListAdapter {
 
 private static class ViewHolder {
 TextView lyricTextView;
 }
 public MyAdapter(Context context, int resId,
 RealmResults<Lyric> realmResults,
 boolean automaticUpdate) {
 super(context, realmResults, automaticUpdate);
 }
 
 @Override
 public View getView(int position, View convertView, ViewGroup parent) {
 ViewHolder viewHolder;
 if (convertView == null) {
 convertView = inflater.inflate(android.R.layout.simple_list_item_1,
 parent, false);
 viewHolder = new ViewHolder();
 viewHolder.lyricTextView = (TextView) convertView.findViewById(android.R.id.text1);
 convertView.setTag(viewHolder);
 } else {
 viewHolder = (ViewHolder) convertView.getTag();
 }
 
 Lyric item = realmResults.get(position);
 viewHolder.lyricTextView.setText(item.getLyricText());
 return convertView;
 }
 
 public RealmResults<Lyric> getRealmResults() {
 return realmResults;
 }
 }
  57. 57. ListAdapter & Recycler Adapters dependencies { compile ‘io.realm:android-adapters:1.4.0' } MyRecyclerViewAdapter extends RealmRecyclerViewAdapter<Promotion, MyRecyclerViewAdapter.ViewHolder> {
 
 private final MyActivity activity;
 
 public RealmRecyclerViewAdapter(@NonNull MyActivity activity, @Nullable OrderedRealmCollection<Lyric> lyrics) {
 super(promoListActivity, lyrics, true);
 this.activity = activity;
 }
 
 @Override
 public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
 View view = LayoutInflater.from(parent.getContext())
 .inflate(R.layout.lyric_list_item, parent, false);
 return new ViewHolder(view);
 }
 
 @Override
 public void onBindViewHolder(final ViewHolder holder, int position) {
 Lyric lyric = getData().get(position);
 holder.lyrcTextView.setText(lyric.getLyricText()); holder.lyricId = lyric.getId());
 }
 
 public class ViewHolder extends RecyclerView.ViewHolder {
 public TextView titleView;
 public String promotionId;
 
 public ViewHolder(View view) {
 super(view);
 lyricTextView = (TextView) view.findViewById(R.id.lyric_itle);
 }
 }
  58. 58. Encryption RealmConfiguration config = new RealmConfiguration.Builder(context)
 .encryptionKey(getKey())
 .build(); • The Realm file can be stored encrypted on disk by passing an encryption key (byte []) • All data persisted to disk is transparently encrypted and decrypted with standard AES-256 encryption
  59. 59. Migrations RealmConfiguration config = new RealmConfiguration.Builder(context)
 .schemaVersion(2) // Must be bumped when the schema changes
 .migration(new MyMigration()) // Migration handler class
 .build(); • Bump the version with each change • Point the RealmConfiguration to you custom RealmMigration Implementation
  60. 60. Migrations RealmConfiguration config = new RealmConfiguration.Builder(context)
 .schemaVersion(2) // Must be bumped when the schema changes
 .migration(new MyMigration()) // Migration handler class
 .build(); public class MyMigration implements RealmMigration {
 public void migrate(DynamicRealm realm, long oldVersion, long newVersion) {
 
 RealmSchema schema = realm.getSchema(); // DynamicRealm exposes an editable schema
 
 if (oldVersion == 0) { // Migrate to version 1: Add a new class
 schema.create("Person")
 .addField("name", String.class)
 .addField("age", int.class);
 oldVersion++; // Bump the version after each updgrade
 }
 
 if (oldVersion == 1) { // Migrate to version 2: Add PK + relationships
 schema.get("Person")
 .addField("id", long.class, FieldAttribute.PRIMARY_KEY)
 .addRealmObjectField("favoriteDog", schema.get("Dog"))
 .addRealmListField("dogs", schema.get("Dog"));
 oldVersion++;
 }
 }
 }
  61. 61. Migrations public class MyMigration implements RealmMigration {
 public void migrate(DynamicRealm realm, long oldVersion, long newVersion) {
 
 RealmSchema schema = realm.getSchema(); // DynamicRealm exposes an editable schema
 
 if (oldVersion == 0) { // Migrate to version 1: Add a new class
 schema.create("Person")
 .addField("name", String.class)
 .addField("age", int.class);
 oldVersion++; // Bump the version after each updgrade
 }
 
 if (oldVersion == 1) { // Migrate to version 2: Add PK + relationships
 schema.get("Person")
 .addField("id", long.class, FieldAttribute.PRIMARY_KEY)
 .addRealmObjectField("favoriteDog", schema.get("Dog"))
 .addRealmListField("dogs", schema.get("Dog"));
 oldVersion++;
 }
 }
 }
  62. 62. Realm Browser
  63. 63. Resources • Realm - https://realm.io/ • Source Code - https://github.com/realm/realm-java • Code Samples • Presentation Examples
 https://github.com/ericmaxwell2003/ roboguiceRealmNaeNae • Credible Software - http://credible.software

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