Better Data Persistence on Android

Better Data Persistence on Android

Eric MaxwellCredible Software

What to Expect

• Android Storage Options

• Focus on SQLite / Database Storage

• Make it better using the Realm Mobile Database

Android Storage Options

• Shared Preferences



• Disk Storage • Internal • External



• Disk Storage • Internal • External

• Relational Database w/ SQLite

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

Nae Nae Assistant App

• List of Nae Nae Lyrics

• Add New

• Delete

• Persistent across launches

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>

Simple Data Objectpublic 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; } }

Activity - Lifecycle Eventspublic 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.

Activity - Events Add/Removepublic 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

Custom SQLiteOpenHelperpublic 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); } }

Lyric Datasourcepublic 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;}

Using SQLite Pros

• No additional dependencies

• Built in programatic transaction management

• Built in creation and upgrade event handling

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); } }

Update the data modelpublic 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; } }

Update the Datasourcepublic 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 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;}

Add the columns to our SQLiteOpenHelperpublic 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, " + " ); " ; ...}

How about a second tablepublic 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 " + " ); " ; ...}

Or a many to many relationshippublic 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 + ") "+ " ); " ;

...}

Using SQLite Cons

• Queries / Updates are very tedious

• Changes become cumbersome

• Relationships between an object graph must be manually managed

Realm Mobile Database Replacement

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

Fast Queries

https://realm.io/news/introducing-realm/


Faster Counts



Slower Inserts



How it works

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; }

Easy to add / relate objectstry(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();}

Updates must be wrapped in transactionstry(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();}

Updates must be wrapped in transactionstry(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( );

1 to Manytry(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

Many to Manytry(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

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 chainableRealmResults<Dog> allRex = results.where() .contains("name", "rex") .findAll();

// Or they can be combinedRealmResults<Dog> result2 = realm.where(Dog.class) .greaterThan("age", 8)

.equalTo(“owner.name", "Tim") .contains("name", "rex") .findAll();

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 ascendingresult.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();

Query Conditions

• between, greaterThan, lessThan, greaterThanOrEqualTo & lessThanOrEqualTo

• equalTo, notEqualTo, in, not & distinct

• contains, beginsWith & endsWith

• isNull & isNotNull

• isEmpty & isNotEmpty

Realm Object Field Types

• Java primitives

• Wrapper types

• byte[] for blob

• Realm Object

• RealmList<? extends RealmObject>

Realm Annotations

• @Required - Not Null

• @Ignore - Transient

• @PrimaryKey - string or integer (short, int or long)

• @Index - Implicitly set by Primary Key

Integrating Realm

Realm Installation

1. Add a classpath dependency to the project level build.grade filebuildscript { 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'

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); } }

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

Lyric Datasourcepublic 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 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;}

Lyric Datasourceprivate 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(); } });}

Application / Activity - Lifecycle Eventspublic 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); }}



... }

Keep reference

Get new instance of realm datasource

on create and pass to the datasource to

use.

1




... }

Keep reference



use.

For getDefaultInstance to work, we must

set the default configuration once

1

2




... } Close on destroy

Keep reference



use.

For getDefaultInstance to work, we must

set the default configuration once

1

2

3


Checkpoint

• Remove SQLite DataHelper

• Made our datasource code easier to read

• Reduced Code:

SQLite RealmLyric 28 40

Activity 77 72DataSource 92 61

MySQLiteHelper 41 0Application 0 21

Total 238 194

Additional Realm Features

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(); } }

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()

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. } });

Insert JSON Directly // Insert from a stringr.beginTransaction();r.createObjectFromJson(Lyric.class, "{ lyricText: \"Bidi-bidi-bop\", " + "id: \"864dee8a-d9ac-4e5a-a843-e051ad2d6e8a\" }");r.commitTransaction();

// Insert multiple items using a InputStreamInputStream is = new FileInputStream(new File("path_to_file"));r.beginTransaction();try { r.createAllFromJson(Lyric.class, is); r.commitTransaction();} catch (IOException e) { r.cancelTransaction();}

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; }}


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); } }

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

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

MigrationsRealmConfiguration 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++; } }}

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++; } }}

Realm Browser

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

https://realm.io/

https://github.com/realm/realm-java

https://github.com/ericmaxwell2003/roboguiceRealmNaeNae

http://credible.software