Android Data Persistence

Android: data persistence
Romain Rochegude
2016.09.30
1

Introduction
• POO basics: modeling the domain
• Modeling domain objects and their interactions
• Data bound with a remote API
• Need of a local database
3

The “raw” way
private static final String
SQL_CREATE_ENTRIES =
"CREATE TABLE REPO (" +
"_ID INTEGER PRIMARY KEY," +
"NAME TEXT)";
SQL_DELETE_ENTRIES =
"DROP TABLE IF EXISTS REPO ";
5

• Subclass SQLiteOpenHelper
public class ReposDbHelper extends
SQLiteOpenHelper {
public static final int
DATABASE_VERSION = 1;
public static final String
DATABASE_NAME = "repos.db";
public ReposDbHelper(Context
context) {
super(context, DATABASE_NAME,
null, DATABASE_VERSION);
} 6

//...
public void onCreate(SQLiteDatabase
db) {
db.execSQL(SQL_CREATE_ENTRIES);
}
public void onUpgrade(SQLiteDatabase
db, int oldVersion, int
newVersion) {
db.execSQL(SQL_DELETE_ENTRIES);
onCreate(db);
}
}
7

• Get an instance of SQLiteOpenHelper
ReposDbHelper dbHelper =
new ReposDbHelper(getContext());
8

• Put Information into a Database
SQLiteDatabase db =
dbHelper.getWritableDatabase();
ContentValues values = new
ContentValues();
values.put("name", "a sample name");
long newRowId = db.insert("REPO", null,
values);
9

• Read Information from a Database
SQLiteDatabase db =
dbHelper.getReadableDatabase();
String[] projection = { "_id", "name" };
String selection = "NAME = ?";
String[] selectionArgs = { "a sample
name" };
String sortOrder = "NAME DESC";
10

Cursor cursor = db.query(
"REPO",
projection,
selection,
selectionArgs,
null,
null,
sortOrder);
cursor.moveToFirst();
long itemId = cursor.getLong(
cursor.getColumnIndexOrThrow("_ID")
);
11

The ContentProvider way
• Provide a ContentProvider subclass
dedicated to the application
public class RepoProvider extends
ContentProvider {
}
12

• Define a specific UriMatcher and configure
available URI
public class RepoProvider extends
ContentProvider {
private static final UriMatcher
sUriMatcher =
new
UriMatcher(UriMatcher.NO_MATCH);
}
13

static {
sUriMatcher.addURI("fr.test.app.provider",
"repo", 1);
sUriMatcher.addURI("fr.test.app.provider",
"repo/#", 2);
}
14

• Override various CRUD methods
public Cursor query(
Uri uri,
String[] projection,
String selection,
String[] selectionArgs,
String sortOrder) {
//...
15

//...
switch (sUriMatcher.match(uri)) {
case 2:
selection = selection + "_ID = "
+ uri.getLastPathSegment();
break;
default:
//...
}
16

• Use it through a ContentResolver instance
mCursor = getContentResolver().query(
"fr.test.app.provider/repo/2",
mProjection,
mSelectionClause,
mSelectionArgs,
mSortOrder);
17

• Refer to the open-sourced Google’s iosched
application
• Helpful libraries to simplify the deal with a
ContentProvider:
• ProviGen
• AutoValue: Cursor Extension
18

Async management
• Perform CRUD operations outside of the main
thread
19

Query data using Loader
• To query the ContentProvider in an
Activity, make it implementing
LoaderManager.LoaderCallbacks<Cursor>
public class ReposListActivity
extends FragmentActivity
implements
LoaderManager.LoaderCallbacks<Cursor>
{
}
20

• Start loading data with a loader identiﬁer
getLoaderManager()
.initLoader(LOADER_REPOS, null,
this);
• Implement LoaderCallbacks. . .
21

• . . . to create the CursorLoader
@Override
public Loader<Cursor> onCreateLoader(
int id, Bundle bundle) {
if(id == LOADER_REPOS) {
return new CursorLoader(
this,
"fr.test.app.provider/repo",
mProjection,
null, null, null);
}
//...
} 22

• . . . and deal with result
@Override
public void
onLoadFinished(Loader<Cursor> loader,
Cursor cursor) {
if(loader.getId() == LOADER_REPOS){
// ...
}
}
23

• See also: AsyncQueryHandler
24

The well-known: ORMLite
• Declare your model using ORMLite annotations
@DatabaseTable(tableName = "REPO")
public class RepoEntity {
@DatabaseField(columnName = "_ID",
generatedId = true)
public long _id;
@DatabaseField
public String name;
}
26

• declare the corresponding DAO
public class DAORepo extends
BaseDaoImpl<RepoEntity, Long> {
public DAORepo(ConnectionSource cs)
throws SQLException {
this(cs, RepoEntity.class);
}
//...
}
27

• subclass OrmLiteSqliteOpenHelper
public class DatabaseHelperTest
extends OrmLiteSqliteOpenHelper {
DATABASE_NAME = "test.db";
private static final int
DATABASE_VERSION = 1;
//...
28

//...
public DatabaseHelperTest(
Context context) {
super(context,
DATABASE_NAME,
null,
DATABASE_VERSION,
R.raw.ormlite_config);
}
//...
29

//...
@Override
public void onCreate(SQLiteDatabase db,
ConnectionSource cs) {
TableUtils.createTable(cs,
RepoEntity.class);
}
@Override
public void onUpgrade(SQLiteDatabase db,
ConnectionSource cs, int oldVersion,
int newVersion) {
//...
}
30

• get the requested DAO
DatabaseHelperTest helper = //...
ConnectionSource cs =
helper.getConnectionSource();
DatabaseTableConfig<RepoEntity>
tableConfig =
DatabaseTableConfigUtil.fromClass(cs,
RepoEntity.class);
DAORepo dao = new DAORepo(cs,
tableConfig); 31

• perform CRUD operations
// create
RepoEntity repo =
new RepoEntity("a sample name");
dao.create(repo);
32

// read
List<RepoEntity> repos =
dao.queryBuilder()
.where()
.eq("name", "a sample name")
.query();
33

• Performance: orm-gap gradle plugin
buildscript {
repositories {
mavenCentral()
}
dependencies {
classpath
'com.github.stephanenicolas.ormgap'
+ ':ormgap-plugin:1.0.0-SNAPSHOT'
}
}
apply plugin: 'ormgap' 34

• generate an ORMLite configuration file that
boosts DAOs creations
• to use this file
public RepoDatabaseHelper(Context
context) {
super(context,
DATABASE_NAME,
null,
DATABASE_VERSION,
R.raw.ormlite_config);
}
35

The attractive way: requery
• Object mapping
• SQL generator
• RxJava and Java 8 support
• No reﬂection, compile-time processing and
generation
• Relationships support
• Callback method (@PostLoad)
• Custom type converters
36

• Deﬁne object mapping
@Entity
abstract class Repo {
@Key @Generated
int id;
String name;
}
37

• Easy to perform SQL queries
Result<Repo> repos = data
.select(Repo.class)
.where(Repo.NAME.lower().like("%sample%"))
.orderBy(Repo.ID.desc())
.get();
38

Async management: RxJava
• Get a speciﬁc instance of SingleEntityStore
DatabaseSource dbSource =
new DatabaseSource(context,
Models.DEFAULT, "test.db", 1);
Configuration conf =
dbSource.getConfiguration();
SingleEntityStore<Persistable> data =
RxSupport.toReactiveStore(new
EntityDataStore<>(conf));
39

• and use it the RX way
data.select(RepoEntity.class)
.get()
.subscribeOn(Schedulers.newThread())
.subscribe(/*...*/)
40

Conclusion
• Personal assessments of each way
ContentProvider ORMLite requery
setup - + +
performance + - +
readability - + +
maintainability - + +
42

Android Data Persistence

Recommended

More Related Content

What's hot (20)

Viewers also liked (15)

Similar to Android Data Persistence (20)

More from Romain Rochegude (6)

Recently uploaded (20)

Android Data Persistence