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![• 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](https://image.slidesharecdn.com/talkandroiddatapersistence-161003161631/75/Android-Data-Persistence-10-2048.jpg)
![• Override various CRUD methods
public Cursor query(
Uri uri,
String[] projection,
String selection,
String[] selectionArgs,
String sortOrder) {
//...
15](https://image.slidesharecdn.com/talkandroiddatapersistence-161003161631/75/Android-Data-Persistence-15-2048.jpg)
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Similar to Android Data Persistence
Android Data Persistence
- 1. Android: data persistence RomainRochegude 2016.09.30 1
- 2.
- 3. Introduction • POO basics:modeling the domain • Modeling domain objects and their interactions • Data bound with a remote API • Need of a local database 3
- 4.
- 5. The “raw” way privatestatic final String SQL_CREATE_ENTRIES = "CREATE TABLE REPO (" + "_ID INTEGER PRIMARY KEY," + "NAME TEXT)"; private static final String SQL_DELETE_ENTRIES = "DROP TABLE IF EXISTS REPO "; 5
- 6. • Subclass SQLiteOpenHelper publicclass 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
- 7. //... 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
- 8. • Get aninstance of SQLiteOpenHelper ReposDbHelper dbHelper = new ReposDbHelper(getContext()); 8
- 9. • Put Informationinto a Database SQLiteDatabase db = dbHelper.getWritableDatabase(); ContentValues values = new ContentValues(); values.put("name", "a sample name"); long newRowId = db.insert("REPO", null, values); 9
- 10. • Read Informationfrom a Database SQLiteDatabase db = dbHelper.getReadableDatabase(); String[] projection = { "_id", "name" }; String selection = "NAME = ?"; String[] selectionArgs = { "a sample name" }; String sortOrder = "NAME DESC"; 10
- 11. Cursor cursor =db.query( "REPO", projection, selection, selectionArgs, null, null, sortOrder); cursor.moveToFirst(); long itemId = cursor.getLong( cursor.getColumnIndexOrThrow("_ID") ); 11
- 12. The ContentProvider way •Provide a ContentProvider subclass dedicated to the application public class RepoProvider extends ContentProvider { } 12
- 13. • Define aspecific UriMatcher and configure available URI public class RepoProvider extends ContentProvider { private static final UriMatcher sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH); } 13
- 14.
- 15. • Override variousCRUD methods public Cursor query( Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) { //... 15
- 16. //... switch (sUriMatcher.match(uri)) { case2: selection = selection + "_ID = " + uri.getLastPathSegment(); break; default: //... } 16
- 17. • Use itthrough a ContentResolver instance mCursor = getContentResolver().query( "fr.test.app.provider/repo/2", mProjection, mSelectionClause, mSelectionArgs, mSortOrder); 17
- 18. • Refer tothe open-sourced Google’s iosched application • Helpful libraries to simplify the deal with a ContentProvider: • ProviGen • AutoValue: Cursor Extension 18
- 19. Async management • PerformCRUD operations outside of the main thread 19
- 20. Query data usingLoader • To query the ContentProvider in an Activity, make it implementing LoaderManager.LoaderCallbacks<Cursor> public class ReposListActivity extends FragmentActivity implements LoaderManager.LoaderCallbacks<Cursor> { } 20
- 21. • Start loadingdata with a loader identifier getLoaderManager() .initLoader(LOADER_REPOS, null, this); • Implement LoaderCallbacks. . . 21
- 22. • . .. 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
- 23. • . .. and deal with result @Override public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) { if(loader.getId() == LOADER_REPOS){ // ... } } 23
- 24. • See also:AsyncQueryHandler 24
- 25.
- 26. 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
- 27. • declare thecorresponding DAO public class DAORepo extends BaseDaoImpl<RepoEntity, Long> { public DAORepo(ConnectionSource cs) throws SQLException { this(cs, RepoEntity.class); } //... } 27
- 28. • subclass OrmLiteSqliteOpenHelper publicclass DatabaseHelperTest extends OrmLiteSqliteOpenHelper { private static final String DATABASE_NAME = "test.db"; private static final int DATABASE_VERSION = 1; //... 28
- 29. //... public DatabaseHelperTest( Context context){ super(context, DATABASE_NAME, null, DATABASE_VERSION, R.raw.ormlite_config); } //... 29
- 30. //... @Override public void onCreate(SQLiteDatabasedb, ConnectionSource cs) { TableUtils.createTable(cs, RepoEntity.class); } @Override public void onUpgrade(SQLiteDatabase db, ConnectionSource cs, int oldVersion, int newVersion) { //... } 30
- 31. • get therequested DAO DatabaseHelperTest helper = //... ConnectionSource cs = helper.getConnectionSource(); DatabaseTableConfig<RepoEntity> tableConfig = DatabaseTableConfigUtil.fromClass(cs, RepoEntity.class); DAORepo dao = new DAORepo(cs, tableConfig); 31
- 32. • perform CRUDoperations // create RepoEntity repo = new RepoEntity("a sample name"); dao.create(repo); 32
- 33. // read List<RepoEntity> repos= dao.queryBuilder() .where() .eq("name", "a sample name") .query(); 33
- 34. • Performance: orm-gapgradle plugin buildscript { repositories { mavenCentral() } dependencies { classpath 'com.github.stephanenicolas.ormgap' + ':ormgap-plugin:1.0.0-SNAPSHOT' } } apply plugin: 'ormgap' 34
- 35. • generate anORMLite 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
- 36. 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
- 37. • Define objectmapping @Entity abstract class Repo { @Key @Generated int id; String name; } 37
- 38. • Easy toperform SQL queries Result<Repo> repos = data .select(Repo.class) .where(Repo.NAME.lower().like("%sample%")) .orderBy(Repo.ID.desc()) .get(); 38
- 39. 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
- 40. • and useit the RX way data.select(RepoEntity.class) .get() .subscribeOn(Schedulers.newThread()) .subscribe(/*...*/) 40
- 41.
- 42. Conclusion • Personal assessmentsof each way ContentProvider ORMLite requery setup - + + performance + - + readability - + + maintainability - + + 42