Jonathan Lalou's Blog

Posts Tagged ‘ContentProviders’

Lecturer

Mathias Seguy founded Android2EE, specializing in Android training, expertise, and consulting. Holding a PhD in Fundamental Mathematics and an engineering degree from ENSEEIHT, he transitioned from critical J2EE projects—serving as technical expert, manager, project leader, and technical director—to focus on Android. Mathias authored multiple books on Android development, available via Android2ee.com, and contributes articles to Developpez.com.

Abstract

This article explores Mathias Seguy’s in-depth coverage of Android’s advanced components, focusing on service modes, content provider implementations, and optimization strategies. It examines unbound/bound services, URI-based data operations, and tools like Hierarchy Viewer for performance tuning. Within Android’s multitasking framework, the analysis reviews methodologies for lifecycle alignment, asynchronous execution, and resource handling. Through practical code and debugging insights, it evaluates impacts on battery efficiency, data security, and UI responsiveness. This segment underscores patterns for robust architectures, aiding developers in crafting seamless, power-efficient mobile experiences.

Differentiating Service Modes and Lifecycle Integration

Services bifurcate into unbound (autonomous post-start) and bound (interactive via binding). Mathias illustrates unbound for ongoing tasks like music playback:

startService(new Intent(this, MyService.class));

Bound for client-service dialogue:

private ServiceConnection connection = new ServiceConnection() {
    public void onServiceConnected(ComponentName name, IBinder service) {
        myService = ((MyBinder) service).getService();
    }
    public void onServiceDisconnected(ComponentName name) {
        myService = null;
    }
};
bindService(new Intent(this, MyBoundService.class), connection, BIND_AUTO_CREATE);

Lifecycle syncing uses flags: isRunning/isPaused toggle with onStartCommand()/onDestroy(), ensuring tasks halt on service termination, averting leaks.

Constructing Efficient Content Providers

Providers facilitate inter-app data exchange via URIs. Define via extension, with UriMatcher for parsing:

private static final UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);
static {
    matcher.addURI(AUTHORITY, TABLE, COLLECTION);
    matcher.addURI(AUTHORITY, TABLE + "/#", ITEM);
}

Implement insert():

@Override
public Uri insert(Uri uri, ContentValues values) {
    long rowId = db.insert(DBHelper.MY_TABLE, null, values);
    if (rowId > 0) {
        Uri result = ContentUris.withAppendedId(CONTENT_URI, rowId);
        getContext().getContentResolver().notifyChange(result, null);
        return result;
    }
    throw new SQLException("Failed to insert row into " + uri);
}

Manifest exposure with authorities/permissions secures access.

Asynchronous Enhancements and Resource Strategies

AsyncTasks/Handlers offload UI: Extend for doInBackground(), ensuring UI updates in onPostExecute().

Resource qualifiers adapt to locales/densities: values-fr/strings.xml for French.

Databases: SQLiteOpenHelper with onCreate() for schema.

Debugging and Performance Tools

Hierarchy Viewer inspects UI hierarchies, identifying overdraws. DDMS monitors threads, heaps; LogCat filters logs.

Permissions: Declare in manifest for features like internet.

Architectural Patterns for Resilience

Retain threads across rotations; synchronize for integrity.

Implications: These techniques optimize for constraints, enhancing longevity and usability in diverse hardware landscapes.

Mathias’s guidance refines development, promoting sustainable mobile solutions.

Links:

• Lecture video
• Mathias Seguy on LinkedIn

Lecturer

Mathias Seguy founded Android2EE, specializing in Android training, expertise, and consulting. Holding a PhD in Fundamental Mathematics and an engineering degree from ENSEEIHT, he transitioned from critical J2EE projects—serving as technical expert, manager, project leader, and technical director—to focus on Android. Mathias authored multiple books on Android development, available via Android2ee.com, and contributes articles to Developpez.com.

Abstract

This article delves into Mathias Seguy’s continuation of essential Android development concepts, emphasizing services for background tasks, content providers for data sharing, and patterns for lifecycle synchronization. Building on foundational elements, it analyzes implementation strategies for bound/unbound services, CRUD operations in providers, and thread management with handlers/AsyncTasks. Within Android’s resource-constrained environment, the discussion evaluates techniques for internationalization, resource optimization, and database integration. Through detailed code examples, it assesses implications for application responsiveness, data integrity, and cross-app interoperability, guiding developers toward efficient, maintainable architectures.

Implementing Services for Background Processing

Services enable persistent operations independent of UI, running in the application’s main thread—necessitating offloading to avoid ANRs. Mathias distinguishes unbound (started via startService(), autonomous) from bound (via bindService(), allowing communication).

Lifecycle binding is critical: Align service states with calling components using booleans for running/pausing. Code for an unbound service:

public class MyService extends Service {
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        // Start task
        return START_STICKY; // Restart if killed
    }
    @Override
    public void onDestroy() {
        // Cleanup
    }
}

Bound services use Binder for IPC:

public class MyBoundService extends Service {
    private final IBinder binder = new LocalBinder();
    public class LocalBinder extends Binder {
        MyBoundService getService() {
            return MyBoundService.this;
        }
    }
    @Override
    public IBinder onBind(Intent intent) {
        return binder;
    }
}

These ensure tasks like downloads persist, enhancing user experience without freezing interfaces.

Crafting Content Providers for Data Exposure

Content providers standardize data access across apps, using URIs for queries. Mathias outlines creation: Extend ContentProvider, define URIs via UriMatcher.

CRUD implementation:

@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
    SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
    qb.setTables(DBHelper.MY_TABLE);
    if (matcher.match(uri) == ITEM) {
        qb.appendWhere(DBHelper.ID + "=" + uri.getLastPathSegment());
    }
    return db.query(qb.getTables(), projection, qb.getWhere(), selectionArgs, null, null, sortOrder);
}

Manifest declaration:

<provider
    android:name=".MyProvider"
    android:authorities="com.example.provider"
    android:exported="true"
    android:readPermission="com.example.READ"
    android:writePermission="com.example.WRITE" />

This facilitates secure sharing, like contacts or media, promoting modular ecosystems.

Asynchronous Patterns and Resource Management

Asynchrony prevents UI blocks: Handlers for UI updates, AsyncTasks for background work. Pattern: Bind threads to activity lifecycles with flags.

onRetainNonConfigurationInstance() passes objects across rotations (pre-Fragments):

@Override
public Object onRetainNonConfigurationInstance() {
    return myThread;
}
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    myThread = (MyThread) getLastNonConfigurationInstance();
    if (myThread == null) {
        myThread = new MyThread();
    }
}

Resources: Externalize strings in values/strings.xml for localization; use qualifiers like values-fr for French.

These patterns optimize for device variability, ensuring fluid performance.

Database Integration and Permissions

SQLite via SQLiteOpenHelper manages schemas:

public class DBHelper extends SQLiteOpenHelper {
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE " + MY_TABLE + " (_id INTEGER PRIMARY KEY, name TEXT);");
    }
}

Permissions in manifest control access, balancing security with functionality.

Testing and Project Management Strategies

Unit tests with JUnit; instrumentation via AndroidJUnitRunner. Maven for builds, Hudson/Jenkins for CI.

Implications: These foster reliable apps, mitigating fragmentation. In enterprise mobility, they enable scalable, secure solutions.

Mathias’s methodical breakdown equips developers for real-world challenges.

Links:

• Lecture video
• Mathias Seguy on LinkedIn