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Android - Basic Steps (ContentProvider)

ContentProvider


Represents a repository of structured data
  • Is better than SQLite DB, because you can share data across multiple applications
  • Encapsulates data sets
  • The access is through ContentResolver
URI

ContentProviders referenced by URIs
    • Format: CONTENT://AUTHORITY/PATH/ID
      • Content - Schee indicating data that is managed by content provider
      • Authority - Id for the content provider
      • Path - 0 or more segments indicating the type of data to be accessed
      • Id - Specific record
    • Example
      • ContactsContract.Contacts.CONTENT_URI = "content://com.android.contects/contacts/"
      • Retrive in this case all the table because is missing the id

ContentResolver

  • Presents a DB-style interface for read and wite data
  • Provide service as Change notification
How to use
  • Get a reference to ContentResolver
    • Context.getContentResolver()
Types
  • Brower - Bookmarks, history
  • Call log - Telephone usage
  • Contacts
  • Media - Gallery image
  • UserDictionary - predictive spelling
Methods
  • ContentResolver.Query
    • Cursosr query(
      • Uri uri    - ContentProvider Uri
      • String[] projection    - Columns to retrieve
      • String selection     - SQL selection pattern
      • String[] selectionArgs   - SQL pattern args
      • String sortOrder  - Sort order
    • )
    • Returns a cursos for interating over the set of results
  • ContentResolver.delete(
    • Uri uri,    - ContentProvider Uri
    • String where,  - SQL selection pattern
    • String[] selectArgs  - SQL pattern args
    • )
    • Returns the number of rows deleted
  • ContentResolver.insert(
    • Uri uri,    - ContentProvider Uri
    • ContentValues
    • )
    • Returns the URI of the inserted row
  • ContentResolver.update(
    • Uri uri,    - ContentProvider Uri
    • ContentValues
    • String where,  - SQL selection pattern
    • String[] selectArgs  - SQL pattern args
    • )
    • Returns the number of rows updated

CursorLoader

Use AsyncTask to perform queries on a background thread

How to use
  • Implement LoaderManager's LoaderCallbacks interface
    • Create and Initialize a cursor loader with initLoader()
      • Loader<D> initLoader( int id, Bundle args, LoaderCallbacks<D> callback)
    • Then call  method onCreateLoader()
      • LoaderCallbacks
        • First callback instantiate and return a new loader for the specified id
    • Last call the method onLoadFinished
  •  To reset a loader use
    • onLoaderReset(...)


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