Automatically persisted among application sessions

Transcription

1 STORAGE OPTIONS

2 Storage options SharedPreference Small amount of data, as Key-value pairs Private to an Activity or Shared among Activities Internal storage Small to medium amount of data Private to the application External storage Not private data (songs, video files) Database (SQLite) Structured data Private to the application Content Provider Allow to expose protected data Network Firebase

3 Shared Preferences Persistent map of primitive types Automatically persisted among application sessions Activity.getPreference(mode) Returns: SharedPreference, associated to the activity not accessible from other activities in the same package Context.getSharedPreference(Name,mode) Returns: SharedPreference associated to the package Name of the file used to store the preferences Mode

4 Writing/Reading SharedPreference Call SharedPreference.edit() method Returns an SharedPreference.Editor instance Call put methods to add values Call Editor.commit() to make value persistent Call get methods to retrieve values SharedPreferenceFragment allows for using a simple framework to set preferences

5 Example

6 File Represented by the File class (java.io package) Historically a file can be internal Internal flash memory in the device or external (/sdcard) SD Card Larger storage area Can be private or shared Standard java way to use the file (New I/O) Use stream to write/read from a file

7 File External file are stored in removable storage (i.e., SD card) Check for the presence of the storage before accessing any file Environment.getExternalStorageState() State: Mounted, ReadOnly, etc. Environment is a class (java.os package) providing info about environment variables. Requires permission in the manifest file

8 File explorer (from AS) /data/data Data of apps

9 SQLite Used for structured information Small foot-print relational DB It supports ACID transaction Implements most of the SQL92 standard Stores data into a text file /data/data/<package-name>/databases/ Options to create in-memory DB The adb tool has sql3 command to show the db

10 Credits: Victor Matos, Cleveland State University

11 Credits: Victor Matos, Cleveland State University

12 Credits: Victor Matos, Cleveland State University

13 Content Provider A content provider manages access to a central repository of data ContentProvider is basically a facade -- an API that exposes databases to other processes. It can be implemented in a way where the data is stored in a SQLite database, but it does not have to be. A such a content provider presents data to external applications as one or more tables Permissions are required to use a content provider

14 Main content providers AlarmClock Alarms to fire CallLog contains information about placed and received calls Contact provider Stores all information about contacts. Calendar provider Data stored in the calendar (events, etc.) MediaStore Provider contains meta data for all available media on both internal and external storage devices. Settings global system-level device preferences User Disctionary user defined words for input methods to use for predictive text input. Full list: adb shell dumpsys (look for Content Provider)

15 Content provider Sync with other providers Accessing data Intent App Widgets are miniature application views that can be embedded in other applications, and receive periodic updates. Used for searching suggestions

16 Data sharing with a content provider C R U D

17 Accessing to content provider via a cursor Apps access to a CP through a ContentResolver (proxy) A ContentProvider is created when the first ContentResolver is created

18 Content provider sync

19 Content Provider s URI content://authority/path/id Content = means one want to access a content provider Authority = name of the content provider Path = 0 or more segments indicating the data to be accessed Id = specific item For example: content://com.android.contacts/contacts/directory=0/photo_id/12

20 Accessing a Content provider Clients access to a content provider through a ContentResolver ContentResolver allows access to the provider through a set of dblike methods Insert,Update,Query,Delete

21 ContentResolver query ContentResover.query () allows to access specific data Similar to an SQL query Content URI Columns to retrieve String [] SQL selection pattern - String SQL selection arguments String [] Sort Order - String Returns a Cursor object

22 CursorLoader It is a class that uses an AsyncTask to perform the query in background To use a CursorLoader one has to implement the LoaderCallbacks interface

23 Insert a row

24 Other methods ContenteResolver.update( URI ContentValues SQL selection pattern String SQL selection args String [] Return number of rows updated ContentResolver.delete() URI SQL Selection pattern String SQL Selection args. String [] Returns number of row deleted

25 Accessing content providers via intent Intents may provide indirect access to a content provider. They allow the user to access data in a provider even if your application doesn't have access permissions, either by getting a result intent back from an application that has permissions, or by activating an application that has permissions and letting the user do work in it. Example: Contact provider, Calendar provider

26 Example: Contacts

27 Example: Contacts Rows representing different people, based on aggregations of raw contact rows. Rows containing a summary of a person's data, specific to a user account and type. Rows containing the details for raw contact, such as addresses or phone numbers.

28 Contact via intents Sending an intent to the device's contacts application allows you to access the Contacts Provider indirectly. The intent starts the device's contacts application UI, in which users can do contacts-related work. With this type of access, users can: Pick a contact from a list and have it returned to your app for further work. Edit an existing contact's data. Insert a new raw contact for any of their accounts. Delete a contact or contacts data.

29 Example: the calendar provider

30 Example

31 Example: Google calendar Provider Interface (rest,etc)

32 MediaStore provider The Media provider contains meta data for all available media on both internal and external storage devices.

33 Example: take a picture

34 Example: take a picture

35 Another example android.provider.mediastore.images.media

36 Example: playing music

37 Account Manager Provides access to a centralized registry of the user's online accounts. The user enters credentials (username and password) once per account, granting applications access to online resources with "one-click" approval.

38 Firebase: Real time DB

39 Firebase: Real time db

40 Exampe

41 Example

42 Firebase: supported techonogies

43 Firebase products

44 MongoDB Document based NoSQL DB REST-like API

45 DataBinding Library It is possible to declaratively associate values in the layout to a data object Data Object setter getter Layout with reference to a data object Binding to a data object

46 DataBinding: simple example

47 DataBinding: simple example

48 DataBinding: simple example Name of the layout file

49 DataBinding library Allow to add listeners Notify data change to the UI Can be used in ListView, RecyclerView, etc..