The Android File System

1
The Android File System

• Onboard Linux Architecture
• User privileges
• Initially quite limited some directories hidden
• Rooting gives users super user access
• Procedure is different for different devices
• Destroying the operation of the device bricking
• Onboard data Applications have their reserved
  storage areas (sandbox)
• External data
• SD card or USB connection
• Public shared /mnt/sdcard/
• Writing to external storage has no security
  protection

2
Managing Data (Alternatives)

• Application Direct Access Read only from res/raw
  or assets directories
• Web-based Interact through web-URLs to access
  cloud-based data
• Direct File I/O Read/write files onboard or on
  SD cards
• Use Standard Java stream and Random Access File
  classes
• Restriction Onboard file I/O restricted to
  application sandbox
• Restriction SD card writes requires access
  permission
• Preferences Key/Value pairs of data
• Database Tables Use the built-in SQL-Lite
  database facility
• Increase functionality
• Content Providers expose data to other
  applications
• Services background processes that run detached
  from any view

3
Application Direct Access

• Static application files
• Custom codecs that are not widely supported
• XML-based configuration data
• Store either in res/raw or in assets
• res/raw enables creating sub-directories for
  specific device configurations
• Files stored either in res/raw or in assets are
  not pre-compiled by Android
• Files stored directly in the application are
  read-only and cannot be modified
• Access using standard Java I/O operationsInputSt
  ream is app.getResources().openRawResource(R.raw
  .foo) in BufferedReader in new
  BufferedReader(new InputStreamReader(is)))Input
  Stream rawRes context.getAssets().open(foo.bar"
  ) Reader r new BufferedReader(new
  InputStreamReader(rawRes, "UTF8"))

Note Use lower case alphanumerics to name files
in res/raw
4
Downloading Files

• Downloading quickly degrades battery life
• Solutions
• Pre-fetch A single large download has less
  impact than multiple smaller downloads
• Reuse existing connections rather than
  reestablishing them
• Schedule regular downloads at the longest
  intervals that are possible
• Bundle non-time sensitive requests together

5
Download XML from Server
Requires ltuses-permission androidname "
android.permission.INTERNET " /gt

• String myFeed getString(R.string.my_feed)
  // HTTP Web address
• try
• URL url new URL(myFeed) // Create a new
  HTTP URL connection
• URLConnection connection url.openConnection()
  
• HttpURLConnection httpConnection
  (HttpURLConnection)connection int
  responseCode httpConnection.getResponseCode()
  
• if (responseCode HttpURLConnection.HTTP_OK)
• InputStream in httpConnection.getInputStream(
  )
• processStream(in) // Use standard Java
  DOM parsing classes
• catch (MalformedURLException e)
  Log.d(TAG, "Malformed URL", e)
• catch (IOException e) Log.d(TAG, "IO
  Exception.", e)

6
Download Using Download Manager

• DownloadManager m (DownloadManager)getSystemServi
  ce(Context.DOWNLOAD_SERVICE)
• long myReference m.enqueue(new
  Request(Uri.parse(R.string.webLoc)))
• BroadcastReceiver receiver new
  BroadcastReceiver()
• _at_Override public void onReceive(Context
  context, Intent intent)
• long reference intent.getLongExtra(Download
  Manager.EXTRA_DOWNLOAD_ID, -1)
• if (myReference reference)
• Query query new Query()
• Cursor cursor downloadManager.query(query.set
  FilterById(reference))
• if (cursor.moveToFirst())
• int fileX cursor.getColumnIndex(DownloadM
  anager.COLUMN_LOCAL_FILENAME)
• int uriX cursor.getColumnIndex(DownloadManag
  er.COLUMN_LOCAL_URI) String
  fileName cursor.getString(fileX), fileUri
  cursor.getString(uriX)
• // TODO Do something with the file.
  
• cursor.close()
• registerReceiver(receiver,
• new IntentFilter(DownloadManager.ACTION_DOWNLOAD
  _COMPLETE) )

Note The cursor object contains information
about downloaded files
7
Listen for Downloaded Files

• ltreceiver androidname".DownloadReceiver"
  androidexported"true" androidicon"_at_drawable/d
  ownload_icon" gt
• ltintent-filtergt
• ltaction androidname"android.intent.action.DOWNLO
  AD_COMPLETE"/gt
• lt/intent-filtergtlt/receivergt
• IntentFilter f new IntentFilter(DownloadManager.
  ACTION_DOWNLOAD_COMPLETE))
• registerReceiver(receiver, f)
• BroadcastReceiver receiver new
  BroadcastReceiver()
• _at_Override public void onReceive(Context
  context, Intent intent)
• String id DownloadManager.EXTRA_DOWNLOAD_ID
  
• long references intent.getLongArrayExtra(id)
  // Array of downloaded file ids
• for (long reference references)
• String mime getMimeTypeForDownloadedFile
  (reference)
• // Handle files that this
  activity recognizes.

8
Specifying Download Locations
Note We cannot download to internal storage
using DownloadManager

• Default Location A shared download cache with
  system generated file names
• Overriding the download location
  requires ltuses-permission androidname
• "android.permission.WRITE_EXTERNAL_STORAGE" /gt
• To designate an arbitrary path in external
  storage Request request new Request(uri)
• request.setDestinationUri(Uri.fromFile(f))
• To designate a standard external download folder
  for the application request.setDestinationInExte
  rnalFilesDir(this, Environment.DIRECTORY_DOWNL
  OADS, fileName)
• To designate location which shares with music
  players request.setDistinationInExternalPublicDi
  r (Environment.DIRECTORY_MUSIC, fileName)

9
SD Card File IO

• SD Card path getExternalStorageDirectory()
• How Use standard Java File I/O
• Notes
• Manifest "android.permission.WRITE_EXTERNAL_STORA
  GE"
• Application manifests can set preference to SD
  Card installation
• Check SD Availability in Java Environment.getExte
  rnalStorageState().equals(Environment.MEDIA_MOUNTE
  D)
• Convention write to /Android/data/ltpackage_namegt/
  files/
• ExampleFile sdCard Environment.getExternalStor
  ageDirectory()File dir new File
  (sdcard.getAbsolutePath() "
  /Android/data/ltpackage_namegt/files/
  ")dir.mkdirs() // Make directories with
  missing parents.File file new File(dir,
  "filename") // Instantiate a file object
• FileOutputStream f new FileOutputStream(file)
  // Open for writing

10
Writing to Internal Storage

• Writing to internal storage
• Each application has a designated directory to
  which to write files
• There is a maximum storage amount, varying per
  device
• Flags exist to control inter-application access
• MODE_PRIVATE - No access for other applications
• MODE_WORLD_READABLE - Read access for other
  applications
• MODE_WORLD_WRITABLE - Write access for other
  applications
• MODE_WORLD_READABLE MODE_WORLD_WRITABLE - Read
  / Write access
• Open file for writing new BufferedWriter( new
  OutputStreamWriter( openFileOutput(fileName,
  MODE_PRIVATE)))

11
Onboard File I/O

• Write to a designated place for each application
• Where /data/data/package/files/ using onboard
  storage
• How Use standard java.io classes, with relative,
  not absolute, paths
• Applications can
• Write into its application directory
• Create subdirectories
• Give read/write permissions to other applications
  (MODE_PRIVATE, MODE_WORLD_READABLE
  MODE_WORLD_WRITABLE)
• Android Helper classes in the Context object
• getDir(String fileName, int permissions) Creates
  or access directory
• getFilesDir() Get absolute path to application
  directory
• getCacheDir() Get non-permanent temporary
  storage directory
• openFileInput(String fileName) Open a file for
  input
• openFileOutput(String fileName, int permissions)
  Create a new file

Note There is also a sharedPreferences directory
for preferences, a databases directory for SQLite
tables, and a cache directory
12
Copy File from Server

• public void DownloadFile(String fileURL, String
  fileName)
•   try   HttpURLConnection c
  (HttpURLConnection) fileURL.openConnection() c.s
  etRequestMethod("GET") c.setDoOutput(false)
  // Tru for POST with intent to send to
  server c.connect() // Establish connection with
  server InputStream in c.getInputStream() //
  Ready to read File root Environment.getExterna
  lFilesDir(null) // Application area
• // Prepare output stream
• FileOutputStream out new FileOutputStream(new
  File(root, fileName)) byte buffer new
  byte1024 int len 0 // Note the buffer
  overflow possibility while ((len
  in.read(buffer)) gt 0)   out.write(buffer, 0,
  len)   // Write block
• f.close()
• catch (Exception e)   Log.d("Downloader",
  e.getMessage()) 

13
Preferences

• Initial Purpose
• Persistent storage for user options
• Analogous to cookies in Web-based applications
• More General Purpose
• Maintains the application state across
  terminations and restarts
• Provides mechanism for applications to
  persistently store additional data without using
  SQL or Files
• Preferences Framework
• Define preferences
• Display settings
• Persist user selections

14
Accessing Shared Preference Data

• // getPreferences is a method in the Activity
  class
• SharedPreferences prefs getPreferences(Activity
  .MODE_PRIVATE)
• int intValue getInt("IntKey", 22)
• long longValue getLong("LongKey", 0)
• String name getString("NameKey", "")
• int floatValue getFloat("FloatKey", 0.0)
• int booleanValue getBoolean("BoolKey", false)
• SetltStringgt set getStringSet("SetKey", 22)
• MapltString, ?gt keysAndValues getAll()

• Notes
• The second argument is the default if the key was
  not previously stored
• There is no getDouble() method

15
Modifying SharedPreference Data

• SharedPreferences preferences
  getPreferences(Activity.MODE_PRIVATE)
• // or getSharedPreferences("fileName")
• SharedPreferences.Editor editor
  preferences.edit()
• editor.putInt("IntKey", 22)
• editor.putLong("LongKey", 0)
• editor.putString("NameKey", "")
• editor.putFloat("FloatKey", 0.0)
• editor.putBoolean("BoolKey", false)
• editor.commit()

• Notes
• puts can be chained editor.putInt(intKey,
  22).putLong(LongKey, 0)
• editor.apply() works asynchronously,
  editor.commit() is synchronous
• editor.clear() erases all of the preference keys
• editor.remove(Key) deletes a preference
• Shared preferences use a file name for
  multi-activity sharing

16
Preference Views

• Preference Screen
• The view on the left
• View on the right appears When the user clicks
  after preference screen clicked
• Selection Screen
• Modal Dialog on the right
• Saves selection and disappears after a user
  selection

17
Step 1 Defining Preferences
XML Listing (in res/xml) for the preferences
shown on the previous screen

• lt?xml version"1.0" encoding"utf-8"?gt lt!--
  /res/xml/flightoptions.xml --gt
• ltPreferenceScreen xmlnsandroid"http//schemas.an
  droid.com/apk/res/android"
• androidkey"flight_option_preference"
• androidtitle"_at_string/PrefTitle"
  androidsummary"_at_string/PrefSummary"gt
• ltListPreference androidkey"_at_string/SelectedS
  ortOption"
• androidtitle"_at_string/ListTitle"
  androidsummary"_at_string/ListSummary"
• androidentries"_at_array/FlightSortOptions" andro
  identryValues"_at_array/FlightSortValues"
• androiddialogTitle"_at_string/ChooseFlightOptions
  "
• androiddefaultValue"_at_string/SortDefaultValue"
  /gt
• lt/PreferenceScreengt
• public class FlightPreferenceActivity extends
  PreferenceActivity
• _at_Override protected void onCreate(Bundle
  savedInstanceState)
• super.onCreate(savedInstanceState)
• addPreferencesFromResource(R.xml.flightoptions)
  

18
Define Strings in res/values

• lt?xml version"1.0" encoding"utf-8"?gt
• ltresourcesgt
• ltstring name"AppName"gtPreferences Demolt/stringgt
• ltstring name"PrefTitle"gtMy Preferenceslt/stringgt
• ltstring name"PrefSummary"gtSet Search
  Optionslt/stringgt
• ltstring name"ListTitle"gtFlight Optionslt/stringgt
• ltstring name"ListSummary"gtSet Search
  Optionslt/stringgt
• ltstring-array name"FlightSortOptions"gt
• ltitemgtTotal Costlt/itemgtltitemgt of
  Stopslt/itemgtltitemgtAirlinelt/itemgtlt/string-arraygt
• ltstring-array name"FlightSortValues"gt
• ltitemgt0lt/itemgtltitemgt1lt/itemgtltitemgt2lt/itemgtlt/s
  tring-arraygt
• ltstring name"ChooseFlightOptions"gtChoose Flight
  Optionslt/stringgt
• ltstring name"SortDefaultValue"gt1lt/stringgt
• ltstring name"SelectedSortOption"gtSelected Sort
  Optionlt/stringgt
• ltstring name"menu_prefs_title"gtSettingslt/stringgt
  
• ltstring name"menu_quit_title"gtQuitlt/stringgt
• lt/resourcesgt

19
Manifest

• lt?xml version"1.0" encoding"utf-8"?gt lt!--
  AndroidManifest.xml --gt
• ltmanifest xmlnsandroid"http//schemas.android.co
  m/apk/res/android"
• package"com.syh" androidversionCode"1"
  androidversionName"1.0"gt
• ltapplication androidicon"_at_drawable/icon"
  androidlabel"_at_string/AppName"gt
• ltactivity androidname".MainActivity"
  androidlabel"_at_string/AppName"gt
• ltintent-filtergtltaction androidname"android.inte
  nt.action.MAIN" /gt
• ltcategory androidname"android.intent.category.
  LAUNCHER" /gt
• lt/intent-filtergt
• lt/activitygt
• ltactivity androidname".PreferenceActivity"
  androidlabel"_at_string/PrefTitle"gt
• ltintent-filtergtltaction androidname"com.syh.inten
  t.action.FlightPreferences" /gt
• ltcategory androidname"android.intent.category.P
  REFERENCE" /gt
• lt/intent-filtergt
• lt/activitygtlt/applicationgtltuses-sdk
  androidminSdkVersion"3" /gtlt/manifestgt

20
Define Main Android Activity

• // This is MainActivity.java
• _at_Override public void onCreate(Bundle
  savedInstanceState)
• super.onCreate(savedInstanceState)
• setContentView(R.layout.main) // Assuming
  there is a TextView layout
• tv (TextView)findViewById(R.id.text1)
• setOptionText() // Helper method to get user
  preference and adjust view
• _at_Override public boolean onCreateOptionsMenu(Menu
  menu)
• MenuInflater inflater getMenuInflater()
• // Inflate main menu XML with link to preference
  option
• inflater.inflate(R.menu.mainmenu, menu)
• return true // Menu is now active

21
Main Activity Selection Responses

• _at_Override public boolean onOptionsItemSelected
  (MenuItem item)
• if (item.getItemId() R.id.menu_prefs)
• Intent intent new Intent().setClass(this,
  com.syh.PreferenceActivity.class)
• this.startActivityForResult(intent, 0) //
  Second parameter is for a switch in listener
• else if (item.getItemId() R.id.menu_quit)
  finish()
• return true // Start preference menu when its
  item is selected
• _at_Override public void onActivityResult(int
  reqCode, int resCode, Intent data)
• super.onActivityResult(reqCode, resCode,
  data)
• SharedPreferences prefs getDefaultSHaredPrefere
  nces(this)
• String key this.getResources().getString(R.stri
  ng.SelectedSortOption)
• String default this.getResources().getString(R.
  string.SortDefaultValue)
• String selection prefs.getString(key ,
  default)
• String optionText this.getResources().getStri
  ngArray(R.string.FlightSortOptions)
• tv.setText("option " pref " ("
  optionTextInteger.parseInt(pref) ")")

22
CheckBoxPreference (/res/xml/chkbox.xml)

• lt?xml version"1.0" encoding"utf-8"?gt
• ltPreferenceScreen
• xmlnsandroid "http//schemas.android.com/apk/re
  s/android"
• androidkey"flight_columns_pref"gt
• ltCheckBoxPreference androidkey"show_airline_col
  umn_pref"
• androidtitle"Airline" androidsummary"Show
  Airline column" /gt
• ltCheckBoxPreference androidkey"show_departure_c
  olumn_pref"
• androidtitle"Departure" androidsummary"Show
  Departure column" /gt
• ltCheckBoxPreference androidkey"show_arrival_col
  umn_pref"
• androidtitle"Arrival" androidsummary"Show
  Arrival column" /gt
• ltCheckBoxPreference androidkey"show_total_trave
  l_time_column_pref"
• androidtitle"Total Travel Time"androidsummary
  "Show Total Travel Time column" /gt
• ltCheckBoxPreference androidkey"show_price_colum
  n_pref"
• androidtitle"Price" androidsummary"Show
  Price column" /gt
• lt/PreferenceScreengt

Note For Radio Buttons, use the List Preference
23
Using Check Box Preferences

• // CheckBoxPreferenceActivity.java
• import android.os.Bundle
• import android.preference.PreferenceActivity
• public class CheckBoxPreferenceActivity extends
  PreferenceActivity
• _at_Override protected void onCreate(Bundle
  savedInstanceState)
• super.onCreate(savedInstanceState)
• addPreferencesFromResource(R.xml.chkbox)

• // Access preference in an activity
• SharedPreferences prefs getSharedPreferences("fi
  leName")
• Boolean option prefs.getBoolean("show_price_colu
  mn_pref", false)

24
EditTextPreference

• lt?xml version"1.0" encoding"utf-8"?gt
• ltPreferenceScreen xmlnsandroidhttp//schemas.and
  roid.com/apk/res/android
• androidtitleSet Package Name"
• androidsummary"Set the package name for
  generated code"gt
• ltEditTextPreference androidkey"package_name_pref
  erence"
• androidtitle"Set Package Name"
  androiddialogTitle"Package Name"
• androidsummary"Set the package name for
  generated code" /gt
• lt/PreferenceScreengt

25
Categories of Preferences

• lt?xml version"1.0" encoding"utf-8"?gt
• ltPreferenceScreen xmlnsandroid"http//schemas.an
  droid.com/apk/res/android"
• androidkey"using_categories_in_root_screen"
  androidtitle"Categories"
• androidsummary"Using Preference Categories"gt
• ltPreferenceCategory xmlnsandroidhttp//schemas.a
  ndroid.com/apk/res/android
• androidkey"meats_category" androidtitle"Meats
  " androidsummary"Meat preferences"gt
• ltCheckBoxPreference androidkey"fish_selection_p
  ref" androidtitle"Fish"
• androidsummary"Fish is great for the healthy"
  /gt
• ltCheckBoxPreference androidkey"chicken_selectio
  n_pref" androidtitle"Chicken"
• androidsummary"A common type of poultry" /gt
• ltCheckBoxPreference androidkey"lamb_selection_p
  ref" androidtitle"Lamb"
• androidsummary"Lamb is a young sheep"
  /gtlt/PreferenceCategorygt
• ltPreferenceCategory xmlnsandroidhttp//schemas.a
  ndroid.com/apk/res/android
• androidkey"vegi_category" androidtitle"Vegeta
  bles" androidsummary"Vegetable preferences"gt
• ltCheckBoxPreference androidkey"tomato_selection
  _pref" androidtitle"Tomato "
• androidsummary"It's actually a fruit" /gt
• ltCheckBoxPreference androidkey"potato_selection
  _pref" androidtitle"Potato"
• androidsummary"My favorite vegetable"
  /gtlt/PreferenceCategorygtlt/PreferenceScreengt

Purpose Provide titles to groups of similar
preferences
26
Preference Fragments

• Android versions 3.0 and newer recommend using
  fragments for preferences instead of activities
• Check Android Version if (Build.VERSION.SKK_INTlt
  Build.VERSION_CODES.HONEYCOME)
• / Use preference activity approach /
  
• else / Use preference fragment approach /
  
• Implementation Steps
• Define preference screens in XML (as shown on
  previous slides)
• Add PreferenceFragment to the activity using the
  FragmentManager
• Create the PreferenceFragment class

27
Preference Fragment in an Activity

• public class PreferenceFragmentActivity extends
  Activity
• _at_Override public void onCreate(Bundle
  savedInstanceState)
• super.onCreate(savedInstanceState) setConten
  tView(R.layout.main) FragmentManager manager
  getFragmentManager() FragmentTransaction
  trans manager.beginTransaction() MyFragment
  fragment new MyFragment() trans.replace(andro
  id.R.id.content, fragment1) trans.addToBackSta
  ck(null)
• trans.commit()

Note Dont add the fragment to the application
manifest
28
Preference Fragment Class

• public class MyFragment extends
  PreferenceFragment
• _at_Override public void onCreate(Bundle
  savedInstanceState)
• super.onCreate(savedInstanceState) //
  configure the preferences from an XML
  file addPreferencesFromResource(R.xml.preferenc
  es)
• PreferenceManager manager getPreferenceManager
  ()
• SharedPreferences shared manager.getSharedPref
  erences()
• shared.registerOnSharedPreferenceChangeListener(
  this)
• onSharedPreferenceChanged(SharedPreferences
  pref, String key)
• / Handle preference change here /

29
SQLite

• Android SQLite
• Lightweight database system
• Standards-compliant
• Single Tier (no server involved)
• Open source
• Standard SQL queries
• SELECT ID, CITY, STATE FROM STATION WHERE LAT_N
  gt 39.7
• Application content providers provide
• Standard interface to SQL tables to other
  applications
• For application private tables, content providers
  are not needed

30
Authorities / URI
Purpose Publish application SQL tables and data
for external activity access

• Definition An authority is a registered name on
  an android device (ex Content Provider name.
  Authorities must be unique on the system.
• Registration Accomplished in an application
  manifest
• Syntax com.company.someProvider
• Examples org.acorns.LessonProvider or
  com.android.provider.BookProvider
• Analogy Authorities are to Android what domain
  names are to the Web
• Activity access using URIs
• Syntax content//authority-name/path-segment/path
  -segment/
• Access book table content//com.anroidbook.provid
  er.BookProvider/books
• Access particular book content//com.anroidbook.
  provider.BookProvider/books/12
• Activity Interface Through Content Providers,
  which fill in abstract methods

31
MIME Types
Purpose Indicate a type of data that a content
provider deals with

• Definition Industry standard way to indicate a
  particular data format
• Syntax Two text strings separated by slashes
• First part (category) application, audio, image,
  text, video, etc
• Second Part (codec) html, css, xml, pdf, rtf,
  etc.
• Examples text/htm, application/pdf, image/jpeg,
  audio/mpeg, etc.
• Android MIME Types (Similar syntax as standard
  MIME types)
• First Part
• Access single items vnd.android.cursor.item
• Access multiple items vnd.android.cursor.dir
• Second Part vnd.yourCompany.type
• Examples vnd.android.cursor.dir/vnd.google.note
  or vnd.android.cursor.item/vnd.google.note

32
Content Provider Framework

• An application registers its content provider
  using its manifest
• The code for the content provider is written
• An application request data using the published
  MIME type
• Android looks through the registered manifests
  for an appropriate provider
• The provider activity is launched to manipulate
  or return data
• If more than one provider exists, the user
  selects the one to use
• Android Built-in content providers
  content//media/internal/images/,
  content//media/external/images/,content//contac
  ts/people/

33
Content Providers
A well-defined interface to data for application
access

• Register an authority using the
  AndroidManifest.xml file
• Definition An authority is a registered name
• Analogy authority is to an Android device what a
  domain name is to the Internet
• Syntax ( Using a package name minimizes
  redundancies on a system)ltprovider
  androidname"fooProvider" androidauthorities"c
  om.company.fooProvider" /gt
• Exampleltprovider androidname"
  com.acorns.LessonProvider" androidauthorities"c
  om.acorns.provider.Lessons" /gt
• Another application exampleltprovider
  androidnameNotePadProvider" androidauthoritie
  s"com.google.provider.NotePad" /gt

34
MIME Types
Acronym Multipurpose Internet Mail Extension

• Specifies the data type an activity can process
• Register in the AndroidManifest.xml file
• Example "vnd.android.cursor.dir/vnd.google.note"
  OR "vnd.android.cursor.dir/vnd.google.note"
• Sample Syntax vnd.android.cursor.ltoptgt/vnd.compan
  y.type
• vnd non-standard type (vendor)
• android.cursor required for ContentProvider
  Manifest registrations
• item single record dir collection of records
• google company name
• note content type
• AndroidManifest.xml registrationltdata
  androidmimeType"vnd.android.cursor.dir/vnd.googl
  e.note" /gt

35
Referring to a Content Provider

• URI and URL
• Uniform resource identifier (URI) Identifies the
  name of a resource, but not necessarily
  information regarding its location
• Uniform resource Location (URL) is a URI, that
  identifies a resource location
• Text usage URI for content providers URL for
  referring to Web locations
• URI of a content providercontent//com.company.fo
  oProvider/content//com.acorns.provider.Lessons/
  content//com.google.provider.NotePad/
• Note Android provided shortcut URIs contacts
  for com.google.android.contacts
• Refer to the notes SQLite notes
  tablecontent//com.google.provider.NotePad/notes/
  
• Refer to the tenth notecontent//com.google.provi
  der/NotePad/notes/10

36
Register the Provider

• ltprovider androidname"NotePadProvider"
• androidauthorities"com.google.provid
  er.NotePad" /gt
• ltactivity androidname"NotesList"
  androidlabel"_at_string/title_notes_list"gt
• ltintent-filtergt
• ltaction androidname"android.intent.action
  .MAIN" /gt
• ltcategory androidname"android.intent.cate
  gory.LAUNCHER" /gt
• lt/intent-filtergt
• ltintent-filtergt
• ltaction androidname"android.intent.action.VIEW"
  /gt
• ltdata androidmimeType"vnd.android.cursor.dir/vn
  d.google.note" /gt
• lt/intent-filtergtltintent-filtergt
• ltaction androidname"android.intent.action.
  GET_CONTENT" /gt
• ltdata androidmimeType"vnd.android.cursor.item/v
  nd.google.note" gt
• lt/intent-filtergt lt/activitygt

37
Implement the Provider

• Plan the Database
• Extend the ContentProvider class
• Fill in a variety of methods to be overloaded
• onCreate() When the database is created
• onUpgrade() When the database layout changes
• getType() Return the MIME data type
• query() Handle queries to the data
• insert(), delete(), and update() methods

38
A Managed Query in Content Provider
Purpose Query SQL lite table for relevant data
(cursor) Definition An Android cursor is a
collection of rows of data

• // Specify needed columns
• string projection new string
• People._ID, People.NAME, People.NUMBER
• // Specivy URI using static Contacts constants
• Uri contactUri Contacts.People.CONTENT_URI
• // Invoke a content provider query
• Cursor cursor managedQuery( contactUri,
• projection, //Which columns to return
• null, null, // Selection and WHERE clauses
• Contacts.People.NAME " ASC") // Order-by
  (ascending by name)

Other classes exist (ex SQLiteQueryBuilder) for
using standard SQL strings
39
Navigating through a cursor

• Manipulate the cursor (row pointer)
• if (cursor.moveToFirst() false)
• cursor.isBeforeFirst(), cursor.isAfterLast,
  cursor.isClosed()
• while (cursor.moveToNext()) / code here /
• for (cursor.moveToFirst() !cursor.isAfterLast()
  cur.moveToNext)
• Get column numbers from names
• int nameColumn cursor.getColumnIndex(People.NAME
  )
• int phoneColumn cursor.getColumnIndex(People.NUM
  BER)
• Get Data from column
• String name cursor.getString(nameColumn)
• String number cursor.getString(phoneColumn)
• Prerequisites Know column names, data types,
  column name to index relationship

After a query, the cursor points before the
first use moveToFirst() use moveToNext() for
the initial access
40
Other Access Methods

• Add
• ContentValues values new ContentValues()
• values.put(BookProviderMetaData.BookTableMetaData.
  BOOK_NAME, "book1")
• values.put(BookProviderMetaData.BookTableMetaData.
  BOOK_AUTHOR, "author-1")
• ContentResolver resolve context.getContentResolv
  er()
• URI uri BookProviderMetaData.BookTableMetaData.C
  ONTENT.URI
• Uri inserted resolve.insert(uri, values)
• Delete Assume that bookIndex is pre-defined
• ContentResolver resolve context.getContentResolv
  er()
• URI uri BookProviderMetaData.BookTableMetaData.C
  ONTENT.URI
• Uri delURI uri.withAppendedPath(uri,
  Integer.toString(bookIndex))
• resolve.delete(delUri, null, null)
• Count
• URI uri BookProviderMetaData.BookTableMetaData.C
  ONTENT.URI
• Cursor cursor activity.managedQuery(uri, null,
  null, null, null)
• Int numberOfRecords cursor.getCount()
• cursor.close()

See next slide for symbolic constant definitions
41
BookProviderMetaData class
42
Content Resolver

• Definition A Content Resolver is an Android
  class that matches the URI to an available
  Content Provider that can handle the data
• Purpose Separate the provider from the data,
  enabling the possibility of multiple content
  providers available to handle the same data types
• Access Use a collection of method calls to
  insert, retrieve, delete, update data records
• Example (insert a new note into the notepad)
• ContentResolver resolver activity.getContentRe
  solver()
• Uri newUri resolver.insert(Notepad.Notes.CONTE
  NT_URI, values)

Note values is an instance of the ContentValues
class
43
Store Files in an SQLite Database

• Steps
• Create the SQLite table with a column called
  _data
• Get a writeable output stream
• Write the file to the reserved column name _data
• I/O Example
• //Use a content resolver to insert the record
• ContentResolver contentResolver
  activity.getContentResolver()
• Uri newUri contentResolver.insert(Notepad.Notes
  .CONTENT_URI, values)
• //Use the content resolver to get an output
  stream directly
• OutputStream outStream contentResolver().openOu
  tputStream(newUri)
• writeFileToRecord(outStream)
• outStream.close()

ContentValues object contains a set of values
Note The data is actually stored in a separate
area. The _data column contains the Uri reference
to the data
44
DataBase Helper

• Purpose
• Manage database creation and version management
• Responsible for creating and upgrading an SQLite
  database
• Defer database opening and updating to the first
  use
• Avoids blocking application startup with compute
  intensive database upgrades
• Contains methods for getWritableDatabase and
  getReadableDatabase
• Simplifies Content Provider access to files
• Eliminates concern over whether the application
  was terminated
• Implementation
• Create a class that extends SQLiteOpenHelper
• Override onCreate() and onUpgrade() methods

45
Helper Code (Two tables Employees, Department)
This application will need to override onCreate
and onUpgrade

• public class DatabaseHelper extends
  SQLiteOpenHelper
• static final String dbName"demoDB"
• static final String employees"Employees"
• static final String colID"EmployeeID"
• static final String colName"EmployeeName"
• static final String colAge"Age"
• static final String colDept"Dept"
• static final String depts"Department"
• static final String colDeptID"DeptID"
• static final String colDeptName"DeptName"
• static final String viewEmps"ViewEmps"
• public DatabaseHelper(Context context) //
  Constructor
• super(context, dbName, null / Extension to
  cursor class /, 1 / version /)

46
Helper Example (cont.)

• public void onCreate(SQLiteDatabase db)
• db.execSQL("CREATE TABLE " "depts
• " (" colDeptID " INTEGER PRIMARY KEY , "
  colDeptName " TEXT)")
• db.execSQL("CREATE TABLE "employees
• " (" colID " INTEGER PRIMARY KEY
  AUTOINCREMENT, "
• colName " TEXT, " colAge " Integer, "
• colDept " INTEGER NOT NULL , FOREIGN KEY ("
  colDept ") REFERENCES "
• deptTable" ("colDeptID"))")
• db.execSQL("CREATE TRIGGER fk_empdept_deptid ""
  BEFORE INSERT ON "employees
• " FOR EACH ROW BEGIN" " SELECT CASE WHEN (
  (SELECT " colDeptID " FROM " depts "
  WHERE " colDeptID "new." colDept " ) IS
  NULL)"
• " THEN RAISE (ABORT, 'Foreign Key Violation')
  END" " END")
• db.execSQL("CREATE VIEW " viewEmps " AS
  SELECT " employees "." colID
• " AS _id," " " employees "." colName
  ", " employees "." colAge ", "
• depts "." colDeptName "" " FROM "
  employees " JOIN " depts
• " ON " employees "." colDept" " depts
  "." colDeptID )

47
Helper Example (cont.) Upgrading the DB
Called when the version number in the constructor
changes

• public void onUpgrade(SQLiteDatabase db, int
  oldVersion, int newVersion)
• db.execSQL("DROP TABLE IF EXISTS "employees)
• db.execSQL("DROP TABLE IF EXISTS "depts)
• db.execSQL("DROP TRIGGER IF EXISTS
  dept_id_trigger")
• db.execSQL("DROP TRIGGER IF EXISTS
  dept_id_trigger22")
• db.execSQL("DROP TRIGGER IF EXISTS
  fk_empdept_deptid")
• db.execSQL("DROP VIEW IF EXISTS "viewEmps)
• onCreate(db)

Note The activity can respond to menu selections
to insert, remove, and update rows
48
Using a Database helper

• Helper new Helper(context, Helper.DATABASE_NAME,
  null, Helper.VERSION)
• SQLiteDatabase db Helper.getWritableDatabase()
  // Perform query
• Cursor cursor db.query(Helper.DATABASE_TABLE,
  result_columns, where,
• whereArgs, group, having, order)
• SQLiteDatabase db hoardDBOpenHelper.getWritableD
  atabase() // Insert row
• db.insert(HoardDBOpenHelper.DATABASE_TABLE, null,
  newValues)
• SQLiteDatabase db hoardDBOpenHelper.getWritableD
  atabase() // Update row
• db.update(Helper.DATABASE_TABLE, newValues,
  where, whereArgs)
• SQLiteDatabase db Helper.getWritableDatabase()
  // Delete matching rows
• db.delete(Helper.DATABASE_TABLE, where,
  whereArgs)

49
Find media titles and albums
Using the Android provided Media Store Content
Provider

• String projection MediaStore.Audio.AudioC
  olumns.ALBUM,
• MediaStore.Audio.AudioColumns.TITLE
• Uri uri MediaStore.Audio.Media.EXTERNAL_CONTENT_
  URI
• Cursor cursor getContentResolver().query(uri,
  projection, null, null, null)
• int aX cursor.getColumnIndexOrThrow(MediaStore.Au
  dio.AudioColumns.ALBUM)
• int tX cursor.getColumnIndexOrThrow(MediaStore.
  Audio.AudioColumns.TITLE)
• String result new Stringcursor.getCount()
  
• while (cursor.moveToNext())
• String title cursor.getString(tX), album
  cursor.getString(aX)
• resultcursor.getPosition() title " ("
  album ")"
• cursor.close()

Other Native Content Providers Browser,
Contacts, Calendar, Call log
50
Accessing the Contact List

• int iDCol ContactsContract.Contacts.ID
• int nameCol ContactsContract.Contacts.DISPLAY_N
  AME
• Uri uri ContactsContract.Contacts.CONTENT_URI
• String projection iDCol, nameCol
• Cursor cursor getContentResolver().query(uri,
  projection, null, null, null)
• int nameIndex cursor.getColumnIndexOrThrow(name
  Col)
• int idIndex cursor.getColumnIndexOrThrow(contact
  IDCol)
• String result new Stringcursor.getCount()
• while(cursor.moveToNext())
• String name cursor.getString(nameIndex)
• String id cursor.getString(idIndex)
• resultcursor.getPosition() name " (" id
  ")"
• cursor.close()

51
Searchable Applications

• Expose the application to search-facilities
• Alternatives
• Search bar appearing after hardware search button
  pressed or a program method call
• Search widget placed somewhere on the application
  view
• Quick Search implemented as a home screen widget
• Enable voice search

52
Making an Application Searchable

• In the manifest
• Create an xml file with the searchable attributes
• Mark the application searchable
• Define the intent for the activity processing
  searches
• Either create a search activity
• Launch when the search is initiated
• Process and display the results
• Or use a search dialog (floating search box)
• Hidden by default, but can be initiated by
  calling onSearchRequested(), which is an Activity
  class method
• If the device doesnt contain a dedicated search
  button, add a menu option or widget that calls
  onSearchRequested()
• Or use the SearchView widget

53
Searchable configuration in res/xml
Filename searchable.xml

• lt?xml version"1.0" encoding"utf-8"?gtltsearchable
  xmlnsandroidhttp//schemas.android.com/apk/res
  /android
•     androidlabel"_at_string/app_label
•     androidhint"_at_string/search_hint"
  gtlt/searchablegt
• The label (required attribute) becomes visible
  when search is launched and contains the search
  application name
• The hint appears in the search box before users
  enter a query. It contains a hint about what can
  be searched
• Other attributes are for search suggestions and
  voice search

54
Searchable launch in Manifest

• ltapplicationgt
• ltactivity androidname".SearchActivity
• androidlaunchMode"singleTop"gt
• ltintent-filtergt
• ltaction androidname"android.intent.action.SEAR
  CH" /gt
• lt/intent-filtergt
• ltmeta-data androidname"android.app.searchable"
  
• androidresource"_at_xml/searchable" /gt
• lt/activitygt
• Note singleTop prevents multiple instances on
  the back stack

55
Search Activity

• _at_Overridepublic void onCreate(Bundle
  savedInstanceState)
•   super.onCreate(savedInstanceState)
• setContentView(R.layout.search)
• // Get the intent, verify the action and get the
  query
• Intent intent getIntent()
• if (Intent.ACTION_SEARCH.equals(intent.getAction(
  )))
• String query intent.getStringExtra(SearchMana
  ger.QUERY)
• doMySearch(query) // Process the request

56
Services

• Services handle background events separate from a
  View
• Services reside in the main thread of the
  launching process! Use thread facilities to
  avoid blocking the main thread
• Only foreground activities have a higher
  priority, so services are rarely terminated by
  the OS
• Proper Handling
• Main activity makes requests
• Service starts worker threads to perform requests
• Bind services to the main thread
• Callbacks to the main activity completes
  transactions.

57
Creating a Service

• Create a class extending the service class
• Register the service in the application
  manifest ltservice androidenabled"true"
• androidname".MyService" androidpermission"fo
  o.bar.MY_SERVICE_PERMISSION"/gt
• Start and stop of the service in the main
  activity
• Use separate threads for compute-bound operations
• Bind service to the main activities so the main
  activity can call service class methods and then
  update its user interface views
• Self-terminate the service when it is no longer
  needed

58
Starting and Stopping Services

• Explicitly start My Service
• Intent intent new Intent(this,
  MyService.class)
• // TODO Add extras if required.
• startService(intent)
• Implicitly start a music Service
• Intent intent new Intent(MyMusicService.PLAY_AL
  BUM) intent.putExtra(MyMusicService.ALBUM_NAM
  E_EXTRA, "United")
• intent.putExtra(MyMusicService.ARTIST_NAME_EXTRA,
  "Pheonix")
• startService(intent)
• Explicitly stop My Service
• stopService(new Intent(this, MyService.class))
• Implicitly stop Music Service
• stopService(new Intent(MyMusicService.PLAY_ALBUM)
  )

59
Creating a Bindable Service
Purpose Enable activities to access service
methods

• public class LocalService extends Service
•   private final IBinder binder new
  LocalBinder()  public class LocalBinder extends
  Binder
•   LocalService getService()   return
  LocalService.this  
• _at_Override public void onCreate()
• // TODO Actions to perform when service is
  created.
• // Return instance after activity call
  onBindService() call    _at_Override public
  IBinder onBind(Intent intent)
• return binder 
•     / method for clients /    public int
  getRandomNumber() return Math.random()   

60

• public class BindingActivity extends Activity
  // An Activity using a Bound Service
•     LocalService service boolean bound
  false    private ServiceConnection connection
  new ServiceConnection() // Anonymous instance
• _at_Override public void onServiceConnected(Compon
  entName name,  IBinder service)
• LocalBinder binder(LocalBinder) service  
• servicebinder.getService() boundtrue
  _at_Override   public void onServiceDisconnected
  (ComponentName arg0)
• bound false
•     _at_Override   protected void
  onCreate(Bundle savedInstanceState)
•   super.onCreate(savedInstanceState)
  setContentView(R.layout.main)     _at_Override
  protected void onStart()
• super.onStart() Intent intent new
  Intent(this, LocalService.class)       
  bindService(intent, connection,
  Context.BIND_AUTO_CREATE)      _at_Override
  protected void onStop()
• super.onStop() if (bound)  
  unbindService(connection)  bound false   
      public void onButtonClick(View v)
•     if (bound) int num service.getRandomNum
  ber()
•       Toast.makeText(this, "number "num,
  Toast.LENGTH_SHORT).show()

61
Updating the GUI from a Service

• The activity registers a listening object with
  the service
• The service broadcasts an intent and the activity
  responds
• Use a Handler in an activity
• private final Handler handler new Handler() //
  Process queue of runnables
• private OnClickListener buttonListener new
  OnClickListener()
• public void onClick(View v)
• new Thread(new Runnable()
•   pubic void run() //.... hard work in
  separate thread
•         handler.post(new Runnable()   public
  void run()  // ... update the UI    )
•             ).start()
•         
•     

Note There are other possibilities. For example,
one could use AsyncTask, IntentService or Loader
objects