Lec #3: Files, Preferences, and Content Providernadeem/classes/cs495-F13/... · Tamer Nadeem Dept....

App Development for Smart Devices � �

CS 495/595 - Fall 2013 �

Tamer Nadeem �Dept. of Computer Science�

Lec #3: Files, Preferences, and Content Provider �

Fall 2013 CS 495/595 - App Development for Smart Devices

• Data Storage • Shared Preferences � Data Files

• SQLite � Content Provider

• Discussion on Project Ideas

Objective


• Your options (most complex apps use all) – Shared Preferences

– Bundles

– Local files

– Local database (SQLite)

– Remote database

• Saving data obviously essential

Saving data


• Activity should save its user interface state each time it moves to the background

– Required due to OS killing processes

– Even if you think your app will be in the foreground all the time, you need to do this, because of....

•  Phone calls

•  Other apps

•  The nature of mobile use

Saving UI state

CS 495/595 - App Development for Smart Devices Fall 2013

Shared Preferences


• Simple, lightweight key/value pair (or name/value pair NVP) mechanism

• Support primitive types: Boolean, string, float, long and integer • Stored as XML in the protected application directory on main

memory (/data/data/<package name>/shared_prefs/<YOUR_PREFS_NAME>.xml)

• Shared among application components running in the same application context

Shared Preferences

//Getting Context example public class MyActivity extends Activity { public void method() { Context actContext = this; // since Activity extends Context Context appContext = getApplicationContext();

Context vwContext = ((Button)findViewById(R.id.btn_id)).getContext(); } }


DDMS-File Explorer (Window > Open Perspective > Other... > DDMS)

http://developer.android.com/guide/developing/debugging/ddms.html


Creating and Sharing Prefs public static String MY_PREFS = ”YOUR_PREFS_NAME";

int mode = Activity.MODE_PRIVATE; SharedPreferences mySharedPreferences =

getSharedPreferences(MY_PREFS, mode);

SharedPreferences.Editor editor = mySharedPreferences.edit();

// Store new primitive types in the shared preferences object. editor.putBoolean("isTrue", true); editor.putFloat("lastFloat", 1f); editor.putInt("wholeNumber", 2); editor.putLong("aNumber", 3l); editor.putString("textEntryValue", "Not Empty");

// Commit the changes. editor.commit();


Retrieving Prefs public static String MY_PREFS = "YOUR_PREFS_NAME"; public void loadPreferences() {

// Get the stored preferences int mode = Activity.MODE_PRIVATE; SharedPreferences mySharedPreferences = getSharedPreferences(MY_PREFS, mode);

// Retrieve the saved values. boolean isTrue = mySharedPreferences.getBoolean("isTrue", false); float lastFloat = mySharedPreferences.getFloat("lastFloat", 0f); int wholeNumber = mySharedPreferences.getInt("wholeNumber", 1); long aNumber = mySharedPreferences.getLong("aNumber", 0); String stringPreference = mySharedPreferences.getString("textEntryValue", ""); }


• System-style preference screens

– Familiar

– Can merge settings from other apps (e.g., system settings such as location)

• 3 parts

– Preference Screen Layout (XML)

– Extension of PreferenceActivity

– onSharedPreferenceChangeListener

PreferenceActivity


PreferenceActivity

<?xml version="1.0" encoding="utf-8"?> <PreferenceScreen

xmlns:android="http://schemas.android.com/apk/res/android"> <PreferenceCategory android:title="My Preference Category"/> <CheckBoxPreference android:key="PREF_CHECK_BOX" android:title="Check Box Preference" android:summary="Check Box Preference Description" android:defaultValue="true" /> </PreferenceCategory>

</PreferenceScreen>

• XML (e.g., stored as R/xml/preferences.xml)


• Options

– CheckBoxPreference

– EditTextPreference

– ListPreference

– RingtonePreference

PreferenceActivity


PreferenceActivity

Public class MyPreferenceActivity extends PreferenceActivity {

@Override Public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); addPreferencesFromResource(R.xml.preferences); }

}

In manifest... <activity android:name=“.MyPreferenceActivity”

android:label=“My Preferences”>

To start... Intent I = new Intent(this, MyPreferenceActivity.class); startActivityForResult(i, SHOW_PREFERENCES);


Default Prefs

Context context = getApplicationContext(); SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context); // then Retrieve values using get<type> method

• Default shared prefs are stored in Application Context. Therefore, available to any component:

– Activities – Services – BroadcastReceiver

(/data/data/<package name>/shared_prefs/<package name>_preferences.xml)

• Default shared prefs location:


• Run some code whenever a Shared Preference value is added, removed, modified • Useful for Activities or Services that use SP framework to set application preferences

Prefs change listeners


SP change listeners

public class MyActivity extends Activity implements OnSharedPreferenceChangeListener { @Override public void onCreate(Bundle SavedInstanceState) { // Register this OnSharedPreferenceChangeListener Context context = getApplicationContext(); SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context); prefs.registerOnSharedPreferenceChangeListener(this); }

public void onSharedPreferenceChanged(SharedPreferences prefs,

String key) { // TODO Check the shared preference and key parameters // and change UI or behavior as appropriate.

} }


Bundles


• Activities offer onSaveInstanceState handler – Works like SharedPreferences – Bundle parameter represents key/value map of primitive types that can be used save the Activity’s instance values – Bundle made available as a parameter passed in to the onCreate and onRestoreInstance method handlers – Bundle stores info needed to recreate UI state

Bundles


Saving Bundle @Override public void onSaveInstanceState(Bundle savedInstanceState) { // Save UI state changes to the savedInstanceState. // This bundle will be passed to onCreate if the process is // killed and restarted. savedInstanceState.putBoolean("MyBoolean", true); savedInstanceState.putDouble("myDouble", 1.9); savedInstanceState.putInt("MyInt", 1); savedInstanceState.putString("MyString", "Welcome back to Android"); // etc.

super.onSaveInstanceState(savedInstanceState); }


Restoring Bundle @Override public void onRestoreInstanceState(Bundle savedInstanceState) {

super.onRestoreInstanceState(savedInstanceState);

// Restore UI state from the savedInstanceState. // This bundle has also been passed to onCreate. boolean myBoolean = savedInstanceState.getBoolean("MyBoolean"); double myDouble = savedInstanceState.getDouble("myDouble"); int myInt = savedInstanceState.getInt("MyInt"); String myString = savedInstanceState.getString("MyString");

}


Data Files


Saving/loading files

String FILE_NAME = "tempfile.tmp"; // Create a new output file stream that’s private to this application. FileOutputStream fos = openFileOutput(FILE_NAME,

Context.MODE_PRIVATE); // Open input file stream. FileInputStream fis = openFileInput(FILE_NAME);

• Biggest decision: location

– Local vs Remote

– Internal vs External

• Code is standard Java


• Can only write in current application folder (/data/data/<package_name>/files/<filename>) or external storage (e.g., /mnt/sdcard/<filename>)

– Exception thrown otherwise

• For external, must be careful about availability of storage card

– Behavior when docked – Cards get wiped

Saving/loading files

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE">

</uses-permission>

• SD Card Writing Permission (AndroidManifest.xml)


Check SD card! private static final String ERR_SD_MISSING_MSG = “ERRSD cannot see your SD card.

Please reinstall it and do not remove it."; private static final String ERR_SD_UNREADABLE_MSG = "CITY cannot read your SD

(memory) card. This is probably because your phone is plugged into your computer. Please unplug it and try again.";

public static String getSDCard() throws ERRSDException { if (Environment.getExternalStorageState().equals(Environment.MEDIA_REMOVED)) throw new ERRSDException(ERR_SD_MISSING_MSG); else if (!Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) throw new ERRSDException(ERR_SD_UNREADABLE_MSG);

File sdCard = Environment.getExternalStorageDirectory(); // “/mnt/sdcard” if (!sdCard.exists()) throw new ERRSDException(ERR_SD_MISSING_MSG); if (!sdCard.canRead()) //for writing à sdCard.canWrite() throw new ERRSDException(ERR_SD_UNREADABLE_MSG);

return sdCard.toString(); }


SQLite


• Embedded database for Android

• Supports 3 main data types – TEXT (like Java String) – INTEGER (like Java long) – REAL (like Java double)

• No type checking inherent in SQLite

• Each DB is private to App that created it

• Data Stored at: •  /data/data/<package name>/databases/<db name>

SQLite

Documentation on SQLITE available at: http://www.sqlite.org/sqlite.html Good GUI tool for SQLITE available at: http://sqliteadmin.orbmu2k.de/ SQL and SQLite Language Syntax at: http://www.sqlite.org/lang.html


• Create a subclass of SQLiteOpenHelper – Override at least onCreate() - where you can create tables

– Can also override onUpgrade() - make a modification to the tables structures

• Call getWritableDatabase() to get read/write instance of SQLiteDatabase

– Can then call insert(), delete(), update()

Using SQLite


Subclass SQLiteOpenHelper public class DatabaseHelper extends SQLiteOpenHelper { static final String dbName="demoDB"; static final int dbVersion=1; static final String employeeTable="Employees"; static final String colID="EmployeeID"; static final String colName="EmployeeName"; static final String colAge="Age"; static final String colDept="Dept";

static final String deptTable="Dept"; static final String colDeptID="DeptID"; static final String colDeptName="DeptName";

public DatabaseHelper(Context context) { super(context, dbName, null, dbVersion); } … }


onCreate(SQLiteDatabase db)

public void onCreate(SQLiteDatabase db) { // TODO Auto-generated method stub db.execSQL("CREATE TABLE “ + deptTable + " (“ +

colDeptID + “ INTEGER, “ + colDeptName + " TEXT);"); db.execSQL("CREATE TABLE "+ employeeTable + " (“ +

colID + “ INTEGER, “ + colName + “ TEXT, “ + colAge + " INTEGER, “ + colDept + " INTEGER);");

}


Handling Records SQLiteDatabase db=this.getWritableDatabase();

//Inserting Records ContentValues cv=new ContentValues(); cv.put(colDeptID, 1); cv.put(colDeptName, "Sales"); db.insert(deptTable, colDeptID, cv);

db.execSQL( “INSERT INTO “ + deptTable + “(“ + colDeptID + “,” + colDeptName + “) values (‘2', ‘Services' );" );

//Deleting Record db.delete(deptTable, colDeptID + "=" + dept_1, null); //dept_1=“1”

//Updating Record cv.put(colDeptName, “newIT”); db.update(deptTable, cv, colDeptID + "=?", dept_2); //dept_2=“2”

db.close();

http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html


SQL Select Syntax (see http://www.sqlite.org/lang.html) SQL-select statements are based on the following components

Querying SQL

The first two lines are mandatory, the rest is optional.


• SQLiteDatabase.query() returns a Cursor object that points to results

– Cursor is a iterator. Call moveToNext() to get to next element.

– Cursor can be examined at runtime

•  getCount(), getColumnCount()

•  getColumnIndex(String name)

•  getColumnName(int index)

•  getInt(int index), getLong(int index), getString(int index), etc.

Querying SQLite


Android Simple Queries The signature of the Android’s simple query method is:

Querying SQLite – query()

http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html


Android Simple Queries Example Query the EmployeeTable, find the average salary of female employees supervised by 123456789. Report results by Dno. List first the highest average, and so on, do not include depts. having less than two employees.

Querying SQLite - Example


Cursor - Example


Content Provider


• A content provider makes a specific set of the application's data available to other applications

=> Share data to other apps

• Any app with appropriate permission, can read and write the data.

• Many native databases are available via the content providers, for example Contact Manager

• Common interface for querying the data

Content Provider


• Content providers expose their data as a simple table on a database model

• Every record includes a numeric _ID field that uniquely identifies the record within the table.

About Content Provider


• Content provider exposes a public URI that uniquely identifies its data set:

content://<Authority>/[data_path]/[instance identifier] •  the URI starts with content:// scheme.

•  Authority is a unique identifier for the content provider. Example “contacts”.

•  data_path specifies the kind of data requested. For example, “people” is used to refer to all the contacts within “contacts”.

•  there can be an instance identifier that refers to a specific data instance.

•  content://media/internal/images - return the list of all internal images on the device.

•  content://media/external/images - return the list of all the images on external storage (e.g., SD card) on the device.

•  content://call_log/calls - return a list of all the calls registered in the call log.

•  content://browser/bookmarks - return a list of bookmarks stored in the browser.

•  content://contacts/people/45 - return the single result row, the contact with ID=45.

About Content Provider


•  Browser—Read or modify bookmarks, browser history, or web searches.

•  CallLog—View or update the call history.

•  Contacts—Retrieve, modify, or store the personal contacts. Three-tier data model of tables under a ContactsContract object:

•  ContactsContract.Data—Contains all kinds of personal data. •  ContactsContract.RawContacts—Contains a set of Data objects associated

with a single account or person. •  ContactsContract.Contacts—Contains an aggregate of one or more

RawContacts, presumably describing the same person.

•  MediaStore—Access audio, video, and images.

•  Setting—View and retrieve Bluetooth settings, ring tones, and other device preferences.

Android Native ContentProvider


•  Android defines CONTENT_URI constants for all the providers that come with the platform.

Android Native ContentProvider

•  ContactsContract.CommonDataKinds.Phone.CONTENT_URI (content://com.android.contacts/data/phones)

•  Browser.BOOKMARKS_URI

(content://browser/bookmarks) •  MediaStore.Video.Media.EXTERNAL_CONTENT_URI

(content://media/external/video/media)

Classes section under : http://developer.android.com/reference/android/provider/package-summary.html

(if a provider, CONTENT_URI field exist)


• You need – URI

•  ContactsContract.Contacts.CONTENT_URI

– Names of data fields (result comes in table) •  ContactsContract.Contacts.DISPLAY_NAME

– Data types of those fields •  String

• Remember to modify the manifest file for permissions!

Querying Native Content Provider

To retrieve the contacts: <uses-permission android:name="android.permission.READ_CONTACTS"> </uses-permission>


Query import android.provider.Contacts.People; import android.content.ContentUris; import android.net.Uri; import android.database.Cursor; // Use the ContentUris method to produce the // base URI for the contact with _ID == 23. // à ”content://com.android.contacts/people/23” Uri myPerson = ContentUris.withAppendedId(People.CONTENT_URI, 23); // Alternatively, use the Uri method to produce the base URI. // It takes a string rather than an integer. // à ”content://com.android.contacts/people/23” Uri myPerson = Uri.withAppendedPath(People.CONTENT_URI, "23"); // Then query for this specific record: Cursor cur = managedQuery(myPerson, null, null, null, null);

For more information on URI handling functions: http://developer.android.com/reference/android/net/Uri.html


Query import android.provider.Contacts.People; import android.database.Cursor; // Form an array specifying which columns to return. String[] projection = new String[] { People._ID, People._COUNT, People.NAME, People.NUMBER }; // Get the base URI for the People table in the Contacts content provider. Uri contacts = People.CONTENT_URI; // Make the query. Cursor managedCursor = managedQuery(contacts, projection, // Which columns to return null, // Which rows to return (all rows) null, // Selection arguments (none) // Put the results in ascending order by name People.NAME + " ASC");


• Content Resolver •  getContentResolver().query(…) •  getContentResolver().insert(…) •  getContentResolver().update(…) •  getContentResolver().delete(…)

• Cursor cur = managedQuery(…) is equivalent to Cursor cur = getContentResolver().query(…); startManagingCursor(cur);

• Starting HoneyComb (API level 11) CursorLoader cl = new CursorLoader(this, …); Cursor cur = cl.loadInBackground()

Query


Insert/Update/Delete

private void updateRecord(int recNo, String name) { //appending recNo, record to be updated Uri uri = ContentUris.withAppendedId(People.CONTENT_URI, recNo); ContentValues values = new ContentValues(); values.put(People.NAME, name); getContentResolver().update(uri, values, null, null);

}

private void insertRecords(String name, String phoneNo) { ContentValues values = new ContentValues(); values.put(People.NAME, name); Uri uri = getContentResolver().insert(People.CONTENT_URI, values);

}

private void deleteRecords() { Uri uri = People.CONTENT_URI; getContentResolver().delete(uri, null, null);

}


1.  Set up a system for storing the data •  e.g., SQLite using SQLiteOpenHelper

2.  Extend ContentProvider class to provide access: •  query()—Allows third-party applications to retrieve content. •  insert()—Allows third-party applications to insert content. •  update()—Allows third-party applications to update content. •  delete()—Allows third-party applications to delete content. •  getType()—Allows third-party applications to read each of URI

structures supported. •  onCreate()—Creates a database instance to help retrieve the content.

3. Declare the Content Provider in manifest

Implementing your own Content Provider


Extend Content Provider

public class MyContentProvider extends ContentProvider { public static final String AUTHORITY = "edu.odu.phonenumber"; public static final Uri CONTENT_URI =

Uri.parse("content://"+ AUTHORITY + "/phones"); private MySQLDatabase mDB;

private static final int PHONES = 1; private static final int PHONES_ID = 2; private static final UriMatcher uriMatcher; static{

uriMatcher = new UriMatcher(UriMatcher.NO_MATCH); uriMatcher.addURI(AUTHORITY, “phones", PHONES); uriMatcher.addURI(AUTHORITY, “phones/#", PHONES_ID);

}

public boolean onCreate() { mDB = new MySQLDatabase(getContext()); return true; } … }


Extend Content Provider public class MyContentProvider extends ContentProvider {

…

public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) { Cursor c=null; SQLiteDatabase db = mDB.getWritableDatabase(); switch (uriMatcher.match(uri)) { case PHONES: //get all phones records ... break; case PHONES_ID: //get a particular phone record … break; }

… }

public String getType(Uri uri) {...} public int delete(Uri uri, String selection, String[] selectionArgs) {...} public Uri insert(Uri uri, ContentValues values) {...} public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {...}

}

For more information on URI handling functions: http://developer.android.com/reference/android/net/Uri.html


Manifest

<application android:icon="@drawable/icon" android:label="@string/app_name"> …

<provider android:name=".MyContentProvider" android:authorities=" edu.odu.phonenumber"></provider>

</application>


Project Ideas


•  Security •  ODU Secure App

•  Localization •  Taking random pictures from your cell at home when it is on a table. Could you

locate the phone using the ceiling feature?

•  Medical/health/activity monitoring •  Parkin's disease detection

•  EEG Set

•  Transportation •  Detecting and identifying whether group of people are on the same transportation

unit/same side using correlation of accelerometer, gyro, …

•  Toll Tracking App.

Project’s Idea


•  Education •  Interactive classroom

•  Misc •  Understanding Interface activities power consumption

•  Extension of MagnoTricoder

•  Wound Care App

•  Last Year Projects: •  http://www.cs.odu.edu/~nadeem/classes/cs495-F12/projects.htm

•  http://www.cs.odu.edu/~nadeem/classes/cs495-F11/projects.htm

Project’s Idea


Class Project Timeline

• Goal: obtain hands-on experience

• Semester-long research project to be done individually or in teams of two.

• Students will have the flexibility to either formulate their own project or choose from the ideas suggested by the instructor.

•  Timeline •  Team formation: Due – Sept. 27th, 2013 (team members + team name) •  Project Idea Selection: Due – Oct. 11th, 2013 (One page description) •  Project Proposal Draft: Due – Oct 21th, 2013 (one page proposal +

presentation slides) •  Project Status Update: Due – Nov 11th, 2013 (one page update +

presentation slides) •  Final Project Presentation: Due – Dec 2nd, 2013 (report + presnetation

slides + demo)


Questions?


•  p168: Handling View Events •  p191: Displaying a Long List of Items using the ListView •  p197: Checking which Items are Selected •  p235 Creating the Menu Helper Methods •  p238: Displaying an Option Menu •  p240: Displaying a Context Menu •  p252: Saving Data Using the SharedPreferences Object •  p259: Retrieving and Modifying Preferences •  p263: Saving Data to Internal Storage •  p274: Creating the Database Helper Class •  p279: Adding Contacts to a Table •  p280: Retrieving All Contacts from a Table •  p281: Retrieving a Contact from a Table •  p282: Updating a Contact in a Table •  p283: Deleting a Contact from a Table •  p295: Using the Contacts Content Provider •  p305: Creating Your Own Content Provider

Recommended Assignment: Try It Out

(from previous class)

Database

Shared Preferences

Content Provider


•  Assignment Tracker App •  Due Sunday Sep 29, 11:59pm

Assignment #2: Application Programming (ODUCS App)

Lec #3: Files, Preferences, and Content Providernadeem/classes/cs495-F13/... · Tamer Nadeem Dept....

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