android
Madhukar Kunam 
Week6.pptxCOIT20270 Application Development for Mobile Platforms Week 6: Content Providers
Dr. R. Balsys, CQU, 2018.
Source: Beginning Android Programming with Android Studio, J.F. DiMarzio, 2016
Content Providers
Objectives, to :
share data in Android
use a content provider
CQU - COIT20270 Application Development for Mobile Platforms
Content Providers
Content providers are the recommended way of sharing data in Android application
Content providers provide a consistent interface programming interface across all Android applications
Content providers provide much the same services as databases – add, delete, query, edit
but can be stored as databases, files or over a network
Basic Android content providers include;
Browser – bookmarks, history, etc.
CallLog – missed calls, call details, etc.
Contacts – contact details from address book
MediaStore – for audio, video and images
Settings – device settings and preferences
CQU - COIT20270 Application Development for Mobile Platforms
…Content Providers
A URI is used to query a content provider. Query strings always have the form
content:// <authority> / <path> / <id>
where
authority– name of the content provider. For user defined content providers it is the fully qualified name, eg wrox.com.provider
path– specifies the content provider data path to the service provided
id– specifies the actual record required
Eg. Content://contacts/people/4 the fourth person in the people table of the devices contacts database
Table 8.1 in chapter 8 of the DiMarzio text gives further examples
CQU - COIT20270 Application Development for Mobile Platforms
Using a Content Provider
You must first specify the URI of the content provider
Uri myContacts = Uri.parse(“content://contacts/people/”);
Post Honeycomb devices use CursorLoader() to get a cursor instance to the data, but does not block the application thread
The CursorAdapter object maps data from the source to the destination variables. You set up an array of string, String[], for the column variable and an int[] for the views
You then create a new instance of a SimpleCursorAdapter class variable using the column and view values as parameters
Honeycomb and later requires the addition of a FLAG_REGISTER_CONTENT_OBSERVER argument
You also need to set READ_CONTACTS permission in the Android.manifest file
CQU - COIT20270 Application Development for Mobile Platforms
Pre-defined Querystring Parameters
A number of pre-defined Query string constants are defined including:
Browser.BOOKMARKS_URI
CallLog.CONTENT_URI
MediaStore.Images.Media.INTERNAL_CONTENT_URI
MediaStore.Images.Media.EXTERNAL_CONTENT_URI
Settings.CONTENT_URI
Eg Uri contacts= ContactsContract.Contacts.CONTENT_URI;
If you want to retrieve the 1st setting use Uri settings= ContentUris.withAppendedId(ContactsContract.Contacts.CONTENT_URI, 2);
CQU - COIT20270 Application Development for Mobile Platforms
Printing Cursor objects
Create a method that takes the Cursor variable as input
Use the Cursor classes moveToFirst() and moveToNext() to iterate through the items in the Cursor object
The ContactsContract.Contacts._ID field returns the ID of the contact and the ContactsContract.Contacts.DISPLAY_NAME returns the contacts name
Use ContactsContract.Contacts.HAS_PHONE_NUMBER to determine if the contact has a phone number and then ContactsContract.CommonDataKinds.Phone.NUMBER to access the phone number
CQU - COIT20270 Application Development for Mobile Platforms
Content Providers - Projections
The 3rd parameter of CursorLoader() returns the columns that are returned by the query – this parameter is known as the projection
You can set up an array to contain the columns you wish to return from the data source and pass this as the projection parameter
String[] projection= new String[] {
ContactsContract.Contacts._ID,
ContactsContract.Contacts.DISPLAY_NAME, ContactsContract.Contacts.HAS_PHONE_NUMBER
};
CQU - COIT20270 Application Development for Mobile Platforms
Content Providers - Filtering
The 4th and 5th parameters of CursorLoader() enable you to make a WHERE clause enquiry
CursorLoader cL=new CursorLoader(this, contacts, projection, ContactsContract.Contacts.DISPLAY_NAME” + “ LIKE ‘Ron’ ”, null, null);
You can use the next parameter to supply a list strings to use instead
CursorLoader cL=new CursorLoader(this, contacts, projection, ContactsContract.Contacts.DISPLAY_NAME” + “ LIKE ? ”, new String[] {“Ron”, “Mary”}, null);
CQU - COIT20270 Application Development for Mobile Platforms
Content Providers - Sorting
The last parameter of CursorLoader() enables you to specify an ORDER BY clause of a SQL query
CursorLoader cL=new CursorLoader(this, contacts, projection, ContactsContract.Contacs.DISPLAY_NAME” + “ LIKE ? ”, new String[] {“Ron”, “Mary”}, ContactsContract.Contacts.DISPLAY_NAME” + “ ASC ”);
CQU - COIT20270 Application Development for Mobile Platforms
Creating Your Own Content Provider
To create your own content provider you provide a class that extends the ContentProvider base class
You need to override the following methods;
getType() – to return the MIME type of the data for the URI
onCreate() – called when provider created
query() – receives a client request and returns a Cursor object
insert() – inserts a new record in the content provide
delete() – deletes records in the content provider
update() – updates a record in the content provider
You can store your data in the file system, a database, an XML file or through a web service
CQU - COIT20270 Application Development for Mobile Platforms
…Creating Your Own Content Provider
You then need to define a number of strings such as the PROVIDER_NAME, CONTENT_URI, _ID, a UriMatcher instance, and a SQLiteDatabase with its associated constants
The UriMatcher object is used to parse the content URI through the ContentResolver
You write a SQLiteHelperDatabase class to help manage the database
You then write the implementations for getType(), onCreate(), query(), insert(), delete() and update()
Call notifyChange() of the ContentResolver after insert() and delete()
Modify the Android.Manifest file by adding the <provider> element
CQU - COIT20270 Application Development for Mobile Platforms
Using Your Own Content Provider
You need to create an activity to test your content provider
To add to the provider create a ContentValues object and populate it with the required values for your data object
If the ContentProvider is in the same package as your tester you can directly reference the provider fields, otherwise you need to specify the field names directly
For external packages you need to refer to the content URI using a fully qualified URI
You should then write methods to display the contents of you content provider and to test the update() and delete() methods
CQU - COIT20270 Application Development for Mobile Platforms
