3.App Components-Content Providers

1. Content Providers

　　A content provider manages access to a central repository of data.

　　A provider is part of an Android application, which often provides its own UI for working with the data. However, content providers are primarily

　　　　intended to be used by other applications, which access the provider using a provider client object. Together, providers and provider clients

　　　　offer a consistent, standard interface to data that also handles inter-process communication and secure data access.

2. OverView

　　2.1 Accessing a provider

　　　　An application accesses the data from a content provider with a ContentResolver client object. This object has methods that call

　　　　　　identically-named methods in the provider object, an instance of one of the concrete subclasses of ContentProvider. The

　　　　　　ContentResolver methods provide the basic "CRUD" (create, retrieve, update, and delete) functions of persistent storage.

　　2.2 Content URIs

　　　　A content URI is a URI that identifies data in a provider. Content URIs include the symbolic name of the entire provider (its authority)

　　　　　　and a name that points to a table (a path). When you call a client method to access a table in a provider, the content URI for the

　　　　　　table is one of the arguments.

3. Retrieving Data from the Provider

　　To retrieve data from a provider, follow these basic steps:

　　　　<1> Request the read access permission for the provider.

　　　　<2> Define the code that sends a query to the provider

　　3.1 Requesting read access Permission

　　　　To retrieve data from a provider, your application needs "read access permission" for the provider

　　3.2 Constructing the query

　　3.3 Displaying qurey results

　　3.4 Getting data from qurey results