Android Tutorial

By : Ketan Bhimani

344 

Retrieving Content Provider Data with managedQuery()

We can query the Media Store content provider using the URI much

like we would query a database. We now use the managedQuery()

method to return a managed Cursor containing all image media

available on the SD card.

String[] projection = new String[] { Media._ID, Media.TITLE };
Uri mMedia = Media.EXTERNAL_CONTENT_URI;
Cursor mCursorImages = managedQuery(mMedia, projection, null, null,
Media.DATE_TAKEN + “ ASC”); // Order-by clause.

We have retrieved the records for each piece of media available on

the SD card.

Now we have this Cursor, but we still have some legwork to get our

Gallery widget to display the individual images.

Data-Binding to the Gallery Control

We need to extend the BaseAdapter class for a new type of data

adapter called ImageUriAdapter to map the URI data we retrieved

to the Gallery widget. Our custom Image UriAdapter maps the

Cursor results to an array of GalleryRecord objects, which

correspond to the child items within the Gallery widget. Although

the code for the ImageUriAdapter is too long to show here, we go

over some of the methods you must implement for the adapter to

work properly.

 The ImageUriAdapter() constructor is responsible for mapping the Cursor

to an array of GalleryRecord objects, which encapsulate the base URI and

the individual image’s id. The image id is tacked on to the end of the URI,

resulting in a fully qualified URI for the individual image.

 The getItem() and getItemId() methods return the unique identifier for the

specific image. This is the value we require when the user clicks on a