lec 04
Content Providers
Adapters
CursorLoaders
Advanced Debugging
You can persist data in several ways :
Preferences: key/value pairs (we will talk about these next
lecture)
SQLite: Use a very small RDBMS that is sandboxed to your app
and then expose it to other apps using a content provider
Files: You can read/write files to your raw directory-- avoid this.
Network: store data on the internet and read/write using any
available Internet protocol – avoid this.
All first-class components in Android must be
declared in the manifest file, they include:
Activities
Services
ContentProviders
Receivers (aka BroadcastReceivers)
Existing Content Providers:
http://developer.android.com/reference/android/provider/package-summary.html
These are the built-in Content Providers. You will notice things like:
Contacts, Calendar, MediaStore, Albums, etc.
Each of the .db's are sandboxed in their own application. These dbs can
NOT be accessed outside their application context. To get or expose the
data in the db, you must use a Content Provider
CRUD:
Create
Read
Update
Delete
ContentValues
Android uses ContentValues as a shuttle to pass values into the
ContentResolver.
Then, the ContentResolver to pass values into the
ContentProvider, which in turn communicates to the db
db
ContentProvider
ContentValues
ContentResolver
Anatomy of a URI for content provider
content://edu.uchicago.cs.gerber.restos/restos/34
A
B
A: the scheme – always content
B: the authority
C: optional path
D: individual id
C
D
ADB (Android Dubug Bridge)
adb kill-server
adb start-server
adb get-state
adb devices
Use kill-server / start-server to reboot the adb if your device/emulator is not
communicating with your dev-machine.
Advanced Debugging
Using Log.i Log.e Log.d Log.w Log.v and Log.wtf and use of filters
Advanced Debugging
Exploring the File Explorer /data/data
Push files to your phone
Emulator Control: voice/sms messages
Profiler using a slow() method.
Advanced Debugging
HeirarchyViewer
Must be on the emulator and running
In [c:\java\]android-sdk\tools\hierarchyviewer
http://www.youtube.com/watch?v=PAgE7saQUUY (good video)
Measure/Layout/Draw
CursorLoaders
2 benefits of CursorLoaders:
The query is handled on a background thread for you (courtesy of being build
on AsyncTaskLoader) so large data queries do not block the UI. This is
something the docs recommended you do for yourself when using a plain
Cursor, but now it's done under the hood.
CursorLoader is auto-updating. In addition to performing the initial query, the
CursorLoader registers a ContentObserver with the dataset you requested
and calls forceLoad() on itself when the data set changes. This results in you
getting async callbacks anytime the data changes in order to update the
view.
http://stackoverflow.com/questions/7182920/what-are-thebenefits-of-cursorloaders
CursorLoaders
Calling initLoader() will result in the onCreateLoader() method where you
will construct the query and a new CursorLoader instance, if necessary.
The onLoadFinished() method will be fired each time new data is
available, and will include the latest Cursor for you to attach to the view
or otherwise iterate through.
You will notice that the reference to the cursor in the Adapter is null, this
is because the CursorLoader is now managing the cursor.
http://stackoverflow.com/questions/7182920/what-are-thebenefits-of-cursorloaders
Adapters
An adapter needs to know the following in its constructor
//the context in which it will operate (required)
//the source data (required)
//the list item layout (required)
//the target fields -- if more than one.
//cursor – if this is a cursorAdapter
//you must then set the adapter to the Target View
AdapterViews
The bottom line are all appropriate Target Views
Midterm Assignment – you may use the base code or you may
make your own.
Midterm min requirements:
M
ListActivity that is the
main/launcher
*LA
PA
New/View/Edit list item detail
Activity
PreferencesActitivity for prefs
ActionBar on ListActivity
You may exceed the minimum
requirements.
A
CP
Student presentations:
A: AsyncTask: How to get/parse JSON data (weather data) from RESTful
web service (with recipe)
B: MediaStore: Taking pictures and videos and storing them for use in an app
(not the standard gallery) (with recipe)
C: Voice Recognition: How to use voice recognition inside an app (with
recipe)
D: Tracking locations (using GPS) for a jog or a race. Data capture so that I
can map where I went and how far I traveled, avg speed (with recipe)
Midterm Assignment – you may use the base code or you may
make your own.
Midterm min requirements:
M
ListActivity that is the
main/launcher
*LA
PA
New/View/Edit list item detail
Activity
PreferencesActitivity for prefs
ActionBar on ListActivity
You may exceed the minimum
requirements.
A
CP