Errata

I think it is worth mentioning in the book that eclipse offers a javadoc window which can be used to view details about classes, method and so on. For instance on page 107 of the book START_STICKY is returned as mentioned in another errata entry, information about this can be viewed if you click on it and view the details in the javadoc window!

How do I get around the problem that addPreferencesFromResource(R.xml.prefs); is deprecated?

As I mentioned in my errata on page 111 and the use of a static within the updater this could be used by the application class and then the isServiceRunning method could just return UpdaterService2.updaterRunning(). This makes the code so much clear, resolves various threading issues, makes sure a singleton pattern is in place and also removes the need for a flag in the application and the setServiceRunning() method.

It seems strange that SQLiteOpenHelper is an abstract class and stores the context but doesn't provide a method to be used by a subclass to get it! Is this typical of the way android SDK classes are put together? To me with 15yrs of OO experience I'd view it as a glaring design bug.

The dbHelper has a close() method but you actually call db.close in the finally clause. This does not strike me as a very well structure bit of programming.

Also it strikes me you should not be using the db attribute outside the dbHelper class. The dbHelper class should be performing all database processing. The insertOrIgnore should be in the DbHelper class not in the StatusData class.

Also insertWithOnConflict is used!!!! This isn't available in the version of the SDK we are programming to.

I think you should add this line of code to function onCreate() in YambaAppication (example 9-4)

this.statusData = new StatusData(this);

beacuse without it there is a Null pointer exception.

At the end of example 9-4 there is a Log.d which makes the application write a log row 'Got X status updates'. This row is written everytime the service runs the method fetchStatusUpdates() and is then written as 'Got 20 status updates'. That is, the application always considers all 20 fetched statuses to be new even if they are not.

My understanding is that this is not the idea with this log row. I would consider it better (more clear) to but that log message as 'Got X potentially updated statuses', or to alter the if-logic to include the IDs to check if the statuses are really updates (or already stored in the local database).

The reason for this confusing behavior to me seems to be that the statuses are typically not new, they are old with the same IDs as the ones already stored in the database and as such they will not be written to the database in with the insertOrIgnore method. So, when the SW extracts the latestStatusCreatedAtTime value, it will every time be the same old time value (from the very first database insert, unless a new status has actually been written to the cloud) and therefore the extracted statuses will all be reported as new in comparison even though they are the very same as those already stored locally. Key here is also that 'status.createdAt' is not the time that the status was entered into the cloud service (which to me would be the logical 'created time'), it seems to be the time it is fetched by getFriendsTimeline(). Therefore it is always a recent time although the status as such is same old as last time getFriendsTimeline() was used 60 seconds earlier.

I would like to get my understanding confirmed.

The book introduces the timeline activity and gives xml and code for a version using a text view, it then basically says this isn't a good way of doing it and never gives a complete implementation so that atleast you can see the code working and listing out the tweets in the text view. This is most annoying if you have just entered all the code and created a new screen. Personally I went ahead and made the refactoring changes mentioned a few pages later to add the menu's so that I could atleast see it working before refactoring to use the adaptor. I think the order should be changed so that the code using the textview can be seen to be working and then introduce the better alternatives when the menu and start/stop service are already available on the timeline activity.

In chapter 9, StatusData class has been created to encapsulate and hide database-specific details from the rest of the application.

However, in the mentioned example (and also in rest of chapter 10 talking about ListView, Adapters and Cursors) the DbHelper class and its methods are used explicitly, instead of using the statusData object created in the YambaApplication object. Why is that?

In the onResume of TimelineActivity, wouldn't it be nicer to use something like

cursor = yambaApp.getStatusData().getStatusUpdates();

instead of

cursor = db.query(DbHelper.TABLE, null, null, null, null, null,
DbHelper.C_CREATED_AT + " DESC");

... when the feature of getting all status updates is already available in StatusData class?

Several new menu options have been added without discussion. Also, use of Intent Flags is introduced throughout without discussion as to what they are or how they work. The book overall has been very good with explaining key points as they are introduced, so this looks like an oversight.

At the end of chapter 10 we still depend on the DbHelper.java file because TimelineActivity and TimelineAdapter are still using the database column name strings from that file.

Why not delete that file and replace:

static final String[] FROM = { DbHelper.C_CREATED_AT, DbHelper.C_USER, DbHelper.C_TEXT };

with:
static final String[] FROM = { StatusData.C_CREATED_AT, StatusData.C_USER, StatusData.C_TEXT };

in TimelineAdapter and TimelineActivity?

registerReceiver(receiver, filter);
the two variables are not mentioned in the book, but are seen in the git code as shown below.

protected void onCreate(Bundle savedInstanceState) {
...
receiver = new TimelineReceiver();
filter = new IntentFilter("com.marakana.yamba.NEW_STATUS");
...
}


Suggest to mention it in the book:
Example 11-5. TimelineActivity.java with TimelineReceiver

There is no where in this section of the book that describes how we test the code which checks for data connection lost! It didn't seem to work for me using the emulator and going into airplane mode.

Also where are all these filter names coming from and how do we find them? Eclipse doesn't even offer some of them mentioned in the book at possible shortcut values.

inside <LinearLayout>

android:background="@color/edit_text_background"

I think you should mention that color is user defined.

without defining it cause a problem with the widget:
"Problem Loading Widget"
or
"Problem Loading Gadget"

It says that the compassrose.jpg is in the drawable folder. I downloaded the source code (I typed everything in prior to this!) and the jpg isn't there, also there doesn't appear to be any code for the compass demo.

The AIDL files are needed by the client, I understand this as they are the definition of the interface with the service. However I do not understand how requiring a copy of the message.java class in the client makes good sense! Surely this can lead to all sorts of issues with versioning?

Surely the whole point of having a interface definition is that both parties only need an updated definition and do not rely on the other for an actual class implementation, this just wouldn't make sense. You would need to make sure that both parties client/service(server) were updated at the same time.

Is there some information about versioning we are missing here, or is there some way of defining the message object using AIDL that generates a java class on both sides.

Maybe it's me but AIDL just doesn't seem very well thought out based on the description in the book.

Hi,

I am reading the book on Kindle application on an android device and so it shows me the location instead of page number. The Android SDK Hierarchy Viewer does not work with production phones or tablets. It only works with development emulators. Something you might want to change in next release. Very good book so far. Will come back if I find something else. Cheers.

http://code.google.com/p/android/issues/detail?id=13002