my first complete android app

well, what can i say - it is fun to program for android; i enjoy java and the android apis are ok.
my own android phone is quite old, running android 1.5 so i had to write for api level 3.
i see some improvements in the following apis, when i have time i'll probably try to root and upgrade to 2.1 (no intention to buy a new phone yet).

what else can i say - eclipse is great! so great, i started using it at work, instead of kdeveloper. it definitely is an accomplished platform

on the app itself - it irritated me that there was no sound notification for missed calls, so i thought, why not write one myself (it is only a few days ago, about 4 months since i started working on and off on this app that i found out that there already were couple of solutions for this on the droid market - which is absolutely not surprising).

first of course there was the alarm manager api, but i quickly dismissed it.

i decided to go with a service that checks the status of the calls periodically. but how often should this period reoccur? what if we miss some important notifications?

so i decided to hook the incoming calls intent (actually PhoneStateListener). this worked quite well - after the call is finished, if it wasn't answered my app plugged in and started sounding the alarm every few seconds.
this eventually completed the flow.

there was something strange that i observed. actually the biggest horror a developer may stumble upon - the app worked fine in the emulator, but occasionally when deployed on the phone it wouldn't pick the missed call and remain in obscure state.

so what do you do when you don't know what you program does? hook a logger and watch what your program says it is doing. after some staring at the logger output, it turned out that the system database i read phone calls from (android.provider.CallLog.Calls) registers the (missed) call a few seconds later than the call occured. unfortunately this mismatches the app's own timeline and so - the notification never gets to be fired. the fix was to wait a few seconds before quering the database.

so now i have some more confidence in my app and can show it to the world. i don't think anyone will pay attention, but the satisfaction of getting to "do something" and bring it to completion is priceless.

now if i can only find my way around to actually figuring out how to publish to google play market...

fun with specialized function templates in c++

i was quite sad a few days ago for a reason some of you may be familiar with all to well:
a program was working fine in debug, but didn't return results in release build. luckily this was not in production (phew).

what valgrind said was that some variables weren't initialized. my setup is such that i had to refactor a templated class and add a few templated methods, which were specialized in a few locations. everything built fine and seemingly the workflow shouldn't have allowed for uninitialized variables when the specialized function templates were called. eventually and only in the impossible case that the base template function was called. which was impossible to happen, because the compiler would now to instantiate the correct specialization, right?

right, but not exactly. a few debug prints proved that in release the impossible happened - the base template function was called instead of the specialization. but why??
all the arguments should be giving clear directions to the compiler which function to create and call, so why wasn't it? why my beautifully crafted specialization functions were not called??!!

ok, i tried not specializing, but overloading - something similar to this GOTW, but it didn't quite fit, so on went the struggle making the compiler SEE the specialized templates. what if the argument is not const, what if the number of argument varies, what if the return value is different.
but you have to remember that in debug build everything works fine, so then the compiler does know about the specialization and invokes it, so it isn't the code, may be it is in the compiler settings, or the linker? or the compiler it self??

btw, a simple test case that is similar to the situation worked fine in debug and release:
template.h

struct TestStruct
{
    int intValue;
    char * charValue;

public:
    TestStruct() : intValue(0), charValue(NULL) {};
};

template
unsigned int templatedFunction(const T& value)
{
    assert(false && "not implemented");
    return std::numeric_limits::max();
}

template
class BaseClass
{
public:
    void callFunction(const CC& value)
    {
        templatedFunction(value);
    }
};

template.cpp

#include "template.h"

template <>
unsigned int templatedFunction(const unsigned int& value)
{
    printf("implemented for unsigned int");
    return std::numeric_limits::max();
}

template <>
unsigned int templatedFunction(const TestStruct& value)
{
    printf("implemented for testStruct");
    return std::numeric_limits::max();
}

int main()
{
    BaseClass baseClass;

    unsigned int value = 10;
    TestStruct testStruct;

    baseClass.callFunction(testStruct);
}

 so what, what, what was happeningggggg

the evident conclusion is in release the compiler decides to ignore the specializations, so can we help it see and use them? turns out the solution is so simple i had to kick myself in the backspace i missed it:

forward declare the specializations in the code location were they will be used

yep, somehow this solved it. i know, it is probably on first page of the book C++ templates 101, but well, how often do you have to write explicitly specialized template functions that will be used in a templated class where one of the template arguments is a function, and the other is the return value of the function?
me, not very often


good luck, keep coding!

log4cxx insights

i really liked log4cxx and while i did a thorough research, turned out there were a few things i hadn't realised log4cxx featured or was capable of

- hierarchy is awesome, i had used it with test cases like
log4j.logger.main=ERROR, console, file
log4j.logger.main.another=INFO

where`another` inherits console and file appenders from `main`

but i hadn't realised that if `another` featured, well, another console appender, then the log message would be displayed twice - once for the console appender from `main` and once from `another`

log4j.logger.main.another=INFO, console2

the way to avoid this is to tell log4cxx we don't want the child to inherit any appenders from the parent, like this -
log4j.additivity.main.another=false

it is actually quite evident from the quick tutorial on the log4cxx site, but i guess i kindda missed that


- different log levels for each appender - now i  really hadn't realised that log4cxx was capable of this: when you want console to print all messages, but file output would feature only errors
turns out this can be easilly done with

log4j.appender.console.Threshold=TRACE
log4j.appender.file.Threshold=ERROR

isn't this beautiful!!


there hasn't been official release for log4cxx for quite a few years which might be startling, but then this library is so awesome, i'd rather risk and use it in production then go for another one, or (no way) write a custom framework...

simple android service not starting

i'm new to android.
but it seems a nice platform so far.
been away from java for quite some time and find some syntax shortcuts are quite amazing but on the problem at hand;
i wanted to write a very simple test service and eventually settled for this scenario:
- start an activity
 - on button click the activity starts a service
- thats it!

and this gave me hours of grinding google and stackoverflow, because this very simple service never seemed to start

 one of the first issues was "newinstance failed no ()" that was quite easy to solve thanks to http://stackoverflow.com/questions/2120699/newinstance-failed-no-init. but then non of the debug loggers i put through out the code seemed to be fired i the service i had onCreate(), onStartCommand(), onStart() and none was ever triggered 
 i had big suspicions on the AndroidManifest.xml as it is still quite a blank area for me. startService() returned Null whatever i passed to it. 
my service was declared in the file that countained the activity so the name i tried to input as service android:name were like mainNamespace.Activityname.ServiceName, but this didn't work, nor did mainNamespace.ServiceName, not any of the other attempts 

 to save some hdd space on the blog host - i moved the code of the service outside the file containing the activity class, added new service name in the manifest xml and suddenly i started seeing the debug messages i waited to see for quite some time! 
 so what was i doing wrong? what should've been the name of the service in the manifest xml for the service class contained within the same file? or was it the naming in the Intent constructor? 
 just another android mystery 

 by the way, i had a glimpse of some iOs code, and must say i was startled to extent of appalled - is this C++, or some attribute based language, how do you program in this? maybe i've seen only some weird bits of code, i don't know - but i was hoping for some clean C++ code (Objective-C?) and didn't see any 

 bye..


oh yes - some helpful links, these were very helpful in grabbing some basic knowledge and sample code
- http://zaman91.wordpress.com/2010/04/22/android-how-to-start-a-service-in-application/
- http://marakana.com/forums/android/examples/60.html
- http://stackoverflow.com/questions/4480340/sample-alarmcontroller-application-service-registeration-in-androidmanifest