• init,  source can be found in /system/core/init/init.c, is started first after the kernel finished his job.(init’s pid is 1)
• init process parces the init.rc file which has a specific format called the Android Init Language and sets up the system according to init.rc. There is a readme file that gives information about Android Init Language in the /system/core/init folder. Services are started and system properties are set according to init.rc file.  Also zygote, java and native services started.
• This is the line about zygote in init.rc file

service zygote /system/bin/app_process -Xzygote /system/bin –zygote –start-system-server

• “app_process” source code can be found in “frameworks/cmds/app_process/app_main.cpp”.  ”app_process” calls the static main function in ZygoteInit.java class(frameworks/core/java/com/android/internal/os/)

runtime.start(“com.android.internal.os.ZygoteInit”, startSystemServer);

• ZygoteInit.java’s static main function starts the system server by calling “startSystemServer()” function if proper parameters given. Then “startSystemServer()” calls the static main function of SystemServer.java class(frameworks/base/services/java/com/android/server).
• SystemServer.java’s static main function firstly call native “init1()” function. “init1()” is defined in “android_servers” library function and “init1()” is registered in “frameworks/base/services/jni/com_android_server_SystemServer.cpp” to call “system_init()”
• “system_init()”  is defined in “/frameworks/base/cmds/system_server/library/system_init.cpp”. In “system_init()” function, native services(SurfaceFlinger, AudioFlinger, Camera, MediaPlayer),  Androidruntime is started and “init2()” function in SystemServer.java is called.
• “init2()” function creates a thread that starts all critical services(PowerManager, ActivityManager, Battery, Vibrator,Connectivity, etc.). Lastly “ActivityManagerService”’s “systemReady()” function is called to run third party code.

Ahmet Oguz Mermerkaya - Olcay Ay

• Name: We need to define a name for our build (LOCAL_MODULE := )
• Local Variables: All builds may have some local variables so to start a new build it is good to clear all local variables (include $(CLEAR_VARS))
• Files: We need to write all files we want it to be build (LOCAL_SRC_FILES := main.c)
• Tags: Define tags for build. (LOCAL_MODULE_TAGS := eng development)
• Libraries: If build needs to be linked to other libraries, we need to define them (LOCAL_SHARED_LIBRARIES := cutils)
• Template file: We can define whether our build is executable,library or something else by including template file (include $(BUILD_EXECUTABLE))

BUILD_EXECUTABLE, CLEAR_VARS, etc. variables which are the absolute address of the template files are defined in build/core/config.mk.

Here is a simple Android.mk file that builds an apk

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
# Build all java files in the java subdirectory
LOCAL_SRC_FILES := $(call all-subdir-java-files)
# Name of the APK to build
LOCAL_PACKAGE_NAME := LocalPackage
# Tell it to build an APK
include $(BUILD_PACKAGE)

Last line in Android.mk file builds the APK file. Different source code types must be built differently so we can also use $(BUILD_EXECUTABLE), $(HOST_JAVA_LIBRARY), $(HOST_PREBUILT) etc. variables according to our source code. (Definitions like my-dir, all-subdir-java-files are in build/core/definitions.mk)

we can add LOCAL_MODULE_TAGS variable to Android.mk file to determine that module to be installed in that source code built. Here are the some defined tags and their meanings

• eng
  • Default variant
  • Installs modules tagged with: eng, debug, user, and/or development
  • Installs non-apk modules that have no tags specified.
  • Installs APKs according to the product definition files.
  • adb is enabled by default.
• user
  • Final release
  • Installs modules tagged with user
  • Installs non-apk modules that have no tags specified
  • Install APKs according to the product definition files
  • adb is disabled by default.

• userdebug, Same as user except:
  • Also installs modules tagged with debug
  • adb is enabled by default

These tags is same as build variants that can be specified in “choosecombo” function. “choosecombo” function is available after “source build/envsetup.sh” command.  We can specify build variant in building source code like below

make -j4 PRODUCT-generic-eng

“eng” is the build variant “generic” is the product. The command above will build and install modules according to attributes of “eng” tag mentioned above.

Ahmet Oğuz Mermerkaya

Lately, we have heard some many exciting things about HTML5 so we, the traceper team, decided to learn what the key features are in HTML5 and how we can use them in traceper.

So we are writing this document to help our project team and ankara gtug community members learn somethings about HTML5. This document doesn’t include every aspect of HTML5, it just consist of parts of HTML5 we find important for us.

Equation of HTML5:

HTML5 ~= HTML + CSS + JS

As we understand from equation HTML5 is not comprised of only new tags in html, it is the new web tech. name which includes new features in javascript, css and html and let me summarise some of the exciting features of HTML5. Before start, I think it is important to point that HTML5 is not completely finished and completely supported by all modern browsers and also some guys say that development of HTML5 will continue in next coming 5 years, who knows we will see if we live...

New Tags in HTML5 (Semantic, Media, etc.)

HTML5 comes with new tags which for semantic web, audio, video etc. Using div, instead of table, have been started in 2002 in web designs, it has some advantages but it is a hell for semantic web however HTML5’s new tags are helpful for semantic web. Here is a structure of a web page in HTML4.

class and id fields can be meaningful for us but they are not standard, they may differ from developer to developer so it is almost meaningless for search engines. But in HTML5 there is an standard like this

What if a developer doesn’t obey the rules in HTML5 for instance nav field doesn’t have a content about navigation or  article has a content about header of the web page, the result is probably like that, search engines doesn’t crawl the web site as usual and they produces some unexpected results about web page, lastly web page may not be appear at the right order in the search results.

After mentioning a little about semantic tags, let’s look at some multimedia tags, I think most of us have heard that HTML5 will kill flash, yeap it may, because with HTML5, browsers come with native support audio, video and graphics. We don’t need to use flash to play a video or an audio file. We can use audio and video tags. Here are some examples:

<video>  <!-- to play a video -->
<source src="assets/dizzy.mp4" type="video/mp4" />
</video>

<audio id="audio_with_controls" controls autobuffer>  <!-- to play a mp3 file -->
<source src="http://playground.html5rocks.com/samples/html5_misc/rushus-modal_blues.mp3" type="audio/mpeg" />
</audio>

Here is full list of HTML5 tags with browser compatibility info.

Offline & Storage

HTML5 provides web apps start faster and work even there is no internet connection. Thanks to local storage, App cache, Index DB and SQL DB Specifications.

it is better to use local storage for persistent storage. Here is a simple code snippet

saveButton.addEventListener('click', function () {
window.localStorage.setItem('value', area.value);
window.localStorage.setItem('timestamp', (new Date()).getTime());
}, false);
textarea.value = window.localStorage.getItem('value');

and another code snippet for SQL DB

var db = window.openDatabase("DBName", "1.0", "description", 5*1024*1024); //5MB
db.transaction(function(tx) {
tx.executeSql("SELECT * FROM test", [], successCallback, errorCallback);
});

According to requirements of the web app or personal choice, one can select SQL DB, Index DB, App cache or local storage to store data in client side. Lastly you can try some examples in here, here and here

Connectivity (Realtime / Communication)

Full-duplex, bi-directional communication over the web. Javascript socket ability can make web apps more efficient and more real-time because by client and server mechanism server can send update any time to client also in client-server communication only data is sent, no http headers, this dramatically reduces the bandwidth. Here is a code snippet about WebSocket

var socket = new WebSocket('ws://html5rocks.websocket.org/echo');
socket.onopen = function(event) {
socket.send('Hello, WebSocket');
};
socket.onmessage = function(event) { alert(event.data); }
socket.onclose = function(event) { alert('closed'); }

Also you can look at this example about sockets.

Native Drag&Drop

There is a built-in dnd support in HTML5, as you guess dnd is so simple in browser but not enough, you can also drag file from desktop and drop it on web page or vice versa. You can try this example to drag file from desktop.

Device Access

Beginning with the Geolocation API, Web Applications can present rich, device-aware features and experiences. Incredible device access innovations are being developed and implemented, from audio/video input access to microphones and cameras, to local data such as contacts & events, and even tilt orientation.

2D, 3D, Graphics & Effects

Between SVG, Canvas, WebGL, and CSS3 3D features, you're sure to amaze your users with stunning visuals natively rendered in the browser. Here are some samples:
http://alteredqualia.com/canvasmol/#DNA
http://www.kevs3d.co.uk/dev/asteroids/

CSS3

CSS3 delivers a wide range of stylization and effects, enhancing the web app without sacrificing your semantic structure or performance. Additionally Web Open Font Format (WOFF) provides typographic flexibility and control far beyond anything the web has offered before.

Conclusion

HTML5 with great features will make web apps more responsive, more attractive and more like apps. However not all browsers completely support HTML5 and development of HTML5 isn’t finished yet. Nevertheless, I think there isn’t left too much time to clear most of the apps running directly on operating systems from market.

References

http://www.w3.org/html/logo/
http://html5demos.com/
http://www.html5rocks.com/en/
http://www.alistapart.com/articles/previewofhtml5
http://www.w3schools.com/html5/html5_reference.asp
http://www.w3.org/

Ahmet Oguz Mermerkaya

One feature of this book is that there is a web site with the same name; www.merhabaandroid.net. Readers can ask questions via this website to the writers about the points that they don’t understand.

Merhaba Android 2; is available  on book stores like D&R, Remzi, Inkılap and also it is available on 
pusula.com, 
hepsiburada.com (worldwide shipping),
idefix.com and
kitapyurdu.com.

We need to remind you that the book is written in Turkish languge.

You can learn how to download Android source codes by following instructions on http://source.android.com/source/downloading.html and now, let me give some instructions for how to build Android and run emulator on ubuntu 10.10

• Download packages from here
• Open a terminal and go to directory where you download packages
• Run these command to extract packages and enter the directory

tar -zxf required_packages_to_build_gingerbread_on_10.10.tar.gz

cd archives

• To install all packages in these directory run this command

sudo dpkg -i -R ./

• To make g++ available under /usr/bin, create a symbolic link

sudo ln -s /usr/bin/g++_4.4 /usr/bin/g++

• Go to directory where you download Android sources
• If you are building on 32 bit, then follow the instructions on this step. If your system is 64 bit, you can pass this step
  • Open the file build/core/main.mk and change this line

ifneq (64,$(findstring 64,$(build_arch)))

to

ifneq (i686,$(findstring i686,$(build_arch)))

• Open these files

external/clearsilver/cgi/Android.mk

external/clearsilver/util/Android.mk

external/clearsilver/java-jni/Android.mk

external/clearsilver/cs/Android.mk

change the lines below for each file

LOCAL_CFLAGS += -m64

LOCAL_LDFLAGS += -m64

to

LOCAL_CFLAGS += -m32

LOCAL_LDFLAGS += -m32

• Run these commands

source ./build/envsetup.sh

lunch 1

make

• It can take some time to build Android according to your system and lastly run the emulator

emulator

• Academic Informatics Conference, Inonu University, Malatya, Turkey, Feb 2-4, 2011
• Selcuk University, Konya, Turkey, Dec 26, 2010
• XV. Internet Conference in Turkey, Istanbul, Turkey,  Dec 2-4, 2010 /
• EMO Ankara, Turkey  Nov 27-28, 2010