Android Reference Implementation - Droid Twit

In order to learn Android, we have created an Android application. This android application will help us get actual hands on experience in all the aspects of Android Development. The way we have developed this application is to thing of the design first, implement and keep refactoring the design, until the application gets better. Ofcourse we try to use the best practices mentioned on the Android.

We call this application as Droid Twit application, which is the reference implementation of Twitter on Android.

The application is developed in two parts

1. Small samples to understand a particular android feature or api

2. Integration of the feature or api in the Droid Twit application

The above approach helps developers to learn android

We have created an OpenSource Project

Please note this application is still under development, so please bear with us Introduction Tutorial Features Download Demo APK Demo Video Screenshots Architectural Diagrams Screen Flow Overall Architecture OAuth Authentication First Time Launch Activity Asking Service to fetch tweets Alarm Manager Triggering Service every n minutes When Phone Boots, Broadcast Receiver registers Alarm Manager and Battery Receiver Battery Receiver controls Alarm Manager Introduction This is an Implement of Android Twitter client. This is a reference implementation showcasing how to use all the components of Android to create a Twitter client. Rohit Ghatol and Saurabh Gangarde are the lead developers of this project. Both of them work for QuickOffice and Synerzip Softech. This Reference Implementation is build to train developers in Pune for one of the TechNext Technical Talks. Tutorial The tutorial on how to build a twitter client is available at DroidTwitTutorial Hello World Tutorial List Activity and AsyncTask Tutorial Service Indepth Tutorial BroadCastReceiver Tutorial Hello World Tutorial Source Code http://code.google.com/p/droidtwit/source/browse/#svn%2Ftrunk%2Ftutorials%2FHelloWorld Video Tutorial Part 1 Part 2

List Activity and Async Task Tutorial

Tutorial for List Activity and Async Task

Source Code http://code.google.com/p/droidtwit/source/browse/#svn%2Ftrunk%2Ftutorials%2FListActivity Video Tutorial Features The Android Client uses Alarm Manager to repeatedly fetch tweets from Twitter There is a back ground service for fetching twits and storing it in database There is use of OAuth for authentication Notification Manager is used for notifying users about newer twits Battery Drain is monitored and Twitter Service is closed to help save battery, and when battery is charged then again Twitter Service is started. (Yet to be implemented- Coming soon) In UI side we use shapes and drawable states for background and button images Download Demo APK Disclaimer: Since the application is under development and not gone through entire QA cycle, there could be some crashes in the application. We are striving hard to get you a stable version soon. Meanwhile please focus on the application architecture. Please Download our apk from http://droidtwit.googlecode.com/files/DroidTwit.apk and try it. Demo Video Screenshots Architectural Diagrams Proposed Architecture Screen Flow Overall Architecture Note Phone Boot Receiver, Low Battery Receiver and Alarm Receiver are all Android BroadCast? Receiver. OAuth Authentication First Time Launch Activity Asking Service to fetch tweets Alarm Manager Triggering Service every n minutes When Phone Boots, Broadcast Receiver registers Alarm Manager and Battery BroadCast? Receiver Battery BroadCast? Receiver controls Alarm Manager

Adding Aspect to Android

Programming AspectJ with Android

AspectJ is the defacto choice for AOP program. So far I did not see any one trying AOP concept in Android. However, I did read one blog mentioning, it should be possible, hence I tried it.

AspectJ puts in pointcut across code and can execute advices around those pointcuts. The beautify of this is once you compile your java source, you add these pointcuts and advices to your program by injecting them in the byte code (of already generated class files).

Knowing this I knew aspectJ can be used in Android, as dex relies on .class files.

Stage 1- Let Java compile java to .class files

Stage 2- Let AspectJ compiler inject point cuts and advices to the .class files

Stage 3- Let Dex take these new class files and create .dex file.

There you should have AspectJ working for Android applications.

Case Study: Inject Tracing code to existing Android source.

Given the case that we have an existing android project, we want to trace the call graph of each thread (showing depth) and we also want to show the cumulative time for each method.

Step 1: Create an HelloWorld Android Project

Step 2: Add some code, so we can show some call graph

Run the program and you will see this on your android emulator

Also on the DDMS Log you will see

What we want to achieve?

We want to show the call graph for this flow. We know that the flow is this way

At the same time we would like to print the commutative time each method took

We would like to print this call graph by using AOP concepts. We would like to define pointcuts around all methods of all classes in package "com.test" and print these statements there.

Step 3: Add aspectjrt.jar to classpath of android

Step 4: Add Aspect file - Trace.aj

Following is the cut down version of the same Trace.aj file. See the inline comments

Step 5 - Compile using AspectJ

As we mentioned above we want to

1. Compile java to .class files using javac

2. Inject pointcuts and advices in .class files using aspectj compile

3. Compile these injected .class files into .dex file

For this we will use ant.

Here is the ant build.xml which I used to put aspectj compilation step between compile->dex target

Here is a snippet of my build.xml around compile and dex targets

Here is the complete build.xml for your reference

Run on command prompt or through eclipse

$> ant install

You should see following output for ant

Step 6 - Run the APK which has aspectj integrated into it (after ant install)

The log looks like as follows, just as we wanted.

Source Code

1. DOWNLOAD ANDROID PROJECT ZIP

2. CHECKOUT FROM code.google.com

Cheers,

Rohit Ghatol

Advanced Android Features - GodSpeed

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