Monday, September 24, 2012

Automating build process of an android project using ant

If you have developed your Android project using eclipse you might have noticed that there isn't any ant build.xml file in the project directory. That's because the android plugin itself handles all the necessary tasks. 
In case you want to automate your build process by using a custom build file what should you do? First lets discuss a scenario. Consider you have developed an application and you want to release it for testing. Now you want to create a .CMD file and provide some switches for the testers to do pretty much everything by themselves. For example, updating the code from a version control, building, cleaning and installing on the phone or emulator. By doing this you pretty much have automated everything.

Lets have a look at the 1 possible path which updates the code to the latest version and installs it on the phone attached to the PC via USB connector. We name our command file dist.cmd and it has a switch "-install".
   
    dist.cmd -install

    The steps taken automatically are:

    1. uninstall the app from the phone
    2. updating the code to the latest version
    3. cleaning the bin and gen folders
    4. compiling the code
    5. install fresh copy on the phone
 
With the help of this command you can have the latest code installed on a phone for testing.
    
Now the steps

You can execute the following command in order to create a new android project from command line.
 * Before executing the commands first navigate to the tools directory of your SDK.   
 * Add the platform-tools as well as the tools directories to your PATH (environment variable).
    
android create project --target 1 --name vahidApp --path ./vahidAppProject --activity myActivity --package org.vahid.android

target: id of the android platform library you are building against
name: name of the project
path: location of the project
activity: name of the default activity
package: your package namespace
   
After successful execution of the command one directory will be created (your project directory) in the current folder. Go to the newly created project folder and copy the following files to your own project.

    ant.properties : define key.store, key.alias
    build.xml : add few more ant targets (read later below)
    local.properties : defines address of the SDK
   
We are going to create 2 more files.

    dist.properties: defines address of the ant (android needs Ant version 1.8 or later. If you, for any  reason need to have older versions of Ant on you computer and can not change the ANT_HOME and PATH then, you can have your older versions and add the address of the new one in this property file)
    distribution.cmd: define all the commands and the available options. The commands will find the address of the ant from dist.properties.
   
If you open build.xml you will see that this file imports the android-sdk actual build file. How does it know where is the location of the sdk? well, from local.properties.

Now, you can override or add additional targets after the import tag. For example, we want to clean, update the code to the latest version and create a fresh .apk file and install it on the phone. This can be done by the following ant target.

First uninstall is called which removes the app from the phone. Remember you have to define the package address of your app. Its defined in your manifest.xml. Then cleans the bin and gen directories and calls our custom target "updateProject" which update the code to the latest version from version control and finally, calls "release"from  imported android build file. These sequence of ant calls will create project's .apk file and finally installs it on the phone.

Project's ant build file (added custom targets)

    <target name="uninstall">
        <exec executable="adb">
            <arg value="-d"/>
            <arg value="uninstall"/>
            <arg value="com.sg.distribution"/>
        </exec>
    </target>

    <target name="install" depends="uninstall, create">
         <exec executable="adb">
            <arg value="-d"/>
            <arg value="install"/>
            <arg value="./bin/${ant.project.name}-release.apk"/>
        </exec>
    </target>

    <target name="create" depends="clean">
        <antcall target="updateProject"/>
        <antcall target="release"/>
    </target>

 <target name="updateProject">      
        <echo message="Updating project...."/>
        <exec executable="svn.exe" failonerror="true">
          <arg line="update"/>
        </exec>      
    </target>

By adding these 2 ant targets we can make sure our .apk file is build upon the latest code changes. In second updateProject target we use CollabNet's svn.exe (add it to the path environment variable) and passing a parameter to update the code. Of course, our example uses Subversion as the version control.

dist.cmd command file

@echo off
REM --Begin reading path of ant from a property file
FOR /F "eol=; tokens=2,2 delims==" %%i IN ('findstr "antPath" dist.properties') DO (
set antPath=%%i)
REM --END
SET ANT_HOME=%antPath%
:start
if "%1"=="-install" goto install

:install
call %antPath%\bin\ant install
goto done

:done
shift
if ""%1""=="""" goto endOfFile
goto start
:endOfFile

This file read the ant path from the dist.properties file and set ANT_HOME for just the current session to the path read and execute each ant based on the read path. These code is part of the actual file.

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