Thursday, November 8, 2012

Mobile Development with Phonegap / Cordova

Part 1: Getting set up for Android development on Windows 7

I got a new computer, which freed up my old one for dedicated use as a mobile development platform. My intended approach is to use Phonegap, so I can continue writing in HTML/CSS/JavaScript as I've been doing for 16 years. (then determine whether this method has problems such as slow speed, large app size, etc)

I run Windows and have an Android phone, so this first writeup is about those environments. A future writeup will cover Mac OSX, iOS, and xcode.

THE BASIC IDEA

The basic idea of Phonegap (sorry, I mean Cordova; they changed their name in 2012), is that you create a project folder which contains your HTML, CSS, and JavaScript assets, as well as the Phonegap library. Phonegap effectively acts as a web browser (but it's not), executing the JavaScript and rendering the HTML/CSS, and it brings some non-standard JavaScript features such as cross-domain loading, access to local files, and APIs to the phone's hardware.

Long story short: You start with a project folder, punch in HTML/CSS/JS, and export the whole shebang as an APK.

There are five basic parts to getting started with Phonegap:
* Java Development Kit (JDK), since Phonegap is Java
* Android SDK, since you're writing for Android
* Apache Ant, a build tool for Java apps
* The Cordova library itself, of course
* Eclipse SDK, the all-purpose editor to tie it all together

INSTALLING PREREQUISITES

Do a Google search for "jdk download", find Oracle, download the JDK 7 package, run the installer and click through the menus. Make a note of the directory (something like C:\Program Files\Java\jdk1.7) because you will need it later.

Do a Google search for "android sdk download", download the SDK installer, run it. I prefer to have it directly in my folder C:\Users\Gregor\AndroidSDK so it's easier to find and remember. Note that the SDK will later want to download files and create subfolders, so it should be in your documents and not someplace system-wide such as C:\Program Files. Wherever you install it, keep a note of the folder location because you will need it later.

Do a Google Search for "apache ant binary" and download a binary package. There is no installer, simply unzip it someplace. I put it under C:\Program Files\Apache Ant but had to provide admin privilege. Make a note of this directory, because you will need it later.

All three of these packages will involve some command-line usage later, so we have to set some environment variables.
  • Go into your Start menu, type "environment" and select "Edit environment variables for your account"
  • You'll get a panel listing a few variables such as TEMP, and some self-explanatory buttons such as New and Edit.
  • Set JAVA_HOME to the installation directory for the JDK, e.g. C:\Program Files\Java\jdk1.7
  • Set the PATH to include the JDK's bin directory, e.g. C:\Program Files\Java\jdk1.7\bin
  • Set the PATH to include the Android SDK's tools subdirectory, e.g. C:\Users\Gregor\AndroidSDK\tools
  • Set the PATH to include Apache Ant's bin subdirectory, e.g. C:\Program Files\Apache Ant\bin
Note that the syntax of a PATH is to join together multiple directory names with a semicolon ; character, like this:
C:\Program Files\Java\jdk1.7\bin;C:\Users\Gregor\AndroidSDK\tools;C:\Program Files\Apache Ant\bin
If you already had a PATH set, simply add a ; to the end of it, then add these three new ones.
Now test it by opening a command prompt (if you had one open already, close it and open a new one). Run the following commands and check the output:
# This should display the path of the JDK
echo %JAVA_HOME%

# This should run the Java compiler, which will show some usage help
"%JAVA_HOME%"\bin\javac

# This should run Ant, which will complain that build.xml doesn't exist
ant

# This should launch the Android SDK manager. just close it
android.bat

SETTING UP ECLIPSE & ANDROID

We're not finished yet!

Now Google and download Eclipse SDK (also called Eclipse Classic) and unpack it someplace. There is no installer, just unpack it someplace convenient. I like to put it in C:\Program Files\Eclipse and then drag it into my Start menu.

Now start Eclipse and install the Android Development Tools (ADT) plugin, which allows Eclipse to access the Android SDK.
  • Start Eclipse
  • Go into Help / Add New Software
  • Add a new repository. name it "ADT Plugin" and use the URL https://dl-ssl.google.com/android/eclipse/
  • It will show you a list of default packages which it will download. Click OK and let it download for a little while...
  • When Eclipse restarts, you should be prompted by ADT asking where to find the Android SDK. Tell it to Use Existing SDKs, and then show it where you installed Android SDK.
I prefer to test my future apps on an Android emulator, so I can test multiple OS versions and not risk my phone while I tinker. As such, I will take an extra step here to install several more packages:
  • Open Windows / Android SDK Manager, Look over the list of packages. For various versions of Android OS, the SDK platform and also the Intel x86 Atom System Image. You will need these for the versions of Android OS you want to support.
  • Install the Extras / Intel x86 Emulator Accelerator (HAXM). This enables the Android Virtual Device (AVD) to run much faster than it would without.
  • Click OK, Accept, and wait a while...
If you installed the HAXM, you will need to run an installer too; the SDK Manager downloaded but didn't really install it. Go into your Android SDK folder (C:\Users\Gregor\AndroidSDK\tools), go into Extras / Intel and look for the IntelHaxm.exe setup file. It's a standard wizard: double click, Next, Finish.

Now you're finally done setting up! It's time to make a project!


FINALLY, START A PROJECT!

Download the Phonegap / Cordova package from http://phonegap.com/download It is not an installer, just a ZIP file. Unpack it someplace convenient like C:\Program Files\Phonegap\Cordova 2.2.0

The Cordova distribution supports several different target platforms, all under the lib folder. Naturally, we want to use "lib/android"

To start a new project, use the command-line "create" script. This will create a folder containing various bootstrap elements for your new app: a copy of the Phonegap library, a folder for WWW assets with JS, CSS, and HTML subfolders, and so on.
  • Open a command prompt
  • Type: C:\Program Files\Phonegap\Cordova 2.2.0\lib\Android\bin\create FOLDER_PATH PACKAGENAME PROJECTNAME
  • Exit the command prompt
 FOLDER_PATH - This is the path to the intended folder for your new project, e.g. C:\Users\Gregor\Mobile\Demo Project
PACKAGENAME - A dotted-format app name combined with domain name, e.g. org.greeninfo.demoproject1
PROJECTNAME - The name of your app as you want it to appear, e.g. "Demonstration Project"
Example (don't forget those quotes!):
C:\Program Files\Phonegap\Cordova 2.2.0\lib\Android\bin\create C:\Users\Gregor\Mobile\"Demo Project" org.greeninfo.demoproject1 "Demonstration Project"
Start up Eclipse. Go into File / New / Project, and a wizard will allow you to pick from a set of project templates. Select Android Project From Existing Code, then lead it to the project folder you just created.

You now have an Android project underway! The left-hand panel shows the files in your project (Package Explorer). The right-hand panel will show your program code.

TEST IT RIGHT AWAY

If you're like me, you'll immediately want to make test their own demo. (don't you hate it when someone's own Hello World doesn't work?)

In the Package Explorer (the left-hand side), scroll to the top and right-click on the root object, which is your project. Select Run As / Android Application.

There are three possible things that may happen here:
  1. If your phone is attached and USB Debugging is enabled, or if you have previously created an Android Virtual Device (AVD) , you will be presented with a list of target devices. Pick the one you want to use.
  2. If there is only one Android device (phone or AVD), it will be chosen automatically without prompting you.
  3. If there are no Android devices available (no phones, no AVDs) then you will need to create one or attach one. This is a few New buttons, and selecting your choice of Android OS version (aka SDK level) and amount of virtual storage. It then lets you choose which one to use, or uses the only one.
Now the Android emulator will fire up. Like your real phone, it will take a brief slice of eternity. Eventually you'll unlock the "phone" and browse through the apps. Hey, there it is! Tap it and it works!



Note: I did get an error INSTALL_FAILED_OLDER_SDK and needed to make an adjustment to the Manifest file. See below.

SUCCESS! AND NEXT STEPS...

So far, so good. It was a long and tortuous road, but our environment is set up. For future projects, we just need to run "create" to bootstrap a folder, then open up Eclipse and Run As to test it.

The immediate next step will be development of the app, and this largely means editing HTML, CSS, and JavaScript in the assets folder. Eclipse has the build tools, but for the editing I may fall back to my trusted Komodo Edit.

A followup article will cover the development of my own Hello World app, packaging and permissions via the Manifest file, and actual deployment of a distributable APK file.


FOLLOWUP NOTES: ANDROID OS VERSION, aka SDK LEVEL

A note on terminology: Each version of the Android OS is also referred to as a SDK Level. Android 4.1 Jelly Bean is SDK Level 16. 4.0 Ice Cream Sandwich is SDK Level 15.

The Phonegap starter app probably didn't run when the emulator came up, giving an error of This means that your Manifest file (metadata and configuration about the app, device suport, etc) indicates that the app is for a different version of Android OS.

Check the AndroidManifest.xml file, down at the bottom look for android:minSdkVersion and android:targetSdkVersion In my case, the targetSdkVersion was __VERSION__ instead of a proper number. Setting this to a real number (16 for Jelly Bean) fixed it.

FOLLOWUP NOTES: TIPS AND TROUBLESHOOTING

A note about the Android SDK installation directory. I lied: I really put mine into C:\Program Files\Android SDK. This did mean some additional fussing, though: I had to provide admin privilege to install it, then I had to set the ownership of C:\Program Files\Android SDK to myself, and to grant Full Control to myself. If you have multiple accounts on your computer, this solution may not work. Keep in mind that the SDK will try to download and create files and folders here; if it fails when trying to install packages, check the ownership and permissions.

I chose to install Apache Ant and Cordova to C:\Program Files since it's a convenient place to keep them from cluttering up my documents or my desktop. I did need to provide admin privilege to put the folder there, but it works just fine after that because (unlike Android SDK) these won't make changes later and require special permission.

When running Cordova's "create", it has one very general error message: "missing one of the following". This means that one of those JAVA_HOME or PATH entries is wrong back when you set up JDK, Ant, and Android SDK. Run through those steps again, including the tests.

The Android emulator should be slow but reasonably fast, even on my two-year-old laptop. If it takes more than a few seconds to load, or is really slow, make sure that you have really installed HAXM. Remember, you must download the package via the SDK Manager and then run an installer wizard.

HAXM won't work with some older CPUs, particularly laptop CPUs before 2010. If your CPU is missing the virtualization features, either buy a newer computer or just accept that the emulator will be slow.

If you want to create more Android Virtual Devices (AVDs), e.g. for a new version of Android OS, open Eclipse, go into Window, and select the AVD Manager.

2 comments:

  1. Best set how-to I've come across. Thank you!

    Looking forward to your next post.

    ReplyDelete
  2. awesome, thanks for sharing this.

    I had one problem - the CREATE command didn't work for me with quotes. so I just selected values for FOLDER_PATH and PROJECTNAME that didn't require a space, and omitted the quotes.

    thank you again.

    ReplyDelete