have made Android development much easier, I've long been curious
about the cross-platform phone development apps: you write a simple
app in some common language, like HTML or Python, then run something
that can turn it into apps on multiple mobile platforms, like
Android, iOS, Blackberry, Windows phone, UbuntoOS, FirefoxOS or Tizen.
Last week I tried two of the many cross-platform mobile frameworks:
Kivy and PhoneGap.
Kivy lets you develop in Python, which sounded like a big plus. I went
to a Kivy talk at PyCon a year ago and it looked pretty interesting.
packages them like native applications. PhoneGap seems much more
popular, but I wanted to see how it and Kivy compared.
Both projects are free, open source software.
If you want to skip the gory details, skip to the
summary: how do Kivy and PhoneGap compare?
I tried PhoneGap first.
It's based on Node.js, so the first step was installing that.
Debian has packages for nodejs, so
apt-get install nodejs npm nodejs-legacy did the trick.
You need nodejs-legacy to get the "node" command, which you'll
need for installing PhoneGap.
Now comes a confusing part. You'll be using npm to install ...
something. But depending on which tutorial you're following, it may
tell you to install and use either phonegap or cordova.
Cordova is an Apache project which is intertwined with PhoneGap. After
reading all their FAQs on the subject, I'm as confused as ever about
where PhoneGap ends and Cordova begins, which one is newer, which one
is more open-source, whether I should say I'm developing in PhoneGap
or Cordova, or even whether I should be asking questions on the
#phonegap or #cordova channels on Freenode. (The one question I had,
which came up later in the process, I asked on #phonegap and got a
helpful answer very quickly.) Neither one is packaged in Debian.
After some searching for a good, comprehensive tutorial, I ended up on a
tutorial rather than a PhoneGap one. So I typed:
sudo npm install -g cordova
Once it's installed, you can create a new app, add the android platform
(assuming you already have android development tools installed) and
build your new app:
cordova create hello com.example.hello HelloWorld
cordova platform add android
Error: Please install Android target: "android-22"
Apparently Cordova/Phonegap can only build with its own
preferred version of android, which currently is 22.
Editing files to specify android-19 didn't work for me;
it just gave errors at a different point.
So I fired up the Android SDK manager, selected android-22 for install,
accepted the license ... and waited ... and waited. In the end it took
over two hours to download the android-22 SDK; the system image is 13Gb!
So that's a bit of a strike against PhoneGap.
While I was waiting for android-22 to download, I took a look at Kivy.
As a Python enthusiast, I wanted to like Kivy best.
Plus, it's in the Debian repositories: I installed it with
sudo apt-get install python-kivy python-kivy-examples
They have a nice
tutorial for writing a Hello World app on their site. You write
it, run it locally in python to bring up a window and see what the
app will look like. But then the tutorial immediately jumps into more
advanced programming without telling you how to build and deploy
your Hello World. For Android, that information is in the
Packaging Guide. They recommend an app called Buildozer (cute name),
which you have to pull from git, build and install.
buildozer android debug deploy run
got started on building ... but then I noticed that it was attempting
to download and build its own version of apache
(sort of a Java version of
). I already have ant --
I've been using it for weeks for building my own Java android apps.
Why did it want a different version?
The file buildozer.spec in your project's
directory lets you uncomment and customize variables like:
# (int) Android SDK version to use
android.sdk = 21
# (str) Android NDK directory (if empty, it will be automatically downloaded.)
# android.ndk_path =
# (str) Android SDK directory (if empty, it will be automatically downloaded.)
# android.sdk_path =
Unlike a lot of Android build packages, buildozer will not inherit
variables like ANDROID_SDK, ANDROID_NDK and ANDROID_HOME from your
environment; you must edit buildozer.spec.
But that doesn't help with ant.
Fortunately, when I inspected the Python code for buildozer itself, I
discovered there was another variable that isn't mentioned in the
default spec file. Just add this line:
android.ant_path = /usr/bin
Next, buildozer gave me a slew of compilation errors:
kivy/graphics/opengl.c: No such file or directory
... many many more lines of compilation interspersed with errors
kivy/graphics/vbo.c:1:2: error: #error Do not use this file, it is the result of a failed Cython compilation.
I had to ask on #kivy to solve that one. It turns out that the current
version of cython, 0.22, doesn't work with kivy stable. My choices were
to uninstall kivy and pull the development version from git, or to uninstall
cython and install version 0.21.2 via pip. I opted for the latter option.
Either way, there's no "make clean", so removing the dist and build
directories let me start over with the new cython.
apt-get purge cython
sudo pip install Cython==0.21.2
rm -rf ./.buildozer/android/platform/python-for-android/dist
rm -rf ./.buildozer/android/platform/python-for-android/build
Buildozer was now happy, and proceeded to download and build Python-2.7.2,
pygame and a large collection of other Python libraries for the ARM platform.
Apparently each app packages the Python language and all libraries it needs
into the Android .apk file.
Eventually I ran into trouble because I'd named my python file hello.py
instead of main.py; apparently this is something you're not allowed to change
and they don't mention it in the docs, but that was easily solved.
Then I ran into trouble again:
Exception: Unable to find capture version in ./main.py (looking for `__version__ = ['"](.*)['"]`)
The buildozer.spec file offers two types of versioning: by default "method 1"
is enabled, but I never figured out how to get past that error with
"method 1" so I commented it out and uncommented "method 2".
With that, I was finally able to build an Android package.
The .apk file it created was quite large because of all the embedded
Python libraries: for the little 77-line pong demo,
in the Debian kivy-examples package, the apk came out 7.3Mb.
For comparison, my FeedViewer native java app, roughly 2000 lines of
Java plus a few XML files, produces a 44k apk.
The next step was to make a real mini app.
But when I looked through the Kivy examples, they all seemed highly
specialized, and I couldn't find any documentation that addressed issues
like what widgets were available or how to lay them out. How do I add a
basic text widget? How do I put a button next to it? How do I get
the app to launch in portrait rather than landscape mode?
Is there any way to speed up the very slow initialization?
I'd spent a few hours on Kivy and made a Hello World app, but I
was having trouble figuring out how to do anything more. I needed a
change of scenery.
By this time, android-22 had finally finished downloading.
I was ready to try PhoneGap again.
cordova platforms add android
worked fine. It took a long time, because it downloaded the huge gradle
build system rather than using something simpler like ant. I already have
a copy of gradle somewhere (I downloaded it for the OsmAnd build), but
it's not in my path, and I was too beaten down by this point to figure
out where it was and how to get cordova to point to it.
Cordova eventually produced a 1.8Mb "hello world" apk --
a quarter the size of the Kivy package,
though 20 times as big as a native Java app.
Deployed on Android, it initialized much faster than the Kivy app, and
came up in portrait mode but rotated correctly if I rotated the phone.
to replace pretty much all of the default CSS if you don't want your app
monopolized by the Cordova icon.
The only tricky part was file access: opening a file:// URL
didn't work. I asked on #phonegap and someone helpfully told me I'd
need the file plugin. That was easy to find in the documentation, and
I added it like this:
cordova plugin search file
cordova plugin add org.apache.cordova.file
My final apk, for a small web app I use regularly on Android,
was almost the same size as their hello world example: 1.8Mb.
And it works great: phonegap had no problem playing an audio clip,
something that was tricky when I was trying to do the same thing
from a native Android java WebView class.
Summary: How do Kivy and PhoneGap compare?
This has been a long article, I know. So how do Kivy and PhoneGap compare,
and which one will I be using?
They both need a large amount of disk space for the development environment.
I wish I had good numbers to give you, but I was working with
both systems at the same time, and their packages are scattered all
over the disk so I haven't found a good way of measuring their size. I
suspect PhoneGap is quite a bit bigger, because it uses gradle rather
than ant and because it insists on android-22.
On the other hand, PhoneGap wins big on packaged application size:
its .apk files are a quarter the size of Kivy's.
PhoneGap definitely wins on documentation. Kivy has seemingly lots of
documentation, but its tutorials jumped around rather than following
a logical sequence, and I had trouble finding answers to basic
questions like "How do I display a text field with a button?"
PhoneGap doesn't need that, because the UI is basic HTML and CSS --
limited though they are, at least most people know how to use them.
Finally, PhoneGap wins on startup speed. For my very simple test app,
startup was more or less immediate, while the Kivy Hello World app
required several seconds of startup time on my Galaxy S4.
Kivy is an interesting project. I like the ant-based build, the
straightforward .spec file, and of course the Python language.
But it still has some catching up to do in performance and documentation.
For throwing together a simple app and packaging it for Android, I
have to give the win to PhoneGap.