Python for Android
Go on, tap your app name, then tap the run wheel. After a moment, you should see the spinner dialog appear while your script contacts the Beans'R'Us Web site and requests the current price of coffee (Figure 5). Shortly thereafter, the current price appears in another dialog (Figure 6). Congratulations! The script has been ported to your Android virtual device.
To run a Python script on your physical Android device, install SL4A together with Python for Android on your handset, then transfer your script.
To install SL4A on your physical Android device, enable the Unknown Sources option in your device's Application settings. This setting is required to enable the installation of non-Market apps on your phone. With this done, you can follow the same steps you used when installing SL4A and Python on your emulator. To speed things up a little, install Barcode Scanner from the Android Market and use it to “read” the QR Codes from your desktop screen.
There are a number of ways to get your script onto a real phone. I've found the success of using something like Bluetooth connectivity or USB cabling arrangements can very much depend on the hardware on which you're running. What works on one handset, doesn't on another, and so on. Your mileage may vary depending on your actual device. When I need to transfer a file, I've come to rely on a solution that works no matter which handset I use (as long as the handset can talk to a local Wi-Fi network). What I do is switch on the OpenSSH server on my development PC running Linux, then use the AndFTP file transfer app on the handset to scp files from the desktop to the phone. AndFTP is available from the Android Market as a free download and installs in minutes. Once I connect to my desktop with AndFTP, I can navigate to a directory of my choice, mark the files that I want, then download them to my SD card on the handset.
AndFTP works well, and I've come to depend on it for all my Android file transfers (see Resources). Just be sure to transfer your scripts to /sdcard/sl4a/scripts on the phone to ensure that your script names appear within the SL4A list of scripts.
With your script file transferred to your physical device, start SL4A as before, tap your app's name and tap the run wheel. As expected, your app runs just as it did on the emulator, only faster! I haven't included a screenshot of the app running on a real phone for two reasons. First, it looks exactly the same as it did in the emulator, and second, it's running on your device, so you can take a look at it there!
There's one further kink to SL4A that might interest you. The project includes draft instructions on creating a standalone, downloadable Android APK package (see Resources). Once created, the APK file bundles your custom Python script with information that allows other Android users to install Python for Android automatically onto their handsets and then run your app from the smartphone's main menu of apps. Describing the process of creating the APK likely would take another article, so I leave it to the brave among you to try out the instructions on the SL4A Wiki. To see and learn a little about one such successfully created APK, check out Split Hitter on the Web (see Resources).
Programming your app in Java is not the only option on Android. With SL4A, very capable scripting languages come to Android, taking the platform to a new level of hackability. If you can, get involved. More people means more eyeballs, and more eyeballs means more help and more code. Official support from Google will come if enough programmers get involved, which can only help raise the project's profile within Google's HQ. SL4A is already a good project, and I can only imagine the great project it will be with “official status” bestowed on it by Google. Let's hope this happens sooner rather than later.
You can learn lots more from the wiki documentation hosted at the SL4A Web site. Be sure to browse the Tutorials section of the wiki for links to what others are doing with SL4A. There's also an active (and very friendly) SL4A mailing list that Damon uses to announce new versions, track feature requests, report patches and spread the word about SL4A. If you build an app for Android using SL4A, join the list, and I'll see you there.
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