Steve On Java

One of my coauthors on the upcoming Pro Android Flash title, Oswald Campesato, and I had the pleasure of speaking to the San Francisco Android User Group.  It was a packed audience with around 150 eager Android developers who wanted to hear how they could use Flash on their devices (they were a great audience).  Here is what some of them had to say about the meetup:

• 
  Alec Dara-Abrams

  Stephen and Oswald gave a very good over view of Flash development on Android. Like a number of other SF Android speakers, packing the hour or so with the right level of technical detail. Thanks to them also for being responsive to audience questions – not so easy I’d guess with 100+ people out there past the lighting for the video. I’m looking forward to following Stephen’s blog.

• 
  Drew Dara-Abrams

  Stephen and Oswald gave a good overview of the current state of Flash on Android. Unfortunately the Adobe tools and their book won’t be out until spring, but I appreciated all the working examples of code that Stephen demonstrated. I’ll definitely look for their book when it comes out.

• 
  Francisco Carretero

  Looks like an incredibly useful topic for android for giving android that push to the next level.

As I promised folks in the audience, here is a copy of the full presentation.  Lots of this information was added very recently from different chapters in our book, so it is definitely the latest and greatest source of information on what you can do with Flash on mobile devices:

I will be posting examples from the book on this blog over the next few weeks.  Please follow my blog if you are interested to see the latest examples of Flash Android capabilities.

I have been busily working away at getting Visage ready for developing Android applications. It is a great fit, because Android converts regular Java class files into its special class format, and the Visage compiler happens to generate Java class files. Also, Android is desperately in need of some TLC on their APIs (more on this in a future blog).

So why use Visage for coding Android applications? We do a yearly Hack-a-Thon event at my company (this year called the GXS Xathon). The winning application was written by Tim McNamara, one of my coworkers, and happened to be an Android application.  I decided to do a small port of his code to see if I could improve the maintainability using Visage.  Here is a screenshot of the application:

A base settings page for an application.  It uses a couple edit text fields, several lists, and takes advantage of the summary line to display the current values.  The original version included:

• A Java PreferenceActivity class file
• An XML UI layout descriptor
• Another XML file for array resources

Believe it or not, this is the minimum necessary set of files to create the above screen.  In converting this to Visage, my goal was to get rid of a lot of the redundancy and glue code needed to work across 3 different files.

The end results of the conversion were as follows:

While the numbers are impressive, what really matters is the code.

Here is the final Visage code for the settings page:

public class Settings extends PreferenceActivity {
    var senderPref:ListPreference;
    var receiverPref:ListPreference;
    var statusPref:ListPreference;
    var pollingPref:ListPreference;
    var passwordPref:EditTextPreference;
    var usernamePref:EditTextPreference;

    override var screen = PreferenceScreen { // 1
        preferences: [
            PreferenceCategory { // 1
                "Preferences" // 2
                preferences: [
                    usernamePref = EditTextPreference { // 1...
                        "Username" // 2
                        key: "usernamePref"
                        summary: bind if (usernamePref.text == "") "Currently undefined" else "Current value: {usernamePref.text}" // 3
                    }
                    passwordPref = EditTextPreference {
                        "Password"
                        key: "passwordPref"
                        summary: bind passwordPref.text.replaceAll(".", "*"); // 3
                    }
                    pollingPref = ListPreference {
                        "Polling Interval"
                        key: "pollingPref"
                        defaultValue: "60000"
                        entries: ["30 seconds", "1 minute", "5 minutes", "10 minutes", "15 minutes", "30 minutes", "1 hour"] // 4
                        entryValues: ["30000", "60000", "300000", "600000", "900000", "1800000", "3600000"] // 4
                        summary: bind pollingPref.entry
                    }
                ]
            }
            PreferenceCategory {
                "Filter"
                def CLEAR = "\{Clear Filter\}"; // 5
                preferences: [
                    statusPref = ListPreference {
                        def status = [CLEAR, "HEALTHY", "WARNING", "DOWN"]; // 5
                        "Filter By Status"
                        key: "statusPref"
                        defaultValue: CLEAR
                        entries: status
                        entryValues: status
                        summary: bind if (statusPref.value == CLEAR) "Select a status to filter on." else "Current value: {statusPref.value}"
                    }
                    senderPref = ListPreference {
                        def senders = [CLEAR, for (s in ConnectionService.getSenderNameList()) s];
                        "Filter By Sender"
                        key: "senderPref"
                        defaultValue: CLEAR
                        entries: senders
                        entryValues: senders
                        summary: bind if (senderPref.value == CLEAR) "Select a sender to filter on." else "Current value: {senderPref.value}"
                    }
                    receiverPref = ListPreference {
                        def receivers = [CLEAR, for (r in ConnectionService.getReceiverNameList()) r];
                        "Filter By Receiver"
                        key: "receiverPref"
                        defaultValue: CLEAR
                        entries: receivers
                        entryValues: receivers
                        summary: bind if (receiverPref.value == CLEAR) "Select a receiver to filter on." else "Current value: {receiverPref.value}"
                    }
                ]
            }
        ]
    }
}

While I am not going to include the full original Android code (200 lines is a lot of code!), here are some of the changes that made the Visage version much more succinct (the below bullets match the numbers in the comments above):

1. The Visage object literal syntax is more concise than XML and just as readable!
2. Default properties make the object literal syntax even more concise
3. One bind call can replace dozens of lines of code to setup and instantiate event listeners
4. No need to declare arrays in a separate file (yes, we have real data types)
5. This is a real programming language, so you can use constants and variables to repeat arguments (try doing that in XML!)

All of the technology here is real, but getting a completed set of APIs that covers all of the things you can accomplish in Android is still a work in progress.

If you are interested in helping out with this, please join the Visage Developers mailing list.  I will be posting instructions there soon on how to access the bleeding edge Android Visage repository, and contribute to the growing set of Android APIs.