android internals and memory/processor constraints?

Question

I'm considering creating a screen reader for Android. My questions are as follows. One how much of the internals of Android are exposed through the Java API? I'm looking for things such as system wide notification when text is displayed, notification of a new application being launched, etc. I'd rather not have to modify the kernel source and only allow my app to run on a developer phone. Two, how much processor and memory are left over on the G1 assuming no applications running? Three assuming average use of applications on the phone how much processor and memory are left?
More info
I'm aware that applications should not be designed to work on a specific phone. I picked the G1 because it's the most popular phone currently running Android that I know of. I am looking for lower end system specs that my program would have to fit in, it may run great on a netbook with Android installed but use to much memory and processor to run on most Android handsets.
Update:
There are now two screen reader projects that use Android 1.6, they can be found at http://google-opensource.blogspot.com/2009/10/talkback-open-source-screenreader-for.html http://spiel.thewordnerd.info/

Answer 1

(1) Depends on what you are looking for. You better check for yourself. I am not ware of any assistive technologies in place, but I wasn't looking for them either.

Regarding the two specific capabilities you asked for: (a) Notifications are part of the API. (b) I am not aware that you can be notified on applications being started.

(2/3) I don't the general amount of RAM that is available for apps, but I can give you an practical answer. Your app's process will be killed if it tries to grab more than 16MB. I don't know the exact clock speed, but on the android-dev list it was mentioned that the G1 doesn't run at full speed. The rationale behind it is that among other things more speed would run down the battery much more quickly.

Just another practical matter regarding this question. If you want to discuss the constraints go to the android-dev list.

Answer 2

AFAIK, screen content (text, graphics) of other apps will for security reasons not be exposed in Android. Otherwise one could grab contact info or whatever personal information gets displayed and harvest that for malicious purposes. So developers currently cannot create an Android app that speaks the text displayed by another application, nor capture the screen. This situation is different from Microsoft Windows on the PC, where applications can do pretty much anything they like, such that the user must decide for himself whether the source of any given application is trusted.

Sadly, there is still no screen reader for Android on the market, so it would be great if you or someone else could create it, but it looks like only a direct arrangement with Google could provide the level of trust needed in view of the above security limitations. Since Google is actively working on improving the TTS and integrating it into Donut, it would seem a fairly simple extra step for them to create a basic Narrator-like (as in Windows) screen reader, or offer a similar touch-based accessibility solution as with VoiceOver on the iPhone 3G S.

Best regards,

Peter Meijer

The vOICe for Android http://www.seeingwithsound.com/android.htm