I am currently working on a project which requires me to use an XML document to render a form on an Android device. The form must be fetched and displayed at run-time. I am wondering if there is a way to tag the form XML, transform it using XSLT into an Android layout XML, and then have the device render it.
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1Just be warned. Android does a lot of work to optimize reading and parsing of those files at run-time. So if you roll your own, be prepared for it to inflate a LOT slower.haseman– haseman2009-12-21 20:30:53 +00:00Commented Dec 21, 2009 at 20:30
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3 Answers
Unfortunately you can't just clone LayoutInflater or use other such tricks to do this -- layout inflation is entirely dependent on the view constructors which take an AttributeSet argument, which are entirely dependent on the Context.obtainStyledAttributes method, which itself is entirely dependent on having a pre-processed binary XML file to be able to do reasonably efficient attribute resolution.
An alternative approach you can explore is to use the aapt tool (or more likely a hacked version of it) on your server, to compile the layouts you generate into the appropriate data. Unfortunately we don't currently have a way to contruct an XmlPullParser from a raw binary blob (it must get this blob from the AssetManager), so there is a fair amount of work to do on both the client and server with this approach. I suspect one can come up with something pretty neat, but it will be lots of work.
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illvm
Considering this is something that needs to be prototyped over the next week and a half I'm thinking that this is not an approach I should investigate until a later date. Would you agree with this? I've done building of UIs from XML at run-time before for desktop and web platforms. We also have an implementation for this for a Windows Mobile application. I might just have to mimic those approaches and investigate aapt later when I have some more time or if/when performance issues arise.
hackbod
Yeah this is not a one week project. :) The easiest route would be to just make a simple XML structure that defines what you need for your layouts, without trying to allow for every possible thing an Android layout can do. Parsing that and turning it into the construction of View layout should be fairly simple; you can add new facilities to your XML format as needed.
Android only contains a built-in way to "inflate" layout XML stored as a layout resource in the APK file. If you want to "inflate" similar (or different) XML from other sources, you will have to implement that yourself, perhaps by cloning some logic from the LayoutInflater class.
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The LayoutInflater.inflate method will take an XmlPullParser as an argument so all you need to do is load your dynamically created XML into a PullParser and pass that into the inflater.
