Simple (and not very robust) script that maps the View items of an Android activity layout to an Activity class.

lay2act.rb

#!/usr/bin/env ruby
=begin
  _             ____            _
 | | __ _ _   _|___ \ __ _  ___| |_
 | |/ _` | | | | __) / _` |/ __| __|
 | | (_| | |_| |/ __/ (_| | (__| |_
 |_|\__,_|\__, |_____\__,_|\___|\__|
          |___/

lay2act aims to be a very simple (and not very robust) script that maps the View
items of an Android activity layout to an Activity class. This script does not
fix imports, your IDE has to do it itself.

LICENSE
	"THE BEER-WARE LICENSE" (Revision 42):
	<kevin.gillieron@gw-computing.net> wrote this file. As long as you retain
	this notice you can do whatever you want with this stuff. If we meet some
	day, and you think this stuff is worth it, you can buy me a beer in return
	Kevin Gillieron

DEPENDENCIES
	- ruby (it should work with any version of Ruby)
	- nokogiri (gem install nokogiri)

USAGE
	ruby lay2act ANDROID_LAYOUT ANDROID_ACTIVITY

	where ANDROID_LAYOUT is the path to the Android layout file and
	ANDROID_ACTIVITY is the path to the Android Activity class file.
=end

require 'nokogiri'
require 'fileutils'

class View
	attr_reader :type, :id
	def initialize(type="", id="")
		@type = type
		@id = id
	end
end

class String
	def to_camel
		# http://stackoverflow.com/a/11411200/1061579
		self.split('_').inject([]){ |buffer,e| buffer.push(buffer.empty? ? e : e.capitalize) }.join
	end
end

def parse_id(id="")
	id.sub("@+id/", "")
end

def get_views(xml="")
	doc = Nokogiri.XML(xml)
	views = []
	doc.traverse do |node|
		id = node["android:id"]
		next if id == nil
		views << View.new(node.name, parse_id(id))
	end
	views
end

def fmt_attr(view)
	"\tprivate #{view.type} #{view.id.to_camel};"
end

def gen_attrs(views)
	views.inject([]){ |buffer, v| buffer << fmt_attr(v) }.sort.join("\n")
end

def fmt_assign(view)
	"\t\tthis.#{view.id.to_camel} = (#{view.type}) this.findViewById(R.id.#{view.id});"
end

def gen_assign(views)
	views.inject([]){ |buffer, v| buffer << fmt_assign(v) }.sort.join("\n")
end

def usage(status=1)
	puts "usage: #{File.basename($0)} [ANDROID_LAYOUT] [ANDROID_ACTIVITY]"
	exit status
end

begin
	if ARGV.length == 1 && ["-h", "--help"].include?(ARGV[0])
		usage(0)
		# NOTREACHED
	elsif ARGV.length != 2
		STDERR.puts "Invalid # of arguments!"
		usage
		# NOTREACHED
	end

	layout = ARGV[0]
	activity = ARGV[1]

	xml = File.open(layout).readlines.join
	views = get_views(xml)

	tmpFilename = activity + ".tmp"
	output = File.new(tmpFilename, "w")

	begin
		re = Regexp.new("(this\\.)setContentView\\(R\\.layout\\.#{File.basename(layout, ".xml")}\\);")

		File.open(activity).readlines.each do |line|
			output.puts(line)

			if line =~ /^public class \w+Activity/i
				output.puts(gen_attrs(views) + "\n\n")
			elsif re.match(line)
				output.puts("\n" + gen_assign(views))
			end
		end
	ensure
		output.close
	end

	FileUtils.mv(tmpFilename, activity)
end

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