Fivell/active_admin_active_resource.rb

## active_admin_active_resource.rb
module ActiveAdmin
  module Filters
    module FormtasticAddons
      alias :old_seems_searchable? :seems_searchable?
      def seems_searchable?
        return false if ransacker?
        old_seems_searchable?
      end

      def klass
        @object.try(:object).try(:klass)
      end

      def ransacker?
        klass.try(:_ransackers).try(:key?, method.to_s)
      end

      def scope?
        context = Ransack::Context.for klass rescue nil
        context.respond_to?(:ransackable_scope?) && context.ransackable_scope?(method.to_s, klass)
      end
    end
  end
end

module ActiveAdmin
  module Helpers
    module Collection

      def collection_size(c = collection)
        if c.is_a? ActiveRecord::Relation
          c = c.except :select, :order
          c.group_values.present? ? c.count.count : c.count
        else
          c.respond_to?(:count) ? c.count : 0
        end
      end

    end
  end
end


## payment.rb
class Payment <  MyActiveResource

  schema do
    attribute 'customer_id', :integer
    attribute 'amount', :integer
    attribute 'created_at', :string
    attribute 'success', :boolean
  end

  def self.column_names
    content_columns
  end

  def self.content_columns
    if @content_columns.nil?
      @content_columns = Array.new
      known_attributes.each do |name|
        @content_columns << ResourceColumn.new(name)
      end
    end
    @content_columns
  end

  def self.columns
    content_columns
  end

  class ResourceColumn
    attr_reader :name

    def initialize(name)
      @name = name
    end

    def type
      :string
    end
  end

end

## resource_example.rb
ActiveAdmin.register Payment do

  actions :index
  config.batch_actions = false
  filter :created_at_gteq, as: :date_time_picker

  controller do

    def find_collection
      @search = OpenStruct.new(params[:q] || {})
      result = Payment.find(:all, params: {
                order: params.fetch(:order, 'created_at_desc'),
                page: params.fetch(:page, 1),
                per_page: params.fetch(:per_page, 50),
                q: params[:q] || {}
              })
      #this uses https://github.com/Fivell/activeresource-response,
      # but can be replaced with other  ActiveResource pagination implementation
      limit = result.http_response['X-Limit-Value'].to_i
      offset = result.http_response['X-Offset-Value'].to_i
      total = result.http_response['X-Total-Count'].to_i
      Kaminari.paginate_array(result, limit: limit, offset: offset, total_count: total)
    end
  end
end
	module ActiveAdmin
	module Filters
	module FormtasticAddons
	alias :old_seems_searchable? :seems_searchable?
	def seems_searchable?
	return false if ransacker?
	old_seems_searchable?
	end

	def klass
	@object.try(:object).try(:klass)
	end

	def ransacker?
	klass.try(:_ransackers).try(:key?, method.to_s)
	end

	def scope?
	context = Ransack::Context.for klass rescue nil
	context.respond_to?(:ransackable_scope?) && context.ransackable_scope?(method.to_s, klass)
	end
	end
	end
	end

	module ActiveAdmin
	module Helpers
	module Collection

	def collection_size(c = collection)
	if c.is_a? ActiveRecord::Relation
	c = c.except :select, :order
	c.group_values.present? ? c.count.count : c.count
	else
	c.respond_to?(:count) ? c.count : 0
	end
	end

	end
	end
	end
	class Payment < MyActiveResource

	schema do
	attribute 'customer_id', :integer
	attribute 'amount', :integer
	attribute 'created_at', :string
	attribute 'success', :boolean
	end

	def self.column_names
	content_columns
	end

	def self.content_columns
	if @content_columns.nil?
	@content_columns = Array.new
	known_attributes.each do \|name\|
	@content_columns << ResourceColumn.new(name)
	end
	end
	@content_columns
	end

	def self.columns
	content_columns
	end

	class ResourceColumn
	attr_reader :name

	def initialize(name)
	@name = name
	end

	def type
	:string
	end
	end

	end
	ActiveAdmin.register Payment do

	actions :index
	config.batch_actions = false
	filter :created_at_gteq, as: :date_time_picker

	controller do

	def find_collection
	@search = OpenStruct.new(params[:q] \|\| {})
	result = Payment.find(:all, params: {
	order: params.fetch(:order, 'created_at_desc'),
	page: params.fetch(:page, 1),
	per_page: params.fetch(:per_page, 50),
	q: params[:q] \|\| {}
	})
	#this uses https://github.com/Fivell/activeresource-response,
	# but can be replaced with other ActiveResource pagination implementation
	limit = result.http_response['X-Limit-Value'].to_i
	offset = result.http_response['X-Offset-Value'].to_i
	total = result.http_response['X-Total-Count'].to_i
	Kaminari.paginate_array(result, limit: limit, offset: offset, total_count: total)
	end
	end
	end