module MotionAsync

MotionAsync provides a friendly Ruby wrapper around Android’s AsyncTask.

You can call it directly:

@example

MotionAsync.async do
  # some long task
end

Or include the module to make the async command available wherever you need it

@example

include MotionAsync
...
async do
  # some long task
end

Usage:

Run a block of code in the background:

@example

async do
  # some long operation
end

Specify a block to execute when the operation completes. The return value of the async block is passed in as a parameter:

@example

task = async do
  some_expensive_calculation()
end
task.on :completion do |result|
  p "The result was #{result}"
end

Alternate syntax for the same example:

@example

async.on(:background) do |task|
  some_expensive_calculation()
end.on(:completion) do |result|
  p "The result was #{result}"
end

For progress updates, provide a :progress block, and periodically call progress on the task object in the :background block. The :progress block is executed on the main thread.

@example

async.on(:background) do |task|
  100.times do |i|
    # do some work
    task.progress i
  end
end.on(:progress) do |result|
  p "Progress: #{progress + 1}% complete"
end

:pre_execute is invoked before the async operation begins and :cancelled is called if the task is cancelled.

@example

async.on(:background) do |task|
  # long operation
end.on(:pre_execute) do
  p "About to run a long operation"
end.on(:cancelled) do
  p "Operation cancelled."
end

async returns a reference to the task object (a subclass of AsyncTask); you can hold on to this in case you want to cancel it later. You can see if a task has been cancelled by calling cancelled?

@example @async_task = async do |task|

image_urls.each do |image_url|
  images << load_image(image_url)
  break if task.cancelled?
end

end … def on_stop

@async_task.cancel

end

Delaying execution

The after method works just like async, but takes a float as its first parameter to specify the number of seconds to delay before executing the async block.

after(2) do

p "We did this 2 seconds later"

end

This works fine for relatively short delays (a few seconds at most), but you’d probably want to use a Handler for anything longer.