ThreadedCell

ThreadedCell.py

# coding: utf-8
import threading
import ui
import random, time
from random import randint

pyui_data = ''' [
  {
    "selected" : false,
    "frame" : "{{0, 0}, {270, 288}}",
    "class" : "View",
    "nodes" : [
      {
        "selected" : false,
        "frame" : "{{0, 0}, {270, 42}}",
        "class" : "Label",
        "nodes" : [

        ],
        "attributes" : {
          "font_size" : 22,
          "frame" : "{{60, 128}, {150, 32}}",
          "uuid" : "46C39608-B1DD-4CCC-8817-A72CB062E4F0",
          "text" : "test",
          "alignment" : "center",
          "class" : "Label",
          "name" : "lb",
          "font_name" : "<System-Bold>"
        }
      },
      {
        "selected" : false,
        "frame" : "{{0, 40}, {135, 135}}",
        "class" : "ImageView",
        "nodes" : [

        ],
        "attributes" : {
          "frame" : "{{85, 94}, {100, 100}}",
          "class" : "ImageView",
          "name" : "img1",
          "uuid" : "34C10386-4F29-421F-A4C2-14C6219FB3F9"
        }
      },
      {
        "selected" : false,
        "frame" : "{{135, 40}, {135, 135}}",
        "class" : "ImageView",
        "nodes" : [

        ],
        "attributes" : {
          "frame" : "{{85, 94}, {100, 100}}",
          "class" : "ImageView",
          "name" : "img2",
          "uuid" : "34C10386-4F29-421F-A4C2-14C6219FB3F9"
        }
      },
      {
        "selected" : true,
        "frame" : "{{175, 239}, {80, 32}}",
        "class" : "Button",
        "nodes" : [

        ],
        "attributes" : {
          "border_width" : 0.5,
          "frame" : "{{95, 128}, {80, 32}}",
          "title" : "Test",
          "class" : "Button",
          "uuid" : "35CD0683-8263-41B9-B692-384CA67029A0",
          "corner_radius" : 3,
          "font_bold" : false,
          "font_size" : 15,
          "name" : "btn"
        }
      }
    ],
    "attributes" : {
      "enabled" : true,
      "background_color" : "RGBA(1.000000,1.000000,1.000000,1.000000)",
      "tint_color" : "RGBA(0.000000,0.478000,1.000000,1.000000)",
      "border_color" : "RGBA(0.000000,0.000000,0.000000,1.000000)",
      "flex" : ""
    }
  }
]'''



test_images = ['ionicons-ios7-alarm-32.png', 'ionicons-ios7-alarm-outline-32.png', 'ionicons-ios7-albums-32.png', 'ionicons-ios7-albums-outline-32.png', 'ionicons-ios7-arrow-back-32.png', 'ionicons-ios7-arrow-down-32.png', 'ionicons-ios7-arrow-forward-32.png', 'ionicons-ios7-arrow-left-32.png', 'ionicons-ios7-arrow-right-32.png', 'ionicons-ios7-arrow-thin-down-32.png', 'ionicons-ios7-arrow-thin-left-32.png', 'ionicons-ios7-arrow-thin-right-32.png', 'ionicons-ios7-arrow-thin-up-32.png', 'ionicons-ios7-arrow-up-32.png']


__DEBUG__ = False

class CellBase(object):
	def __init__(self, w, h, item_index, threaded = False,  thread_auto_start = False):
		self.item_index = item_index
		
		if __DEBUG__: self.debug_print('entered init')
		self.width = w
		self.height = h
		
		
		# threading stuff
		self.threading = threaded
		self.event = None
		self.thread = None
		
		# activity indicator
		self.act_ind = None
		
		# flags
		self.data_loaded = False
		self.data_loading_error = 0
		
		# debugging
		self.debug = False
		
		# create the view for the cell.
		self.create_cell_contents()
		if thread_auto_start:
			self.start_thread()
		
		if __DEBUG__: self.debug_print('exit init')
		
	def start_thread(self):
		# if we are threaded, and we have a thread that
		# is alive, bug out. if it made sense, these 
		# exta request could be queued. will try to get
		# this going properly first :)
		if self.threading:
			if self.thread:
				if self.thread.isAlive():
					print 'thread failed - thread still running' # debug
					return
					
			# Was going to try and resuse the thread.
			# apprently, you cant. at least try to clean
			# it up
			# i will look at using thread 'with thread'..
			# apprently the Threading module supports
			# the context manager. i need to read more
			if self.thread:
				self.thread = None
			
			self.thread =threading.Thread(target = self.fetch_data)
			
			self.event = threading.Event()
			self.thread.start()
	
	def start_activity(self):
		# if we dont have an activity indicator
		# create one...
		if not self.act_ind:
			self.act_ind = ui.ActivityIndicator()
			self.act_ind.style = 12
			self.add_subview(self.act_ind)
			
			
		#self.act_ind.center = self.center
		self.act_ind.frame = (0,0, self.act_ind.width, self.act_ind.height)
			
		self.act_ind.start()
		self.act_ind.bring_to_front()
	def stop_activity(self):
		# if we have a activity ind. ,try and stop it
		if self.act_ind:
			self.act_ind.stop()
			
	# this method to be overriden in the child
	def create_cell_contents(self):
		# the place you would typically create your
		# cells ui elements
		#self.add_item_id_label()
		self.border_width = .5
		self._set_row_alt_color('tan', 'orange')
	
	# this method to be overriden in the child
	def fetch_data(self):
		self.start_activity()
		
		for i in range(3):
			if self.event.isSet() : 
				self.stop_activity()
				self.data_loaded = 'False'
				self.data_loading_error = 1
				return
			# same as do something
			time.sleep(random.random())
			
		if not self.event.isSet():
			self.set_bgcolor_to_random()
			
	
		self.stop_activity()
		self.data_loaded = True
		self.data_loading_error = 0
			
	def thread_check(self):
		# blah
		if self.event.isSet():
			self.stop_activity()
			return True
		
		return False
			
			
	# aux , helper methods	
	def random_color(self):
		return(randint(0,255) / 255., randint(0,255) / 255., randint(0,255) / 255.)
	
	def set_bgcolor_to_random(self):
		self.background_color = self.random_color()
	
	def get_random_image(self):
		pass

	def _set_row_alt_color(self, color_1, color_2):
		if not self.item_index % 2:
			self.background_color = color_1
		else:
			self.background_color = color_2
			
	def add_item_id_label(self):
		# just add a label to see the item_index.
		# handy for debugging
		
		txt = '{:,}'.format(self.item_index)
		w, h = 10 * len(txt), 20
		f = (self.width - w, 0, w , h)
		lb = ui.Label( frame = f)
		lb.frame = f
		lb.background_color = 'black'
		lb.text_color = 'white'
		lb.text = txt
		lb.alignment = ui.ALIGN_RIGHT
		self.add_subview(lb)
		lb.bring_to_front()

	# might need this if a single frame
	def layout(self):
		pass
	
	# no need to add a btn to the view for a click
	# event. this works very well.
	# As long as we are ok with the whole cell 
	# ignoring, touch_began, touch_moved. Of course,
	# other opporturnities to use these events.
	# KISS at the moment :)
	def touch_ended(self, touch):
		self.cell_clicked()
	
	# override this method if you want click events
	def cell_clicked(self):
		print self.item_index #debug
		pass
		
	# explicity call this method, to free up
	# resources. whatever they maybe. dont rely on
	# __del__
	# can override this method, but then have to do all
	# your own clean up. The general idea is to get 
	# this method working enough so you dont need to
	# override it.
	# hmmm, will add a callback, that if set, this 
	# method will call it.
	def release(self):
		
		# deal with the threading first
		if self.threading:
			if self.thread:
				if self.thread.isAlive():
					self.event.set()
				
		self.stop_activity()
		
		# call a user release method. one that can
		# be overriden without disturbing this method!
		# Not sure about the placement of this call. 
		# i was tempted to put it at the end of this
		# method, would mean all the subviews would 
		# have been removed! hmmmm, not sure
		self.user_release()
		
		# remove ourself from the superview
		# maybe this is a stupid idea. Maybe
		# smarter for the caller to remove us?
		if hasattr(self, 'superview'):
			self.superview.remove_subview(self)

		# this would not always be required. but
		# i found when a button for example has a
		# action attached, even internal to this
		# class. Memory is not being released unless
		# the subviews are removed. thats only one
		# example. could be others, if using other
		# callbacks such as delegates.
		
		for sv in self.subviews:
			self.remove_subview(sv)
		
		self.thread = None
		
	
	# if you need to release memory/resources in the 
	# child, override this method. Its called from
	# inside the release method. threads are stopped
	# and cleaned up, all views are still avaliable
	# and released after this method returns.
	def user_release(self):
		pass
	
	
	#debugging
	def debug_print(self, msg):
		print '{} , item {}'.format(msg, self.item_index)


class TestCellVirtualViewCell2(ui.View , CellBase):
	def __init__(self, w, h, item_index, Threaded = False, auto_start_thread =True):
		CellBase.__init__(self, w, h , item_index, threaded = Threaded, thread_auto_start = auto_start_thread)
		
		self.cust_view = None
		self.add_item_id_label()
	
	# This method is not threaded, is overrided method
	# from Cellbase. is called automatically.
	def create_cell_contents(self):
		self.cust_view = ui.load_view('Cell_layout')
		self.cust_view.frame = self.frame
		self.add_subview(self.cust_view)
		self.cust_view.border_width = .5
		
		self.cust_view['lb'].text = 'hello world'
		self.cust_view['img1'].image = rand_image()
		
		self.mylabel =  self.cust_view['lb']
		
		# this a limitation i dont understand. 
		# in the thread, i can not access 
		# self.cust_view['img2']. i am sure its easy 
		# to know why, but i dont know why.
		self.img2 = self.cust_view['img2']
		self.start_activity()
		
	# this method is overridden from Cellbase and
	# is called on a thread. is called from Cellbase
	def fetch_data(self):
		# simulate loading a web resource
		time.sleep(random.random())
		
		# this is a method in Cellbase class. 
		# a way to exit the thread
		if self.thread_check():return
		
		time.sleep(random.random())
		if self.thread_check():return
		
		time.sleep(random.random())
		if self.thread_check():return
		
		time.sleep(random.random())
		if self.thread_check():return
		
		time.sleep(random.random())
		if self.thread_check():return
		
		if self.thread_check():return
		self.img2.image = rand_image()
		# in the non threaded code, i can access 
		# self.cust_view['lb'].text, in this method,
		# creates an exeception. basically, 
		# self.cust_view['lb'] evaluates to None 
		
		# THIS FAILS
		#self.cust_view['lb'].text = 'Loaded'
		# THIS IS OK!
		self.mylabel.text = 'Loaded'
		self.stop_activity()
	
def rand_image():
	# just return an image from, a list (subset)
	# of pythonista built in images.
	# testing/demo purposes
	return ui.Image.named(random.choice(test_images))


# for testing purposes, need to write out a pyui file
def create_pyui_file(file_name):
	import os
	import console
	
	if os.path.isfile(file_name):
		return True
	
	result = console.alert('Please pay attention!', 'To proceed, need to write a pyui file to the same directory as this file.', "It's Ok")
	if result <> 1 :
		return False
		
	with open(file_name, 'wb') as file:
		file.write(pyui_data)
		
	return True
	

def StandAloneTest(w, h, present):
	v = ui.View(frame = (0,0,w, h))
	
	item_w = w / 2
	item_h = h / 2
	# in this demo, the cells thread is being started
	# manually at the end of the loop. Can pass
	# True to auto_start_thread and remove the 
	# cell.start_thread() call. 
	for i in range(0,4):
		cell= TestCellVirtualViewCell2(item_w, item_h, i, Threaded = True, auto_start_thread = False)
		cell.frame = ((i % 2) * item_w, (i / 2) * cell.height , cell.width, cell.height)
		v.add_subview(cell)
		cell.start_thread()
	v.present(present)

if __name__ == '__main__':
	pyui_file_name = 'Cell_layout.pyui'
	if create_pyui_file(pyui_file_name):
		w, h = 540, 576
		StandAloneTest(w,h, 'sheet')
	else:
		print 'application aborted!'