[Share] A skeleton for making and testing variable height cells for a ScrollView

JonB

I updated
https://github.com/jsbain/objc_hacks/blob/master/tableview_rowheight.py
and
https://github.com/jsbain/objc_hacks/blob/master/rowheight_example.py

or, in stash just use

git clone https://github.com/jsbain/objc_hacks.git obj_hacks

, in which case you can get updates by cd obj_hacks, then git pull. Then run the rowheight_example script.

I need to handle swizzling in the presence of global clearing. What happens is even though the swizzled method implementation has been retained, its dependencies in the closure are not. I probably need to write the callback to import everything it needs in the def rather than in the module -- or, I need to ensure that dependencies get added to the pythonista_startup module so they don't get cleared.

Phuket2

@JonB l sorry to be a pain. But still does not work. Exactly same as last time. I am definitely using the right version. I used the stash cmd and cloned your git directory. I also restarted Pythonista. Running in 3.5 and have the latest beta from test flight. I tried running from both files.

I get a very strange artifact on the first line. It's been there from the first version I tried. In the pic below, the screen shot is with me pulling down the list so you can see it clearly. Not sure if this is a clue or not. But of course should not be there.

JonB

At a loss here... did you restart pythonista after installing the new script? I am about to upload a new one, which will catch errors and print out if an error is caught. maybe try in pythonista2 as well? It works for me in both betas though. I tried turning off animations as you do, and that works as well, so I am at a loss.... try this new version of tableview_rowheight and see if it spits out errors.

it should look like this

Phuket2

@JonB , hmmmm. Tried the new version. Same Same and not different. I did all you say like restart Pythonista etc. I have even restarted my ipad. I also tried running under 2.7 in the beta 3 app and running in the beta 2.7 app. Each time I see the same result. Also NO errors printed to the console. I seen your error catching statements in the last version. I get exactly the same as the previous pic I posted. Only one caveat to what I said before. I thought I was on the latest 3.x beta. I was not. It had failed to install yesterday. I didn't realise. I can't update it at the moment. There seems to be a global problem with some apple services. I think that's why I can't update right now. But I am only one behind. I will update as soon as I can. Again, I have been trying. Seems weird. You wouldn't think it was a hardware issue. Well, I would think so.
I also tried it (only py 2.7 beta) without disabling the animations in the pythonista_startup , with a forced restart of course. Same result.
I wish I could be more help.

JonB

@Phuket2 If you interested in getting to the bottom of this, lets move the discussion over here
https://github.com/jsbain/objc_hacks/issues/5
I have a set of tests for you to run to help get to the bottom of what is happening...

Phuket2

@JonB , thanks will do.

Phuket2

Just to anyone that had been looking at this thread @JonB resolved the issue I was having with his code ousted here to sizzle. He also mentions in a seperate post. Issues to do with different size data types returned for 32bit and 64bit devices. Anyway it's fixed now. The code is at his git hub repository listed above.
@JonB, thanks for your perseverance. I guess some good info come out of it.

Phuket2

@JonB , sorry I hope you are ok I come back here now you solved the problem.
I have been sided tracked as usual. Trying to learn everything and learning nothing 😱
Ok, to the point.
I just cut up your example to represent how I would like to use the variable height cells. So far ok. It looks very promising. Meaning that getting all the smarts from ui.TableView.

At least in my mind to get this to work the way I think it should work, I had to create a parallel list to store the cells heights to be sure I recover it correctly when your swizzled callback is called.

The reason for my post is maybe I am missing something easy, and can recover the height in a more simple way rather than creating the list.

The other thing is you say:

t_o=objc_util.ObjCInstance(t)
t_o.estimatedRowHeight=44

Is optional. It does not appear it is. Without this seems to create all the cells at once rather than requesting as they come into view. Also crashes without that code.

#!python3
import ui
from random import randint

def make_cell():
	cell = ui.TableViewCell()
	
	h = randint(44, 90)
	cell.height = h
	cell.text_label.text = 'cell height - ' + str(h)
	return cell
	
class MyTableViewDataSource (object):
	def __init__(self):
		self.row_heights = None
	
	def tableview_number_of_sections(self, tableview):
		# Return the number of sections (defaults to 1)
		return 1

	def tableview_number_of_rows(self, tableview, section):
		# Return the number of rows in the section
		num_rows = 500
		if not self.row_heights:
			self.row_heights = [44] * num_rows
		return num_rows

	def tableview_cell_for_row(self, tableview, section, row):
		# Create and return a cell for the given section/row
		cell = make_cell()
		self.row_heights[row] = cell.height
		return cell
		print('in get cell', str(row))
		cell = ui.TableViewCell()
		cell.text_label.text = 'Foo Bar'
		return cell

	def tableview_title_for_header(self, tableview, section):
		# Return a title for the given section.
		# If this is not implemented, no section headers will be shown.
		return 'Some Section'

	def tableview_can_delete(self, tableview, section, row):
		# Return True if the user should be able to delete the given row.
		return True

	def tableview_can_move(self, tableview, section, row):
		# Return True if a reordering control should be shown for the given row (in editing mode).
		return True

	def tableview_delete(self, tableview, section, row):
		# Called when the user confirms deletion of the given row.
		pass

	def tableview_move_row(self, tableview, from_section, from_row, to_section, to_row):
		# Called when the user moves a row with the reordering control (in editing mode).
		pass
		
	def tableview_height_for_section_row(self, tv,section,row):
		print('height -', str(self.row_heights[row]))
		return self.row_heights[row]
		#return 10+(row/5)**2 if row<50 else 10+((100-row)/5)**2

import tableview_rowheight, ui, objc_util
# create a tableview and delegate and datasource, per usual
#tableview_rowheight.setup_tableview_swizzle(False)
t=ui.TableView(frame=(0,0,200,576))
d= MyTableViewDataSource() #ui.ListDataSource([str(x) for x in range(100)])
t.data_source=t.delegate=d

# here i will just create height that grows then shrinks again
#def tableview_height_for_section_row(tv,section,row):
	#return 10+(row/5)**2 if row<50 else 10+((100-row)/5)**2

#d.tableview_height_for_section_row=tableview_height_for_section_row

# this is optional, but speeds up initial display and scrolling
# set to nominal or average height
t_o=objc_util.ObjCInstance(t)
t_o.estimatedRowHeight=44

t.present('sheet')

cook

I wonder if this sort of thing is possible? I don't have any idea because my objc level is 0.1 but it looks very simple compared to other things! What do you think @JonB @Phuket2

http://www.appcoda.com/self-sizing-cells/

JonB

The trick would be getting AutoLayout to work via objc_util. I have seen various autoLayout properties, but have not tried getting them to work.

cook

@JonB where have you seen auto layout properties?

Anyway if we can get this to work it seems quite promising and not much code either! (Hopefully)

I know how to set the estimated row height. When I tried the UITableViewAutomaticDimension ...first of all, I don't know what that is!!! Or how to get it!

JonB

UIViews have a autoresizingMask property, and an addConstraint() method, together these define autolayout, I think. @Webmaster4o, this would be a good addition to ui2, as it gives more powerful layout.

autoresizingMask takes an integer bitmask, which you add up the options you want:

UIViewAutoresizingNone                 = 0
UIViewAutoresizingFlexibleLeftMargin   = 1 << 0
UIViewAutoresizingFlexibleWidth        = 1 << 1
UIViewAutoresizingFlexibleRightMargin  = 1 << 2
UIViewAutoresizingFlexibleTopMargin    = 1 << 3
UIViewAutoresizingFlexibleHeight       = 1 << 4
UIViewAutoresizingFlexibleBottomMargin = 1 << 5

ObjCInstance(v).autoresizeMask=UIViewAutoResizingFlexibleWidth+UIViewAutoResizingWidth

it should be possible to apply these to tableviewcells, and to the tableview itself..

UITableViewAutomaticDimension is -1.0, you set the rowheight to this value.

cook

@jonb ...hmm... This is way over my head. I've tried this but it doesn't work.

import ui
from objc_util import *


class TableData(object):
	def __init__(self):
		self.data = [{'value': str(i), 'height': i+40} for i in range(10)]
	
	def tableview_number_of_rows(self, tableview, section):
		return len(self.data)

	def tableview_cell_for_row(self, tableview, section, row):
		cell = ui.TableViewCell()
		label = ui.Label()
		label.text = self.data[row]['value']
		label.number_of_lines = 0
		label_objc = ObjCInstance(label)
		UIViewAutoresizingFlexibleTopMargin = 1 << 5
		UIViewAutoresizingFlexibleBottomMargin = 1 << 5
		UIViewAutoresizingFlexibleHeight = 1 << 5
		UIViewAutoresizingFlexibleLeftMargin = 1 << 5
		label_objc.autoresizeMask = UIViewAutoresizingFlexibleTopMargin + UIViewAutoresizingFlexibleBottomMargin + UIViewAutoresizingFlexibleHeight + UIViewAutoresizingFlexibleLeftMargin
		label.height = self.data[row]['height']
		cell.content_view.add_subview(label)
		return cell


tv = ui.TableView()
tv.data_source = TableData()
tv_objc = ObjCInstance(tv)
tv_objc.rowHeight = -1.0 #UITableViewAutomaticDimension
tv_objc.estimatedRowHeight = 40.0
tv.present()

... Scratching my head :)

ccc

@cook You have repeated 1 << 5 four times but that is not what @JonB did above. He is flipping different bits while you are flipping the same bit multiple times.

cook

@ccc ... I have no clue what flipping bits do! :)

But even if I apparently flip the bits differently I don't get any bit closer !

I'm in deep water...drowning...and the objc piranhas are coming.

Adjusted code ..maybe a step closer ...(?):

import ui
from objc_util import *


class TableData(object):
	def __init__(self):
		self.data = [{'value': str(i), 'height': i+40} for i in range(10)]
	
	def tableview_number_of_rows(self, tableview, section):
		return len(self.data)

	def tableview_cell_for_row(self, tableview, section, row):
		cell = ui.TableViewCell()
		label = ui.Label()
		label.text = self.data[row]['value']
		label.number_of_lines = 0
		label_objc = ObjCInstance(label)
		UIViewAutoresizingNone = 0
		UIViewAutoresizingFlexibleLeftMargin = 1 << 0
		UIViewAutoresizingFlexibleWidth = 1 << 1
		UIViewAutoresizingFlexibleRightMargin = 1 << 2
		UIViewAutoresizingFlexibleTopMargin = 1 << 3
		UIViewAutoresizingFlexibleHeight = 1 << 4
		UIViewAutoresizingFlexibleBottomMargin = 1 << 5

		label_objc.autoresizeMask = UIViewAutoresizingFlexibleWidth + UIViewAutoresizingFlexibleTopMargin + UIViewAutoresizingFlexibleBottomMargin + UIViewAutoresizingFlexibleHeight
		label.height = self.data[row]['height']
		cell.content_view.add_subview(label)
		return cell


tv = ui.TableView()
tv.data_source = TableData()
tv_objc = ObjCInstance(tv)
tv_objc.rowHeight = -1.0 #UITableViewAutomaticDimension
tv_objc.estimatedRowHeight = 40.0
tv.present()

JonB

Turns out the textlabel already has constraints built in, so all you have to do is:
set number_of_lines=0
set tableview.row_height=-1
set ObjCInstance(tv).estimatedHeight to something nonzero

import ui, faker, random
from objc_util import *

f=faker.Faker()
items=[f.text(random.randint(10,200)) for i in range(20)]

class MyTableViewDataSource (object):

	def tableview_number_of_rows(self, tableview, section):
		# Return the number of rows in the section
		return 20

	def tableview_cell_for_row(self, tableview, section, row):
		# Create and return a cell for the given section/row
		cell = ui.TableViewCell()
		cell.text_label.text = items[row]
		cell.text_label.number_of_lines=0
		return cell


v=ui.TableView()
v.frame=(0,0,320,576)
v.row_height=-1
v.data_source=MyTableViewDataSource()
ObjCInstance(v).estimatedRowHeight=44
v.present('sheet')

Basically we get auto resizing text cells with basically three added lines of code!
@omz -- providing estimatedRowHeight access in ui.TableView would make this more accessible.

cook

@jonb incredible. Will give it a shot.

Thanks for helping (...doing all the work) figure this out. I think it's really useful and also a very easy approach!

cook

@jonb now... Do you think this is possible to do for a view that is added to the content_view of a cell?
Will that require flipping bits?

JonB

turns out autoresizingmask might be the same as flex... addConstraints would be what we want for content_view. I have not tried it yet.

lewisl

I am trying to put images into the rows. This did not work to set a row height.