Polling from a ui.View (built in timers in ui.Views)

Phuket2

This post is deleted!

Phuket2

@enceladus , they thanks for your code samples also.

I modified your update method in the first example. Just quickly, so it would stop after closing the window. Guessing more checks should be done.

def update(self, event_loop):
        if not self.on_screen:
            event_loop.stop()
            return
            
        self.set_needs_display()
        event_loop.call_later(.5, self.update, event_loop)

According to the docs the BaseEventLoop class is not thread safe. I am not good enough to under the implications/restrictions of this both as a standalone as well how it would interact with Pythonista's Threads. Any insights would be appreciated.
Again, for me at least is just to have a reliable and controllable way to easily add a way to call a so called poll/update method on a class, including a ui.View async.

Out of the above implementations again I am not good enough to say which is the best implementation. Appears asyncio is py3+ only. Which is fine by me, other might be looking for a 2.7 solution also.

enceladus

I think that calls in event loop are run on the same thread. Button action (in stop watch example) should be put in the same event loop so that there are no thread-safety issues. As you have mentioned there could be other issues. (My experience in asyncio module is very limited and I am in learning mode.)

def button_action(sender):
    event_loop.call_soon(button_action_event_loop, sender)
    
def button_action_event_loop(sender):
    v1 = sender.superview['view1']    
    if sender.title == 'Reset':
        v1.value = 0
        v1.state = 'stop'
    elif sender.title == 'Start':
        v1.value = 0
        v1.state = 'run'
    elif sender.title == 'Stop':
        v1.state = 'stop'

omz

@Phuket2 I've added something to the latest beta. From the release notes:

In custom ui.View subclasses, you can now implement an update method (no arguments, except for self) that gets called automatically by an internal timer. To make this work, you also have to set the new update_interval attribute. It specifies how often the timer fires (e.g. set to 1.0, the timer fires every second). It defaults to 0.0 (disable update timer) because otherwise this new feature might break existing code that happens to implement a method called update.

I hope this works for you.

Phuket2

@omz , yup pulled another rabbit out of the hat :) was so excited when I seen the email this morning for the new beta. You have seemed to have done a lot. Just did a quick test with the update method. Appears to work perfectly. Just had a button on a form to start and stop the updates by setting the update interval. Very nice. I will do some more tests with opening Dialogs over the top etc... but many thanks, I think this will make a lot of ppl happy. Ok, back to exploring the new features :)

technoway

Is the update_interval, and update, attributes in the latest pythonista?
If now, can I get the beta?

By the way, it would be nice if the update method was an empty method (just "pass") that already existed, so users could set the update_interval and update method in the subclassed view's init method.

And whatever already exists, or is done in the future, thank you for a truly great product!

omz

@technoway It's currently only in the beta. With regards to an empty method in the base class, setting the method in __init__ etc., that's not really possible because the act of implementing the method is a signal to change the behavior (hope that makes sense). The entire update timer machinery isn't initialized at all if your View class doesn't implement update.

technoway

Thank you for the quick reply.

Am I allowed to install the beta version, and if so, where is it?

I am running Pythonista on an iPhone (and iPad too, but I need this particular functionality on my iPhone).

I have purchased both the Python 2.x and the Python 3.x versions of Pythonista for my iPhone.

technoway

Ah, I found the message about sending my apple ID through the e-mail. I'll do that. Thanks again, and sorry for all the noise. (I did search before my last post, but missed the relevant post).

omz

@technoway You should have a beta invite in your email (please check your spam folder if it isn't there).

mikael

@omz, arrgh, spam. I have been patiently waiting for my invite, so long that the spam folder has been purged already. Is it easy for you to resend my invite, or should I just send another request? Sorry.

omz

@technoway I sent the invite to the Gmail address you sent me yesterday. Did you just purge your spam folder?

mikael

@omz, I am not technoway. Sorry for jumping in; I have been waiting for the beta invite in order to test the polling functionality.

omz

@mikael Ah, I'm sorry, I'll send a new invite to the email address you're using for this forum.

mikael

@omz, got it, thanks!

mikael

@omz, some feedback on the update feature, all of it positive:

Very stable and consistent. Stops when the view is closed, no threading hassles.
Very intuitive to use. Changing the update_interval to 0.0 stops updates, and positive numbers start them again.

With my limited Threading skills, I was unable to create stable and predictable UI animations with either ui.delay or custom Threads. With update, no issues. This is my vote for moving the feature out of beta.

omz

@mikael Thanks for your feedback! I appreciate it.

mikael

@Phuket2, thank you for taking this up.

Phuket2

@mikael , thanks all to @omz. When i had to do something threaded or in a loop, I never felt confident about it. I have a small thing now where its just a label update to show when something expires. It's so nice and simple with update mechanism.
My experience has been same as yours. Very stable.

Phuket2

@mikael , I mentioned something in the github issues area about ui.TableViewCell. @omz said just add your view to the cell. I had forgotten @JonB had helped me with this a long time ago. Anyway, i was playing around. The below maybe is not pretty. But I find it interesting and it shows off a few things. Also how well update works. Well i think it does anyway.

EDIT: to see the cool stuff I think you have to tap a cell and also scroll. You can see how things are getting suspended when you scroll. I think its nice

import ui
from random import choice


_color_list = ['purple', 'orange', 'deeppink', 'lightblue', 'cornflowerblue'
               'red', 'yellow', 'green', 'pink', 'navy', 'teal', 'olive',
               'lime', 'maroon', 'aqua', 'silver', 'fuchsia',
               ]


class MyCustomCell(ui.View):
    def __init__(self, parent, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.cell = parent
        self.tableview = None
        self.blink_count = 0
        self.lb = None
        self.frame = self.cell.frame
        self.flex = 'wh'
        self.width -= 10
        self.x = 5
        self.height -= 10
        self.y = 5
        self.alpha = .5
        self.corner_radius = 6

        # this allows the touch events to pass through my subview
        self.touch_enabled = False

        self.update_interval = .2

        lb = ui.Label(frame=(0, 0, 24, 24), bg_color='black',
                      text_color='white', alignment=ui.ALIGN_CENTER)

        lb.center = self.center
        lb.corner_radius = 12

        self.lb = lb
        self.add_subview(lb)

    def rect_onscreen(self):
        '''
        Have to write this method.  Would be nice if this was built in.
        like ui.TableView.is_visible for example.  I know its just some rect
        math, but it means you need to save extra references etc.. to calculate
        it yourself.
        '''
        return True

    def update(self):
        if not self.tableview:
            return

        # I did not implement this yet. A little drunk and having a party today.
        # but gives the idea...
        if not self.rect_onscreen():
            return

        if self.blink_count == 98:
            self.update_interval = 0

        self.blink_count += 1
        self.lb.text = str(self.blink_count)
        self.bg_color = choice(_color_list)


def create_cell():
    '''
    Create and return a ui.TableViewCell. We add a custom ui.View to
    the TableViewCell.content_view. This means our view is sitting on top
    of the normal TableViewCell contents. All is still there.
    Also create an attr in the cell at runtime that points to our custom class.
    I guess this can be done many ways.  I choose this way for the example.
    To me its at least clear for access.
    '''
    cell = ui.TableViewCell()
    myc = MyCustomCell(cell)
    cell.content_view.add_subview(myc)
    cell.my_cell = myc
    return cell


class MyDataSource(object):

    def __init__(self, data):
        self.data = data
        self.sel_item = 0
        self.cells = [create_cell()
                      for _ in range(len(self.data))]

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

    def tableview_cell_for_row(self, tableview, section, row):
        # Create and return a cell for the given section/row
        cell = self.cells[row]
        cell.text_label.text = self.data[row]

        # just showing we can access our class from the my_cell attr
        # we added. In this case I want to save the tableview attr
        cell.my_cell.tableview = tableview
        return cell

    def tableview_did_select(self, tableview, section, row):
        # Called when a row was selected.
        self.select_row(row)

    def select_row(self, sel_row):
        for cell in self.cells:
            cell.accessory_type = ""

        self.cells[sel_row].accessory_type = 'checkmark'
        self.sel_item = sel_row


def get_table(items):
    tbl = ui.TableView(frame=(0, 0, 300, 400))
    tbl.data_source = MyDataSource(items)
    tbl.delegate = tbl.data_source
    return tbl


if __name__ == '__main__':
    v = get_table(['Ian', 'Fred', 'John', 'Paul', 'Gaew', 'Pete',
                   'Ole', 'Christian', 'Mary', 'Susan', 'Juile'
                   'Simone', 'Terry', 'Michael', 'James'])
    v.present(style='sheet', animated=False)