position_stop() problem

[JereKuusela]

So I want to get GPS data.

There is method called position_stop() which should (according to PythonForS60_1_4_2.pdf) Stop an ongoing position request.

I want stop GPS retrieving after 10 seconds so basically I need to know a way to stop GPS retrieving.

But when I run stop_position() my program will just quit (even quit Python program).

import positioning

def cb(event):
global GData
GData = event
#gps() will store gps data
gps()
positioning.stop_position()

def getGPS():
positioning.select_module(270526858)
positioning.set_requestors([{"type":"service","format":"application","data":"test_app"}])
positioning.position(course=0,satellites=0, callback=cb, interval=10000000, partial = 1)

[miohtama]

So I want to get GPS data.

There is method called position_stop() which should (according to PythonForS60_1_4_2.pdf) Stop an ongoing position request.

I want stop GPS retrieving after 10 seconds so basically I need to know a way to stop GPS retrieving.

But when I run stop_position() my program will just quit (even quit Python program).

stop_position() must be called in the main thread and not in 1) callback 2) any other thread.

[JereKuusela]

Ok, thanks for the clarification.

[gtannus]

I want a function that tries for 1 minute to get a valid GPS data and than stop GPS. But this has to run in a thread (application might not stop for 1 minute). It seems that gps callback and thread do not work well together. Any ideas?

[mauso]

stop_position() must be called in the main thread and not in 1) callback 2) any other thread.

Is this how it's gonna be in the future too? Because I'd like to use positioning in a multi-threaded application.

[aya42]

I want a function that tries for 1 minute to get a valid GPS data and than stop GPS. But this has to run in a thread (application might not stop for 1 minute). It seems that gps callback and thread do not work well together. Any ideas?

The general structure of a PyS60 program seems to be:

1. Set everything up
2. Wait on an e32.Ao_lock()
3. Process events from other active objects, until you want to quit
4. Signal the lock, and exit

Point is that most of the time, you're at step 3, so as long as none of your event handlers block the main thread, you can do virtually everything in a single thread.

According to the docs, if you use a callback, positioning.position() won't block the thread, so why d'ya need another thread?

I can't test this, cos I'm too lazy to resign PythonScriptShell with permission to use positioning, but...

import e32, positioning

lock = e32.Ao_lock()
data = None
timer = e32.Ao_timer()

def stopApp():
    lock.signal()

def startSearch():
    positioning.position(<insert other params here>, callback=searchCallback)
    timer.after(60, stopSearch)

def stopSearch():
    positioning.stop_position()

def searchCallback(d):
    if dataIsValid(d):
        timer.cancel()
        global data
        data = d
        stopSearch()
        # Do other stuff here

def dataIsValid(d):
    # I guess it's up to you to decide when you have enough info
    if <insert condition here>:
        return True
    else:
        return False

# Setup app here

lock.wait()

As a general rule, most IO functions have a non-blocking option. The only time you really need another thread is when you're CPU-bound (e.g. doing some serious number-crunching) for longer than you're prepared to let the UI be unresponsive for (maybe 100ms or so).

Now, having said all that, if point #1 in the following is true, which I can't confirm...

stop_position() must be called in the main thread and not in 1) callback 2) any other thread.

...then you'll have to do something more complicated, like either wrapping the start/stop positioning method in an e32.ao_callgate(), or if that doesn't work, you'll have to replace the Ao_lock() with something like...

import e32, positioning

running = True
data = None
timer = e32.Ao_timer()
callQueue = []

def stopApp():
    global running
    running = False

def callInMainAo(func, args = (), kwargs = {}):
    callQueue.append((func, args, kwargs))

def startSearch():
    callInMainAo(positioning.position, (<insert other params here>), {'callback': searchCallback})
    timer.after(60, stopSearch)

def stopSearch():
    callInMainAo(positioning.stop_position)

def searchCallback(d):
    if dataIsValid(d):
        timer.cancel()
        global data
        data = d
        stopSearch()
        # Do other stuff here

def dataIsValid(d):
    # I guess it's up to you to decide when you have enough info
    if <insert condition here>:
        return True
    else:
        return False

# Setup app here

while running:
    if not callQueue:
        e32.ao_sleep(0.1)
        continue
    while callQueue:
        func, args, kwargs = calls.pop(0)
        apply(func, args, kwargs)

Just make sure you don't push a blocking call onto the call queue.