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How to compile Qt location example ?

How can I compile the following example?
running these commands does not do it:
qmake -project
qmake
make

http://wiki.forum.nokia.com/index.ph...cation_Example

Re: How to compile Qt location example ?

I didn't check the example, but I suppose there is a .pro file already so you don't need to run "qmake -project". Try running:
qmake <filename>.pro
make

Replace <filename> with the actual name of the .pro file.

Re: How to compile Qt location example ?

Unfortunately, there isn't. The example consists of a single C file containing GTK+ code. :( I would also really like to know how to get the location info in a Qt application.

Re: How to compile Qt location example ?

tmsha,
you can build the sample as follow.
gcc main.c `pkg-config --cflags --libs gtk+-2.0 hildon-1 liblocation`

Re: How to compile Qt location example ?

Hi,

Quote:

Originally Posted by sjaensch (Post 501708)

Unfortunately, there isn't. The example consists of a single C file containing GTK+ code. :( I would also really like to know how to get the location info in a Qt application.

To understand how the liblocation works, please have a look at the developer guide and the liblocation API docs. Further the example is explained in the guide, which is linked on the wiki-page of the example as well. But please be aware, that the general information, you find there is a bit outdated. But the discription of the location example is quite ok.

And I've requested a better documentation on the example's page itself, and It will be improved soon.

Daniel

Re: How to compile Qt location example ?

Quote:

Originally Posted by danielwilms (Post 504731)

I did all of that already and I'm happy to report that I successfully added liblocation support to my Qt application. Still, I find the example lacking, especially considering that it describes itself as a Qt example when clearly it has nothing to do with it.

I have no experience with glib/GTK+ coding. Here are some pointers as to what could be improved:

Use Qt for the UI (obviously).
Show how to integrate the glib event loop into the Qt event loop. My use case: try to get a GPS fix, but show a dialog that allows the user to abort the operation.
How do I need to modify .pro files to make my project compile with liblocation?

As I said, I was able to solve all of these problems. But it also meant that I spent a weekend implementing a feature that could have taken just a few hours at most.

Re: How to compile Qt location example ?

Quote:

Originally Posted by sjaensch (Post 504769)

Use Qt for the UI (obviously).
Show how to integrate the glib event loop into the Qt event loop. My use case: try to get a GPS fix, but show a dialog that allows the user to abort the operation.
How do I need to modify .pro files to make my project compile with liblocation?

As I said, I was able to solve all of these problems. But it also meant that I spent a weekend implementing a feature that could have taken just a few hours at most.

Thanks for the feedback, I will bring them up! Sorry if parts of the documentation weren't clear enough. We will try to improve that.

Daniel

Re: How to compile Qt location example ?

Quote:

Originally Posted by sjaensch (Post 504769)

Use Qt for the UI (obviously).
Show how to integrate the glib event loop into the Qt event loop. My use case: try to get a GPS fix, but show a dialog that allows the user to abort the operation.
How do I need to modify .pro files to make my project compile with liblocation?

As I said, I was able to solve all of these problems. But it also meant that I spent a weekend implementing a feature that could have taken just a few hours at most.

Sounds good. Can you give some pointers on how to do it? Specifially how to integrate the glib event loop with Qt?

I just need to get some gps coordinates from time to time.

Re: How to compile Qt location example ?

Well, I figured it out also. I guess there was no documentation because it was so simple.

Liblocation (and any glib libs, as far as I understood) will run fine inside the Qt event loop. You basically just use the library as you would in a Gtk application.

Re: How to compile Qt location example ?

Hi,

just a small hint. Since the thread started there have been some news. So you could have a look at the QtMobility project for getting the location as well. There is a first tech preview in extras-devel. It is not ready yet, but definitely worth to have a look!

Daniel

Re: How to compile Qt location example ?

Quote:

Originally Posted by kimitake (Post 504647)

tmsha,
you can build the sample as follow.
gcc main.c `pkg-config --cflags --libs gtk+-2.0 hildon-1 liblocation`

I just compiled the example as you described and copied over to the device and run. it compiles and runs without any errors but the program never gets a fix location. is this example working? do I need to do something else to give permission for location services?

thanks

Re: How to compile Qt location example ?

Quote:

Originally Posted by brink (Post 543491)

Hi

I am trying to use location API in a very simple Python QT application but it ends up with a segmentation fault. The code is actually modified from the version using gobject main loop.

It seems that the code crashes (on N900) when I call control.start(). The code can not be obviously tested on scratchbox because there is no GPS available. Any ideas what is wrong?

-- JariM

Code:

import sys

import pdb

from PyQt4 import QtCore, QtGui

import location





def on_error(control, error, data):

    print "location error: %d... quitting" % error

    data.quit()



def on_changed(device, data):

    if not device:

        return

    if device.fix:

        if device.fix[1] & location.GPS_DEVICE_LATLONG_SET:

            print "lat = %f, long = %f" % device.fix[4:6]

            data.stop()



def on_stop(control, data):

    print "quitting"

    data.quit()



def start_location(data):

    data.start()

    return False

    

    

#loop = gobject.MainLoop()



app = QtGui.QApplication(sys.argv)

myWindow = QtGui.QMainWindow()



control = location.GPSDControl.get_default()

device = location.GPSDevice()

control.set_properties(preferred_method=location.METHOD_USER_SELECTED, preferred_interval=location.INTERVAL_DEFAULT)



control.connect("error-verbose", on_error, app)

device.connect("changed", on_changed, control)

control.connect("gpsd-stopped", on_stop, app)

pdb.set_trace()

print device.status



control.start()

#gobject.idle_add(start_location, control)

#loop.run()





myWindow.show()



# Now we can start the UI.

sys.exit(app.exec_())

Re: How to compile Qt location example ?

@multisil: Have you been able to fix your problem with the segmentation fault?

Greetings,
bartenst

Re: How to compile Qt location example ?

Quote:

Originally Posted by bartenst (Post 615319)

@multisil: Have you been able to fix your problem with the segmentation fault?

Greetings,
bartenst

Yes. I have a solution for having QT Main Loop for UI and GTK+ loop for GPS device. The solution is to create a separate thread for GPS (as a QThread). In your main app you have to initialize the thread, but not actually start it before your QT main loop has started. So you have to post a QTimer event to your QT Main Loop to start the GTK+ loop. Also, you have to take care of closing the thread when your app is closing, so you have to implement a method for this in you main app class.

So my main.py would be (I suppose you have a simple QT Designer created UI file my_ui.py with one button (myBtn) and text label (msgLabel)):

Code:

import sys

from my_ui import *

from GPSConnection import *



class myWindow(QtGui.QMainWindow):



#

# Constructor

#

    def __init__(self, parent=None):

      super(myWindow, self).__init__()



#

#  UI myBtn button click handler.

#     

    def myBtnClicked(self):

        if self.gps.fix:

            msg = "Lat: " + str(self.gps.lat) + " Lon: " + str(self.gps.lon)

            self.ui.msgLabel.setText(QtGui.QApplication.translate("MainWindow", msg, None, QtGui.QApplication.UnicodeUTF8))



#

# Application is about to close. We have to clean up the GPS related things, namely

# close the GPS device and quit the GPSConnection thread.

#

    def closingApp(self):

        print "Closing..."

        if self.gps.running:

            self.gps.control.stop()

            self.gps.loop.quit()

       

#

# Handler for a timer event that should happen when the QT Main Loop has started.

# We can safely start the GPSConnection thread, that has its own GTK+ event loop.

#              

    def singleUpdate(self):

        print "Start timer"

        if self.gps.running == False:

            self.gps.run()



#****************************************************************#

#* MAIN APPLICATION                                             *#

#****************************************************************#



#       

# We instantiate a QApplication

#

app = QtGui.QApplication(sys.argv)

MainWindow = myWindow()

MainWindow.ui = Ui_MainWindow()

MainWindow.ui.setupUi(MainWindow)

MainWindow.gps = GPSConnection(app)

MainWindow.show()



#

# Timer for launching the GPS when app starts. The GPSConnection can not be started

# before the QT Main Loop, so this ensures that it starts after we have started

# processing events in the QT Main Loop. GPSConnection class uses GTK+ main loop

# and that is just ok, since we are running GPSConnection in its own thread.

#

gpsLaunchTimer = QtCore.QTimer()

gpsLaunchTimer.singleShot(1000, MainWindow.singleUpdate)



#

# Signals that enable us to catch the event when app is closing 

# so we can close the GPS device and thread. We propably do not need both.

#

QtCore.QObject.connect(app,QtCore.SIGNAL("aboutToQuit()"), MainWindow.closingApp)

#QtCore.QObject.connect(app,QtCore.SIGNAL("lastWindowClosed()"), MainWindow.closingApp)



# 

# Now we can start the UI & QT Main Loop.

#

sys.exit(app.exec_())

and GPSConnection class in GPSConnection.py:

Code:

import os

import location

from PyQt4 import QtCore

import gobject



# This class implements a GPS connection class to the gps device.

# The class can be safely used in QT applications, because this

# class is supposed to be running in its own thread. Also, the

# class implements its own GTK+ event loop.

#

# The GPSConnection thread must not be started before the QT Main

# loop. Instead, use QTimer to generate a start event for the 

# GPSConnection thread. This way, the even is prosessed

# in the QT Main Loop after the loop has been started.

#

# Also, you should implement closingApp method in your QT main loop 

# (in you main window QObject) that takes care of shutting down the 

# GPS device and stops the GPSConnection thread.

#

class GPSConnection (QtCore.QThread) :



#

# Constructor

#

    def __init__(self, app, parent=None):

        super(GPSConnection, self).__init__()

        self.control = location.GPSDControl.get_default()

        self.GPSDevice = location.GPSDevice()

        self.control.set_properties(preferred_method=location.METHOD_USER_SELECTED, preferred_interval=location.INTERVAL_DEFAULT)

        self.GPSDevice.connect("changed", self.onChanged, self.control)

        self.control.connect("error-verbose", self.onError, self)

        self.control.connect("gpsd-stopped", self.onStop, self.control)

        self.lat = 0.0

        self.lon = 0.0

        self.fix = False

        self.running = False

        self.app = app

        self.loop = None

 

#

# GPS error callback handler

#

    def onError (self, control, error, data):

        print "location error: %d... quitting" % error

        self.running = False

        

        if error == location.ERROR_USER_REJECTED_DIALOG:

            print "User didn't enable requested methods"

        elif error == location.ERROR_USER_REJECTED_SETTINGS:

            print "User changed settings, which disabled location"

        elif error == location.ERROR_BT_GPS_NOT_AVAILABLE:

            print "Problems with BT GPS"

        elif error == location.ERROR_METHOD_NOT_ALLOWED_IN_OFFLINE_MODE:

            print "Requested method is not allowed in offline mode"

        elif error == location.ERROR_SYSTEM:

            print "System error"

    

#

# Handler for stopping the GPS device.

#

    def onStop (self, control, data):

        if self.running:

            self.running = False

            print "In onStop method"

            data.stop()



#

# Callback handler for the event when location fix has changed.

#    

    def onChanged (self, device, data):

        print "In inChanged method"

        if not device:

            return

        if device.fix:

            if device.fix[1] & location.GPS_DEVICE_LATLONG_SET:

                self.lat = device.fix[4]

                self.lon = device.fix[5]

                self.fix = True

                    

#

# Start the GPS device.

#

    def start_location(self, data):

        data.start() 

        return False



#

# Start the GTK+ main loop. The loop initializes the start_location callback which actually

# runs the GPS device.

#

    def run(self):

        print "In run"

        self.running = True

        self.loop = gobject.MainLoop()

        gobject.idle_add(self.start_location, self.control)

        self.loop.run()

Hope this helps!

Re: How to compile Qt location example ?

@multisil: Thanks a lot for your posting - it helps me a lot! :)

Re: How to compile Qt location example ?

@multisil: Thanks, it works... but the Segmentation fault comes anyway

I have taken your GPSConnection class unchanged, and initialised it in the way you have done it in the second file. My stripped down application window has a single QListWidget and opens QMessageBox on demand. The application works flawlessly unless I allow start of GPSConnection thread, only start, NO data manipulations. Within a minute or two of using QListWidget and QMessageBox there comes SIGSEGV.

Sorry it does not work in my case, but thanks anyway for the idea and sort of working example.