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|Further Reading||Qt Signals and Slots in python, Introduction to PyQT4, Using PyKDE4|
The aim of this tutorial is to give a sample class to include Notifications and Jobs to your own python programms, so the user can see what is going on (for example a backup system, that tells you that is backuping right now). It assumes a basic working knowledge of Python and PyKDE4. For now only the Job part is mentioned, 'cause that is the only part I've created right now.
To add the Notification part also to this tutorial.
We start with a minimal KDE Appliciation (Using PyKDE4):
#! /usr/bin/python # -*- coding: utf-8 -*- if __name__ == "__main__": import sys from PyKDE4.kdecore import KCmdLineArgs, KAboutData, KLocalizedString, ki18n from PyKDE4.kdeui import KApplication appName = "default" catalog = "" programName = ki18n ("default") version = "1.0" description = ki18n ("Default Example") license = KAboutData.License_GPL copyright = ki18n ("(c) 2010 Sandro Knauß") text = ki18n ("none") homePage = "techbase.kde.org" bugEmail = "firstname.lastname@example.org" aboutData = KAboutData (appName, catalog, programName, version, description, license, copyright, text, homePage, bugEmail) KCmdLineArgs.init (sys.argv, aboutData) app = KApplication () </code> == Job class == The first step is to have a look to the [http://api.kde.org]. The intersting on is: * [http://api.kde.org/pykde-4.3-api/kdecore/KJob.html KJob(KDE 4.3-PyKDE4)]- unfortunately this documention is only available for KDE 4.3. So we have also a look to the actual C++ Doumentation * [http://api.kde.org/4.x-api/kdelibs-apidocs/kdecore/html/classKJob.html KJob(KJob 4.x-C++API)] So it is easy to write a small Job-Class: <syntaxhighlight lang="python"> from PyQt4.QtCore import QObject,QTimer,QString from PyKDE4.kdecore import KJob class MyJob(KJob): def __init__(self,parent=QObject()): KJob.__init__(self,parent) #We want to have a Suspenable and Killable Job self.setCapabilities(KJob.Capabilities(KJob.Suspendable|KJob.Killable)) #Just a maximum Variable self.max=25 #index self.i=0 def start(self): #initalizing for work self.i=0 #start the actual work in another thread #this function has to terminate, before the work is done QTimer().singleShot(0, self.doWork) def doWork(self): #the actual work try: #if we are killed or suspended just return if self.error() or self.isSuspended(): return except RuntimeError: #if this class is killed before a RuntimeError will raise return #do a peace of hard work self.i+=1 #fortunately we have made a peace of work #-> show this to everybody KJob.setPercent(self,self.i*4) if self.i==self.max: #jeah we have done the bunch of work #send the result signal for showing, that we ended the work self.emitResult() return #just go to sleep for 1000ms than go on QTimer().singleShot(1000, self.doWork) def doSuspend(self): #the surounding function from KJob makes the isSuspended() become True #returns True for signaling that this class supports to suspend return True def doResume(self): #start with work again QTimer().singleShot( 0, self.doWork ) #return True for signaling that this class supports resuming return True def doKill(self): #return True for signaling that we support killing return True </code> ===What is going on?=== * '''MyJob.__init__''': First we create the class and initialize the counter ''i'' and the maximum ''max''. To make is visible for others we set the Capacities, so this job is suspendable and killable. * '''MyJob.start''': Here the pre working setting are made, we will se later for what we use this. After initalizing the Work we start the actual work by using a QTimer. The start method should start the asyncron. * '''MyJob.doWork''': Do actual work and handle, if this job is killed or suspended. * '''MyJob.doSuspend'''/'''MyJob.doResume'''/'''MyJob.doKill''': These function indicate that this feature is supported by this class. ===How to use?=== Just create a instance of this class and start it: <syntaxhighlight lang="python"> job=MyJob(app) job.start() </code> ===We want to know when the jobs done?=== Create a '''SLOT''' to the '''result'''-signal: <syntaxhighlight lang="python"> def handleResult(job): #handleResult Function #it is called when the job is terminating if job.error(): print 'error happend' else: print 'job has terminated successfully' #for terimation the complete application sys.exit() job.result.connect(handleResult) </code> Now we also add '''app.exec_()''' at the end of the main part, to prevent the program to stop before the job is stopped. ===Visual feedback=== Till now, a normal user doesn't see anything what is going on. To change it we have to register the Job to a JobTracker. Now a user will see a progressbar and a suspend and a stop button. So we modify the start method: <syntaxhighlight lang="python"> from PyKDE4.kio import KIO ... def start(self): #register the Job to the JobTracker KIO.getJobTracker().registerJob(self) self.i=0 QTimer().singleShot(0, self.doWork) </code> === Conclusion === Here is the [[Development/Languages/Python/PyKDE_Knotify_Tutorial/MyJob.py|full code]] of this example. Is is very easy to create a Job and make it visible to normal users. Unfortunately I have problems with setting the heading and description, so this will be added in later versions.