Languages/Python/PyKDE Knotify Tutorial
Abstract
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.
Further plans
To add the Notification part also to this tutorial.
Instruction
We start with a minimal KDE Appliciation (Using PyKDE4):
#! /usr/bin/python # -*- coding: utf-8 -*- if __name__ == "__main__": importsys fromPyKDE4.kdecoreimport KCmdLineArgs, KAboutData, KLocalizedString, ki18n fromPyKDE4.kdeuiimport 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 = "[email protected]" aboutData = KAboutData (appName, catalog, programName, version, description, license, copyright, text, homePage, bugEmail) KCmdLineArgs.init (sys.argv, aboutData) app = KApplication ()
Job class
The first step is to have a look to the [1]. The intersting on is:
- 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
- KJob(KJob 4.x-C++API)
So it is easy to write a small Job-Class:
fromPyQt4.QtCoreimport QObject,QTimer,QString fromPyKDE4.kdecoreimport KJob classMyJob(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 defstart(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) defdoWork(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) defdoSuspend(self): #the surounding function from KJob makes the isSuspended() become True #returns True for signaling that this class supports to suspend return True defdoResume(self): #start with work again QTimer().singleShot( 0, self.doWork ) #return True for signaling that this class supports resuming return True defdoKill(self): #return True for signaling that we support killing return True
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:
job=MyJob(app) job.start()
We want to know when the jobs done?
Create a SLOT to the result-signal:
defhandleResult(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)
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:
fromPyKDE4.kioimport KIO ... defstart(self): #register the Job to the JobTracker KIO.getJobTracker().registerJob(self) self.i=0 QTimer().singleShot(0, self.doWork)
Setting the job title and description
Now you have the running job and a user can see nice progressbar. However, there is no visible information what job is currently running and what it is doing. To change it we have to emit signal KJob.description in our method MyJob.doWork:
defdoWork(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) self.description.emit(self, "Our Splendid Job", ("Source","counter"), ("Destination","dummy")) 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)
The parameters of this signal are the sending job (anything else than self doesn't make sense here), job title, and two tuples consising of two strings arbitrary that can be used to denote some job details. (consider them as a key-value pair).
Conclusion
Here is the full code of this example.
Is is very easy to create a Job and make it visible to normal users.