Important: Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

[Moved] How to use QProcess in a loop?



  • Hi All,
    How to use QProcess in a loop and update QProgressBar in Main thread?

    thanks,



  • Don't. Just use the asynchronic API of QProcess (using signals & slots) and you do not need a loop.



  • Hi Andre,

         I have designed a Custom QDialog which has QProgessBar in StatusBar.
    

    I am processing some process which performs some file conversions. Here i have 100s of files to convert and while conversion i have to update the progressbar simultaneously.
    please give some sample code which deals with this kind of case.


  • Moderators

    That sounds like a good job for "Qt Concurrent":http://doc.qt.nokia.com/4.7-snapshot/threads-qtconcurrent.html:-) Check the documentation and examples that come with it.



  • Hi Tobias Hunger,
    well i am using PySide so the one you are suggesting is not available.It would be great if you give me an alternative way to achieve this.

    In My case,

    i have a custom QDialog with 3 QPushButtons-Convert,Cancel,Finished and QProgressBar,QThread,QProcess

    I am running QProcess inside QThread. and created a signal which sends the progressbar value to Main Thread.
    here i am getting an Error: Cannot create children for a parent that is in a different thread

    the 'Convert Button' does the bulk file conversions. So when user clicks on it,
    i am running QThread.

    please help me.



  • Did you read the "wiki article":http://developer.qt.nokia.com/wiki/Threads_Events_QObjects on threading?



  • Hi All,
    Please tell me why i am not able to update progressbar without freezing UI
    @import sys,os

        self.thread=Thread()
        self.thread.setFiles(self.fileNames,self.exe_path)
        self.connect(self.thread,QtCore.SIGNAL("setProgressValue(int)"),self.updateProgressBar)
        self.connect(self.thread,QtCore.SIGNAL("updateLogInfo(QString)"),self.updateLogInfo)
        self.connect(self.thread, QtCore.SIGNAL("finished()"), self.threadFinished)
        self.connect(self.thread, QtCore.SIGNAL("terminated()"), self.threadTerminated)
        self.thread.start()
    

    class Thread(QtCore.QThread):
    setProgressValue=QtCore.Signal(int)
    updateLogInfo=QtCore.Signal(str)
    def init(self,parent=None):
    QtCore.QThread.init(self,parent)
    self.moveToThread(self)
    def setFiles(self,files,exe_path):
    print "setFiles"
    self.files=files
    self.exe_path=exe_path

    def startProcessing(self):
        self.count=0
        self.process=QtCore.QProcess()
        self.process.setReadChannel(QtCore.QProcess.StandardOutput)
        self.process.setProcessChannelMode(QtCore.QProcess.MergedChannels)
        self.connect(self.process,QtCore.SIGNAL("readyReadStandardOutput()"),
        self,QtCore.SLOT("readyReadOutput()"))
        #self.connect(self.process,QtCore.SIGNAL("readyRead()"),
        self,QtCore.SLOT("readyRead()"))
        self.connect(self.process,QtCore.SIGNAL("readyReadStandardError()"),
        self,QtCore.SLOT("readyReadErrorOutput()"))
        self.connect(self.process,QtCore.SIGNAL("finished(int)"),self,QtCore.SLOT("processFinished(int)"))
        self.process.error.connect( self.processError )
        
        for filename in self.files:
            arguments=[]
            arguments.append(filename)
            self.process.start(self.exe_path,arguments)
                
            if self.process.waitForStarted():
                self.process.waitForBytesWritten()
                if not self.process.waitForFinished():
                    print "exe failed:",self.process.errorString()
    def run(self):
        QtCore.QTimer.singleShot(0,self,QtCore.SLOT("startProcessing()"))
        self.exec_()
    
    def readyRead(self):
        if not self.process:
            return 
        print "readyRead"
        result=self.process.readAllStandardOutput()
        self.updateLogData(str(result.data()))
        
    def readyReadOutput(self):
        if not self.process:
            return 
        print "readyReadOutput"
        result=self.process.readAllStandardOutput()
        self.updateLogData(str(result.data()))
        
    def readyReadErrorOutput(self):
        if not self.process:
            return 
        print "readyReadErrorOutput"
        error=self.process.readAllStandardError()
        self.updateLogData(str(error.data()))
                
    def processFinished(self,exitCode):
        if self.process.exitStatus()==QtCore.QProcess.ExitStatus.CrashExit:
            self.updateLogData(self.process.errorString())
        print "processFinished"
        self.updateProgressBarValue(self.count)
        
    def processError(self):
        if not self.process:
            return 
        print "processError"
        self.updateLogData(self.process.errorString())
        
    def updateProgressBarValue(self,value):
        self.emit(QtCore.SIGNAL("setProgressValue(int)"),value)
        
    def updateLogData(self,data):
        self.emit(QtCore.SIGNAL("updateLogInfo(QString)"),data)
    

    @



  • Moved to the language bindings forum.



  • Where is "Moved to the language bindings forum." link please!



  • I moved this thread to the mentioned forum. You find the link at the top of the page in the bread crumbs just above the thread title.


Log in to reply