Python PyQT：如何从工作线程调用GUI函数？ [英] Python PyQT: How to call a GUI function from a worker thread?

问题描述

我有一个pyqt gui，并调用一个漫长的进程（ffmpeg），我把一个单独的线程不阻止gui。然后，当一个更长命令列表的命令完成时，我想更新一个进度条。问题是，我不能在工作线程中调用gui线程中的一个函数。所以我可以在工作线程中运行一个代码，但是当我用while循环更新进度条并读取代码值时，gui将再次被阻止。我该如何解决呢我目前使用python线程，而不是Qthread。
Thx为任何帮助！

 导入线程，pexpect 
 
 self.cmd_list = [ 'ffmpeg -i file outfile'，'等等] 
 
 self.stop_proc = False 
 self.executeCMD（）
 
 def spawn_ffmpeg_cmd（self） 
 for cmd in self.cmd_list：
 if self.stop_proc == False：
 thread = pexpect.spawn（cmd）
打印\\\
started：％s％cmd 
 cpl = thread.compile_pattern_list（[pexpect.EOF，frame = * \d + fps = * \d +，'（。+）']）
 
 while True：
i = thread.expect_list（cpl，timeout = None）
如果i == 0：＃EOF 
打印子进程退出
 self.pgticker + = 1 
 break 
 elif i == 1：
 frame_number_fps = thread.match.group（0）
 print frame_number_fps 
 thread.close 
 elif i == 2：
 pass 
 self.startButton.setEnabled（True）
 
 
 def executeCMD（self）：
 self.startButton.setEnabled （False）
 self.pgticker = 0 
 threading.Thread（target = self.spawn_ffmpeg_cmd，name =_ proc）。start（）
 
 
 def stopprocess （self）：
 self.stop_proc = True 
 self.cmd_list = [] 
 os.system（'pkill ffmpeg'）
 self.pgticker = len（self.cmd_list） 
 self.startButton.setEnabled（True）
 
 
 def updateProgress（self）：
 pgfactor = 100 / len（self.cmd_list）
 progress = 0.0 
 progress = pgfactor * int（self.pgticker）
 self.progressBar.setProperty（value，progress）
  

解决方案

简而言之：移动到 QThread 并使用Qt的信号和插槽，在线程之间进行通信的方式。

这个答案提供了一些这样的例子：
https://stackoverflow.com/a/6789205/2319400

在你的情况下，使用上面的SomeObject版本可能如下所示：

  class Worker QtCore.QObject）：
 
 madeProgress = QtCore.pyqtSignal（[int]）
 finished = QtCore.pyqtSignal（）
 
 def __init __（self，cmdlist） 
 self.cmdlist = cmdlist 
 
 def run（self）：
 for icmd，cmd in enumerate（self.cmdlist）：
＃执行你的工作
＃processCommand（cmd）
 
＃我们已经取得进展的信号
 self.madeProgress.emit（icmd）
 
＃发出完成的信号 - 重新完成
 self.finished.emit（）
  

然后将此工作人员移动到 QThread 您创建的实例。
按照链接答案的模式，您可以将 madeProgress 信号
连接到 setValue 进度条的插槽：

  workerThread = QThread（）
 workerObject = Worker（cmdlist）
 workerObject.moveToThread（workerThread）
 workerThread.started.connect（workerObject.run）
 workerObject.finished.connect（workerThread.quit）
 
＃创建一个具有最小/最大值根据
＃你的cmdlist的长度
 progressBar = QProgressBar（）
 progressBar.setRange（0，len（cmdlist））
 
＃连接工作进度信号与进度条
 workerObject.madeProgress.connect（progressBar.setValue）
 
＃启动线程（同时启动您的工作）
 workerThread.start（）
  

I have a pyqt gui and calling a long process (ffmpeg) which I put on a separate thread to not block the gui. I then want to update a progress bar when one command of a longer list of commands finishes. The problem is, that I can't call a function in the gui thread out of the worker thread. So I let run a ticker in the worker thread, but when I update the progress bar with a while loop and reading the ticker value, the gui gets blocked again. How can I solve this. I used currently python threading and not Qthread. Thx for any help!

import threading, pexpect

self.cmd_list = ['ffmpeg -i file outfile','and so on']

self.stop_proc = False
self.executeCMD()

def spawn_ffmpeg_cmd(self):
    for cmd in self.cmd_list:
        if self.stop_proc == False:
            thread = pexpect.spawn(cmd)
            print "\nstarted: %s" % cmd
            cpl = thread.compile_pattern_list([pexpect.EOF,"frame= *\d+ fps=*\d+",'(.+)'])

            while True:
                i = thread.expect_list(cpl, timeout=None)
                if i == 0: # EOF
                    print "the sub process exited"
                    self.pgticker += 1
                    break
                elif i == 1:
                    frame_number_fps = thread.match.group(0)
                    print frame_number_fps
                    thread.close
                elif i == 2:
                    pass
    self.startButton.setEnabled(True)


def executeCMD(self):
    self.startButton.setEnabled(False)
    self.pgticker = 0
    threading.Thread(target=self.spawn_ffmpeg_cmd, name="_proc").start()


def stopprocess(self):
    self.stop_proc = True
    self.cmd_list = []
    os.system('pkill ffmpeg') 
    self.pgticker = len(self.cmd_list)
    self.startButton.setEnabled(True)


def updateProgress(self):  
    pgfactor = 100 / len(self.cmd_list)
    progress = 0.0
    progress = pgfactor*int(self.pgticker)
    self.progressBar.setProperty("value", progress)

解决方案

In short: Move to QThread and use Qt's signals and slots, they are the preferred way to communicate between threads.

This answer provides some examples how this could look like: https://stackoverflow.com/a/6789205/2319400

In your case, using the "SomeObject" version from the above could look like this:

class Worker(QtCore.QObject):

    madeProgress = QtCore.pyqtSignal([int])
    finished = QtCore.pyqtSignal()

    def __init__(self, cmdlist):
        self.cmdlist = cmdlist

    def run(self):
        for icmd, cmd in enumerate(self.cmdlist):
            # execute your work
            # processCommand(cmd)

            # signal that we've made progress
            self.madeProgress.emit(icmd)

        # emit the finished signal - we're done
        self.finished.emit()

Then move this worker to a QThread instance you create. Following the pattern from the linked answer, you can then connect the madeProgress signal to the setValue slot of a progressbar:

workerThread = QThread()
workerObject = Worker(cmdlist)
workerObject.moveToThread(workerThread)
workerThread.started.connect(workerObject.run)
workerObject.finished.connect(workerThread.quit)

# create a progressbar with min/max according to
# the length of your cmdlist
progressBar = QProgressBar()
progressBar.setRange(0, len(cmdlist))

# connect the worker's progress signal with the progressbar
workerObject.madeProgress.connect(progressBar.setValue)

# start the thread (starting your worker at the same time)
workerThread.start()

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