Question

我试图从多个线程更新pyqt QProgressBar，根据我的理解，最好的方法是将信号发送回主GUI线程（我尝试将QProgressBar对象传递给工作线程）虽然它似乎确实有效但我在翻译中得到了大量的警告。在下面的代码中，我设置了一个progressSignal信号并将其连接到一个线程（现在）只打印发出的任何信息。然后我从每个线程中发出总百分比。我知道这可以在线程之外工作，只需在第47行抛出一个随机发射，这确实是通过。然而，第36行的发射不会触发任何东西，所以它似乎永远不会通过......

import Queue, threading
from PyQt4 import QtCore
import shutil
import profile

fileQueue = Queue.Queue()

class Communicate(QtCore.QObject):

    progressSignal = QtCore.pyqtSignal(int)

class ThreadedCopy:
    totalFiles = 0
    copyCount = 0
    lock = threading.Lock()

    def __init__(self, inputList, progressBar="Undefined"):
        self.totalFiles = len(inputList)

        self.c = Communicate()
        self.c.progressSignal.connect(self.updateProgressBar)

        print str(self.totalFiles) + " files to copy."
        self.threadWorkerCopy(inputList)


    def CopyWorker(self):
        while True:
            self.c.progressSignal.emit(2000)
            fileName = fileQueue.get()
            shutil.copy(fileName[0], fileName[1])
            fileQueue.task_done()
            with self.lock:
                self.copyCount += 1
                percent = (self.copyCount * 100) / self.totalFiles
                self.c.progressSignal.emit(percent)

    def threadWorkerCopy(self, fileNameList):

        for i in range(16):
            t = threading.Thread(target=self.CopyWorker)
            t.daemon = True
            t.start()
        for fileName in fileNameList:
            fileQueue.put(fileName)
        fileQueue.join()
        self.c.progressSignal.emit(1000)

    def updateProgressBar(self, percent):
        print percent

更新：

带有gui的样本。这个运行但非常不稳定，它经常崩溃，UI做了一些奇怪的事情（进度条没有完成，等等）

Main.py：

import sys, os
import MultithreadedCopy_5
from PyQt4 import QtCore, QtGui

def grabFiles(path):
    # gets all files (not folders) in a directory
    for file in os.listdir(path):
        if os.path.isfile(os.path.join(path, file)):
            yield os.path.join(path, file)

class MainWin(QtGui.QWidget):

    def __init__(self):
        super(MainWin, self).__init__()
        self.initUI()

    def initUI(self):
        self.progress = QtGui.QProgressBar()

        box = QtGui.QVBoxLayout()
        box.addWidget(self.progress)
        goBtn = QtGui.QPushButton("Start copy")
        box.addWidget(goBtn)

        self.setLayout(box)

        goBtn.clicked.connect(self.startCopy)

    def startCopy(self):
        files = grabFiles("folder/with/files")
        fileList = []
        for file in files:
            fileList.append([file,"folder/to/copy/to"])

        MultithreadedCopy_5.ThreadedCopy(fileList, self.progress)

def main():
    app = QtGui.QApplication(sys.argv)
    ex = MainWin()
    ex.show()
    sys.exit(app.exec_())

if __name__ == "__main__":
    main()

MultithreadedCopy_5.py：

import Queue, threading
from PyQt4 import QtCore
import shutil
import profile

fileQueue = Queue.Queue()

class Communicate(QtCore.QObject):

    progressSignal = QtCore.pyqtSignal(int)

class ThreadedCopy:
    totalFiles = 0
    copyCount = 0
    lock = threading.Lock()

    def __init__(self, inputList, progressBar="Undefined"):
        self.progressBar = progressBar
        self.totalFiles = len(inputList)

        self.c = Communicate()
        self.c.progressSignal.connect(self.updateProgressBar, QtCore.Qt.DirectConnection)

        print str(self.totalFiles) + " files to copy."
        self.threadWorkerCopy(inputList)


    def CopyWorker(self):
        while True:
            fileName = fileQueue.get()
            shutil.copy(fileName[0], fileName[1])
            fileQueue.task_done()
            with self.lock:
                self.copyCount += 1
                percent = (self.copyCount * 100) / self.totalFiles
                self.c.progressSignal.emit(percent)

    def threadWorkerCopy(self, fileNameList):
        for i in range(16):
            t = threading.Thread(target=self.CopyWorker)
            t.daemon = True
            t.start()
        for fileName in fileNameList:
            fileQueue.put(fileName)
        fileQueue.join()

    def updateProgressBar(self, percent):
        self.progressBar.setValue(percent)

#profile.run('ThreadedCopy()')

Answer 1

您的示例存在两个主要问题。

首先，发出信号的对象是在main / gui线程中创建的，因此它发出的任何信号都不会是跨线程的，因此不是线程安全的。对此明显的解决方案是在工作线程的目标函数中创建信号对象 - 这意味着每个线程必须有一个单独的实例。

其次，目标函数内的while循环永远不会终止，这意味着在当前复制操作完成后，每个ThreadedCopy对象将保持活动状态。由于所有这些对象共享同一队列，因此如果尝试重复复制操作，则行为将变得不可预测。显而易见的解决方案是在队列为空时突破while循环。

下面是 MultithreadedCopy_5.py 的重写，应该可以解决这些问题。但是，正如评论中所述，我仍然强烈建议在这种情况下使用QThread而不是python线程，因为它可能会提供更强大，更易于维护的解决方案。

import Queue, threading
from PyQt4 import QtCore
import shutil
import profile

fileQueue = Queue.Queue()

class Communicate(QtCore.QObject):
    progressSignal = QtCore.pyqtSignal(int)

class ThreadedCopy:
    totalFiles = 0
    copyCount = 0
    lock = threading.Lock()

    def __init__(self, inputList, progressBar="Undefined"):
        self.progressBar = progressBar
        self.totalFiles = len(inputList)
        print str(self.totalFiles) + " files to copy."
        self.threadWorkerCopy(inputList)

    def CopyWorker(self):
        c = Communicate()
        c.progressSignal.connect(self.updateProgressBar)
        while True:
            try:
                fileName = fileQueue.get(False)
            except Queue.Empty:
                break
            else:
                shutil.copy(fileName[0], fileName[1])
                with self.lock:
                    self.copyCount += 1
                    percent = (self.copyCount * 100) / self.totalFiles
                    c.progressSignal.emit(percent)
                fileQueue.task_done()

    def threadWorkerCopy(self, fileNameList):
        if fileQueue.empty():
            for i in range(16):
                t = threading.Thread(target=self.CopyWorker)
                t.daemon = True
                t.start()
            for fileName in fileNameList:
                fileQueue.put(fileName)
            fileQueue.join()

    def updateProgressBar(self, percent):
        self.progressBar.setValue(percent)

Answer 2

主要问题是发送信号和接收之间的时间延迟，我们可以使用processEvents()缩短时间：

您可以在程序繁忙时偶尔调用此功能执行长操作（例如复制文件）。

def CopyWorker(self):
    while True:
        fileName = fileQueue.get()
        shutil.copy(fileName[0], fileName[1])
        fileQueue.task_done()
        with self.lock:
            self.copyCount += 1
            print(self.copyCount)
            percent = (self.copyCount * 100) / self.totalFiles
            self.c.progressSignal.emit(percent)
            QtCore.QCoreApplication.processEvents()

pyqt从线程线程发出信号

2 个答案: