PyQT线程化的最简单方法

Question

我在PyQt中有一个带有功能的GUI
addImage(image_path)。容易想象，当新图像应添加到QListWidget中时被调用。为了检测文件夹中的新图像，我使用了threading.Threadwithwatchdog来检测文件夹中的文件更改，然后该线程addImage直接调用。

QPixmap出于线程安全的原因，这会产生不应在gui线程之外调用的警告。

使此线程安全的最佳和最简单的方法是什么？QThread？信号/插槽？QMetaObject.invokeMethod？我只需要从线程传递一个字符串到addImage。

Answer 1

我相信最好的方法是使用信号/插槽机制。这是一个例子。（注意：请参阅下面的 EDIT ，指出我的方法可能存在的缺陷）。

from PyQt4 import QtGui
from PyQt4 import QtCore

# Create the class 'Communicate'. The instance
# from this class shall be used later on for the
# signal/slot mechanism.

class Communicate(QtCore.QObject):
    myGUI_signal = QtCore.pyqtSignal(str)

''' End class '''


# Define the function 'myThread'. This function is the so-called
# 'target function' when you create and start your new Thread.
# In other words, this is the function that will run in your new thread.
# 'myThread' expects one argument: the callback function name. That should
# be a function inside your GUI.

def myThread(callbackFunc):
    # Setup the signal-slot mechanism.
    mySrc = Communicate()
    mySrc.myGUI_signal.connect(callbackFunc)

    # Endless loop. You typically want the thread
    # to run forever.
    while(True):
        # Do something useful here.
        msgForGui = 'This is a message to send to the GUI'
        mySrc.myGUI_signal.emit(msgForGui)
        # So now the 'callbackFunc' is called, and is fed with 'msgForGui'
        # as parameter. That is what you want. You just sent a message to
        # your GUI application! - Note: I suppose here that 'callbackFunc'
        # is one of the functions in your GUI.
        # This procedure is thread safe.

    ''' End while '''

''' End myThread '''

在GUI应用程序代码中，应该创建新的Thread，为其提供正确的回调函数，然后使其运行。

from PyQt4 import QtGui
from PyQt4 import QtCore
import sys
import os

# This is the main window from my GUI

class CustomMainWindow(QtGui.QMainWindow):

    def __init__(self):
        super(CustomMainWindow, self).__init__()
        self.setGeometry(300, 300, 2500, 1500)
        self.setWindowTitle("my first window")
        # ...
        self.startTheThread()

    ''''''

    def theCallbackFunc(self, msg):
        print('the thread has sent this message to the GUI:')
        print(msg)
        print('---------')

    ''''''


    def startTheThread(self):
        # Create the new thread. The target function is 'myThread'. The
        # function we created in the beginning.
        t = threading.Thread(name = 'myThread', target = myThread, args = (self.theCallbackFunc))
        t.start()

    ''''''

''' End CustomMainWindow '''


# This is the startup code.

if __name__== '__main__':
    app = QtGui.QApplication(sys.argv)
    QtGui.QApplication.setStyle(QtGui.QStyleFactory.create('Plastique'))
    myGUI = CustomMainWindow()
    sys.exit(app.exec_())

''' End Main '''

编辑

三菠萝先生和布伦丹·阿贝尔先生指出了我的作风。确实，该方法在这种特定情况下效果很好，因为您可以直接生成/发射信号。当处理按钮和小部件上的内置Qt信号时，您应该采用另一种方法（如Brendan
Abel先生的回答中所指定）。

three_pineapples先生建议我在StackOverflow中启动一个新主题，以便与GUI进行线程安全通信的几种方法进行比较。我会深入研究问题，明天再做:-)