PySide 中未处理的信号

Question

我有一个 PySide 应用程序。在此应用程序中，主函数在线程 (AnalysisThread) 中运行。在这个线程中，我用 python 记录器记录了一些东西。然后我添加了一个自定义记录器，它基本上用字符串触发信号。这个信号可能在主线程（GUI线程）中处理，但显然插槽永远不会被触发，但我确信信号self.messageWritten.emit函数被调用（调试器确认这一点）。我做错了什么？

class LogStream(QtCore.QObject):
    messageWritten = QtCore.Signal(str)
    signal_test = QtCore.Signal()

    def write(self, msg):
        if not self.signalsBlocked():
            self.messageWritten.emit(msg)


class QtHandler(logging.Handler):
    def __init__(self, stream):
        logging.Handler.__init__(self)
        self.stream = stream

    def emit(self, record):
        record = self.format(record)
        if record:
            self.stream.write('%s\n' % record)

class AnalysisThread(QtCore.QThread):
    processing_ended = QtCore.Signal()
    processing_failed = QtCore.Signal(Exception, list)

    def __init__(self, analysis):
        super(AnalysisThread, self).__init__()
        self.analysis = analysis

    def run(self):
        try:
            process = Process(target=self.analysis.analyze)
            process.start()
            process.join()
        except Exception as err:
            exec_info = sys.exc_info()
            self.processing_failed.emit(err, exec_info)
        finally:
            self.processing_ended.emit()

class ProcessView(QtGui.QMainWindow):

    def __init__(self):
        super(ProcessView, self).__init__()
        # Log Stream
        self.stream = LogStream()
        self.stream.messageWritten.connect(self.on_log_written)

    def go(self):
        analysis = MyAnalysis()
        # Handler
        handler = QtHandler(self.stream)
        handler.setFormatter(logging.Formatter('(%(levelname)s-%(name)s)  %(message)s'))
        analysis.log.addHandler(handler)
        self.processing = AnalysisThread(analysis)
        self.processing.processing_ended.connect(self.on_processing_ended)

 self.processing.processing_failed.connect(self.on_processing_failed)
        self.processing.start()

    def on_log_written(self, msg):
        print('Message: {}'.format(msg))  # never called

编辑

为了澄清，它是一个多线程应用程序，也是一个多进程应用程序......

Answer 1

由于您在多线程环境中工作，请尝试在连接信号和插槽时指定 Qt.QueuedConnection。

例如：

self.stream.messageWritten.connect(self.on_log_written, QtCore.Qt.QueuedConnection)

Answer 2

回答

我终于找到了解决办法。如前所述，我的应用程序使用多处理，并且日志出现在子进程中，因此父进程永远不会收到信号警报。解决方案是使用multiprocessing.Pipe 在子进程和父进程之间创建“链接”。一个实现可能是

class Streamer(QtCore.QThread):
    messageWritten = QtCore.Signal(str)

    def __init__(self, pipe):
        super(Streamer, self).__init__()
        self.pipe = pipe

    def run(self):
        while True:
            try:
                msg = self.pipe.recv()
            except EOFError:
                break
            else:
                self.messageWritten.emit(msg)

class QtHandler(logging.Handler):
    def __init__(self, stream):
        """Instantiate handler

        :param stream: multiprocessing.Pipe
        """
        logging.Handler.__init__(self)
        self.stream = stream

    def emit(self, record):
        record = self.format(record)
        if record:
            self.stream.send('%s\n' % record)

class ProcessView(QtGui.QMainWindow):

    def __init__(self):
        super(ProcessView, self).__init__()
        # Log Stream
        mother_pipe, child_pipe = Pipe()
        self.stream = child_pipe
        self.streamer = Streamer(mother_pipe)
        self.streamer.daemon = True
        self.streamer.start()
        self.streamer.messageWritten.connect(self.on_log_written)

    def on_log_written(self, msg):
        self.ui.textBrowser_log.insertPlainText(msg)
        txt_max = self.ui.textBrowser_log.verticalScrollBar().maximum()
        self.ui.textBrowser_log.verticalScrollBar().setValue(txt_max)

解释：

主线程 (GUI) 启动。在初始化时，它创建一个multiprocesing.Pipe 来与一个子进程通信，以及一个监听管道末端的守护进程。所以在子进程启动后，它最终会记录一些东西。 QtHandler 拦截消息并通过管道发送。守护进程在管道的另一端接收消息并通过信号messageWritten 将其转发给GUI 线程。最后，这个信号由一个槽处理，将它写入一个QTextBrowser，滚动条被刷新到