PyQt-如果已经在运行UI，如何检测并关闭UI? [英] PyQt - how to detect and close UI if it's already running?

问题描述

我正在从Maya中启动UI.如果尚未关闭UI，则再次运行UI将完全冻结Maya(错误事件循环已在运行")

I'm starting the UI from within Maya. If the UI hasn't been closed, running the UI again will completely freeze Maya (with the error "Event Loop is already running")

在重新运行脚本之前手动关闭UI可以防止其冻结.但是我想那不是很实际.

Manually closing the UI before re-running the script will prevent it from freezing up. But I guess that's not really practical.

有没有一种方法可以检测我要运行的UI是否已经存在?并可能用力将其关闭?

Is there a way to detect if the UI I'm trying to run already exists? And possible force close it?

推荐答案

这是使用 QLockFile :

from PyQt5 import QtCore, QtWidgets

lockfile = QtCore.QLockFile(QtCore.QDir.tempPath() + '/my_app_name.lock')

if lockfile.tryLock(100):
    app = QtWidgets.QApplication([])
    win = QtWidgets.QWidget()
    win.setGeometry(50, 50, 100, 100)
    win.show()
    app.exec()
else:
    print('app is already running')

---

Qt Wiki上提供了一些相当简单的C ++解决方案，这些解决方案似乎不再存在.我将其中一个移植到PyQt，并在下面提供了示例脚本.最初的C ++解决方案已分为两类，因为可能不需要消息传递功能.

---

There were a couple of fairly straightforward C++ solutions given on the Qt Wiki which no longer seem to exist. I ported one of them to PyQt, and have provided a sample script below. The original C++ solution has been split into two classes, because the messaging facility may not be needed.

PyQt5 :

from PyQt5 import QtWidgets, QtCore, QtNetwork

class SingleApplication(QtWidgets.QApplication):
    messageAvailable = QtCore.pyqtSignal(object)

    def __init__(self, argv, key):
        super().__init__(argv)
        # cleanup (only needed for unix)
        QtCore.QSharedMemory(key).attach()
        self._memory = QtCore.QSharedMemory(self)
        self._memory.setKey(key)
        if self._memory.attach():
            self._running = True
        else:
            self._running = False
            if not self._memory.create(1):
                raise RuntimeError(self._memory.errorString())

    def isRunning(self):
        return self._running

class SingleApplicationWithMessaging(SingleApplication):
    def __init__(self, argv, key):
        super().__init__(argv, key)
        self._key = key
        self._timeout = 1000
        self._server = QtNetwork.QLocalServer(self)
        if not self.isRunning():
            self._server.newConnection.connect(self.handleMessage)
            self._server.listen(self._key)

    def handleMessage(self):
        socket = self._server.nextPendingConnection()
        if socket.waitForReadyRead(self._timeout):
            self.messageAvailable.emit(
                socket.readAll().data().decode('utf-8'))
            socket.disconnectFromServer()
        else:
            QtCore.qDebug(socket.errorString())

    def sendMessage(self, message):
        if self.isRunning():
            socket = QtNetwork.QLocalSocket(self)
            socket.connectToServer(self._key, QtCore.QIODevice.WriteOnly)
            if not socket.waitForConnected(self._timeout):
                print(socket.errorString())
                return False
            if not isinstance(message, bytes):
                message = message.encode('utf-8')
            socket.write(message)
            if not socket.waitForBytesWritten(self._timeout):
                print(socket.errorString())
                return False
            socket.disconnectFromServer()
            return True
        return False

class Window(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()
        self.edit = QtWidgets.QLineEdit(self)
        self.edit.setMinimumWidth(300)
        layout = QtWidgets.QVBoxLayout(self)
        layout.addWidget(self.edit)

    def handleMessage(self, message):
        self.edit.setText(message)

if __name__ == '__main__':

    import sys

    key = 'app-name'

    # send commandline args as message
    if len(sys.argv) > 1:
        app = SingleApplicationWithMessaging(sys.argv, key)
        if app.isRunning():
            print('app is already running')
            app.sendMessage(' '.join(sys.argv[1:]))
            sys.exit(1)
    else:
        app = SingleApplication(sys.argv, key)
        if app.isRunning():
            print('app is already running')
            sys.exit(1)

    window = Window()
    app.messageAvailable.connect(window.handleMessage)
    window.show()

    sys.exit(app.exec_())

PyQt4 :

# only needed for python2
import sip
sip.setapi('QString', 2)

from PyQt4 import QtGui, QtCore, QtNetwork

class SingleApplication(QtGui.QApplication):
    messageAvailable = QtCore.pyqtSignal(object)

    def __init__(self, argv, key):
        QtGui.QApplication.__init__(self, argv)
        # cleanup (only needed for unix)
        QtCore.QSharedMemory(key).attach()
        self._memory = QtCore.QSharedMemory(self)
        self._memory.setKey(key)
        if self._memory.attach():
            self._running = True
        else:
            self._running = False
            if not self._memory.create(1):
                raise RuntimeError(self._memory.errorString())

    def isRunning(self):
        return self._running

class SingleApplicationWithMessaging(SingleApplication):
    def __init__(self, argv, key):
        SingleApplication.__init__(self, argv, key)
        self._key = key
        self._timeout = 1000
        self._server = QtNetwork.QLocalServer(self)
        if not self.isRunning():
            self._server.newConnection.connect(self.handleMessage)
            self._server.listen(self._key)

    def handleMessage(self):
        socket = self._server.nextPendingConnection()
        if socket.waitForReadyRead(self._timeout):
            self.messageAvailable.emit(
                socket.readAll().data().decode('utf-8'))
            socket.disconnectFromServer()
        else:
            QtCore.qDebug(socket.errorString())

    def sendMessage(self, message):
        if self.isRunning():
            socket = QtNetwork.QLocalSocket(self)
            socket.connectToServer(self._key, QtCore.QIODevice.WriteOnly)
            if not socket.waitForConnected(self._timeout):
                print(socket.errorString())
                return False
            if not isinstance(message, bytes):
                message = message.encode('utf-8')
            socket.write(message)
            if not socket.waitForBytesWritten(self._timeout):
                print(socket.errorString())
                return False
            socket.disconnectFromServer()
            return True
        return False

class Window(QtGui.QWidget):
    def __init__(self):
        QtGui.QWidget.__init__(self)
        self.edit = QtGui.QLineEdit(self)
        self.edit.setMinimumWidth(300)
        layout = QtGui.QVBoxLayout(self)
        layout.addWidget(self.edit)

    def handleMessage(self, message):
        self.edit.setText(message)

if __name__ == '__main__':

    import sys

    key = 'app-name'

    # send commandline args as message
    if len(sys.argv) > 1:
        app = SingleApplicationWithMessaging(sys.argv, key)
        if app.isRunning():
            print('app is already running')
            app.sendMessage(' '.join(sys.argv[1:]))
            sys.exit(1)
    else:
        app = SingleApplication(sys.argv, key)
        if app.isRunning():
            print('app is already running')
            sys.exit(1)

    window = Window()
    app.messageAvailable.connect(window.handleMessage)
    window.show()

    sys.exit(app.exec_())

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