在Dash回调中显示PyQt5元素_问答-阿里云开发者社区

在我的Python Dash应用程序中，我想显示一些PyQt5窗口弹出窗口。这些是从回调内部激活的。

不幸的是，当显示弹出窗口时，我在控制台中收到此警告：

警告：未在main（）线程中创建QApplication。

我的问题：如果从Python Dash回调内部调用它，如何在main（）线程中创建QApplication？

在下面，您可以找到代表mwe的代码。如果运行此代码段，则会看到警告。显然，当从回调内激活QApplication时，它不在主线程上运行（我猜是app.run_server（）已在主线程上运行）。我如何修改它，以便QApplication位于主线程中？

该示例类似于PyQt5 GUI中的Use Dash（plot.ly），但不相同（我希望Dash中的pyqt5，而不是pyqt5中的Dash）。

import os, dash
from PyQt5.QtWidgets import QApplication,QMainWindow
from PyQt5.QtCore import QCoreApplication
import dash_html_components as html
from dash.dependencies import Input, Output

class MainWindow(QMainWindow):
    #some Qpop up
    pass

app = dash.Dash()

app.layout = html.Div(children=[
    html.H1(children='Hello Dash'),
    #button which, if pressed, created a QApplication in a non-main thread
    html.Button("show pop up", id="button"),
    html.H2(children='', id='result')
    ])

#The callback which creates the pop up I want to show.
#This is activated when the button "show pop up" is pressed, and causes the warning to appear
@app.callback(
Output(component_id='result', component_property='children'),
[Input(component_id='button', component_property='n_clicks')]
)   
def popUp(n_clicks):
    if not n_clicks:
        raise dash.exceptions.PreventUpdate
    app = QCoreApplication.instance()
    if app is None:
        app = QApplication([os.getcwd()])
    mainWin = MainWindow()
    mainWin.show()
    app.exec_()
    return "You saw a pop-up"

if __name__ == '__main__':
    app.run_server(debug=False)

问题来源：stackoverflow

import functools import os import threading from PyQt5 import QtCore, QtWidgets import dash import dash_html_components as html from dash.dependencies import Input, Output class MainWindow(QtWidgets.QMainWindow): closed = QtCore.pyqtSignal() def closeEvent(self, event): self.closed.emit() super().closeEvent(event) class Manager(QtCore.QObject): def __init__(self, parent=None): super().__init__(parent) self._view = None @property def view(self): return self._view def init_gui(self): self._view = MainWindow() @QtCore.pyqtSlot() def show_popup(self): if self.view is not None: self.view.show() qt_manager = Manager() app = dash.Dash() app.layout = html.Div( children=[ html.H1(children="Hello Dash"), html.Button("show pop up", id="button"), html.H2(children="", id="result"), ] ) @app.callback( Output(component_id="result", component_property="children"), [Input(component_id="button", component_property="n_clicks")], ) def popUp(n_clicks): if not n_clicks: raise dash.exceptions.PreventUpdate loop = QtCore.QEventLoop() qt_manager.view.closed.connect(loop.quit) QtCore.QMetaObject.invokeMethod( qt_manager, "show_popup", QtCore.Qt.QueuedConnection ) loop.exec_() return "You saw a pop-up" def main(): qt_app = QtWidgets.QApplication.instance() if qt_app is None: qt_app = QtWidgets.QApplication([os.getcwd()]) qt_app.setQuitOnLastWindowClosed(False) qt_manager.init_gui() threading.Thread( target=app.run_server, kwargs=dict(debug=False), daemon=True, ).start() return qt_app.exec_() if __name__ == "__main__": main()

在Dash回调中显示PyQt5元素

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