Change label in QML when button is pressed using PyQt5 in python

Question

I'm trying to do a simple task with PyQt5 and QML: have a button that changes a label when it is clicked. I've been able to execute a python function when the button is pressed, but I don't know how to change the text in the label.

This is a minimal example:

main.py

from PyQt5.QtWidgets import *
from PyQt5.QtQml import *
from PyQt5.QtCore import *

import sys

def onClicked():
    print('handler called')

if __name__ == '__main__':
    app = QApplication(sys.argv)

    engine = QQmlApplicationEngine()
    engine.load(QUrl('main.qml'))

    win = engine.rootObjects()[0]
    button = win.findChild(QObject, 'myButton')
    button.messageRequired.connect(onClicked)

    sys.exit(app.exec_())

main.qml

import QtQuick 2.7
import QtQuick.Controls 2.3
import QtQuick.Window 2.3

ApplicationWindow{
    title: qsTr('Quomodo')
    id: mainWindow
    width:  480
    height: 640
    visible: true

    Column {
        anchors.horizontalCenter: parent.horizontalCenter
        spacing: 8
        padding: 8

        Button {
            signal messageRequired
            objectName: "myButton"
            text: qsTr("Work")
            highlighted: true
            onClicked: messageRequired()
        }

        Label {
            text: qsTr("Time")
            anchors.horizontalCenter: parent.horizontalCenter
        }

    } 
}

How can I change the text of the label to "Next", for instance?

Note: This is not a duplicate of QML not taking ownership of object received from PyQt slot. That question is about ownership of the data between Python and QML, and doesn't answer this question.

score 2 · Accepted Answer · answered May 01 '18 at 13:56

Try it:

from PyQt5.QtGui  import QGuiApplication
from PyQt5.QtQml  import QQmlApplicationEngine
from PyQt5.QtCore import QObject, pyqtSignal, pyqtSlot, QUrl


class Main(QObject):
    def __init__(self):
        QObject.__init__(self)

    # signal sending string
    # necessarily give the name of the argument through arguments=['textLabel']
    # otherwise it will not be possible to pick it up in QML
    textResult = pyqtSignal(str, arguments=['textLabel'])

    @pyqtSlot(str)
    def textLabel(self, arg1):
        # do something with the text and emit a signal
        arg1 = arg1.upper()
        self.textResult.emit(arg1)


if __name__ == "__main__":
    import sys
    app    = QGuiApplication(sys.argv)
    engine = QQmlApplicationEngine()
    main   = Main()
    engine.rootContext().setContextProperty("main", main)
    engine.load(QUrl('main.qml'))
    engine.quit.connect(app.quit)
    sys.exit(app.exec_())

main.qml

import QtQuick 2.7
import QtQuick.Controls 2.3
import QtQuick.Window 2.3

ApplicationWindow{
    title: qsTr('Quomodo')
    id: mainWindow
    width:  480
    height: 640
    visible: true

    Column {
        anchors.horizontalCenter: parent.horizontalCenter
        spacing: 8
        padding: 8

        Button {
            objectName: "myButton"
            text: qsTr("Work")
            highlighted: true
            onClicked: {
                // call the slot to process the text
                main.textLabel("Next")
            }
        }

        Label {
            id: textResult
            text: qsTr("Time")
            anchors.horizontalCenter: parent.horizontalCenter
        }
    } 

    // Here we take the result of text processing
    Connections {
        target: main

        // Signal Handler 
        onTextResult: {
            // textLabel - was given through arguments=['textLabel']
            textResult.text = textLabel
        }
    }      
}

Perfect. Thank you very much! – user936580 May 01 '18 at 17:58 — user936580, May 01 '18 at 17:58

Change label in QML when button is pressed using PyQt5 in python

1 Answers1