在线程中的PyQt的lineEdit中引入文本

Question

How can I introduce a text in a lineEdit from a thread that are getting the data whithout colapse the program? The important line is in the class "fil" where it shows Principal.self.aplicacio.actual_lineEdit.setText(self.temp)

    # !/usr/bin/env python
# -*- coding: utf-8 -*-

import sys
import serial
import threading
from time import sleep
from PyQt4 import QtCore, QtGui
from temperaturaUI import Ui_Form


class Principal(QtGui.QWidget):
    def __init__(self):
        QtGui.QWidget.__init__(self)

        self.aplicacio = Ui_Form()
        self.aplicacio.setupUi(self)

        self.aplicacio.sortir_Button.clicked.connect(exit)

        self.aplicacio.connectar_Button.clicked.connect(self.connectar)

    def connectar(self):
        try:
            arduino = serial.Serial('/dev/ttyACM0', 9600)
            print "Connectat amb èxit"
            temperatura = fil(0, arduino, self.aplicacio.actual_lineEdit)
            temperatura.start()
        except:
            print "Impossible connectar a l'Arduino"


class fil(threading.Thread):
    def __init__(self, temp, serie, line):
        threading.Thread.__init__(self)
        self.temp = temp
        self.serie = serie
        self.line = line

    def run(self):
        try:
            while 1:
                self.temp = self.serie.readline()
                if self.temp != 0:
                     **Principal.self.aplicacio.actual_lineEdit.setText(self.temp)**
                sleep(0.2)
        except:
            print "Error al llegir de l'Arduino"



def main():
    app = QtGui.QApplication(sys.argv)
    aplicacio = Principal()
    aplicacio.show()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()

Answer 1

You can use signals . You would add a signal to the fil class that emits the new text:

class fil(threading.Thread):
    update_line_edit = pyqtSignal(str)
    def __init__(self, temp, serie, line):
        ...

    def run(self):
        try:
            while True:
                self.temp = self.serie.readline()
                if not self.temp:
                    update_line_edit.emit(self.temp)
        ...

Then, simply connect that signal to a slot function in your Principal class:

class Principal(QtGui.QWidget):
    def __init__(self):
        ...

    def connectar(self):
        try:
            arduino = serial.Serial('/dev/ttyACM0', 9600)
            print "Connectat amb èxit"
            temperatura = fil(0, arduino, self.aplicacio.actual_lineEdit)
            temperatura.change_line_edit.connect(self.update_line_edit)
        ...

    def update_line_edit(self, text):
        self.aplicacio.actual_lineEdit.setText(text)

Answer 2

There are a few ways to do this correctly.

The first is to use a QThread instead of a python thread. You can then use Qt signals to pass a message back from the fil thread to the Qt MainThread and append the message to the QLineEdit there. Another similar approach is to continue using a Python thread, but place your message in a Python Queue.Queue() object. This Queue is then read by a secondary QThread, whose sole purpose is to read messages out of the Queue and emit a signal back to the MainThread.

The common feature of these two methods is that you only access Qt GUI objects from the MainThread and use signals/slots to communicate between threads. Here are some other questions where I've answered similar questions (you should be able to adapt them to your program):

• Redirecting stdout and stderr to a PyQt4 QTextEdit from a secondary thread
• Syncing activity in PyQt QThreads

However, since answering those questions, my colleagues and I have created a project that helps simplify writing multi-threaded Qt applications. The project is called qtutils and is on PyPi so it can be installed with pip or easy_install (just run pip install qtutils or easy_install qtutils from a commandline/terminal window).

This library has (among others) some functions inmain and inmain_later which will run a specified method in the Qt MainThread (regardless of the thread the call is made from) synchronously or asynchronously. Documentation on how to use these methods is here . I've modified your example code to use my inmain method and put the code here: http://pastebin.com/QM1Y6zBx -- obviously you need to install qtutils for it to work!