Catch final signal from QTimer object - python-3.x

Question

I have a simple PyQt script. When I click a button, it starts a QTimer object and increments a progress bar. What I want is to change the label of my text when my progress bar reaches 100%. It worked for me once, but I can't get it to work anymore. What am I doing wrong?
Here's the main part of my code.
class MainWindow(QWidget):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
self.setWindowTitle('QProgressBar demo')
self.timerButton = QPushButton("Start", self)
self.timerButton.clicked.connect(self.timerStart)
self.timerObject = QTimer(self)
#self.timerObject.destroyed.connect(lambda:self.timerButton.setText("Finished") )
self.timerObject.destroyed.connect(lambda:print("Called" ))
self.progressBar = QProgressBar(self)
self.progressBar.setGeometry(10, 20, 290, 25)
self.timerButton.move(110,150)
self.progressBar.move(10,100)
self.increment = 0
self.resize(300, 300)
self.show()
#pyqtSlot()
def headsUp(self):
if(self.increment >= 100):
self.timerObject.stop()
else:
self.increment += 1
self.progressBar.setValue(self.increment)
return
def timerStart(self):
if (self.timerObject.isActive()):
self.timerObject.stop()
self.timerButton.setText("Resume")
else:
self.timerObject.timeout.connect(self.headsUp)
self.timerButton.setText("Pause")
self.timerObject.start(100)

Answer 1

destroyed is only issued when you delete the object, that a QTimer peer does not imply that it is deleted from memory, therefore it does not emit that signal, a possible solution is to create a signal for the QProgressBar when the value takes the maximum value as shown below:
import sys
from PyQt5 import QtCore, QtWidgets
class ProgressBar(QtWidgets.QProgressBar):
finished = QtCore.pyqtSignal()
def __init__(self, *args, **kwargs):
super(ProgressBar, self).__init__(*args, *kwargs)
self.valueChanged.connect(self.on_valueChanged)
#QtCore.pyqtSlot(int)
def on_valueChanged(self, val):
if val == self.maximum():
self.finished.emit()
class MainWindow(QtWidgets.QWidget):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
self.setWindowTitle('QProgressBar demo')
self.timerButton = QtWidgets.QPushButton("Start", self)
self.timerButton.clicked.connect(self.timerStart)
self.timerObject = QtCore.QTimer(self)
self.progressBar = ProgressBar(self)
self.progressBar.finished.connect(lambda: print("Called" ))
self.increment = 0
lay = QtWidgets.QVBoxLayout(self)
lay.addWidget(self.progressBar)
lay.addWidget(self.timerButton)
self.resize(300, 300)
#QtCore.pyqtSlot()
def headsUp(self):
if self.increment >= 100:
self.timerObject.stop()
else:
self.increment += 1
self.progressBar.setValue(self.increment)
#QtCore.pyqtSlot()
def timerStart(self):
if self.timerObject.isActive():
self.timerObject.stop()
self.timerButton.setText("Resume")
else:
self.timerObject.timeout.connect(self.headsUp)
self.timerButton.setText("Pause")
self.timerObject.start(100)
if __name__ == '__main__':
app = QtWidgets.QApplication(sys.argv)
w = MainWindow()
w.show()
sys.exit(app.exec_())
Another best option is to use QTimeLine and its finished signal:
import sys
from PyQt5 import QtCore, QtWidgets
class MainWindow(QtWidgets.QWidget):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
self.setWindowTitle('QProgressBar demo')
self.timerButton = QtWidgets.QPushButton("Start", self)
self.timerButton.clicked.connect(self.timerStart)
self.timerObject = QtCore.QTimeLine(1000, self)
self.timerObject.setFrameRange(0, 100)
self.progressBar = QtWidgets.QProgressBar(self)
self.timerObject.frameChanged.connect(self.progressBar.setValue)
self.timerObject.finished.connect(lambda: print("Called" ))
lay = QtWidgets.QVBoxLayout(self)
lay.addWidget(self.progressBar)
lay.addWidget(self.timerButton)
self.resize(300, 300)
#QtCore.pyqtSlot()
def timerStart(self):
if self.timerObject.state() == QtCore.QTimeLine.Running:
self.timerObject.stop()
self.timerButton.setText("Resume")
else:
self.timerButton.setText("Pause")
self.timerObject.resume()
if __name__ == '__main__':
app = QtWidgets.QApplication(sys.argv)
w = MainWindow()
w.show()
sys.exit(app.exec_())

Answer 2

This isn't working because you are connecting to the timers destoryed signal, but the timer is not being destroyed. To use this code as is, call self.timerObject.deleteLater() after you stop the timer.