How can I launch a QWidget after pressing a submenu (QAction) in QGis3.4?

Question

I need your help I am developing a dialog box (which I will call toolraster) in QGis to interact with raster layers. I want it to display when I click on a menu I insert in the QGis interface.

I created Toolraster as a class that extends QtWidgets, a QWidget. Create the QAction and connect it to the toolraster instance function. Create the submenu with iface.pluginMenu().addSeparator() and iface.pluginMenu().addAction(activar). Example below.

The problem: when I run the menu the dialog box opens and closes instantly. It doesn't report any errors

When I perform the same procedure with a QInputDialog or a QMessageBox it doesn't present any problems.

But with a class like this it is a problem:

from qgis import PyQt
from qgis.PyQt import QtWidgets

class test(QWidget):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("clase de prueba")
        layout = QVBoxLayout()
        widgets = [QCheckBox,
            QComboBox,
            QDateEdit,
            QDateTimeEdit,
            QDial,
            QDoubleSpinBox]
        for w in widgets:
            layout.addWidget(w())
            
        self.setLayout(layout)

def activar():
    h=test()
    h.show()

test_action=QAction("Menu de prueba")
test_action.triggered.connect(activar)
iface.pluginMenu().addSeparator()
iface.pluginMenu().addAction(test_action)

Note: when I execute the function activar() in the console the same thing happens, if I insert the show() inside the class too

Answer 1

You should move the h = test() outside of activar function (tested and it works). While doing this, you will also avoid creating as many widgets as you push on the button and instead create one widget and show/hide it.

from qgis import PyQt
from qgis.PyQt import QtWidgets

class test(QWidget):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("clase de prueba")
        layout = QVBoxLayout()
        widgets = [QCheckBox,
            QComboBox,
            QDateEdit,
            QDateTimeEdit,
            QDial,
            QDoubleSpinBox]
        for w in widgets:
            layout.addWidget(w())
            
        self.setLayout(layout)

h=test()


def activar():
    h.show()

test_action=QAction("Menu de prueba")
test_action.triggered.connect(activar)
iface.pluginMenu().addSeparator()
iface.pluginMenu().addAction(test_action)