Check if button is pressed in QGIS 3 module

Question

There is a plugin I wrote for QGIS and I added some buttons there. From main launch Python script I need to check is specific button is clicked and according to that do some stuff.

I saw a default condition in main script:

def run(self):
    if self.first_start == True:
        self.first_start = False
        self.dlg = frame_builderDialog()
    self.dlg.show()
    result = self.dlg.exec_()
    if result:
        pass
        'or do something'

In this case I can catch event if I had an "OK\Cancel" button. But I have another simple buttons. I tried to catch them using something like

result_btn = self.dlg.pushButton.clicked

where pushButton is one of the buttons taken from script with dialog, but nothing were returned.

What should be done here?

Answer 1

In python you have "events" and "events handler". when an event occurs they usually (not always...) generate a signal that can be caught by the event handler.

for example :

curLayer.selectionChanged.connect(self.test)

the event is selectionChanged and the event handler is the function handling the signal received (in that case the handler should be a function (written by you) called test (or any other naming ofc).

your snippet :

result_btn = self.dlg.pushButton.clicked

Is meaningless (imho ...)

So ... in your case u should try an

self.dlg.pushButton.clicked.connect(self.my_event_handler)

And write an my_event_handler function of course.

Answer 2

You could connect the pushButton to a function so that when it is clicked, it will do something:

result_btn = self.dlg.pushButton.clicked.connect(self.someFunction)

Answer 3

The event handler function looks something like this:

def handlepushbutton(self,flag):
    QgsMessageLog.logMessage("clicked on a button", "DEBUG")

And in the run() method you set the handler to call the handlepushbutton() method:

self.dlg.pushButton.clicked.connect(self.handlepushbutton)

pushButton is the name of the push button in QtDesigner. Subsequent buttons in the same dialogbox are named pushButton_2, pushButton_3, etc.