QCameraViewfinder in .ui file.

igorr

Hi everybody,

I am trying to implement camera in my app and facing a problem with using QCameraViewfinder. I use an .ui file to define the GUI. I have promoted a Widget (or I also tried promoting a Frame) to QCameraViewfinder, but I still get the error message ModuleNotFoundError: No module named 'qcameraviewfinder'.
The only one similar question I found on this forum was this one: https://forum.qt.io/topic/93288/adding-qcameraviewfinder-in-ui-file and it didn't help.

The idea to use this method comes from the camera app example in this project: https://github.com/Friz-zy/PyQt5_QCamera_Example. But I also noticed, that if I try to import the .ui file with the code provided in this project, it doesn't work as well.
So where's the mistake?

I am also grateful for all the advices on implementing camera interface. I am using PyQt5 5.15.0, Windows 10, python 3.7

eyllanesc

@igorr You have the following errors:

The "header file" must be "PyQt5/QtMultimediaWidgets" or "PyQt5.QtMultimediaWidgets".
When promoting, the base class must be used, but QFrame is not a base class of QCameraViewfinder so I had to change it to QWidget, which is one of its base classes.
You cannot and should not inherit from 2 QObjects, in your case QApplication and QMainWindow.

main.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>900</width>
    <height>667</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <widget class="QGroupBox" name="groupBox">
    <property name="geometry">
     <rect>
      <x>20</x>
      <y>10</y>
      <width>791</width>
      <height>581</height>
     </rect>
    </property>
    <property name="title">
     <string>GroupBox</string>
    </property>
    <widget class="QCameraViewfinder" name="viewfinder" native="true">
     <property name="geometry">
      <rect>
       <x>90</x>
       <y>70</y>
       <width>541</width>
       <height>361</height>
      </rect>
     </property>
    </widget>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>900</width>
     <height>30</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <customwidgets>
  <customwidget>
   <class>QCameraViewfinder</class>
   <extends>QWidget</extends>
   <header>PyQt5.QtMultimediaWidgets</header>
   <container>1</container>
  </customwidget>
 </customwidgets>
 <resources/>
 <connections/>
</ui>

main.py

import os.path
import sys

from PyQt5.uic import loadUi
from PyQt5.QtWidgets import QApplication, QMainWindow
from PyQt5.QtMultimedia import QCamera


CURRENT_DIRECTORY = os.path.dirname(os.path.realpath(__file__))


class MainWindow(QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)

        path = os.path.join(CURRENT_DIRECTORY, "GUI", "main.ui")
        loadUi(path, self)

        self.qcamera = QCamera()
        self.qcamera.setViewfinder(self.viewfinder)
        self.qcamera.start()


if __name__ == "__main__":

    app = QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec_())

SGaist

Hi and welcome to devnet,

From what I saw, they are not using promotion. You could do the same.

eyllanesc

please share the .ui file

igorr

Thanks for your replies!
@SGaist, I don't quite get what you mean.

I am sorry, here is the .ui file and some minimal code, using which one can reproduce the probelm.

The .ui file:

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>900</width>
    <height>667</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <widget class="QGroupBox" name="groupBox">
    <property name="geometry">
     <rect>
      <x>20</x>
      <y>10</y>
      <width>791</width>
      <height>581</height>
     </rect>
    </property>
    <property name="title">
     <string>GroupBox</string>
    </property>
    <widget class="QCameraViewfinder" name="viewfinder">
     <property name="geometry">
      <rect>
       <x>90</x>
       <y>70</y>
       <width>541</width>
       <height>361</height>
      </rect>
     </property>
     <property name="frameShape">
      <enum>QFrame::StyledPanel</enum>
     </property>
     <property name="frameShadow">
      <enum>QFrame::Raised</enum>
     </property>
    </widget>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>900</width>
     <height>21</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <customwidgets>
  <customwidget>
   <class>QCameraViewfinder</class>
   <extends>QFrame</extends>
   <header>qcameraviewfinder.h</header>
   <container>1</container>
  </customwidget>
 </customwidgets>
 <resources/>
 <connections/>
</ui>

And the code:

from PyQt5.Qt import *
from PyQt5.uic import *
import sys


class MainWindow(QApplication, QMainWindow):

    def __init__(self):

        super(QApplication, self).__init__(sys.argv)

        path = 'C:/Users/admin/PycharmProjects/ExampleProject/GUI/main.ui'
        self.w = loadUi(path)
        self.w.show()

if __name__ == '__main__':

    app = QApplication(sys.argv)
    w = MainWindow()
    sys.exit(app.exec_())

JonB

@igorr said in QCameraViewfinder in .ui file.:
QCameraViewfinder is a Qt-supplied class, yet you seem to be defining it as your own custom class deriving from QFrame?

igorr

@JonB well that was not really my intention. I just didn't find QCameraViewFinder in the Qt Designer. As far as I understood, if I want to use some Qt element which is not in the designer, I can just promote other element.
So obviously it is not true, but I don't know then how to implement QCameraViewfinder in the Qt Designer.

JonB

@igorr

I can just promote other element.

Yes, but it can't just be a random one :) [Unless I'm misunderstanding!]

QCameraViewfinder ultimately derives from QWidget but not from QFrame.

See the topic https://forum.qt.io/topic/93288/adding-qcameraviewfinder-in-ui-file, and the pic at https://postlmg.cc/vc81nsqj. Note how that example derives from/extends QWidget. Try that!

igorr

This post is deleted!

igorr

@JonB

As first I actually tried to promote a QWidget, because I saw in the documentation that QCameraViewfinder is derived from it. I don't remember, why I came to idea to try this with the QFrame (Maybe after some hours of frustration). But unfortunately it doesn't work with QWidget either:(
Here's the .ui file with QWidget as base class

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>900</width>
    <height>667</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <widget class="QGroupBox" name="groupBox">
    <property name="geometry">
     <rect>
      <x>20</x>
      <y>10</y>
      <width>791</width>
      <height>581</height>
     </rect>
    </property>
    <property name="title">
     <string>GroupBox</string>
    </property>
    <widget class="QCameraViewfinder" name="widget" native="true">
     <property name="geometry">
      <rect>
       <x>340</x>
       <y>180</y>
       <width>371</width>
       <height>251</height>
      </rect>
     </property>
    </widget>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>900</width>
     <height>21</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <customwidgets>
  <customwidget>
   <class>QCameraViewfinder</class>
   <extends>QWidget</extends>
   <header>qcameraviewfinder.h</header>
   <container>1</container>
  </customwidget>
 </customwidgets>
 <resources/>
 <connections/>
</ui>

And here a screenshot:

JonB

@igorr said in QCameraViewfinder in .ui file.:

But unfortunately it doesn't work with QWidget either:(

I don't really know, other than trying to follow what that other post said it did and worked.

As for "not work": you won't see anything in Designer, only at runtime?

Separately, in that Object Inspector you see "no entry" signs against 3 of your widgets. That means you have not assigned a layout in Designer to each of them, you should do that to make them look right at runtime.

igorr

@JonB yes, I only encounter an error when running the python code. When looking at the Traceback, it seems for me like PyQt still tries to create a custom widget instead of using the existing QCameraViewfinder class.

Thanks for the hint about the layout! I wasn't aware of this issue.

Traceback (most recent call last):
  File "C:\Users\admin\PycharmProjects\ExampleProject\main1.py", line 22, in <module>
    w = MainWindow()
  File "C:\Users\admin\PycharmProjects\ExampleProject\main1.py", line 16, in __init__
    self.w = loadUi(path)
  File "C:\Users\admin\PycharmProjects\newGUI\venv\lib\site-packages\PyQt5\uic\__init__.py", line 238, in loadUi
    return DynamicUILoader(package).loadUi(uifile, baseinstance, resource_suffix)
  File "C:\Users\admin\PycharmProjects\newGUI\venv\lib\site-packages\PyQt5\uic\Loader\loader.py", line 66, in loadUi
    return self.parse(filename, resource_suffix)
  File "C:\Users\admin\PycharmProjects\newGUI\venv\lib\site-packages\PyQt5\uic\uiparser.py", line 1037, in parse
    actor(elem)
  File "C:\Users\admin\PycharmProjects\newGUI\venv\lib\site-packages\PyQt5\uic\uiparser.py", line 828, in createUserInterface
    self.traverseWidgetTree(elem)
  File "C:\Users\admin\PycharmProjects\newGUI\venv\lib\site-packages\PyQt5\uic\uiparser.py", line 806, in traverseWidgetTree
    handler(self, child)
  File "C:\Users\admin\PycharmProjects\newGUI\venv\lib\site-packages\PyQt5\uic\uiparser.py", line 273, in createWidget
    self.traverseWidgetTree(elem)
  File "C:\Users\admin\PycharmProjects\newGUI\venv\lib\site-packages\PyQt5\uic\uiparser.py", line 806, in traverseWidgetTree
    handler(self, child)
  File "C:\Users\admin\PycharmProjects\newGUI\venv\lib\site-packages\PyQt5\uic\uiparser.py", line 273, in createWidget
    self.traverseWidgetTree(elem)
  File "C:\Users\admin\PycharmProjects\newGUI\venv\lib\site-packages\PyQt5\uic\uiparser.py", line 806, in traverseWidgetTree
    handler(self, child)
  File "C:\Users\admin\PycharmProjects\newGUI\venv\lib\site-packages\PyQt5\uic\uiparser.py", line 264, in createWidget
    self.stack.push(self.setupObject(widget_class, parent, elem))
  File "C:\Users\admin\PycharmProjects\newGUI\venv\lib\site-packages\PyQt5\uic\uiparser.py", line 228, in setupObject
    obj = self.factory.createQObject(clsname, name, args, is_attribute)
  File "C:\Users\admin\PycharmProjects\newGUI\venv\lib\site-packages\PyQt5\uic\objcreator.py", line 100, in createQObject
    factory = self.findQObjectType(classname)
  File "C:\Users\admin\PycharmProjects\newGUI\venv\lib\site-packages\PyQt5\uic\objcreator.py", line 125, in findQObjectType
    w = module.search(classname)
  File "C:\Users\admin\PycharmProjects\newGUI\venv\lib\site-packages\PyQt5\uic\Loader\qobjectcreator.py", line 114, in search
    module = __import__(mname, {}, {}, (cls,))
ModuleNotFoundError: No module named 'qcameraviewfinder'

JonB

@igorr
I have never used promotion to get a supplied widget into designer, only one I create myself. So I don't know.

If you were C++ the line in the .ui file:

<header>qcameraviewfinder.h</header>

would require you to have created, or it to find, a qcameraviewfinder.h header file. From Python I think your

ModuleNotFoundError: No module named 'qcameraviewfinder'

is the equivalent. I think you will need a qcamerafinder Python module to satisfy this.

If you cannot figure how to deal with this, you do not have to put that QCameraViewfinder in as a widget in Designer. You could just create it dynamically at runtime and put it into the right place in your UI.

eyllanesc

@igorr You have the following errors:

The "header file" must be "PyQt5/QtMultimediaWidgets" or "PyQt5.QtMultimediaWidgets".
When promoting, the base class must be used, but QFrame is not a base class of QCameraViewfinder so I had to change it to QWidget, which is one of its base classes.
You cannot and should not inherit from 2 QObjects, in your case QApplication and QMainWindow.

main.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>900</width>
    <height>667</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <widget class="QGroupBox" name="groupBox">
    <property name="geometry">
     <rect>
      <x>20</x>
      <y>10</y>
      <width>791</width>
      <height>581</height>
     </rect>
    </property>
    <property name="title">
     <string>GroupBox</string>
    </property>
    <widget class="QCameraViewfinder" name="viewfinder" native="true">
     <property name="geometry">
      <rect>
       <x>90</x>
       <y>70</y>
       <width>541</width>
       <height>361</height>
      </rect>
     </property>
    </widget>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>900</width>
     <height>30</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <customwidgets>
  <customwidget>
   <class>QCameraViewfinder</class>
   <extends>QWidget</extends>
   <header>PyQt5.QtMultimediaWidgets</header>
   <container>1</container>
  </customwidget>
 </customwidgets>
 <resources/>
 <connections/>
</ui>

main.py

import os.path
import sys

from PyQt5.uic import loadUi
from PyQt5.QtWidgets import QApplication, QMainWindow
from PyQt5.QtMultimedia import QCamera


CURRENT_DIRECTORY = os.path.dirname(os.path.realpath(__file__))


class MainWindow(QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)

        path = os.path.join(CURRENT_DIRECTORY, "GUI", "main.ui")
        loadUi(path, self)

        self.qcamera = QCamera()
        self.qcamera.setViewfinder(self.viewfinder)
        self.qcamera.start()


if __name__ == "__main__":

    app = QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec_())

igorr

@eyllanesc thanks a lot! Changing the header file name helped. I have also fixed the multiple inheritance.
I hope I will be able to avoid such problems in the future.