Placeholder for a custom widget

Question

I am loading a QMainWIndow base from a *.ui file. Also, i have a custom widget i want to place somewhere on the form. Currently i put in the .ui file an empty QVBoxLayout named placeholder, and in the QMainWindow subclass do self.placeholder.addWidget(my_custom_widget)

The only thing i don't like in this approach is that the empty layout does not have its own size. I can have a layout with one cell and with a dummy widget (QLabel for example) with the size i want, and replace this widget and then add my custom widget, but the method seems too much for me.

What is your approach for such a task?

I am using Python (PyQt4)

score 32 · Accepted Answer · answered Jan 26 '13 at 18:50

Here is an easy little tutorial on how to promote a widget:

Right click on the widget you are going to use as placeholder and select Promote To....
Fill in the Promoted Clases pop-up dialog fields:
- Base Class Name: QWidget in this case.
- Promoted Class Name: The class name you used to define the widget for which you are creating the placeholder, here it is MyWidget
- Header File: /path/to/MyWidget.py is the path to the file in which MyWidget is placed.
Once you click Add, the class is created and displayed, select it and click Promote. You are done promoting.
Here is what you should see in your Object Inspector panel, the name of the class is no longer QWidget, it's MyWidget instead.

In the file at /path/to/MyWidget.py I have a class named MyWidget, and the content is something like this:

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

from PyQt4 import QtGui

class MyWidget(QtGui.QWidget):
    def __init__(self, parent=None):
        super(MyWidget, self).__init__(parent)

        self.labelHello = QtGui.QLabel(self)
        self.labelHello.setText("This is My Widget")

        self.layout = QtGui.QHBoxLayout(self)
        self.layout.addWidget(self.labelHello)

Just a smll remark: at least at my installation, the full file path to the library was not working. I had to change it to a python style import and afterwards it worked great! — OBu, Jun 15 '14 at 06:25
@OBu, Yeah. Need to change it to python based import, thank you for for the suggestion. — Chandan Gm, Jun 10 '22 at 17:43

score 4 · Answer 2 · answered Jan 23 '13 at 13:54

You should place a QWidget in the QtDesigner and then promote it to your custom widget. For more details check this link : http://doc.qt.digia.com/qt/designer-using-custom-widgets.html

Another option would be to create a QtDesigner plugin for your widget, but this would be useful only if you need to place in into multiple uis.

score 3 · Answer 3 · answered Jan 26 '13 at 06:18

Well, not having a better solution for now, i ended up with a QVBoxLayout with one cell with a spacer in it:

enter image description here

FormClass, BaseClass = uic.loadUiType('main_window.ui')
assert BaseClass is QtGui.QMainWindow


class MainWindow(QtGui.QMainWindow, FormClass):

    def __init__(self):
        super().__init__()

        # uic adds a function to our class called setupUi
        # calling this creates all the widgets from the .ui file
        self.setupUi(self)

        # my custom widget
        self.web_view = WebView(self, WebPage(self, self.print_to_console))
        # replace placeholder with our widget
        self.placeholder_layout.takeAt(0)  # remove placeholder spacer
        # and replace it with our widget
        self.placeholder_layout.addWidget(self.web_view)

Placeholder for a custom widget

3 Answers3

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