two different main code loaded the same .ui file and the one is working and other not, why?

[Daniel Breeze]

this is gonna drive me crazy.

working code is here

import sys
from PySide6 import QtCore, QtGui, QtWidgets
from PySide6.QtUiTools import QUiLoader

loader = QUiLoader()
app = QtWidgets.QApplication(sys.argv)
window = loader.load("mainwindow.ui", None)
window.show()
sys.exit(app.exec())

not working is here, and this code form official webside link text

import sys
from PySide6.QtUiTools import QUiLoader
from PySide6.QtWidgets import QApplication
from PySide6.QtCore import QFile, QIODevice

if __name__ == "__main__":
    app = QApplication(sys.argv)

    ui_file_name = "mainwindow.ui"
    ui_file = QFile(ui_file_name)
    if not ui_file.open(QIODevice.ReadOnly):
        print(f"Cannot open {ui_file_name}: {ui_file.errorString()}")
        sys.exit(-1)
    loader = QUiLoader()
    window = loader.load(ui_file)
    ui_file.close()
    if not window:
        print(loader.errorString())
        sys.exit(-1)
    window.show()

    sys.exit(app.exec())

here is mianwindow.ui code

<?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>959</width>
    <height>731</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <layout class="QHBoxLayout" name="horizontalLayout">
    <item>
     <widget class="QWidget" name="widgetLeft" native="true">
      <property name="minimumSize">
       <size>
        <width>350</width>
        <height>0</height>
       </size>
      </property>
      <layout class="QVBoxLayout" name="verticalLayout">
       <item>
        <widget class="QWidget" name="widget" native="true">
         <layout class="QFormLayout" name="formLayout">
          <item row="0" column="0">
           <widget class="QLabel" name="label">
            <property name="text">
             <string>温室大棚类型</string>
            </property>
           </widget>
          </item>
          <item row="0" column="1">
           <widget class="QComboBox" name="comboBox"/>
          </item>
          <item row="1" column="0">
           <widget class="QLabel" name="label_2">
            <property name="text">
             <string>风向（度）</string>
            </property>
           </widget>
          </item>
          <item row="1" column="1">
           <widget class="QComboBox" name="comboBox_2"/>
          </item>
         </layout>
        </widget>
       </item>
       <item>
        <widget class="QWidget" name="widget_2" native="true">
         <layout class="QVBoxLayout" name="verticalLayout_2">
          <item>
           <widget class="QGroupBox" name="groupBox">
            <property name="title">
             <string>尺寸</string>
            </property>
            <layout class="QFormLayout" name="formLayout_2">
             <item row="0" column="0">
              <widget class="QLabel" name="label_3">
               <property name="text">
                <string>跨度（mm）</string>
               </property>
              </widget>
             </item>
             <item row="0" column="1">
              <widget class="QComboBox" name="comboBox_3"/>
             </item>
             <item row="1" column="0">
              <widget class="QLabel" name="label_4">
               <property name="text">
                <string>脊高（mm）</string>
               </property>
              </widget>
             </item>
             <item row="1" column="1">
              <widget class="QComboBox" name="comboBox_4"/>
             </item>
             <item row="2" column="0">
              <widget class="QLabel" name="label_5">
               <property name="text">
                <string>后屋面投影（mm）</string>
               </property>
              </widget>
             </item>
             <item row="2" column="1">
              <widget class="QComboBox" name="comboBox_5"/>
             </item>
             <item row="3" column="0">
              <widget class="QLabel" name="label_6">
               <property name="text">
                <string>北墙倾角（度）</string>
               </property>
              </widget>
             </item>
             <item row="3" column="1">
              <widget class="QComboBox" name="comboBox_6"/>
             </item>
             <item row="4" column="0">
              <widget class="QLabel" name="label_7">
               <property name="text">
                <string>北墙高（mm）</string>
               </property>
              </widget>
             </item>
             <item row="4" column="1">
              <widget class="QComboBox" name="comboBox_7"/>
             </item>
            </layout>
           </widget>
          </item>
         </layout>
        </widget>
       </item>
       <item>
        <spacer name="verticalSpacer">
         <property name="orientation">
          <enum>Qt::Vertical</enum>
         </property>
         <property name="sizeHint" stdset="0">
          <size>
           <width>20</width>
           <height>158</height>
          </size>
         </property>
        </spacer>
       </item>
       <item>
        <widget class="QWidget" name="widget_3" native="true">
         <layout class="QHBoxLayout" name="horizontalLayout_2">
          <item>
           <widget class="QPushButton" name="pushButton_3">
            <property name="minimumSize">
             <size>
              <width>50</width>
              <height>0</height>
             </size>
            </property>
            <property name="maximumSize">
             <size>
              <width>50</width>
              <height>16777215</height>
             </size>
            </property>
            <property name="text">
             <string>查询</string>
            </property>
           </widget>
          </item>
          <item>
           <widget class="QPushButton" name="pushButton_2">
            <property name="minimumSize">
             <size>
              <width>50</width>
              <height>0</height>
             </size>
            </property>
            <property name="maximumSize">
             <size>
              <width>50</width>
              <height>16777215</height>
             </size>
            </property>
            <property name="text">
             <string>输出</string>
            </property>
           </widget>
          </item>
          <item>
           <widget class="QPushButton" name="pushButton">
            <property name="minimumSize">
             <size>
              <width>50</width>
              <height>0</height>
             </size>
            </property>
            <property name="maximumSize">
             <size>
              <width>50</width>
              <height>16777215</height>
             </size>
            </property>
            <property name="text">
             <string>退出</string>
            </property>
           </widget>
          </item>
         </layout>
        </widget>
       </item>
      </layout>
     </widget>
    </item>
    <item>
     <widget class="QWidget" name="widgetRight" native="true">
      <layout class="QVBoxLayout" name="verticalLayout_3">
       <item>
        <widget class="QWidget" name="widget_4" native="true">
         <property name="minimumSize">
          <size>
           <width>400</width>
           <height>400</height>
          </size>
         </property>
         <layout class="QHBoxLayout" name="horizontalLayout_3">
          <item>
           <widget class="QWidget" name="widget_5" native="true">
            <property name="minimumSize">
             <size>
              <width>400</width>
              <height>400</height>
             </size>
            </property>
           </widget>
          </item>
          <item>
           <spacer name="horizontalSpacer">
            <property name="orientation">
             <enum>Qt::Horizontal</enum>
            </property>
            <property name="sizeHint" stdset="0">
             <size>
              <width>0</width>
              <height>20</height>
             </size>
            </property>
           </spacer>
          </item>
         </layout>
        </widget>
       </item>
       <item>
        <widget class="QColumnView" name="columnView"/>
       </item>
      </layout>
     </widget>
    </item>
   </layout>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>959</width>
     <height>22</height>
    </rect>
   </property>
   <widget class="QMenu" name="menu">
    <property name="title">
     <string>文件</string>
    </property>
    <addaction name="actionasd"/>
    <addaction name="action123"/>
   </widget>
   <addaction name="menu"/>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
  <action name="actionasd">
   <property name="text">
    <string>打开图片</string>
   </property>
  </action>
  <action name="action123">
   <property name="text">
    <string>退出</string>
   </property>
  </action>
 </widget>
 <resources/>
 <connections/>
</ui>

[SGaist]

Hi and welcome to devnet,

Which version of PySide6 ?
On which platform ?

[JonB]

@Daniel-Breeze said in two different main code loaded the same .ui file and the one is working and other not, why?:

not working is here,

In what way "not working"? Did you step through it to make sure where it got to?

[Daniel Breeze]

@JonB

I change that like this

import sys

from PySide6.QtWidgets import QApplication
from PySide6.QtUiTools import QUiLoader


if __name__ == "__main__":
    app = QApplication(sys.argv)

#    ui_file_name = "mainwindow.ui"
#    ui_file = QFile(ui_file_name)
#    if not ui_file.open(QIODevice.ReadOnly):
#        print(f"Cannot open {ui_file_name}: {ui_file.errorString()}")
#        sys.exit(-1)
    print("hah")
    loader = QUiLoader()
    print("hah")
    window = loader.load("mainwindow.ui")
#    ui_file.close()
#    if not window:
#        print(loader.errorString())
#        sys.exit(-1)
    window.show()

    sys.exit(app.exec())

and I run the program with debugging, when it execute loader = QUiLoader() it stoped, and it can't execute next line. like there is one "hah" be printed

[JonB]

@Daniel-Breeze
Although it seems the wrong way round to me, in your "working" first code case you have the loader = QUiLoader() statement before you create the QApplication() object. Try moving your creation of QUiLoader() to come before QApplication() in the second non-working case?

[Daniel Breeze]

@JonB
thanks a lot, solved. but if you need create loader first, why that official example didn't, I'am really confused.

[JonB]

@Daniel-Breeze
I'm actually surprised that works. You would think the QApplication ought to come first, but it was the most obvious difference I could spot.

[friedemannkleint]

If this is 6.6; it might be a manifestation of https://bugreports.qt.io/browse/QTBUG-118317 .