玛雅独立与pyside2

Question

When I want to add a QtWidget in maya standalone, error says "QWidget: Cannot create a QWidget without QApplication".

from PySide2 import QtWidgets
import maya.standalone
maya.standalone.initialize()

QtWidgets.QPushButton()

maya.standalone.uninitialize()

then I add a QApplication,error says: "A QApplication instance already exists."

from PySide2 import QtWidgets
import maya.standalone
import sys
maya.standalone.initialize()

QtWidgets.QApplication(sys.argv)
QtWidgets.QPushButton()

maya.standalone.uninitialize()

I use QApplication.instance() I can get a 'QGuiApplication' reference,so I know that maya.standalone() which will create the qApp, but how to create a QWidget(such as dialog...)

================================================================

from PySide2 import QtWidgets
import maya.standalone
maya.standalone.initialize()
print(QtWidgets.QApplication.instance())     
maya.standalone.uninitialize()

This is the full log:

pymel.core : INFO : Updating pymel with pre-loaded plugins: renderSetup
Warning: file: C:/Program Files/Autodesk/Maya2018/scripts/startup/initialStartup.mel line 179: Y-axis is already the Up-axis
Warning: file: C:\Users\a\Documents\maya\2018\prefs\filePathEditorRegistryPrefs.mel line 4: filePathEditor: Attribute 'aiImage.filename' is invalid or is not designated 'usedAsFilename'.
Warning: file: C:\Users\a\Documents\maya\2018\prefs\filePathEditorRegistryPrefs.mel line 5: filePathEditor: Attribute 'aiPhotometricLight.aiFilename' is invalid or is not designated 
'usedAsFilename'.
Warning: file: C:\Users\a\Documents\maya\2018\prefs\filePathEditorRegistryPrefs.mel line 6: filePathEditor: Attribute 'aiStandIn.dso' is invalid or is not designated 'usedAsFilename'.
Warning: file: C:\Users\a\Documents\maya\2018\prefs\filePathEditorRegistryPrefs.mel line 7: filePathEditor: Attribute 'aiVolume.filename' is invalid or is not designated 'usedAsFilename'.
AbcExport v1.0 using Alembic 1.7.5 (built Feb  6 2018 18:28:08)
Initialized VP2.0 renderer {
  Version : 2016.11.40.12. Feature Level 5.
  Adapter : GeForce RTX 3090/PCIe/SSE2
  Vendor ID: 4318. Device ID : 8708
  Driver : .
  API : OpenGL V.4.6.
  Max texture size : 16384 * 16384.
  Max tex coords : 32
  Shader versions supported (Vertex: 5, Geometry: 5, Pixel 5).
  Shader compiler profile : (Best card profile)
  Active stereo support available : 0
  GPU Memory Limit : 24576 MB.
  CPU Memory Limit: 62178.5 MB.
  MultiDraw consolidation: enabled
}
OpenCL evaluator is attempting to initialize OpenCL.
Detected 1 OpenCL Platforms: 
 0: NVIDIA Corporation. NVIDIA CUDA. OpenCL 1.2 CUDA 11.2.162.
 Supported extensions: cl_khr_global_int32_base_atomics cl_khr_global_int32_extended_atomics cl_khr_local_int32_base_atomics cl_khr_local_int32_extended_atomics cl_khr_fp64 cl_khr_byte_addressable_store cl_khr_icd cl_khr_gl_sharing cl_nv_compiler_options cl_nv_device_attribute_query cl_nv_pragma_unroll cl_nv_d3d10_sharing cl_khr_d3d10_sharing cl_nv_d3d11_sharing cl_nv_copy_opts cl_nv_create_buffer cl_khr_int64_base_atomics cl_khr_int64_extended_atomics cl_khr_device_uuid
OpenCL evaluator choosing OpenCL platform NVIDIA Corporation.
OpenCL evaluator is unable to find a GPU device that can share VBOs with OpenGL.
Warning: file: C:/Program Files/Autodesk/Maya2018/scripts/startup/autoLoadPlugin.mel line 35: Loading plug-in "lookdevKit" has resulted in changes to the scene that may need to be saved.
AbcImport v1.0 using Alembic 1.7.5 (built Feb  6 2018 18:28:08)

<PySide2.QtGui.QGuiApplication object at 0x000001828E9D9108>

Answer 1

The initialize() function creates a QGuiApplication if there is no previous QXApplication, so one possible is to create a QApplication before invoking that function:

app = QtWidgets.QApplication(sys.argv)
maya.standalone.initialize()