I encountered an exception while using “briefcase build android" in toga0.4

[wanglifeng95]

My code works normally in toga0.31. But in toga0.4, my new project with same code works normally on Windows while using "briefcase create" , "briefcase build" , "briefcase run" or "briefcase create android".I encountered an exception while using “briefcase build android" in toga0.4.The code is as follows：

class HelloWorld(toga.App):

    def startup(self):
        self.count = 1
        self.box = toga.Box(style=Pack(direction=COLUMN))
        main_box = toga.Box(style=Pack(direction=COLUMN))
        for n in range(0, 100):
            label = toga.Label(f"label {n}")
            self.box.add(label)
        main_scroll = toga.ScrollContainer(style=Pack(flex=1))
        main_scroll.content = self.box
        addWidgetsBut = toga.Button("Add Label", on_press=self.butEvent)
        main_box.add(main_scroll)
        main_box.add(addWidgetsBut)
        self.main_window = toga.MainWindow(title=self.formal_name)
        self.main_window.content = main_box
        self.main_window.show()

    def butEvent(self, widget):
        print(f"New label {self.count}")
        label = toga.Label(f"New label {self.count}")
        self.box.add(label)
        self.count += 1

def main():
    return HelloWorld()

The error that occurred is as follows:

Warning: Python version 3.9 may have fewer packages available. If you experience problems, try switching to version 3.8.

> Task :app:preBuild UP-TO-DATE
> Task :app:preDebugBuild UP-TO-DATE
> Task :app:mergeDebugNativeDebugMetadata NO-SOURCE
> Task :app:extractPythonBuildPackages

> Task :app:generateDebugPythonRequirements FAILED
Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "D:\soft\PycharmProjects\python9\helloworld\build\helloworld\android\gradle\app\build\generated\python\bp\chaquopy\pip_install.py", line 23, in <module>
    from pip._internal.utils.misc import rmtree
  File "D:\soft\PycharmProjects\python9\helloworld\build\helloworld\android\gradle\app\build\generated\python\bp\pip\_internal\utils\misc.py", line 20, in <module>
    from pip._vendor import pkg_resources
  File "D:\soft\PycharmProjects\python9\helloworld\build\helloworld\android\gradle\app\build\generated\python\bp\pip\_vendor\pkg_resources\__init__.py", line 58, in <module>
    from pip._vendor.six.moves import urllib, map, filter
ModuleNotFoundError: No module named 'pip._vendor.six.moves'

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:generateDebugPythonRequirements'.
> Process 'command 'py'' finished with non-zero exit value 1

  To view full details in Android Studio:
  * Click the 'Build: failed' caption to the left of this message.
  * Then scroll up to see the full output.

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 6s
2 actionable tasks: 2 executed
Building...
                                                                                             
Error while building project.

In Toga0.31, it is normal. I saw Toga0.4 and wanted to try out its new features. I created a new project, but there was an error while using “briefcase build android".How to correct the above error？

[rmartin16]

Previously reported here:

• Android build fails if py command finds Python 3.12: ModuleNotFoundError: No module named 'pip._vendor.six.moves' briefcase#1480

The py command is finding Python 3.12 but BeeWare does not yet support building Android packages with Python 3.12.

The simplest workaround may just be uninstalling Python 3.12 until such support is added....which shouldn't be too much longer.

Otherwise, you'll need to ensure that the py command uses an older Python by default.

[wanglifeng95]

Thanks very much. Yes, just delete python3.12. Toga0.4 runs better than previous versions, especially in terms of interface display

[mhsmith]

You don't have to completely uninstall Python 3.12 – just use a different version when you create your Briefcase virtual environment. As long as you installed it with the standard installer from python.org, Chaquopy should be able to find it.

After doing this, you'll also need to re-run briefcase create android.

[wanglifeng95]

Anaconda Python3.9 is used for Briefcase virtual environments，and there was an error not uninstalling Python3.12. When uninstalling it, it becomes normal