Android optioncontainer

[freakboy3742]

Adds an OptionContainer widget for Android.

Android's BottomNavigationBar only allows 5 items. This implementation will allow you to add more items, raising a warning if you have too many, or try to select an index beyond the maximum. If you delete a visible tab (making room for more content), the lowest tab index from the "extra" tabs will be made visible.

Requires beeware/briefcase#1610, because of the need for build_gradle_dependencies and base_theme

TODO:

• Disabling tabs doesn't seem to be working
• I'm not convinced this does colors right - in particular, the background color of the tab bar seems off, given the examples in the Material3 docs
• The content probe for tabs isn't computing the size of content correctly. Possibly related - the background color of tabs aren't being set.

Fixes #2346

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct

[mhsmith]

I'm not convinced this does colors right - in particular, the background color of the tab bar seems off, given the examples in the Material3 docs

They're always changing the recommended style, but it looks basically the same as it does in these screenshots of Electron Cash, so I don't think it's worth looking into.

[mhsmith]

Disabling tabs doesn't seem to be working

It works fine for me, at least for tabs disabled at construction time:

        toga.OptionContainer(
            content=[
                toga.OptionItem(
                    "Blue", toga.Box(style=Pack(background_color="cornflowerblue"))),
                toga.OptionItem(
                    "Green", toga.Box(style=Pack(background_color="green")), enabled=False),
                toga.OptionItem(
                    "Red", toga.Box(style=Pack(background_color="red"))),
            ],
            ...

There's no visual difference, because inactive tabs are already gray, but the Green tab no longer responds to clicks.

[mhsmith]

The content probe for tabs isn't computing the size of content correctly

The Container base class requires resize_content to be called to set the available space, otherwise it'll default to zero. I've just pushed a commit that fixes this, at least for the simple red/green/blue example above.