add listener to TrayMenuController

[ledwardchow]

Add listener to support cryptomator/cryptomator#2489

[overheadhunter]

Could you add some JavaDoc (just a line or two, explaining what implementers are expected to do with the given listener).

Edit: Also I just noticed onBeforeShow is a terrible name, as it suggests this has something to do with showTrayIcon(...). I see two options:

1. Either set up the listener during showTrayIcon(...) (add a new nullable param)
2. Or rename this method to onBeforeOpenMenu(...)

[ledwardchow]

Could you add some JavaDoc (just a line or two, explaining what implementers are expected to do with the given listener).

Edit: Also I just noticed onBeforeShow is a terrible name, as it suggests this has something to do with showTrayIcon(...). I see two options:

1. Either set up the listener during showTrayIcon(...) (add a new nullable param)
2. Or rename this method to onBeforeOpenMenu(...)

I've committed changes for option 2).

[overheadhunter]

Looks good, however can you please undo the xml file, as it is unrelated?

@infeo While I'm fine with this, we should at least discuss whether it is a more consistent API design to set all listeners during showTrayIcon. Or whether this mixed approach is acceptable? See listener A vs listener B. We could also opt for setting all listeners in separate methods and remove defaultAction from showTrayIcon(). I leave this up to you, since you will have to live with it for the foreseeable future 😉

[ledwardchow]

Looks good, however can you please undo the xml file, as it is unrelated?

done!