feat(android): add requestEnable method

[pwespi]

closes #590

[gregoiregentil]

Thank you for taking of #590. But don't you think that RequestEnable API should be integrated into Enable API? Because it takes care of the same feature but with different Android version. Am I clear in my comment? Or do you think that the user should check the Android version in his typescript logic?

[peitschie]

Just in case it's of any interest, here's an example of how this intent-based approach can be wired up so the success/fail result can still be returned via the promise-based API: https://github.com/don/cordova-plugin-ble-central/blob/073c80dbc269341a4822663bde85d090e98d32c4/src/android/BLECentralPlugin.java#L1332-L1350 (obviously, some adaption required!)

(Just driving by while checking if I needed this change too!)

[gregoiregentil]

My understanding (my wish) is to keep only the Enable call in my app. And in the Android code of the plugin, it should detect that we are in version 33+ of Android, so then it should use onActivityResult as explained in the previous comment, which will trigger the OS to show the new popup for the user to enable Bluetooth. Am I misunderstanding?

[pwespi]

Thank you all for your feedback.

I understand that you would like to have a single method to call in your app. My goal was that requestEnable would become that method. It should handle the result properly, as mentioned by @peitschie (thank you for the link!). This will be fixed with: #595.

In general I'd like to avoid that a method has a different implementation depending on the SDK version (which is not always possible). And the implementation with ACTION_REQUEST_ENABLE actually works on all supported Android versions. Therefore my plan was to have the new method requestEnable which supports all version and deprecate enable. I should probably have used the implementation with ACTION_REQUEST_ENABLE from the beginning, like the cordova-plugin-ble-central plugin does, and never have used the bluetoothAdapter.enable(). The Android documentation says:

The enable() method is provided only for applications that include a user interface for changing system settings, such as a "power manager" app.

So it was meant for "power manager" apps, and not for apps that just use Bluetooth. That's another reason why I would like to deprecate it.

@gregoiregentil Once #595 is merged, would you be able to switch to requestEnable completely, or is there a problem with that?