How to access Android APIs in a toga app

[diamondStar35]

Greetings everyone.
I am planning to build a python application using toga, and i am looking for a way to access android TTS (Text to speech) API to speak some text to screen readers. But i don't know how can I access android classes using toga. Is there a way to access android classes? Possibly by using "pyjnius", But "pyjnius" requires access to the app's main activity. Would it be possible with toga?
Would "plyer" work with toga? I am not sure. Could somebody provide a clear path? I would appreciate that.
Thank you.

[freakboy3742]

Yes, there is a way to access Android classes; however, BeeWare uses Chaquopy, rather than Pyjnius. The syntax for accessing Java classes is similar to that used by Pjnius, but not drop-in identical; see the documentation for details.

It might be possible to use Plyer, but there will likely be some adaptation work required - either an adaptation layer to convert the usage of Pyjnius APIs into the comparable Chaquopy APIs; or to update Plyer to use Chaquopy APIs directly.

Alternatively, you could write code directly against the TTS libraries using the Chaquopy APIs. The primary benefit of using a layer like Plyer is platform independence; but if you're only targeting Android, those benefits may not be a major concern.

[diamondStar35]

@freakboy3742
Could you please provide an example on how to use Chaquopy APIs in my python app? Would be appreciated. :)

[mhsmith]

The "Chaquopy" link in @freakboy3742's previous comment already contains many examples.

[diamondStar35]

@mhsmith
I saw the examples, but most of them talk about embedding python inside a native java application, which is not the case. I am trying to find a way just to access android classes inside a toga app.

[mhsmith]

An Android app is a native Java application. You don't need to pay attention to the details of how to embed and start Python, because Briefcase will handle that for you. But all the other material about accessing Java classes and objects from Python is still applicable. In fact, that's how Toga itself works.

[diamondStar35]

@mhsmith
So, i can use "import android" or "from android import something" and it will work?
Because like i said, most examples on Chaquopy website do not use python to interact with java classes, but they use Chaquopy to embed a python library into an android app. so i just need a clear example using python to demonstrate how to do that using Chaquopy.
Also, I've seen something called "Rubicon-java" which is also a project of beeware. Is that still used?

[freakboy3742]

Essentially yes - import android will work in a BeeWare app.

If you want other examples of Chaquopy usage, the Android backend for Toga is entirely written using Chaquopy. The implementation of a widget like Button may be a helpful reference.

Rubicon Java is no longer used. Toga switched to using Chaquopy around 3 years ago.

[mhsmith]

Unfortunately import android will not work: you need to import a specific class using the from X import Y syntax. The reason for this is that Java provides no way to detect whether a Java package exists or not, or to list all the classes inside it.

[diamondStar35]

So, one more thing.
How to get the application context? I have seen this, from toga_android/hardware/camera.py:
self.context = self.interface.app._impl.native.getApplicationContext()
Is this correct in all cases?

[mhsmith]

Yes, but the app here is your toga.App object, so if you're writing code in the context of a toga.App subclass, you can just refer to it as self.