android: Add interface MainThreadScope that simplifies CoroutineScope implementation

[cypressious]

Consider adding an interface

interface MainThreadScope : CoroutineScope {
    val job: Job

    override val coroutineContext: CoroutineContext
        get() = Dispatchers.Main + job
}

that simplifies the implementation of CoroutineScope.

If this is considered useful, I would be glad to create a PR.

[fvasco]

Consider to use an helper class

class CoroutineScopeHelper(dispatcher: CoroutineDispatcher = Dispatchers.Default, job: Job = Job()) : CoroutineScope {
    override val coroutineContext: CoroutineContext = dispatcher + job
}

class MyCode : CoroutineScope by CoroutineScopeHelper(Dispatchers.Main) {

    fun cancel() {
        coroutineContext.cancel()
    }
}

[elizarov]

You can already simplify its implementation in the following way:

class MyClass : CoroutineScope {
    override val coroutineContext: CoroutineContext = Dispatchers.Main + Job()
}

Then, whenever you need to cancel a job, just use coroutineContext.cancel(). Does it help? Do we need to introduce any extra abstraction to ... ? It is already just one line.

[qwwdfsad]

I've ended up with a more elegant proposal, so I am closing this one.
See #829