Presenter having Handler in Android MVP pattern

Question

Is it okay a presenter having Android Handler?
I know presenters should not have any Android related objects, but I really don't have any clear answer.

Here's the thing, this presenter runs a disk IO task on another thread, meanwhile, the activity has to change its view.

These jobs are supposed to be done concurrently. So I decided to pass the activity's handler as an argument and let presenter send message to activity like this:

class FooPresenter: FooContract.Presenter {
    …
    private fun doDiskIOTask(handler: Handler) {
            handler.sendEmptyMessage(0)
        do_something_on_new_thread_and_join()
        handler.sendEmptyMessage(1)
    }
    …
}

The activity has to know when the task is started and finished both and change view. Could you tell me if I'm doing it any wrong or the better way?

Answer 1

Passing a Handler to the presenter doesn't sound like a good idea, you wouldn't be able to unit test it. I think a better approach would be to just call a method on the view and then run on UI thread from there. If your view interface is an Activity you can use the very convenient runOnUiThread method, e.g.

class MyActivity : AppCompatActivity, FooContract.View {

    override fun emptyMessage0Method(){
        runOnUiThread { 
            // manipulate views here
        }
    }

}