Rxjava AndroidSchedulers.mainThread() means UI thread?

Question

My code is like this:

.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(AndroidSchedulers.mainThread())
.subscribe ({
    adapter.notifyDataSetChanged()
})

but i got an error: Only the original thread that created a view hierarchy can touch its views. so i change it to :

.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(AndroidSchedulers.mainThread())
.subscribe ({
        runOnUiThread(Runnable {
            adapter.notifyDataSetChanged()
 })
 }

It makes sense.So I am confused. I had thought the .observeOn(AndroidSchedulers.mainThread()) means the code in the subscribe block runs on ui thread, but how I got this error?

Answer 1

The problem is with the code here:

.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(AndroidSchedulers.mainThread())

You can not subscribe on the UI thread as you noticed, you'll get an exception:

Only the original thread that created a view hierarchy can touch its views.

What you should do is to subscribe on I/O thread and observe on UI thread:

.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe ()

Answer 2

Something like this will work:

observerable.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread()) //works Downstream
.subscribe ({
   adapter.notifyDataSetChanged()
})