Does a runnable in a service run on the UI thread

Question

In Android, when I create a runnable inside a service and run it, while I realize it runs in its own thread, is this thread somehow part of the UI thread? In other words, if the runnable carried out a long process, would it affect the UI?

EDIT:

private class SomeRunnable implements Runnable
{
  @Override
  public void run()
  {
    try
    {

    }
  }
}

SomeRunnable runnable = new SomeRunnable();
(new Handler()).postDelayed(runnable, 1000);

Solution 1

Docs:

A services runs in the same process as the application in which it is declared and in the main thread of that application,

Different thread:

Thread t = new Thread(new MyRunnable());
t.start();

UI/Service Thread:

Handler h = new Handler();
h.post(new MyRunnable());

Solution 2

No it is not part of UI thread, I assume by Runnable you mean a new thread that you execute by calling start().

Regardless if you start a new Thread in a service or activity it will not be part of the UI thread (unless you call something like join())

Edit

Since you are running a Runnable object with Handler, so it depends on where you initialize your handler. Service runs in the main thread, so initializing the handler in a service or activity will make the code be posted to the UI thread

Note, you need a single Handler object per your thread; so avoid creating a new one with every time e.g. (new Handler()).postDelayed(runnable, 1000); should be avoided and instead handler.postDelayed(runnable, 1000); where handler is an instance variable initialized in your service/activity class

Comments

[David Wasser]

Your assumption "...while I realize it runs in its own thread..." is not true. A Runnable can run anywhere, it depends on where you run it. For example, if you simply create a Handler in your Service and then post your Runnable using the Handler, it will run on the main (UI) thread.

[David Wasser]

If all you want to do is run the Runnable in a separate Thread, you don't need AsyncTask. Just do: new Thread(new SomeRunnable()).start();

[Johann]

But that refers to a service. My question is about launching a runnable from a service.

[Johann]

User117 seems to indicate otherwise. Are you sure?

[Johann]

I see conflicting responses posted here. Some seem to say yes and others say no.

[S.D.]

@AndroidDev The first piece of code launches a Runnable on a separate thread, completely unrelated to UI thread. The second piece of code runs the Runnable on same thread on which service is running, and it will effect UI thread.

[iTech]

Your question needs more clarification, what exactly you mean by Runnable. I mentioned it clearly if you start a new Thread by calling start(), it will be different from the UI Thread

[David Wasser]

@AndroidDev Yes, because there are different ways to "create a Runnable". If you will update your post with the code you use to "create a Runnable" then we can probably give you a better answer.

[Johann]

See the code I added above in my original post. There is no start.

[David Wasser]

See my comment to your question. That Runnable runs on the main (UI) thread.

[Johann]

I have never heard of running a Runnable with start. I am only familiar with runOnUiThread and using a Handler. I am familiar with starting Threads with start() however.

[Johann]

I am launching it with a Handler, so according to you, it must be running on the UI thread.

[Johann]

I don't use (new Handler()). I only posted that to show I use a Handler. I do in fact only create the handler once and it's a private member.

[S.D.]

@AndroidDev In case of handler, it will run on thread which executed new Handler() like you created handler in onBind() of service, that handler points to service thread now.