Running code in main thread from another thread

Question

In an android service I have created thread(s) for doing some background task.

I have a situation where a thread needs to post certain task on main thread\'s message

Answer 1

for Kotlin, you can use Anko corountines:

update

doAsync {
   ...
}

deprecated

async(UI) {
    // Code run on UI thread
    // Use ref() instead of this@MyActivity
}

Answer 2

As a commenter below pointed correctly, this is not a general solution for services, only for threads launched from your activity (a service can be such a thread, but not all of those are). On the complicated topic of service-activity communication please read the whole Services section of the official doc - it is complex, so it would pay to understand the basics: http://developer.android.com/guide/components/services.html#Notifications

The method below may work in the simplest cases:

If I understand you correctly you need some code to be executed in the GUI thread of the application (cannot think about anything else called "main" thread). For this there is a method on Activity:

someActivity.runOnUiThread(new Runnable() {
        @Override
        public void run() {
           //Your code to run in GUI thread here
        }//public void run() {
});

Doc: http://developer.android.com/reference/android/app/Activity.html#runOnUiThread%28java.lang.Runnable%29

Hope this is what you are looking for.

Answer 3

There is another simple way, if you don't have an access to the Context.

1). Create a handler from the main looper:

Handler uiHandler = new Handler(Looper.getMainLooper());

2). Implement a Runnable interface:

Runnable runnable = new Runnable() { // your code here }

3). Post your Runnable to the uiHandler:

uiHandler.post(runnable);

That's all ;-) Have fun with threads, but don't forget to synchronize them.

Answer 4

The simplest way especially if you don't have a context, if you're using RxAndroid you can do:

AndroidSchedulers.mainThread().scheduleDirect {
    runCodeHere()
}