How to detect UI thread on Android?

Question

Is there a robust way to detect if Thread.currentThread() is the Android system UI thread in an application?
I would like to put some asserts in my model co

Answer 1

As of API level 23 the Looper has a nice helper method isCurrentThread. You could get the mainLooper and see if it's the one for the current thread this way:

Looper.getMainLooper().isCurrentThread()

It's practically the same as:

Looper.getMainLooper().getThread() == Thread.currentThread()

but it could be a bit more readable and easier to remember.

Answer 2

Couldn't you use the runOnUiThread method in the Activity class?See..

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

Answer 3

Besides checking looper, if you ever tried to logout thread id in onCreate(), you could find the UI thread(main thread) id always equals to 1. Therefore

if (Thread.currentThread().getId() == 1) {
    // UI thread
}
else {
    // other thread
}

Answer 4

I think that best way is this:

 if (Looper.getMainLooper().equals(Looper.myLooper())) {
     // UI thread
 } else {
     // Non UI thread
 }

Answer 5

public boolean onUIThread() {
    return Looper.getMainLooper().isCurrentThread();

}

But it requires API level 23

Answer 6

Common practice to determine the UI Thread's identity is via Looper#getMainLooper:

if (Looper.getMainLooper().getThread() == Thread.currentThread()) {
  // On UI thread.
} else {
  // Not on UI thread.
}

From API level 23 and up, there's a slightly more readable approach using new helper method isCurrentThread on the main looper:

if (Looper.getMainLooper().isCurrentThread()) {
  // On UI thread.
} else {
  // Not on UI thread.
}