java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare(); [duplicate]

Answer 1

From http://developer.android.com/guide/components/processes-and-threads.html :

Additionally, the Android UI toolkit is not thread-safe. So, you must not manipulate your UI from a worker thread—you must do all manipulation to your user interface from the UI thread. Thus, there are simply two rules to Android's single thread model:

1. Do not block the UI thread
2. Do not access the Android UI toolkit from outside the UI thread

You have to detect idleness in a worker thread and show a toast in the main thread.

Please post some code, if you want a more detailed answer.

After code publication :

In strings.xml

"You are getting late do it fast"

In YourWorkerThread.java

Toast.makeText(getApplicationContext(), getString(R.string.idleness_toast), 
    Toast.LENGTH_LONG).show();

Don't use AlertDialog, make a choice. AlertDialog and Toast are two different things.