According to Android doc, "...Additionally, the Andoid 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:
Do not block the UI thread Do not access the Android UI toolkit from outside the UI thread"
That seems very plausible, but is it correct that the compiler does NOT complain at all if a programmer violates the second rule?