Please explain this code.

Question

private static final int TIME_INTERVAL = 2000;
private long mBackPressed;

@Override
public void onBackPressed()
{
if (mBackPressed + TIME_INTERVAL > System.currentTimeMillis())
{
super.onBackPressed();
return;
}
else { Toast.makeText(getBaseContext(), "Tap back button in order to exit", Toast.LENGTH_SHORT).show(); }

mBackPressed = System.currentTimeMillis();
}

Answer 1

It's a "press back twice to exit" code.
By the time you press back once, the current system time in milliseconds is stored in the mBackPressed variable. Every time you click the back button, the difference of "currentTime - lastClickTime" is calculated based on that variable and if its less than 2000 millis (2 secs) its considered as a consequtive doubleclick, if the user re-taps the back button after more than 2 seconds, its not considered as a doubletap...

Answer 2

if you don't know it, a toast is a rounded rectangle at the two sides which displays a piece of text

it has two display times, long or short

just a back button snippet