Clicking the back button twice to exit an activity

I have noticed this pattern in a lots of android apps and games recently. When clicking the hardware back button to exit the application , a toast message comes up  with message "Please click back again to exit the application". i was wonder when i saw it first time and tried to implement same logic in my own android application and now finally i knew it how we can achieve this.so here in this post i would like to share this awesome code.

You need to implement the below code on onBackPressed() override method:

boolean doubleBackToExitPressedOnce = false;

@Override
public void onBackPressed() {
    if (doubleBackToExitPressedOnce) {
        super.onBackPressed();
        return;
    }

    this.doubleBackToExitPressedOnce = true;
    Toast.makeText(this, "Please click BACK again to exit", Toast.LENGTH_SHORT).show();

    new Handler().postDelayed(new Runnable() {

        @Override
        public void run() {
            doubleBackToExitPressedOnce=false;                       
        }
    }, 2000);
}