Confirm Exit OnBackpressed click back twice.

@Overridepublic void onBackPressed() {
    confirmExit(MainActivity.this);
}

import android.support.v4.app.ActivityCompat;

public static boolean doubleBackToExitPressedOnce = false;

@TargetApi(Build.VERSION_CODES.JELLY_BEAN)
public static void confirmExit(AppCompatActivity context) {
    if (doubleBackToExitPressedOnce) {
        ActivityCompat.finishAffinity(context);
    }

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

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

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