뒤로가기 두번 누르면 종료

적용할 페이지

public class MainActivity extends ActionBarActivity {

    private BackPressCloseHandler backPressCloseHandler;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        backPressCloseHandler = new BackPressCloseHandler(this);
    }

    public void onBackPressed(){
        backPressCloseHandler.onBackPressed();
    }
}

[BackPressCloseHandler.java]

public class BackPressCloseHandler {

    private long backKeyPressedTime = 0;
    private Toast toast;
    private Activity activity;

    public BackPressCloseHandler(Activity context) {
        this.activity = context;
    }

    public void onBackPressed(){
        if(System.currentTimeMillis() > backKeyPressedTime + 2000){
            backKeyPressedTime = System.currentTimeMillis();
            showGuide();
            return;
        }
        if (System.currentTimeMillis() <= backKeyPressedTime + 2000){
            activity.finish();
            toast.cancel();
        }
    }

    public void showGuide(){
        toast = Toast.makeText(activity, "뒤로 버튼을 한번 더 누르시면 종료됩니다.", Toast.LENGTH_LONG);
        toast.show();
    }

}