Q:

Buttons don't react after onBackPressed()

I'm programming a small game, on the start screen, there are different options, like to start the game which starts a new activity.  But the other buttons like 'legal stuff' or 'tutuorial' only show a new XML layout via setContentView. 
Right now I'm trying to get the BackButton to work when you are in one of those layouts (so you get back to the start screen when pressing it).  I'm using the method onBackPressed() but also tried it with onKeyDown (same effect in my case).  All I'm doing in that method is to use setContentView to bring up the start screen layout again. 
The problem is, once I get back to the start screen, the buttons do not work.  They become orange when pressed, but nothing happens. 
Any suggestions what I need to change? 
My (shortened) activity:
public class Startbildschirm extends Activity {

    private int mSchwierigkeit = Const. LEICHT;

    public void onCreate (Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.startbildschirm);
        getWindow().setFlags(WindowManager. LayoutParams. FLAG_FULLSCREEN, WindowManager. LayoutParams. FLAG_FULLSCREEN);

        schwierigkeitListener();
        impressumListener();
        highscoreListener();
        tutorialListener();
        startListener();

    }

    private void schwierigkeitListener () {
        Button einfach = (Button) findViewById(R.id.radioEinfach);
        einfach.setOnClickListener(new View. OnClickListener() {

            public void onClick(View v) {
                mSchwierigkeit = Const. LEICHT;
            }
        });

        Button mittel = (Button) findViewById(R.id.radioMittel);
        mittel.setOnClickListener(new View. OnClickListener() {

            public void onClick(View v) {
                mSchwierigkeit = Const. MITTEL;
            }
        });

        Button schwer = (Button) findViewById(R.id.radioSchwer);
        schwer.setOnClickListener(new View. OnClickListener() {

            public void onClick(View v) {
                mSchwierigkeit = Const. SCHWER;
            }
        });
    }

    private void impressumListener () {
        Button impressum = (Button) findViewById(R.id.buttonImpressum);
        impressum.setOnClickListener(new View. OnClickListener() {

            public void onClick(View v) {
                setContentView(R.layout.impressum);             
            }
        });
    }

    private void highscoreListener () {
        Button highscore = (Button) findViewById(R.id.buttonHighscore);
        highscore.setOnClickListener(new View. OnClickListener() {

            public void onClick(View v) {
                String highscoreImp = getOldHighscore();
                setContentView(R.layout.highscore);
                TextView highscoreanzeige = (TextView) findViewById(R.id.highscore); 
                highscoreanzeige.setText(highscoreImp+" "+"sekunden");
            }
        });
    }

    private void tutorialListener () {
        Button tutorial = (Button) findViewById(R.id.buttonTutorial);
        tutorial.setOnClickListener(new View. OnClickListener() {

            public void onClick(View v) {
                setContentView(R.layout.tutorial);
            }
        });
    }

    private void startListener () {
        Button start = (Button) findViewById(R.id.buttonStart);
        start.setOnClickListener(new View. OnClickListener() {

            public void onClick(View v) {
                Intent startSpiel = new Intent(Startbildschirm.this, Spiel.class);
                Bundle giveSchwierigkeit = new Bundle();
                giveSchwierigkeit.putInt("schwierigkeit", mSchwierigkeit);
                startSpiel.putExtras(giveSchwierigkeit);
                startActivity(startSpiel);
            }
        });
    }

    public void onBackPressed () {
        setContentView(R.layout.startbildschirm);
    }

}

A:

@laalto comment absolutly right so in that case put below method or
just recall OnCreate view method in onBackPressed()
public void onBackPressed () {
        onCreate(null);
    }

Or second way
public void onBackPressed () {
           setContentView(R.layout.startbildschirm);
            schwierigkeitListener();
        impressumListener();
        highscoreListener();
        tutorialListener();
        startListener();
        }

thats it...

