android - How do I save the state of my activity?

How do I save the way my Activity is so when closed with the backed button and resumed it will be the same way it was when closed.

this is my Activity code:

public class Levels extends Activity{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setTheme(android.R.style.Theme_NoTitleBar_Fullscreen);
        setContentView(R.layout.levels);


        final EditText anstext1 = (EditText) findViewById(R.id.anstext1);
        Button button1 = (Button) findViewById(R.id.button1);

        button1.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {   
                 String result = anstext1.getText().toString();
                 if(result.equals("they"))

                     setContentView(R.layout.social);
                 else 
                   Toast.makeText(getApplicationContext(), "Wrong", Toast.LENGTH_LONG).show();
            }
        });
        }
}