Why do OnCreate should be called only once on the start of Activity?

Question

I would like to know, why OnCreate() is called only once at the start of an activity?

Can we call OnCreate() more than once in the same activity?

If yes, than how can we call it? can anyone give an example?

Thanks a lot!!!

Answer 1

Why would you want to called it again? unless the activity is reconstructed, which is called by system. You cannot call OnCreate manually , it is the same reason why you won't call setContentView() twice. as docs:

onCreate(Bundle) is where you initialize your activity. Most importantly, here you will usually call setContentView(int) with a layout resource defining your UI, and using findViewById(int) to retrieve the widgets in that UI that you need to interact with programmatically. Once you finish init your widgets Why would you?

UPDATE I take some words back, you CAN do this manually but I still don't understand why would this be called. Have you tried Fragments ?
Samplecode:

public class MainActivity extends Activity implements OnClickListener {
        private Button btPost;
        private Bundle state;
        private int counter = 0;

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            state = savedInstanceState;
            btPost = (Button) findViewById(R.id.btPost);
            btPost.setOnClickListener(this);
            Toast.makeText(getBaseContext(), " " + counter, Toast.LENGTH_LONG)
                    .show();
        }

        @Override
        public void onClick(View v) {
            counter++;
            this.onCreate(state);
        }
    }