Is it normal for the "activity.onCreate()" method to be called multiple times

You might want to read through the documentation on the Activity lifecycle.

OnCreate will only be called one time for each lifetime of the Activity. However, there are a number of situations that can cause your activity to be killed and brought back to life. Thus, onCreate will be called again.

To support this properly, you can save state information in onSaveInstanceState and restore it fron the state bundle you get in on create.

Other than the expected cases, I have observed that only those activities (onCreate) are called twice which are creating new Thread or Runnable. (I believe this to be a bug in Android).

The solution is simple (though you may not like it :p)

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

        if(savedInstanceState == null){
            // everything else that doesn't update UI
        }
    }