why , the position of setContentView() is creating Error
<p>why , this is NOT-OK , it is creating errors .  </p>

<pre><code>super.onCreate(savedInstanceState);

btn = ( Button ) findViewById(R.id.button);
btn.setOnClickListener(this);

setContentView(R.layout.activity_according_to_book);
</code></pre>

<p>and if i am putting "<strong>setContentView(R.layout.activity_according_to_book);</strong>" at Second line just after "<strong>super.onCreate(savedInstanceState);</strong>" , it is not creating Errors .</p>

<pre><code>super.onCreate(savedInstanceState);
setContentView(R.layout.activity_according_to_book);

btn = ( Button ) findViewById(R.id.button);
btn.setOnClickListener(this);
</code></pre>
