instantiating inside of onCreate compared to outside of it. why?

Issue

most every example of Android code is done like example 2 shown below, why is that so much better than what is shown in examaple 1?

example 1

    class TestActivity extends Activity() {

    HelperClass helperClass = new HelperClass();

    EditText extiText = (EditText) findViewById(R.id.editText1);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);


    }

    }

example 2

    class TestActivity extends Activity() {

    HelperClass helperClass;

    EditText editText;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    helperClass = new HelperClass();

    editText = (EditText) findViewById(R.id.editText1);

    }

    }

Solution

You can do

HelperClass helperClass = new HelperClass(); 

But you can't do

 EditText extiText = (EditText) findViewById(R.id.editText1); 

like example 1.

Because the layout file in loaded when onCreate in called for setContentView(R.layout.layout); and because R.id.editText1 is a part of this layout, you have not access to it until layout gets loaded.

Read about onCreate()

Answered By - Pankaj Kumar