main_screen cannot be resolved or is not a field error showing even i setup the resources correctly
<p>In the following code main_screen can not be resolved or not a field  and button IDs also showing same error here I validated the res folder still i am getting these errors for IDs only.</p>

<pre><code>public class MainScreenActivity extends Activity {
    Button btnViewProducts;
    Button btnNewProduct;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main_screen);

    // Buttons
    btnViewProducts = (Button) findViewById(R.id.btnViewProducts);
    btnNewProduct = (Button) findViewById(R.id.btnCreateProduct);

    // view products click event
    btnViewProducts.setOnClickListener(new View.OnClickListener() {

        public void onClick(View view) {
            // Launching All products Activity
            Intent i = new Intent(getApplicationContext(),
                    AllProductsActivity.class);
            startActivity(i);

        }
    });
</code></pre>
