title: findViewById returns null
body: <p>I have code:</p>
  
  <pre><code>public class HelloWorld extends Activity {
  
  private Button buttonOk;
  private Button buttonCancel;
  
  private OnClickListener buttonOkListener = new OnClickListener() {
      public void onClick(View v){
          EditText editText = (EditText)findViewById(R.id.input);
  
          CharSequence textFromInput = (CharSequence) editText.getText();
          Context context = getApplicationContext();
          int duration = Toast.LENGTH_SHORT;
  
          Toast toast = Toast.makeText(context,textFromInput,duration);
          toast.show();
      }
  };
  
  private OnClickListener buttonCancelListener = new OnClickListener() {
      public void onClick(View v){
          EditText editText = (EditText)findViewById(R.id.input);
  
          CharSequence textFromInput = (CharSequence) editText.getText();
          Context context = getApplicationContext();
          int duration = Toast.LENGTH_SHORT;
  
          Toast toast = Toast.makeText(context,textFromInput,duration);
          toast.show();
      }
  };
  
  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle icicle) {
      super.onCreate(icicle);
      // ToDo add your GUI initialization code here
  
      setContentView(R.layout.main);
  
      buttonOk = (Button)findViewById(R.id.buttonOk);
      buttonCancel = (Button)findViewById(R.id.buttonCancel);
  
      buttonOk.setOnClickListener(buttonOkListener);
      buttonCancel.setOnClickListener(buttonCancelListener);
  }
  }
  </code></pre>
  
  <p>and the layout file:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"&gt;
  &lt;TextView
      android:id="@+id/label"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:text="Wpisz swoje imię:"/&gt;
  &lt;EditText
      android:id="@+id/input"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:background="@android:drawable/editbox_background"
      android:layout_below="@id/label"/&gt;
  &lt;Button
      android:id="@+id/buttonOk"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_below="@id/input"
      android:layout_alignParentRight="true"
      android:layout_marginLeft="10dip"
      android:text="OK" /&gt;
  &lt;Button
      android:id="@+id/buttonCancel"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_toLeftOf="@id/buttonOk"
      android:layout_alignTop="@id/buttonOk"
      android:text="Anuluj" /&gt;
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>Line with buttonCancel.setOnClickListener(buttonCancelListener); throws an Exception because buttonCancel is null. What i am doing wrong?</p>