title: android crash when using setVisibility(View.VISIBLE)
body: <p>I seem to be getting application crashes at:</p>
  
  <blockquote>
    <p>parent.findViewById(R.id.a_1).setVisibility(View.VISIBLE);</p>
  </blockquote>
  
  <p>not sure what im doing wrong</p>
  
  <p>code is below</p>
  
  <p><strong>layouttext.java</strong></p>
  
  <pre><code>    public class layouttest extends Activity {
   private Spinner solvefor; 
   private ArrayAdapter&lt;CharSequence&gt; featuresAdapter; 
   private List&lt;CharSequence&gt; featuresList; 
  
      /** Called when the activity is first created. */
      @Override
      public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.main);
          featuresList = new ArrayList&lt;CharSequence&gt;(); 
          featuresAdapter = new ArrayAdapter&lt;CharSequence&gt;(this, android.R.layout.simple_spinner_item, featuresList); 
          featuresAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); 
          solvefor = ((Spinner) layouttest.this.findViewById(R.id.solvefor)); 
          solvefor.setAdapter(featuresAdapter); 
          featuresAdapter.add("Velocity"); 
          featuresAdapter.add("Time"); 
          featuresAdapter.add("Distance"); 
          solvefor.setOnItemSelectedListener(new MyOnItemSelectedListener());
      }
  }
  </code></pre>
  
  <p><strong>MyOnItemSelectedListener.java</strong>
      package android.example.layouttest;</p>
  
  <pre><code>import android.view.View;
  import android.widget.AdapterView;
  import android.widget.AdapterView.OnItemSelectedListener;
  import android.widget.Toast;
  
  public class MyOnItemSelectedListener implements OnItemSelectedListener {
   private static final int SPINNER_OPTION_FIRST = 0; 
      private static final int SPINNER_OPTION_SECOND = 1;
   public void onItemSelected(AdapterView&lt;?&gt; parent, View view, int pos, long id) {
     switch(pos) { 
           case SPINNER_OPTION_FIRST: { 
            Toast.makeText(parent.getContext(), "0", Toast.LENGTH_LONG).show();
            break;
           } 
           case SPINNER_OPTION_SECOND: { 
            Toast.makeText(parent.getContext(), "1", Toast.LENGTH_LONG).show();
            parent.findViewById(R.id.a_1).setVisibility(View.VISIBLE);
            parent.findViewById(R.id.a_2).setVisibility(View.VISIBLE);
            break;
           } 
    }  
   }   
   public void onNothingSelected(AdapterView&lt;?&gt; parent) {      
     // Do nothing.    
     }
  }
  </code></pre>