title: How to disable / enable dialog negative positive buttons?
body: <p>Please look at  the custom dialog below. I have an edittext field on the dialog and if the text field is empty I would like to disable the <code>positiveButton</code>. I can get a charListener for the text field but I am not sure how I am going to set the <code>positivebutton</code> to disable or enable from that listener? What is the reference for the positive and negative buttons?</p>
  
  <pre><code> case DIALOG_TEXT_ENTRY:
      // This example shows how to add a custom layout to an AlertDialog
      LayoutInflater factory = LayoutInflater.from(this);
      final View textEntryView = factory.inflate(R.layout.alert_dialog_text_entry, null);
      return new AlertDialog.Builder(AlertDialogSamples.this)
          .setIconAttribute(android.R.attr.alertDialogIcon)
          .setTitle(R.string.alert_dialog_text_entry)
          .setView(textEntryView)
          .setPositiveButton(R.string.alert_dialog_ok, new DialogInterface.OnClickListener() {
              public void onClick(DialogInterface dialog, int whichButton) {
                  /* User clicked OK so do some stuff */
              }
          })
          .setNegativeButton(R.string.alert_dialog_cancel, new DialogInterface.OnClickListener() {
              public void onClick(DialogInterface dialog, int whichButton) {
                  /* User clicked cancel so do some stuff */
              }
          })
          .create();
  }
  </code></pre>