title: issues passing a value from the activity to the Datasource
body: <p>After trying to get a text from the database i got this error:</p>
  
  <pre><code>12-21 09:54:10.948: E/AndroidRuntime(25745): FATAL EXCEPTION: main
  12-21 09:54:10.948: E/AndroidRuntime(25745): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ggservice.democracy/com.ggservice.democracy.sondaggioActivity}: android.database.sqlite.SQLiteException: near "=": syntax error: , while compiling: SELECT _id, preferita, nome FROM sondaggi WHERE _id=
  </code></pre>
  
  <p><strong>this is the call:</strong></p>
  
  <pre><code>Cursor values = datasource.getDomanda(strcategory );
          if (values.moveToFirst()) // data?
                 System.out.println(values.getString(values.getColumnIndex("domanda"))); 
  
                 values.close(); 
  </code></pre>
  
  <p><strong>And it calls this:</strong></p>
  
  <pre><code>public Cursor getDomanda(String id) {
              List&lt;sondaggi&gt; domande = new ArrayList&lt;sondaggi&gt;();
  
              Cursor cursor = database.query(MySQLiteHelper.TABLE_SONDAGGI,
                      allCategorieColumns, MySQLiteHelper.COLUMN_ID + "=", new String[] { id }, null, null, null);
  
              cursor.moveToFirst();
              while (!cursor.isAfterLast()) {
                sondaggi sondaggio = cursorToSondaggi(cursor);
                domande.add(sondaggio);
                cursor.moveToNext();
              }
  
              return cursor;
            }
  </code></pre>
  
  <p>the id seams empty, but i know there is a value there, i have tested the variable passage. i mean, if i Toast the strcategory it return the right value.</p>