3 Answers

• this is my solution for pickers with one column:

  picker.clear = function(){
      if(picker.columns[0]) {
          var col = picker.columns[0];
          var len = col.rowCount;
              for(var x = len-1; x >= 0; x-- ){
                      var row = col.rows[x];
                      col.removeRow(row);
              }
      }
  }
  

• thePicker.columns = null;

• Daniel was close but .columns=null is crashing for me.

  partPicker.columns = [];
  partPickerData = [];
  

  is working. Picker is created and loaded from a database by:

  partPicker = Ti.UI.createPicker({
      left: 0,  width: 320, bottom: 215
  });
  
  while (rows.isValidRow()) {
      partPickerData.push({
          title: rows.field(0),
          fontSize: 16
      });
      rows.next();
  }
  partPicker.add(partPickerData);