Tutorial :Flex: Custom Item Renderer For Combobox controls truncates text


I've implemented a custom item renderer that I'm using with a combobox on a flex project I'm working on. It displays and icon and some text for each item. The only problem is that when the text is long the width of the menu is not being adjusted properly and the text is being truncated when displayed. I've tried tweaking all of the obvious properties to alleviate this problem but have not had any success. Does anyone know how to make the combobox menu width scale appropriately to whatever data it's rendering?

My custom item renderer implementation is:

<?xml version="1.0" encoding="utf-8"?>  <mx:HBox xmlns:mx="http://www.adobe.com/2006/mxml"      styleName="plain" horizontalScrollPolicy="off">         <mx:Image source="{data.icon}" />      <mx:Label text="{data.label}" fontSize="11" fontWeight="bold" truncateToFit="false"/>    </mx:HBox>  

And my combobox uses it like so:

    <mx:ComboBox id="quicklinksMenu" change="quicklinkHandler(quicklinksMenu.selectedItem.data);" click="event.stopImmediatePropagation();" itemRenderer="renderers.QuickLinkItemRenderer" width="100%"/>  

EDIT: I should clarify on thing: I can set the dropdownWidth property on the combobox to some arbitrarily large value - this will make everything fit, but it will be too wide. Since the data being displayed in this combobox is generic, I want it to automatically size itself to the largest element in the dataprovider (the flex documentation says it will do this, but I have the feeling my custom item renderer is somehow breaking that behavior)


Just a random thought (no clue if this will help):

Try setting the parent HBox and the Label's widths to 100%. That's generally fixed any problems I've run into that were similar.


Have you tried using the calculatePreferredSizeFromData() method?

protected override function calculatePreferredSizeFromData(count:int):Object  


This answer is probably too late, but I had a very similar problem with the DataGrid's column widths.

After much noodling, I decided to pre-render my text in a private TextField, get the width of the rendered text from that, and explicitly set the width of the column on all of the appropriate resize type events. A little hack-y but works well enough if you haven't got a lot of changing data.


You would need to do two things:

  • for the text, use mx.controls.Text (that supports text wrapping) instead of mx.controls.Label
  • set comboBox's dropdownFactory.variableRowHeight=true -- this dropdownFactory is normally a subclass of List, and the itemRenderer you are setting on ComboBox is what will be used to render each item in the list

And, do not explicitly set comboBox.dropdownWidth -- let the default value of comboBox.width be used as dropdown width.


If you look at the measure method of mx.controls.ComboBase, you'll see that the the comboBox calculates it's measuredMinWidth as a sum of the width of the text and the width of the comboBox button.

    // Text fields have 4 pixels of white space added to each side      // by the player, so fudge this amount.      // If we don't have any data, measure a single space char for defaults      if (collection && collection.length > 0)      {          var prefSize:Object = calculatePreferredSizeFromData(collection.length);            var bm:EdgeMetrics = borderMetrics;            var textWidth:Number = prefSize.width + bm.left + bm.right + 8;          var textHeight:Number = prefSize.height + bm.top + bm.bottom                       + UITextField.TEXT_HEIGHT_PADDING;            measuredMinWidth = measuredWidth = textWidth + buttonWidth;          measuredMinHeight = measuredHeight = Math.max(textHeight, buttonHeight);      }  

The calculatePreferredSizeFromData method mentioned by @defmeta (implemented in mx.controls.ComboBox) assumes that the data renderer is just a text field, and uses flash.text.lineMetrics to calculate the text width from label field in the data object. If you want to add an additional visual element to the item renderer and have the ComboBox take it's size into account when calculating it's own size, you will have to extend the mx.controls.ComboBox class and override the calculatePreferredSizeFromData method like so:

  override protected function calculatePreferredSizeFromData(count:int):Object    {        var prefSize:Object = super.calculatePrefferedSizeFromData(count);        var maxW:Number = 0;        var maxH:Number = 0;        var bookmark:CursorBookmark = iterator ? iterator.bookmark : null;        var more:Boolean = iterator != null;          for ( var i:int = 0 ; i < count ; i++)        {            var data:Object;            if (more) data = iterator ? iterator.current : null;            else data = null;            if(data)            {                var imgH:Number;                var imgW:Number;                  //calculate the image height and width using the data object here                  maxH = Math.max(maxH, prefSize.height + imgH);                maxW = Math.max(maxW, prefSize.width + imgW);            }            if(iterator) iterator.moveNext();        }          if(iterator) iterator.seek(bookmark, 0);        return {width: maxW, height: maxH};   }  

If possible store the image dimensions in the data object and use those values as imgH and imgW, that will make sizing much easier.


If you are adding elements to the render besides an image, like a label, you will also have to calculate their size as well when you iterate through the data elements and take those dimensions into account when calculating maxH and maxW.

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