Flex custom item renderer for the displayed item in the combobox

Question

I am using a custom item renderer in a combobox to display a custom drawing instead of the default text label.

This works fine for the dropdown list but the displayed item ( when the list is closed) is still the textual representation of my object.

Is there a way to have the displayed item rendered the same way as the one in the dropdown?

Answer 1

By default you cannot do this. However, if you extend ComboBox you can add this functionality easily. Here is a quick example, it is a rough version and probably needs testing / tweaking but it shows how you could accomplish this.

package
{
    import mx.controls.ComboBox;
    import mx.core.UIComponent;

    public class ComboBox2 extends ComboBox
    {
        public function ComboBox2()
        {
            super();
        }

        protected var textInputReplacement:UIComponent;

        override protected function createChildren():void {
            super.createChildren();

            if ( !textInputReplacement ) {
                if ( itemRenderer != null ) {
                    //remove the default textInput
                    removeChild(textInput);

                    //create a new itemRenderer to use in place of the text input
                    textInputReplacement = itemRenderer.newInstance();
                    addChild(textInputReplacement);
                }
            }
        }

        override protected function updateDisplayList(unscaledWidth:Number, unscaledHeight:Number):void {
            super.updateDisplayList(unscaledWidth, unscaledHeight);

            if ( textInputReplacement ) {
                textInputReplacement.width = unscaledWidth;
                textInputReplacement.height = unscaledHeight;
            }
        }
    }
}

Answer 2

I tried the above solution, but found that the selectedItem did not display when the combobox was closed. A extra line of code was required to bind the itemRenderer data property to the selectedItem:

            if ( !textInputReplacement ) {
                    if ( itemRenderer != null ) {
                            //remove the default textInput
                            removeChild(textInput);

                            //create a new itemRenderer to use in place of the text input
                            textInputReplacement = itemRenderer.newInstance();

                            // ADD THIS BINDING:
                            // Bind the data of the textInputReplacement to the selected item
                            BindingUtils.bindProperty(textInputReplacement, "data", this, "selectedItem", true);

                            addChild(textInputReplacement);
                    }
            }

Answer 3

I've extended Dane's code a bit further. In some cases clicking did not open the drop box with my renderer and I noticed that the normal Flex ComboBox skins did not fire. Thus in replaceTextInput() I added some additional event listeners and save a reference to the ComboBox button used to display the skins. Now it behaves just like the normal ComboBox.

Here's the code:

    package
    {
    import flash.events.Event;
    import flash.events.KeyboardEvent;
    import flash.events.MouseEvent;

    import mx.binding.utils.BindingUtils;
    import mx.controls.Button;
    import mx.controls.ComboBox;
    import mx.core.IFactory;
    import mx.core.UIComponent;
    import mx.events.DropdownEvent;

    /**
     * Extension of the standard ComboBox that will use the assigned 'itemRenderer'
     * for both the list items and the selected item.
     * 
     * Based on code from:
     * http://stackoverflow.com/questions/269773/flex-custom-item-renderer-for-the-displayed-item-in-the-combobox
     */
    public class ComboBoxFullRenderer extends ComboBox
    {
    protected var textInputReplacement:UIComponent;
    private var _increaseW:Number = 0;
    private var _increaseH:Number = 0;


    /**
     * Keeps track of the current open/close state of the drop down list. 
     */
    protected var _isOpen:Boolean = false;

    /**
     * Stores a reference to the 'Button' which overlays the ComboBox.  Allows
     * us to pass events to it so skins are properly triggered. 
     */
    protected var _buttonRef:Button = null;


    /**
     * Constructor. 
     */
    public function ComboBoxFullRenderer() {
        super();
    }


    /**
     * Sets a value to increase the width of our ComboBox to adjust sizing. 
     * 
     * @param val Number of pixels to increase the width of the ComboBox.
     */
    public function set increaseW(val:Number):void {
        _increaseW = val;
    }

    /**
     * Sets a value to increase the height of our ComboBox to adjust sizing. 
     * 
     * @param val Number of pixels to increase the height of the ComboBox.
     */
    public function set increaseH(val:Number):void {
        _increaseH = val;
    }


    /**
     * Override the 'itemRenderer' setter so we can also replace the selected
     * item renderer.
     *  
     * @param value The renderer to be used to display the drop down list items
     *   and the selected item.
     */
    override public function set itemRenderer(value:IFactory):void {
        super.itemRenderer = value;
        replaceTextInput();
    }


    /**
     * Override base 'createChildren()' routine to call our 'replaceTextInput()'
     * method to replace the standard selected item renderer.
     *  
     * @see #replaceTextInput();
     */
    override protected function createChildren():void {
        super.createChildren();
        replaceTextInput();
    }


    /**
     * Routine to replace the ComboBox 'textInput' child with our own child
     * that will render the selected data element.  Will create an instance of
     * the 'itemRenderer' set for this ComboBox. 
     */
    protected function replaceTextInput():void {
        if ( !textInputReplacement ) {
            if ( this.itemRenderer != null && textInput != null ) {
                //remove the default textInput
                removeChild(textInput);

                //create a new itemRenderer instance to use in place of the text input
                textInputReplacement = this.itemRenderer.newInstance();
                // Listen for clicks so we can open/close the drop down when
                // renderer components are clicked.  
                textInputReplacement.addEventListener(MouseEvent.CLICK, _onClick);
                // Listen to the mouse events on our renderer so we can feed them to
                // the ComboBox overlay button.  This will make sure the button skins
                // are activated.  See ComboBox::commitProperties() code.
                textInputReplacement.addEventListener(MouseEvent.MOUSE_DOWN, _onMouseEvent);
                textInputReplacement.addEventListener(MouseEvent.MOUSE_UP, _onMouseEvent);
                textInputReplacement.addEventListener(MouseEvent.ROLL_OVER, _onMouseEvent);
                textInputReplacement.addEventListener(MouseEvent.ROLL_OUT, _onMouseEvent);
                textInputReplacement.addEventListener(KeyboardEvent.KEY_DOWN, _onMouseEvent);

                // Bind the data of the textInputReplacement to the selected item
                BindingUtils.bindProperty(textInputReplacement, "data", this, "selectedItem", true);

                // Add our renderer as a child.
                addChild(textInputReplacement);

                // Listen for open close so we can maintain state.  The
                // 'isShowingDropdown' property is mx_internal so we don't
                // have access to it. 
                this.addEventListener(DropdownEvent.OPEN, _onOpen);
                this.addEventListener(DropdownEvent.CLOSE, _onClose);

                // Save a reference to the mx_internal button for the combo box.
                //  We will need this so we can call its dispatchEvent() method.
                for (var i:int = 0; i < this.numChildren; i++) {
                    var temp:Object = this.getChildAt(i);
                    if (temp is Button) {
                        _buttonRef = temp as Button;
                        break;
                    } 
                }
            }
        }
    }


    /**
     * Detect open events on the drop down list to keep track of the current
     * drop down state so we can react properly to a click on our selected
     * item renderer.
     *  
     * @param event The DropdownEvent.OPEN event for the combo box.
     */
    protected function _onOpen(event:DropdownEvent) : void {
        _isOpen = true;
    }


    /**
     * Detect close events on the drop down list to keep track of the current
     * drop down state so we can react properly to a click on our selected
     * item renderer.
     *  
     * @param event The DropdownEvent.CLOSE event for the combo box.
     */
    protected function _onClose(event:DropdownEvent) : void {
        _isOpen = false;
    }


    /**
     * When we detect a click on our renderer open or close the drop down list
     * based on whether the drop down is currently open/closed.
     *  
     * @param event The CLICK event from our selected item renderer.
     */
    protected function _onClick(event:MouseEvent) : void {
        if (_isOpen) {
            this.close(event);
        } else {
            this.open();
        }
    }


    /**
     * React to certain mouse/keyboard events on our selected item renderer and
     * pass the events to the ComboBox 'button' so that the skins are properly
     * applied.
     *  
     * @param event A mouse or keyboard event to send to the ComboBox button.
     * 
     */
    protected function _onMouseEvent(event:Event) : void {
        if (_buttonRef != null) {
            _buttonRef.dispatchEvent(event);
        }
    }
    } // end class
    } // end package

Answer 4

Thank you maclema and Maurits de Boer. I added a couple more things to this class to make it fit my needs:

• I overrode set itemRenderer so that this will work if you set the itemRenderer through AS instead of mxml. I moved the text input replacement code to its own function to avoid duplication.

• I added setters for 'increaseW' and 'increaseH' to resize the combobox if necessary because my renderer was too big for the combobox at first.

• I subtracted 25 from the textInputReplacement width so it doesn't ever overlap the dropdown button... may be better to use something more proportional to accommodate different skins and such.

Code:

package
{
 import mx.binding.utils.BindingUtils;
 import mx.controls.ComboBox;
 import mx.core.IFactory;
 import mx.core.UIComponent;

    public class ComboBox2 extends ComboBox
    {
        public function ComboBox2()
        {
                super();
        }

        protected var textInputReplacement:UIComponent;
        private var _increaseW:Number = 0;
        private var _increaseH:Number = 0;

  public function set increaseW(val:Number):void
  {
   _increaseW = val;
  }

  public function set increaseH(val:Number):void
  {
   _increaseH = val;
  }

  override public function set itemRenderer(value:IFactory):void
  {
   super.itemRenderer = value;
   replaceTextInput();
  }

        override protected function createChildren():void 
        {
                super.createChildren();
    replaceTextInput();

        }

        override protected function updateDisplayList(unscaledWidth:Number, unscaledHeight:Number):void {

          unscaledWidth += _increaseW;
          unscaledHeight += _increaseH;

                super.updateDisplayList(unscaledWidth, unscaledHeight);

                if ( textInputReplacement ) {
                        textInputReplacement.width = unscaledWidth - 25;
                        textInputReplacement.height = unscaledHeight;
                }
        }

        protected function replaceTextInput():void
        {
         if ( !textInputReplacement ) {
                        if ( this.itemRenderer != null ) {
                                //remove the default textInput
                                removeChild(textInput);

                                //create a new itemRenderer to use in place of the text input
                                textInputReplacement = this.itemRenderer.newInstance();
                                addChild(textInputReplacement);

                                // ADD THIS BINDING:
                             // Bind the data of the textInputReplacement to the selected item
                             BindingUtils.bindProperty(textInputReplacement, "data", this, "selectedItem", true);

                             addChild(textInputReplacement);

                        }
                }
        }
    }
}

Answer 5

I was looking for a way to do this using the Spark ComboBox.

This thread was very useful to me but so far there have only been answers on how to do it using an mx:ComboBox. I thought that I should append my answer on how to do it using a spark ComboBox.

1. Create a new skin of the ComboBox
2. Hide and disable the textInput
3. Insert your own component

This is what the skin would look like:

<s:SparkSkin>

    <... Lots of other stuff/>

    <s:BorderContainer height="25">
        <WHATEVER YOU NEED HERE!/>
    </s:BorderContainer>

    <!-- Disable the textInput and hide it -->
    <s:TextInput id="textInput"
        left="0" right="18" top="0" bottom="0" 
        skinClass="spark.skins.spark.ComboBoxTextInputSkin"

        visible="false" enabled="false"/> 


</s:SparkSkin>

With the Spark ComboBox this process is very easy and does not require you to extend ComboBox.

Answer 6

I found an easier way of changing the renderer for the selected element. This one only works if your element inherits from the TextInput class, in Flex 4.0 or above.

In Flex v4.5, in ComboBase.createChildren at line 1177, you will find that the class definable for the textInput can be passed using the style key textInputClass:

// Mechanism to use MXFTETextInput. 
var textInputClass:Class = getStyle("textInputClass");            
if (!textInputClass || FlexVersion.compatibilityVersion < FlexVersion.VERSION_4_0)
{
    textInput = new TextInput();
}
else
{
   textInput = new textInputClass();
}

Just change the value of this key in the constructor of your combo and now you have your own renderer for the selectedItem.

public function ComboAvailableProfessor()
{
    super();

    itemRenderer = new ClassFactory( ProfessorAvailableListItemRenderer );
    setStyle( 'textInputClass', ProfessorAvailableSelectedListItemRenderer );
}

Finally you must bind the data property to the selectedItem property in your combo in order to get data displayed.

override protected function createChildren():void
{
    super.createChildren();

    BindingUtils.bindProperty( textInput, 'data', this, 'selectedItem', true );
}