Home > Adobe Flex > Extending the Flex TextInput control to colorize background on focus

Extending the Flex TextInput control to colorize background on focus

Normal Flex TextInput controls automatically give you that “halo” border whenever the user highlights or sets focus to a text field. Although when Flex first came out, I thought the halo border was a very slick way to show focus, but now I want it to be even more obvious to the user as they tab through a form a select a field for text entry.

First thing I did was create a new ActionScript component that extended TextInput. My new control would work every bit the same as the standard TextInput and only wanted to alter what happens when the fields focus event was fired. Luckily, all I had to do was override the focusIn and focusOut handler’s, call super() to execute any standard logic in the parent method, and set my styles.

The resulting component ended up like this:

package components
	import flash.events.FocusEvent;
	import mx.controls.TextInput;
	 * Extends normal TextInput control but overrides focusIn and focusOut handlers
	 * to colorize the background color of the TextInput control differently when
	 * highlighted/focused
	public class MyTextInput extends TextInput
		 * Constructor
		public function MyTextInput()
		 * Overrides focusInHandler to colorize background on focusIn events
		override protected function focusInHandler(event:FocusEvent):void
			super.focusInHandler( event );
			//backgroundFocusInColor derived from master style-sheet
			this.setStyle('backgroundColor', getStyle('backgroundFocusInColor'));
		 * Overrides focusOutHandler to reset background on focusOut events
		override protected function focusOutHandler(event:FocusEvent):void
			super.focusOutHandler( event );
			//backgroundFocusOutColor derived from master style-sheet
			this.setStyle('backgroundColor', getStyle('backgroundFocusOutColor'));

Note the getStyle function calls. Typically, I keep all style-related colors and property values stored in a master style-sheet for my applications. This keeps the style-related values out of the views so I can easily manage them in one place.

For this new control, I defined a component-level type (or “class”) selector in my master CSS. Since this component extends TextInput, the normal styles for TextInput also apply, whereas the styles specified in the MyTextInput selector apply only to this control. Keep in mind, the “backgroundFocusInColor” and “backgroundFocusOutColor” properties are entirely made up and are not real component style properties, but it is totally legal to come up with your own style properties!

	backgroundFocusInColor	: #DFF8FF;
	backgroundFocusOutColor : #FEFFAF;

Lastly, anywhere in my views I wish to use this component, I simply specify the newly built control:

<components:MyTextInput id="myTextInput" />

That’s it!

Categories: Adobe Flex Tags:
  1. March 20th, 2009 at 08:49 | #1

    Hey Erich,

    Thanks for your work. I am definitely a “newbe” (the newbeest one) in Flex and actually looking to find a way to extend Flex pre-built components library with my own.
    I am searching “Degrafa” tool now for tiles and repetitive patterns in application background. Kinda confusing at this point.

  2. Ismael
    May 25th, 2009 at 12:19 | #2

    A simpler implementation, using the fucusIn and focusOut events:

    private function textFocusIn(ev:FocusEvent):void {
    TextInput(ev.currentTarget).setStyle(“backgroundColor”, 0xffff00);

    private function textFocusOut(ev:FocusEvent):void {
    TextInput(ev.currentTarget).setStyle(“backgroundColor”, 0xffffff);

  3. September 9th, 2009 at 08:53 | #3

    Hi! I was surfing and found your blog post… nice! I love your blog. :) Cheers! Sandra. R.

  4. September 17th, 2009 at 11:34 | #4

    Hey Erich,
    Good posts… very clean and simple. I did what you listed here and it worked perfect!! Nice to see a blog where that actually happens.
    I am new to Flex and i was wondering if you had time to answer a question? I would like to change the way the required=true works in the form Item tag. Instead of that red asterisk appearing next to the label is there a way to get an image inside the text input box? I would like a small image to appear in the upper right corner of the box. Any suggestions?

  5. February 4th, 2010 at 22:42 | #5

    Step 1. On focusIn, left side of flex textinput control become light blue,
    Step 2. At the validation, entire control border become red and left side of the control become,

    thick red vertical line,
    Step 3. Now when I gradually delete additional letters from the textinput control, entire red

    outline border automatically removed, but I can see red think line of the left side of the textinput

    control is still there,

    My requirements are,
    1. Validation colors need to change.
    2. After validation, remain left red think vertical line need to change to normal focusIn

    color(light blue)
    Can anyone help me to achieve this, is that event fire, CSS changes, function overwrite.

    Thanks in advanced.

  6. September 27th, 2010 at 21:16 | #6

    This is perfect! Thanks. :)

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