Blue Flex

Today I had to write some code to search for text that matched various file extensions, this should have been a no brainer of a task. But like some things that sound stupidly simple it caught me out.

If you have a string and you use the search method then when it finds something it will return the position. If it doesn’t then it will return -1. So far so good.

Now I could go into huge detail (I did, but it ended up to wordy/dull, so I just deleted it!).
So if you EVER have to search for a string and your string starts with a period ‘.’ then add a double backslash ‘\\’.
If you don’t then the period will match anything! e.g. you want to match ‘.ra’ and the string contains the word brain then ‘brain’.search( ‘.ra’ ) DOES NOT return -1!

use ‘\\.ra’ for correct results.

Not sure why ‘.ra’ doesn’t work, maybe it’s treating the string like a regEx, I know search can take both a string and a regEx so maybe its not looking at its type and guessing that it should be a regEx?? You can’t step into the code either to see why, so just use the \\

Very annoying!

Its quite a common thing with Flex and actionscript projects to create an Object and inside that object it will have many properties.  Something in your view will be bound to the object so that the view changes with the object. So long as you change the entire object this will work fine.

Where this doesn’t work is if you change a property inside the object.

So if we have something like this

[Bindable]			
private var myObject : ObjectDataVO;
 
<view:SomeComponent
...
data="{ myObject }"
...
/>

When we set myObject to something the view component gets updated (great so far).
Lets say the myObject has a property text and the view component uses this to display some visual label, then somewhere in the app I change that property, myObject.text = “something else”;
The binding will not trigger as I haven’t actually changed the myObject, just a property inside it.

So how do we fire the binding manually? Well there is the BindingManager class (note this is an excluded class so you’ll not see it in the autocomplete ).
So in this example if I changed the myObject.text property then I could call

BindingManager.executeBindings( this, ‘myObject.text’, myObject );

This would fire of the binding as if the actual myObject had changed so anything listening in will now get updated.

Sometimes I like to put something up on my blog that’s more as of a bookmark for myself as I know I’ll want to look it up at some point.  So what I’ve got here is a slack, open cross domain policy.

DO NOT USE THIS IN YOUR PRODUCTION CODE
(unless you really need to and understand why you shouldn’t)

This will get rid of any security issues you may be having while in development.

<?xml version="1.0"?>
<!DOCTYPE cross-domain-policy SYSTEM
 "http://www.adobe.com/xml/dtds/cross-domain-policy.dtd">
<cross-domain-policy>
<site-control permitted-cross-domain-policies="all"/>
<allow-access-from domain="*" secure="false"/>
<allow-http-request-headers-from domain="*"
 headers="*" secure="false"/>
</cross-domain-policy>

Working on a mobile project I needed to create a renderer for a list, so I choose to look at the IconItemRenderer which extends the LabelItemRenderer. These have been optimised for mobile use so it seemed a reasonable place to start. On the whole they seem like good classes to use, but if you’ve ever worked with the Datagrid/DataGridBase in the past you will probably know about the white square which comes about from the hardcoded #FFFFFF values inside the DataGridBase!

Well the IconItemRenderer and LabelItemRenderer have a similar issue. So lets just say you create a list and you wish to skin the list exactly how you like or use it in a tile layout or something other than vertical then you will find some lines above and below your renderers which look out of place. You can’t get rid of them no matter what property styles you set.

The fix is pretty straight forward but why does there have to be some hardcoded values in something that is meant to be very versatile?

So inside the LabelItemRenderer around lines 881 you will see the following. It uses these values to draw separators whether you like it or not.

// separators are a highlight on the top and shadow on the bottom
topSeparatorColor = 0xFFFFFF;
topSeparatorAlpha = .3;
bottomSeparatorColor = 0x000000;
bottomSeparatorAlpha = .3;

So the quickest way of dealing with this is to override the drawBackground function in your own class which is created in LabelItemRenderer. This doesn’t get called from IconItemRenderer so you can quite simple copy the entire function and just remove the separator chunk and do not call super from your function which overrides the drawBackground.

Better still would be to change the hard coded values to styles from a CSS file.

var topSeparatorColor : uint = getStyle( 'topSeparatorColor' );
var topSeparatorAlpha : Number = getStyle( 'topSeparatorAlpha' );
topSeparatorAlpha = isNaN( topSeparatorAlpha ) ? 1 : topSeparatorAlpha;

If you’re setting a Number just remember to check for NaN’s in case you haven’t set a style, uints default to 0 anyway.

The other day I wanted to create a function in a class that would take a Function as a parameter and an Array of arguments.  Much like callLater() does, but not doing the whole queuing thing until the next frame.

So how do you call a function that may have any number of arguments. Well here is the code and it should speak for itself.

 protected function checkSomethingThenCallOtherFunction(
    method : Function, args : Array = null ) : void
 {
    if( something.length < someMaxLimit )
    {
        method.apply( null, args );
    }
    else
    {
        //do something else
    }
}

So how easy is that? Pass in the function and an array of arguments, that’s all.

Many times you look something up, do it once and think cool I’ll remember that as it’s simple. Then 1 year later you’ve forgotten the syntax and you can’t find that help/blog page where you learned about it the first time.
Well I needed to add in some debug code that would only be there for debugging, and the last thing I want to do when building a release version is to scan through the code to remove it. So the ideal way is to use a conditional compiler argument.

So in Flashbuilder, under the project properties and then the Flex compiler properties you’ll see something like this

Example for custom arguments

So if you had the following defined, -define=CONFIG::DEBUG,true -define+=CONFIG::SOMETHING_ELSE,false

Then in code you could do the following.

    CONFIG::DEBUG
    private var test : Boolean;
 
    CONFIG::SOMETHING_ELSE
    private function somethingElse() : void
    {
 
    }

The variable and function code will only be included if the compiler argument is true. So in the above example if you called the function ‘somethingElse()’ then this would generate a build error as somethingElse() doesn’t exist. Change the argument to true and it will build fine.

More of a gotcha than a simple tip.

I was customising a DataGrid with various skin parts the other day (Flex 3) and could I get the borderskin to show, heck no! Its been a while since I had to create a DG from scratch so I’d obviously blacked out any previous pain with using the dammed DG.

Anyway why would the borderskin not show? I tried a simple solid border, nope. I tried a custom png graphic taken from Fireworks for the DG’s border, nope. I tried a programmatic skin border and guess what nope – nothing.  The issue was that I had the background alpha set to 1 (which is pretty normal!) and I had set the alternate row colours.

Setting the background alpha to something less than 1 revealed the border so I ended up fudging it by creating the programmatic skin border by whatever the borderThickness is outside the size of the DG.  
So if the DG was meant to be 400px wide and borderThickness was 2, I made the DG 396px wide and drew the border outside that area.  This is what I’ve expect to happen automatically.

Can’t believe I’ve missed this/forgotten this before. Crappy DG.

Redundancy… world shrinking economy… depression… company cutbacks… is this a bleak time or is it a time to make and face new challenges in the RIA world (particularly in the Flex and Actionscript areas)?

Well after the unfortunate news that the company I work for are no longer wishing to partake in the RIA party that’s changing the way we look at and use the web/desktop and hence are making myself redundant. I’m looking at this as a great opportunity to expand my knowledge so that I can work with as many forward thinking companies as possible that deal with Flex/Actionscript/AIR or for that matter any RIA technology.
Also I should now have more time to create and sell my own components, of which I had a cracking idea this morning (more on this later hopefully).

Hect I’ll event look at Silverlight or JavaFX if I get the time or the chance. So anyone out there fancy taking on a new contractor with 4 years+ experience in Flex as well as a bunch of other languages I’ve used along the way before I even heard of Flex.

Feel free to contact me at this address.

I’m going to continue to post hints and tips on anything I do as well as posting any new components so watch this space and feel free to contact me if you need any work done in the UK, remote working is always an option as well.