Musings on AdvancedDataGrid (Part 3)

Review Part 2

The author of the blog post I originally found that inspired this journey said that this method would not cause the selection and rollover indicators to be obscured in the same way as this method. But I really wanted to be able to see these indicators, rather than a tiny edge around each row. So I was determined that I was going to get my AdvancedDatagridItemRenderer to allow me to see these indicators through it.

The first thing I'd tried, just setting the alpha property, hadn't worked. The next thing I tried was to try to use the graphics functions to draw a background like I did in the AdvancedDatagridGroupItemRenderer. Unfortunately, since the AdvancedDatagridItemRenderer does not inherit from UIComponent or DisplayObjectContainer, so it neither had a graphics object of its own nor any way to add one.

So I stuck my nose back into the docs and discovered that my TextField had a colorTransform object that I should be able to manipulate to change the alpha transparency. Well, I was able to change its alpha property, but there was absolutely no visible change.

Finally, I realized I was going to have to leave the Flex world and see what the Flash world had to offer. So I came across this post and was able to get the transparency by changing the blend mode. Still, my AdvancedDatagridItemRenderer and AdvancedDatagridGroupItemRenderer did not match, because the text in the AdvancedDatagridItemRenderer was semitransparent and the AdvancedDatagridGroupItemRenderer text was not. Lesson Number 2: Anything that inherits from TextField is only going to be able to support alpha transparency with difficulty, and even then the entire component, including the text, will be alpha transparent.

So I had the simple idea that I could use the AdvancedDatagridGroupItemRenderer to do all the item rendering.

Tomorrow, I will talk about getting the icons to render properly.

Musings on AdvancedDataGrid (Part 2)

Review Part 1

I'd found a neat little sample that shows how to change the background color on the row by extending AdvancedDataGridItemRenderer (ADGIR) to set the existing background and backgroundColor properties based on a style set on the component.

I had no trouble copying this, but I found that for some reason the entire first column stubbornly refused to pick up my carefully applied color. Undaunted, I set the itemRenderer property of the first column explicitly to my extended ADGIR.

The result I had was closer to what I wanted--most of the cells in that column now had the color my styleFunction had insisted upon--but the ones with the triangle in them remained white. Aha! Clearly this was a different thing altogether, so I went back to the docs and looked for inspiration. It seems that the uncolored cells were being rendered by another component, the AdvancedDataGridGroupItemRenderer (ADGGIR).

So I set about extending that worthy component. At first, I thought I'd be able to just cut and paste the code I'd modified for my ADGIR, but no such luck. Unfortunately, the ADGGIR had no background or backgroundColor properties. So I fell back on more conventional tactics, drawing a rectangular background on the component when the style changed. First lesson: the AdvancedDataGridItemRenderer is based on the Flash TextField component and the AdvancedGridGroupItemRenderer is based on UIComponent. These two components have completely different capabilities and must be dealt with in entirely different ways.

As soon as I saw my extended ADGGIR next to the extended ADGIR, I realized that the ADGIR was not yeilding to my attempts to set its alpha transparency. I'd included code in both to set the alpha transparency, but it was only working in the ADGGIR.

Tomorrow, I'll talk about my attempts to add alpha transparency to the ADGIR.

Musings on AdvancedDataGrid (Part 1)

This last week, I had my first experience with the AdvancedDataGrid component. I knew I needed to have multi-column heirarchical data display. I also needed to be able to dynamically color and also set an icon each row based on the content of the data item. I scoured the docs for a component that would meet these requirements, and the ADG's styleFunction and iconFunction seemed like they would fit the bill perfectly--and ultimately they did. But in the meantime, they led me on a merry chase because the docs didn't include all the pieces I needed to understand what was happening. Ultimately I did understand it, so I thought I'd pass my surmises along in the hope that others can shortcut the many hours I spent on the problem.

Tomorrow, I'll talk about the relationship between AdvancedDataGridItemRenderer and AdvancedDataGridGroupItemRenderer.

Using a CSS TypeSelector with an itemRenderer

Today, I had more fun with item renderers. I had a component I was working on to try to prototype some new functionality, and I had set up styles for it in the <mx:styles> declaration of the Application tag. If I put my component in a container in the main Application, the style came through fine. If I used it as an itemRenderer of a List based class, only the text styles worked.

It seems that when you use a component this way, Flex will assign ListBaseContentHolder as the style name instead of the class name, but for some reason this only negates things like backround colors—text declarations come through just fine. This interesting feature isn't documented anywhere, so it took me a whole day to figure out the fix, which is so simple I wanted to pound my head against the wall till I couldn't see straight.

override protected function commitProperties():void{
this.styleName = this.className;
}

Hope this saves someone some time!

Another good itemRenderer Resource

The longer I use Flex, the more firmly I believe that the key to understanding it is the component life cycle. Specifically, the life cycle as it applies to item renderers. Today on Flex Coders, Douglas Knudsen posted a link to this great presentation on the component life cycle by Eli Greenspan. I can't for the life of me figure out how to bookmark to a pdf, but if I post a link here, I'll be able to find it forever :-).

Great ItemRenderer Resource

I really struggle with itemRenderers--what goes where to make what you want to occur happen when you want it to. So I've been talking to various people and reading, reading, reading trying to make sense of it all. From the posts on the yahoo FlexCoders group, it seems like I'm not the only one experiencing confusion.

I think the biggest problem is that there don't seem to be many "from the ground up" resources on this subject. But that doesn't mean there aren't any. In addition to the Flex help and LiveDocs, which, let's face it, confuse us as much as inform us, there are several blogs that tackle this subject. Today I found Peter Ent's blog, which contains a five part series just on itemRenderers. Thanks, Peter!

Working with Dates in AS3

The Date examples that come with Flex (and, presumably, Flash) are all very well and good, but to me they don't seem to be very...practical. And it doesn't help that the documentation doesn't provide any clues about how to do simple things like, oh, figuring out how many days there are in a month. There's probably very good code for these things in opensource projects like the Flex scheduler, but I think you have to know where to dig.

So I played around with the Date object, and I discovered that you can use numbers outside the integers 1-31 in the date parameter (new Date(year, month, date)) and get some interesting results. Such as if you use 0, you get the last day of the previous month. As you might expect, negative numbers will go further back into the previous month. I suspect numbers higher than the last day of the month you're dealing with will continue into the next month, though I haven't tried it.

What I was trying to do was create an ArrayCollection that could be used as a dataprovider for a TileList and then that TileList could display a calendar page just like what you see when you look at the calendar on your wall...i.e. the first few days might be in the previous month and the last few days might be in the next month, because only February ever has a shot at fitting exactly in a grid that is seven days wide. I figured that I'd share my class, since I'm probably not the first or last person to ever want to do this. Note that it's not finished...you'll need to add the last few days when the end of the month doesn't fall on Saturday, but that's not rocket science.



package com.magnoliamultimedia.vo
{
import mx.collections.ArrayCollection;
public class DisplayMonth
{
private var _year:int;
private var _month:int;
private var _startIndex:int;
private var _dateColl:ArrayCollection;
public function DisplayMonth(monthNumber:int, yearNumber:int)
{
_month=monthNumber;
_year=yearNumber;
var tmpArray:Array=new Array();
var firstDay:Date=new Date(yearNumber, monthNumber);
var lastDay:Date=new Date(yearNumber, monthNumber +1, 0);
var lastDayNum:int = lastDay.date;
_startIndex = firstDay.day;
var tempDay:Date;
var i:int;
//fill blank days before beginning of month
for (i=0; i<_startindex; i++)
tempday = new Date(yearNumber, monthNumber);
tempday.date -= 6-i;
tmpArray.push(tempday);
}
//fill in the rest of the dates here...
}
}
}



Sorry about the crap formatting...I haven't figured out the spiffy scrolling thing some other bloggers manage.

Updated 5/28/10. I noticed that part of the code had been "eaten" by Blogger. I replaced the relevant code, but may not have put back everything that was once there. For a better example of how to do this, look at my GroupingCollection example.