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.

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!