Musings on AdvancedDataGrid (Part 5)

Up to part 4, I've been talking about the AdvancedDataGrid itself and the properties it has that are supposed to make your life easier, like styleFunction and iconFunction. And they do, once you understand them. But now I'd like to turn my attention to the data source I was using to drive my AdvancedDataGrid (ADG).

My AdvancedDataGrid is being used as a menu on an eLearning application. The application has various tasks that the user must complete. Once a task is complete, it is shown again in review mode, which provides the student with remediation on what he did wrong or right. The student can also view reports of what he did in a given task. So each task will be available in three modes: normal, review, and analysis. The mode will be determined by the top-level container.
To this end, I created an array of MenuContainer Value Objects (VO) that contained a number of Task VO's. I assigned these to a HeirarchicalData dataProvider in the ADG. I immediately realized that the itemClick event just gave me the Task VO, and the Task knew nothing about its parent (and rightly so). Apparently, the itemRenderer also knew nothing about where the Task fell in the data structure, nor anything else in the ADG.

I realized it was a slippery problem, since even if I were to loop through the MenuContainers and find the Task that was selected, I would only find the first instance of it. So I decided to wrap my Task class in another class that had two properties, task and UID. In this class, TaskUID, I simply used UIDUtil to create a UID for this instance of the task.

Once I had that accomplished, I decided to take one more squint at the docs before I built a function to loop through and find my TaskUID. I trolled the language reference only on the word hierarchical. I'd looked at the HierarchicalCollectionView before, but the description implies that this is for making flat collections look hierarchical (heck, it actually says it!). However, this class does include a method, getParentItem(), which looked perfect for my needs.

In a wild leap of faith, I cast the event.currentTarget.dataProvider from the itemClick event from HierarchicalData to HierarchicalCollectionView and the method worked! It gave me a reference to the MenuContainer from the TaskUID. I have no idea what the differences are between those classes, so I wouldn't guarantee all methods would work when you do this kind of casting, but this worked for me!

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.