flex-actionscript: Category
Category: flex-actionscript
Making a custom datagrid scrollbar? I hope the width=16…
Posted At: February 2, 2011 10:29 PM | Posted By: Steve Zimmers
Related Categories: flex-actionscript
Flex has a lot of great facilities for styling and skinning, including custom scrollbars. Unfortunately, I’ve discovered that Flex really wants your vertical scrollbars to be 16 pixels wide. When it isn’t, Flex can make some strange layout decisions when first putting it on screen.
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Datagrid item editors and dynamic behavior (part 3/3)
Posted At: March 12, 2008 4:37 AM | Posted By: Steve Zimmers
Related Categories: flex-actionscript
we’re ready to wrap up our functionality now.
in part 1, we defined our problem (validated error reporting in a datagrid cell, plus dynamic validation characteristics) and made a first attempt at a solution.
in part 2, we improved our error handling in the cells.
now, in part 3, we’ll expand our validation logic beyond valid numbers to range checking based on other XML data in the row. this will fulfill our task of creating item editors with dynamic behavior.
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Datagrid item editors and dynamic behavior (part 2/3)
Posted At: March 3, 2008 7:09 PM | Posted By: Steve Zimmers
Related Categories: flex-actionscript
picking up from where we left off in part one, now we want to to improve our user notification when they enter a bad value in our datagrid.
previously, we jumped out of the cell and left it blank. ideally, we want our cell, whose itemEditor is a derived class of TextInput, to behave like a TextInput with bad data. i.e. we would like a red border and an errortip. More
Datagrid item editors and dynamic behavior (part 1/3)
Posted At: February 27, 2008 2:56 AM | Posted By: Steve Zimmers
Related Categories: flex-actionscript
though a lot of validation functionality is available in mxml through validators, i’ve always found it curious that Datagrid seems to be a bit short-changed.
for example, in mxml, i can create a TextInput and give it the ability to accept ranges of numbers, through both the restrict property and assigning it a NumberValidator, but how do we do the same in a Datagrid cell?
further, what happens when we want to dynamically process cell contents based on other data in the same row?
Adobe has a primer here:
http://www.adobe.com/devnet/flex/quickstart/creating_item_editors/
… with help on creating different kinds of item editors. but whenever they give an example of a cell into which you’re meant to enter numbers, they use a NumericStepper. and that’s great, but maybe i don’t always want to use a NumericStepper in my interface. maybe i want to use a TextInput component, just like the rest of the cells. further, we still haven’t addressed the kinds of dynamic behavior i mentioned above.
so what’s the solution? More
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though a lot of validation functionality is available in mxml through validators, i’ve always found it curious that Datagrid seems to be a bit short-changed.
for example, in mxml, i can create a TextInput and give it the ability to accept ranges of numbers, through both the restrict property and assigning it a NumberValidator, but how do we do the same in a Datagrid cell?
further, what happens when we want to dynamically process cell contents based on other data in the same row?
Adobe has a primer here:
http://www.adobe.com/devnet/flex/quickstart/creating_item_editors/
… with help on creating different kinds of item editors. but whenever they give an example of a cell into which you’re meant to enter numbers, they use a NumericStepper. and that’s great, but maybe i don’t always want to use a NumericStepper in my interface. maybe i want to use a TextInput component, just like the rest of the cells. further, we still haven’t addressed the kinds of dynamic behavior i mentioned above.
so what’s the solution?
using the approach on that Adobe page called ‘Using a component as an item editor’, and by delving into a little bit of ActionScript, we can make ourselves a TextInput item editor that can do everything we need.
i’m dividing this topic into 3 posts so we can build to our eventual solution.
let’s take an example:
say you’re building an app for your local high school’s wrestling team. you’ve already written the part of the app to pre-register wrestlers and now you’re working on the screen for weigh-in at the meet.
when wrestlers pre-register, they enter their names and respective weight classes. on the day of the meet, you want your weigh-in screen to flag an error to the user that a wrestler is out of his weight class.
let’s take a first stab at some prototype code. here’s the mxml you’ve written for the weigh-in app (called wrestling.mxml):
(click on the image to run the app)
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical" >
<mx:XMLList id="wrestlers" xmlns="">
<wrestler>
<name> Bob Smith </name>
<weightClass> A </weightClass>
<weight> </weight>
</wrestler>
<wrestler>
<name> Tim McLarry </name>
<weightClass> B </weightClass>
<weight> </weight>
</wrestler>
<wrestler>
<name> Joe Doug </name>
<weightClass> C </weightClass>
<weight> </weight>
</wrestler>
<wrestler>
<name> Larry McTim </name>
<weightClass> D </weightClass>
<weight> </weight>
</wrestler>
</mx:XMLList>
<mx:DataGrid id="weigh_in" editable="true" dataProvider="{wrestlers}" >
<mx:columns>
<mx:DataGridColumn id="wrestler_name" headerText="Name" editable="false" dataField="name" />
<mx:DataGridColumn id="weight_class" headerText="Class" editable="false" dataField="weightClass" />
<mx:DataGridColumn id="weight" headerText="Weight" editable="true" dataField="weight"
itemEditor="WeightEditor" editorDataField="data" />
</mx:columns>
</mx:DataGrid>
<mx:Form >
<mx:FormHeading label="Weight Classes" />
<mx:FormItem label="A" >
<mx:Label text="0-99 lbs." />
</mx:FormItem>
<mx:FormItem label="B" >
<mx:Label text="100-135 lbs." />
</mx:FormItem>
<mx:FormItem label="C" >
<mx:Label text="136-169 lbs." />
</mx:FormItem>
<mx:FormItem label="D" >
<mx:Label text="107-210 lbs." />
</mx:FormItem>
</mx:Form>
</mx:Application>
pretty straightfoward. we’ve got a Datagrid with 3 columns, some test XML to fill in the name and weight class, and a small form letting us know the weight class ranges (which i made up, and likely has no bearing on any realworld scenario).
we’ve also referenced a WeightEditor.mxml, which is this code:
<?xml version="1.0" encoding="utf-8"?>
<mx:TextInput restrict="1234567890,." xmlns:mx="http://www.adobe.com/2006/mxml">
<mx:Script>
<![CDATA[
import mx.events.ValidationResultEvent;
import mx.validators.NumberValidator;
/**
* This method is invoked when the user enters a value in the weight column
* of the weigh_in datagrid. We'll validate the user-entered value as a number
* and return a blank if it's not a number. Otherwise, we'll return what the
* user entered.
*/
override public function get data() : Object
{
var value:String = text;
if (!this.validate(value))
return '';
return value;
}
/**
* This is our validation method. We pass validation if the user has
* entered a non-negative decimal.
*
* @param value The user-entered value
* @return true if we pass validation, false otherwise
*/
protected function validate(value:String) : Boolean
{
var validator:NumberValidator = new NumberValidator();
validator.allowNegative = false;
validator.required = false;
var result:ValidationResultEvent = validator.validate(value);
if (result.type != ValidationResultEvent.VALID)
return false;
return true;
}
]]>
</mx:Script>
</mx:TextInput>
this code is more interesting. first, note that we’ve derived this item editor from TextInput, so it should behave more like the other cells than, say, a NumericStepper would. second, you’ll notice that we set the restrict property straightaway, so we see an immediate benefit that the user can enter only numbers, periods and commas in this field.
we override the data method here to return what the user entered if it’s a number. if it’s not a number (e.g. 5.5.5..5), we’ll return nothing.
why is the method called ‘data’? because that’s the value we specified in the editorDataField in the weight column in the wrestling.mxml file. it doesn’t have to be called ‘data’, you can call it whatever you’d like. but because ‘data’ exists and is considered the default, we have to specify that we’re overriding it.
this is a decent first step, but doesn’t exhibit terribly useful behavior. first, if the user enters something that isn’t a number, the cell erases itself. good for avoiding keeping bad values around, not so good for the user experience. this is something we want to keep in mind for our next iteration.
also note that we haven’t honored, at all, the weight class. we’ll also fix this in a later iteration, and it would be nice if we could provide some meaningful user feedback for what went wrong.
we’ll address user notification in part 2.
(click on the image to run the app)Recent Comments
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Nathan Weber said: That's a good question, and to be honest I don't know a definitive answer. ... MORE
Building a Native Extension | Part 5 – Putting It All Together
Keith said: Thank you for this step-by-step tutorial.
I have a question: suppose the n ... MORE
Where is the iOS SDK?!
joseph saade said: you are right, I am asking about it on adobe's forums.
another workaround ... MORE
Where is the iOS SDK?!
Nathan Weber said: Chances are it's an AIR bug. You should go to the Adobe bug tracker (http: ... MORE
Where is the iOS SDK?!
joseph saade said: I am facing a weird bug for iOS, after specifying ios5.1 SDK location, Flas ... MORE