I made a custom itemRenderer, and need to access a variable in my Project file (mxml). How can I make my public var available in the custom itemRenderer file?
public function lang_f(trans_short:String):String{
if(outerDocument.language == "de"){
...
}
}
Greetings
Markus
You shouldn't access outer document data from within item renderer. It breaks OOP principles such as low coupling etc. You should either set this data to item renderer with data from data provider or extend your list based component to instantiate renderers with that data. And don't think about MXML component as files. The file structure is just a form of representation. You'd better think MXML files as classes or components — in terms of application structure.
To go along with Constantiner's answer, if you still need to access that variable, you can access the variable in your itemRenderer using outerDocument:
outerDocument.myVariableName
Is the variable defined in main file of your application ? If that's the case you can access is using FlexGlobals.topLevelApplication.YOUR_VARIABLE_NAME
However I agree with Constantiner. This violation of OOP principles. But I hope that solves your problem.
Related
How can i access a variable or change the state of an element(like tabNavigator) from one mxml to another mxml in FLEX 4.6??
Each separate MXML file should be viewed as a class, since that is what they are.
In the theory of encapsulation; two classes should not directly access / change each others variables or state. They should use an API provided by the developer of the MXML Class.
If MXML 1 is the parent of MXML 2; then MXML1 can pass data to MXML2 by setting public properties or calling public methods.
MXML2 can pass data to MXML1 by dispatching events.
If MXML1 and MXML2 are not in a parent child relationship; (AKA Both children of the same component as one example) they they should not communicate with each other directly. They should dispatch events which the mutual parent should handle and use to set values or execute methods on it's own children.
From an encapsulation standpoint, that is how it should be done using the built in facilities of ActionScript / Flex.
What a lot of people do as part of building applications is to make use of dependency injection. That was values that are "global to the application" can be shared among multiple components. Another approach to doing this is to use a Singleton. A third approach might be to make use of static values on a class; which can be accessed without accessing an instance of a class.
Forgive me, I'm new to Flash Builder 4 and Actionscript 3 (actually, to programming as a whole beyond some very simplistic stuff). I have watched / read a bunch of tutorials, and started a project but now seem to have hit a wall. The answer is most likely simple, but seems to be alluding me.
How do I (or What approach should I take) to control visual elements, for instance, BorderContainer's, that I created dynamically?
As is, I have an Application containing a BorderContainer and a DataGrid. At runtime, 3 new BorderContainers (which are dragable, and resizeable) are created based on XML data that contains X & Y co-ordinates, and Height and Width values, and then added to the pre-existing BorderContainer. How would I go about getting the properties of these children BorderContainers to be displayed and remain up-to-date in the DataGrid (such as when they are moved/resized)?
My intentions in the future would be to have a custom component which displays a summary of these items in a separate area (think photoshop "layers" control, but much more simplistic), but wanted to get a better understanding of what's going on first.
Any input, documentation, examples, etc. is all appreciated. Again, I apologize for what may be an incredibly easy solution, or if any of my language is unclear, I'm new to this ^_^;
I would create an ArrayCollection of the BorderContainers with their various properties set (also make sure you call addElement on the parent BorderContainer). Make sure your ArrayCollection is declared as Bindable, then set it as the dataProvider for your DataGrid. Then specify the columns for your DataGrid based on whatever properties you want to display (height, width, etc). Now whenever the properties of the BorderContainers change, the DataGrid will automatically update.
Assuming a pure AS3 project, the best approach is to build a dictionary of your objects.
Let's also assume you've created identifiers for the components, or can easily create them at runtime.
var containers:Dictionary = new Dictionary();
private function _init():void
{
//some loop to create objects
containers[newObject.name] = newObject;
}
Later you can quickly access it by just grabbing the hashed index from the containers dictionary.
Now, assuming a Flex project, we have a few more approaches we can take:
DisplayObjectContainer implements getChildByName()
Group implements getElementAt, and numElements to iterate over, check names, and return value expected.
Personally, I still prefer the dictionary approach...
As for keeping things up to date, you can look into Binding (typically a Flex-only solution) or more appropriately investigate the events dispatched:
Event.RESIZE
Event.MOVE
etc.
In the handlers, just update your UI!
HTH, otherwise post more info and we'll see what we can figure out.
i have in my flex application various mxml components that all need to show stats based on the same data. how can i go about doing that? do i need some mvc framework like cairngrom or puremvc for that or can i do it without them?
any design ideas?
You don't need any framework for that. Do you know about data-binding?
http://www.flexafterdark.com/docs/Flex-Binding
This way you can set your data as dataprovider for many components. For example to show your data in dataGrid you set in mxml it's attribute
dataProvider="{yourDataArrayCollectionIdentifier}"
and in your arrayCollection declaration you need to set metatag [Bindable]
[Bindable] var yourDataArrayCollectionIdentifier : ArrayCollection;
there are other datatypes you can use as dataprovider, just arrayCollection is the most common
There are a handful of approaches to this. For encapsulation purposes, you should isolate your shared data out into a separate class; possibly a Value Object although it does't have to be.
Then create a public variable property in each MXML Component of this classes type. When you create the instance of each mxml component, pass in your 'global' instance of the data class.
You don't need to use an MVC framework, but the Cairngorm Model Locator could also be used to address this problem. The Model Locator is a singleton. You'd store your data inside the singleton instance; and then each MXML Component would reference the singleton for the data. Creating an external dependency like this breaks encapsulation, though. I much prefer the parameter passing route for non-application specific components.
package
{
public class ApplicationViewModel
{
[Bindable] public var message:String = "";
}
}
You can now use this message across your MXML where you make the instance of that.
A singleton class is used in different scenarios where you want to hold some information of all states. A better example would be Chess Board, where your board is Singleton class and its state should never change as you have to keep track of all coins moved across the board and its position.
You are injecting this message variable in the views where you want to show the data.
I have a Flex application which references a separate MXML file as a template for a custom component. I create instances of the component dynamically several times in my program, but I need to get a handle that will allow me to modify that instance of the component as desired.
I pass specific information to this component on instantiation using bindable public variables in the component's MXML file. I add it to my main program using addChild().
I want to update the component's progressbar as necessary and I want to remove it from the box to which I addChild'd it.
What's the easiest/best way to get a variable that will give me predictable access to each component so I can easily manipulate the components as necessary? Some research suggests creationComplete, but I decided it was faster to just ask than to go through lots of different experiments and come up blank.
Thanks for all the help. : )
Can you not just keep a list of your components in an array? Presumably you have an object reference when you create them and call addChild() on their parent. Why not just put them in an array at the same time?
var list_of_controls:Array = new Array();
var new_Object:<yourType>;
new_Object = new <yourType>();
parent.addChild(new_Object);
list_of_controls.push(new_Object);
then you can get at them...
var my_Object:<yourType>;
for each (my_Object in list_of_controls)
{
// do something
}
You would have to make sure you dispose of them properly when you re done because the reference in your array would keep them in existence until cleared.
If you decide that you want to use getChildren() instead - which you could - take the time to read the documentation because I think it returns a new array with each call.
I hope that helps.
I'm re-writing an MXML item renderer in pure AS. A problem I can't seem to get past is how to have each item renderer react to a change on a static property on the item renderer class. In the MXML version, I have the following binding set up on the item renderer:
instanceProperty={callInstanceFunction(ItemRenderer.staticProperty)}
What would be the equivalent way of setting this up in AS (using BindingUtils, I assume)?
UPDATE:
So I thought the following wasn't working, but it appears as if Flex is suppressing errors thrown in the instanceFunction, making it appear as if the binding itself is bad.
BindingUtils.bindSetter(instanceFunction, ItemRenderer, "staticProperty");
However, when instanceFunction is called, already initialized variables on the given instance are all null, which was the cause of the errors referenced above. Any ideas why this is?
You have 2 options that I am aware of:
Option 1
You can dig into the code that the flex compiler builds based on your MXML to see how it handles binding to static properties. There is a compiler directive called -keep-generated-actionscript that will cause generated files to stick around. Sleuthing through these can give you an idea what happens. This option will involve instantiating Binding objects and StaticPropertyWatcher objects.
Option 2
There is staticEventDispatcher object that gets added at build time to classes containing static variables see this post http://thecomcor.blogspot.com/2008/07/adobe-flex-undocumented-buildin.html. According to the post, this object only gets added based on the presence of static variables and not getter functions.
Example of Option 2
Say we have a class named MyClassContainingStaticVariable with a static variable named MyStaticVariable and another variable someobject.somearrayproperty that we want to get updated whenever MyStaticVariable changes.
Class(MyClassContainingStaticVariable).staticEventDispatcher.addEventListener(
PropertyChangeEvent.PROPERTY_CHANGE,
function(event:PropertyChangeEvent):void
{
if(event.property == "MyStaticVariable")
{
someobject.somearrayproperty = event.newValue as Array;
}
});
I think you need to respond to the "PropertyChanged" event.
If you're going to do that, use a singleton instead of static. I don't think it will work on a static. (If you have to do it that way at all, there are probably a couple ways you could reapproach this that would be better).
var instance:ItemRenderer = ItemRenderer.getInstance();
BindingUtils.bindProperty(this, "myProperty", instance, "theirProperty");
After fiddling with this for a while, I have concluded that this currently isn't possible in ActionScript, not even with bindSetter. It seems there are some MXML-only features of data bindings judging by the following excerpt from the Adobe docs (though isn't it all compiled to AS code anyways)?
You cannot include functions or array
elements in property chains in a data
binding expression defined by the
bindProperty() or bindSetter() method.
For more information on property
chains, see Working with bindable
property chains.
Source: http://livedocs.adobe.com/flex/3/html/help.html?content=databinding_7.html
You can create a HostProxy class to stand in for the funciton call. Sort of like a HostFunctionProxy class which extends from proxy, and has a getProperty("functionInvokeStringWithParameters") which will invoke the function remotely from the host, and dispatch a "change" event to trigger the binding in typical [Bindable("change")] Proxy class.
You than let the HostProxy class act as the host, and use the property to remotely trigger the function call. Of course, it'd be cooler to have some TypeHelperUtil to allow converting raw string values to serialized type values at runtime for method parameters (splitted by commas usually).
Example:
eg.
var standInHost:Object = new HostFunctionProxy(someModelClassWithMethod, "theMethodToCall(20,11)");
// With BindingUtils.....
// bind host: standInHost
// bind property: "theMethodToCall(20,11)"
Of course, you nee to create such a utlity to help support such functionality beyond the basic Flex prescription. It seems many of such (more advanced) Flex bindings are usually done at compile time, but now you have to create code to do this at runtime in a completely cross-platform Actionscript manner without relying on the Flex framework.