1 :: Is it possible to make httpService Requests synchronous in adobe flex?
No.
Basically, what we are about to do is creating XMLHttpRequest with Javascript in Flex, and
calling a server data with the parameters we will give to the object.
e.g. xmlHttpRequest.open("GET","http://localhost/Default.aspx",false);
1. Request Type: GET or POST
2. Requested URL
3.Communication Type: true for asynchronous, false for synchronous.
2 :: I need to load an image from flickr into my application. Do I need a crossdomain.xml file on
flickr?
File is already there , we need to register our ip address to flicker’s crossdomain.xml
Since the images are located on a flickr server like farm1.static.flickr.com and there is no
crossdomain.xml file on that server (there is a crossdomain.xml for api.flickr.com so you can use
the api) that means you can’t get access to the bitmapData of the loaded images when you load
them from flickr. This is dumb, but that’s the way it is. So you can load images just fine, but the
reflection class copies the bitmapData of the image, so that doesn’t work if you load them
straight from the flickr server. I also wanted to set bitmap smoothing to true on the images so the
thumbnails don’t look as pixelated, and that also requires access to the bitmapData of the loaded
image.
So the answer is to create a proxy that loads the flickr image so it appears to come from the same
domain.
3 :: What is the difference between httpService and Data Service?
The services-config.xml configuration file is required at compile time if the Flex application uses
Flex Data Services. In the case of RPC services, this applies to all applications that use
RemoteObject or proxy-based WebService or HTTPService.
4 :: How do you generate random numbers within a given limit with actionscript?
Math.round(Math.random() * (high - low)) + low
5 :: Have you built any components with actionscript? If so explain how you did it?
6 :: How do you implement push on a flex applications?
Using BlazeDS Server, LiveCycle Data Services
7 :: I am going to add images into a tag. How will it resize itself in adobe flex actionscript?
To let Flex resize the image as part of laying out your application, set the height or width
properties to a percentage value. Flex attempts to resize components with percentage values for
these properties to the specified percentage of their parent container.
Or by default, Flex does not resize the image. The scaleContent property has a default value of
true, therefore, Flex scales the image as it resizes it to fit the specified height and width. The
aspect ratio is maintained by default, so the image may not completely fill the designated space.
Set the scaleContent property to false to disable scaling. Set the maintainAspectRatio property to
false to allow an image to fill all available space regardless of its dimensions.
8 :: What is a resource Manager in flex actionscript?
The ResourceManager — now handles access to all localized resources in an application. Any
components that extend UIComponent, Formatter, or Validator now have a new resourceManager
property, which lets you easily access the singleton instance of this manager. If you’re writing
some other kind of class that needs to use the ResourceManager, you can call
ResourceManager.getInstance() to get a reference to it.
9 :: What are the similarities between java and flex?
Both can be used as client application, both have packages, OOP based , support XML , import
external packages, up casting, support ArrayCollection ,almost same primitive data types, both
support class library packaging( .jar , .swc).
10 :: What is the dynamic keyword used for in flex actionscript?
Specifies that instances of a class may possess dynamic properties added at runtime. If you use
the dynamic attribute on a class, you can add properties to instances of that class at runtime.
Classes that are not marked as dynamic are considered sealed, which means that properties
cannot be added to instances of the class.
11 :: How do you implement push with flex data services?
Using Blaze DS Server & LCDS
12 :: What are the methods called when a UI component is intialized?
All components dispatch the following events that let you specify ActionScript to initialize a
component:
preInitialize
Dispatched when a component has been created in a rough state, and no children have been
created.
initialize
Dispatched when a component and all its children have been created, but before the component
size has been determined.
creationComplete
Dispatched when the component has been laid out and the component is visible (if appropriate).
13 :: Can you write to the file system from flex?
Yes .
14 :: What is a drag manager in adobe flex actionscript?
The Flex Drag and Drop Manager lets you select an object, such as an item in a List control, or a
Flex control, such as an Image control, and then drag it over another component to add it to that
component.
15 :: How do we call javascript from Flex actionscript?
Using the ExternalInterface API to access JavaScript from Flex and Using the navigateToURL()
method in Flex. The navigateToURL() method is in the flash.net package
flash.external.ExternalInterface.call(function_name:String[, arg1, ...]):Object;
navigateToURL(request:URLRequest, window:String):void
16 :: How do you use a repeater in actionscript?
17 :: what are three ways to skin a component in flex?
Skinning is the process of changing the appearance of a component by modifying or replacing
its visual elements. These elements can be made up of images, SWF files, or class files that
contain drawing API methods.
There are several ways that you can define skins: inline, by using the setStyle() method, and by
using Cascading Style Sheets (CSS).
18 :: How do we use css styles in flex?
External styles are defined in a separate file and can be used in any MXML file that references the
CSS file. You reference a CSS file into an MXML file with the source property of the
tag, as follows:
Embedded styles are defined in an MXML file and can only be used in that file. Embedded styles
are defined with the
Inline styles are defined in an MXML tag and can only be used in that tag. Inline styles are
defined as follows:
19 :: What is the difference between sealed class and dynamic classes in flex?
Classes are sealed by default, i.e. properties cannot be added dynamically at runtime.
* Dynamic classes can add additional dynamic properties at runtime; sealed classes cannot.
* Sealed classes conserve memory because no internal hash table is needed to store dynamic
properties, and the compiler can provide better error feedback.
20 :: What is MVC and how do you relate it to flex apps?
(Separation of concerns) The goal of the Model-View-Controller (MVC) architecture is that by
creating components with a well-defined and limited scope in your application, you increase the
reusability of the components and improve the maintainability of the overall system. Using the
MVC architecture, you can partition your system into three categories of components:
* Model components Encapsulates data and behaviors related to the data.
* View components Defines your application's user interface.
* Controller components Handles the data interconnectivity in your application.
21 :: What is state? what is the difference between states and ViewStack in flex?
The State class defines a view state, a particular view of a component. For example, a product
thumbnail could have two view states; a base view state with minimal information, and a rich
view state with additional information. The overrides property specifies a set of child classes to
add or remove from the base view state, and properties, styles, and event handlers to set when
the view state is in effect.
You use the State class in the states property of Flex components. You can only specify a states
property at the root of an application or a custom control, not on child controls.
Difference between states and ViewStack in flex:
* View Stack is to handle different MXML file eg TAB control and states is the transition within
single MXML file.
* ViewStack should be used were there is complete change in the controls used and States
should be used when you just want to add or remove a
few components based on certain conditions.
* ViewStates are virtual state of an existing page apearing at an instance i.e. only one state can
be shown at a time
while viewStack are collection of different view containers which can be shown at a time
22 :: How does item renderer work? How do we add item renderer at runtime in flex?
Each list control has a default mechanism for controlling the display of data, or view, and lets
you override that default. To override the default view, you create a custom item renderer.
Note: With reusable inline item renderers you use data binding to bind to the item renderer.
When you use a component as an item renderer, you do not use data binding but specify the
name of the custom component to use as an item renderer.
Add itemrendrer at run time:
Create the basic item renderer. One of the things I needed to accomplish with my item renderer
was the ability to add it to different columns (ie the dataField was not always the same). This
meant I needed a way from within the renderer to determine what column it was bound to so I
could get and display the correct data. To do this the renderer needs to implement the
IDropInListItemRenderer. This interface allows the renderer to have access to information about
the list and column it is in via the BaseListData and DataGridListData classes. The
DataGridListData gives you everything you need to get the data required to make a flexible,
reusable renderer.
To Modify itemrenderer at runtime we Need to use mx.core.ClassFactory. Basically, in order to
change a Flex itemRenderer at runtime, you need to cast it to a type ClassFactory.
23 :: What keyword allows you to refer to private variables of a class in flex?
Private keyword , this keyworld (? ) in flex
24 :: How polymorphism works on actionscript?
25 :: How do we overload functions in actionscript?
Method overloading using namespaces. (?)
26 :: What is dynamic keyword used for in actionscript?
Dynamic classes, which allow you to programmatically add new properties and behavior to
classes during the run-time. Just add the magic keyword dynamic to the class definition:
dynamic class Person {
var name:String;
}
Now let’s add dynamically two variables name and age and the function printme() to the object of
type Person:
Person p= new Person();
p.name=”Joe”;
p.age=25;
p.printMe = function () {
trace (p.name, p.age);
}
p.printMe(); // Joe 25
27 :: What are sealed classes in flex?
A sealed class possesses only the fixed set of properties and methods that were defined at
compile-time; additional properties and methods cannot be added. This makes stricter
compile-time checking possible, resulting in more robust programs.
28 :: What are runtime shared libraries in flex?
Macromedia Flex 1.5 you can build runtime shared libraries (RSLs) that can be individually
loaded, cached, and used by multiple applications.
Use Flex 3 runtime-shared-libraries (RSLs) to reduce the size of your applications and thereby
reduce the time required to download the application. RSLs are just SWF files whose code is
used as a shared library between different application SWF files. There are two kinds of RSLs,
signed and unsigned. Signed RSLs are libraries that are signed by Adobe and may be stored in
the Flash Player Cache, which can be accessed by applications from any domain. This means if
your application is using a signed RSL, the RSL may not even need to be downloaded if the RSL
is already in the Flash Player Cache. The signed RSL may have been put into the Flash Player
Cache by visiting another web site that was using the same signed RSL. Signed RSLs have a
"swz" extension.
Unsigned RSLs are normal SWF files and are not loaded into the Flash Player Cache. Instead,
these RSLs rely on the browser's cache to keep them from being downloaded.
29 :: What is cairnghorm in flex? how do we use it?Have you worked with Cairnghorn in flex?
Cairngorm is the lightweight micro-architecture for Rich Internet Applications built in Flex or AIR.
A collaboration of recognized design patterns, Cairngorm exemplifies and encourages
best-practices for RIA development advocated by Adobe Consulting, encourages best-practice
leverage of the underlying Flex framework, while making it easier for medium to large teams of
software engineers deliver medium to large scale, mission-critical Rich Internet Applications.
The benefits of the Cairngorm architecture are realized when developing complex RIA
applications with multiple use-cases and views, with a team of developers, and with a
multi-disciplinary development team that includes designers as well as creative and technical
developers.
How is the MVC pattern carried out in a Flex + Cairngorm application?
- Model:???? Role of the ModelLocator & Model Objects
- View:???? Role of View Components & Event Objects
Controller: Role of the FrontController & Command Objects
30 :: What keyword allows us to implement abstraction better In flex?
Flex does not support abstart class directly.
* StumbleUpon
* Digg
* Delicious
* Twitter
* FaceBook
* LinkedIn
* Google
* Yahoo
* MySpace
* Tell Your Friend
31 :: What design patterns have you used? in Actionscript and java?
1. Creational Pattern
* Factory Method Pattern
* Singleton Pattern
2. Structural Patterns
* Decorator Pattern
* Adapter Pattern
* Coposite Pattern
3. Behavioral Patterns
* Command Pattern
* Observer Pattern
* Template Metod Pattern
* State Pattern
* Strategy Pattern
4. Multiple Patterns
* MVC Pattern
* Symetric Proxy Pattern
32 :: Explain how binding works in mxml components in flex?
Binding in MXML
Lets look at the following code…
Here you are binding the text property of the TextInput to the label. So whatever you type in the
textInput automatically reflects in the label. That’s the power of Binding…
The best practice for defining components that return information back to the main application is
to design the component to dispatch an event that contains the return data. In that way, the main
application can define an event listener to handle the event and take the appropriate action. You
also use events in data binding. The following example uses the Bindable metadata tag to make
useShortNames a bindable property. The implicit setter for the useShortNames property
dispatches the change event that is used internally by the Flex framework to make data binding
work.
33 :: What is the difference between ChangeWatcher.watch, and BindingUtils.bindProperty?
ChangeWatcher:
Acts like the watch on AS2. It watches a variable for changes and when something happens fires
an event. Make sure you call the canWatch to ensure that you can watch it!
There are 3 ways to specify the second parameter, the chain.
1. A String containing the name of a public bindable property of the host object.
ChangeWatcher.watch(this, "myvar", handler)
2. An Object in the form: { name: property name, access: function(host) { return host[name] } }.
The Object contains the name of a public bindable property, and a function which serves as a
getter for that property.
ChangeWatcher.watch(this, { name:"myvar", getter: function():String { return "something" }},
handler);
3. A non-empty Array containing any combination of the first two options. This represents a
chain of bindable properties accessible from the host. For example, to watch the property
host.a.b.c, call the method as: watch(host, ["a","b","c"]
BindingUtils.bindProperty
Works pretty much the same way as the watch, but instead of having to handle and event it
allows you to immediately bind two properties one-way.
The first two parameters are for the the target, the second parameters are the triggers.
BindingUtils.bindProperty( this, "va1", this, "var2");
Note : Make sure you add the flex framework.swc to your project Library Path to have access to
the mx.binding.util class.
34 :: Why would you want to keep a reference to a ChangeWatcher and call unwatch()?
So we can reattach the watcher again & We can change the source object (of changewatcher) by
reset method.
The ChangeWatcher class defines utility methods that you can use with bindable Flex properties.
These methods let you define an event handler that is executed whenever a bindable property is
updated.
unwatch () method:
Detaches this ChangeWatcher instance, and its handler function, from the current host. You can
use the reset() method to reattach the ChangeWatcher instance, or watch the same property or
chain on a different host object.
public function unwatch():void
35 :: How do you add event listeners in mxml components. Now AS3 components?
* addEventListener(type:String, listener:Function, useCapture:Boolean = false, priority:int = 0,
useWeakReference:Boolean = false):void
* removeEventListener(type:String, listener:Function, useCapture:Boolean = false):void
* dispatchEvent(event:Event):Boolean
* hasEventListener(type:String):Boolean
* willTrigger(type:String):Boolean
36 :: What does calling preventDefault() on an event do? How is this enforced?
Cancels an event's default behavior if that behavior can be canceled.. For example, the
doubleClick event has an associated default behavior that highlights the word under the mouse
pointer at the time of the event. Your event listener can cancel this behavior by calling the
preventDefault() method.
You can use the Event.cancelable property to check whether you can prevent the default
behavior associated with a particular event. If the value of Event.cancelable is true, then
preventDefault() can be used to cancel the event; otherwise, preventDefault() has no effect.
37 :: What is the problem with calling setStyle()
Calling the setStyle() method can result in decreased performance. Use it only when necessary.
You should try to apply style sheets rather than use the setStyle() method because it is
computationally expensive. This method should only be used when you are changing an object's
styles during run time.
You cannot get or set style properties directly on a component as you can with other properties.
Instead, you set style properties at run time by using the getStyle() and setStyle() ActionScript
methods.
38 :: Explain the difference between creating an effect and setting the target as opposed to
adding an effectListener?
To create a behavior, you define a specific effect with a unique ID and bind it to the trigger.
For example, the following code creates two zoom effects: one for shrinking the component
slightly, and one for reverting it to its original size. These effects are assigned, by using their
unique IDs, to the mouseDownEffect and mouseUpEffect triggers on the Button component.
39 :: How do we identify a component created in a repeater using flex?
If currentIndex value is greater than startIndex value means a component is created in Repeater.
We can use count property to find number of children.
A Repeater component executes initially when it is instantiated. If the Repeater component's
dataProvider property exists, it proceeds to instantiate its children, and they instantiate their
children, recursively.
The Repeater component re-executes whenever its dataProvider, startingIndex, or count
properties are set or modified either explicitly in ActionScript, or implicitly by data binding.
When a Repeater component re-executes, it destroys any children that it previously created
(assuming the recycleChildren property is set to false), and then reinstantiates its children based
on the current dataProvider property.
40 :: Differences between defining bindings in MXML and ActionScript?
There are a few differences between defining data bindings in MXML at compile time and in
defining them at runtime in ActionScript:
* You cannot include ActionScript code in a data binding expression defined by the
bindProperty() or bindSetter() method. Instead, use the bindSetter() method to specify a method
to call when the binding occurs.
* You cannot include an E4X expression in a data binding expression defined in ActionScript.
* 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.
* The MXML compiler has better warning and error detection support than runtime data bindings
defined by the bindProperty() or bindSetter() method.
41 :: Can I dynamically instantiate a WebService or HTTPService in ActionScript?
Flex 1.5 does not support this. First declare the tags in MXML and then manipulate the URLs,
request objects, and so forth using ActionScript.
42 :: Can I load CSS style sheets dynamically at runtime?
Dynamic loading of CSS files is not supported in Flex. CSS in Flex is processed on the server
side during MXML compilation rather than on the client side at runtime. There is a trick though:
A CSS file can be compiled into a separate SWF file and loaded dynamically into the application
using the Loader component.
43 :: When I set visible="false", the component still takes up space and appears in the tab order.
Why is that?
You can often achieve the "display=none" effect by setting the height/width to zero when you set
it invisible, and then set it back to a fixed value or to undefined when you make it visible again.
44 :: Why are my ValueObject member variables undefined in the results from my RemoteObject
requests?
Flash Player deserializes objects in a special order that can confuse developers used to object
serialization from other RPC systems. When a strongly typed object is returned to the player, it
first creates an instance from the prototype of the registered class without calling the
constructor. It then populates the object with the properties sent in the result. Finally, it calls the
constructor without arguments.
If your ValueObject constructor expects arguments to initialize an instance, be sure to check
whether arguments were actually sent to the constructor before overriding member variable
values.
45 :: Why do strongly typed objects appear as "undefined" in the NetConnection Debugger?
The NetConnection Debugger is an old utility from the early days of Flash Remoting that some
developers still find useful. It has an issue, however, displaying types that have been registered
with Object.registerClass(). If your Flex server is installed locally, we suggest enabling
server-side "debug" level logging in /WEB-INF/flex/gateway-config.xml to watch the raw trace
information in the Flex server console/logs from the AMF Gateway as it processes your
RemoteObject requests.
Flex Builder also includes a Network Debugger that allows you to monitor AMF traffic.
46 :: How do I get access to the J2EE session from my RemoteObjects?
The AMF Gateway provides access to the current HttpServletRequest instance in a thread local
variable. The session can be obtained from the request, as follows:
flashgateway.Gateway.getHttpRequest().getSession();
47 :: Can I resize the Internet Explorer browser window from Flex?
Use getURL() to communicate with JavaScript in the HTML wrapper:
getURL('javascript:window.resizeTo(1050,900)');
48 :: Can Flex applications communicate with each other on the client?
See the LocalConnection API in the flex documentation.
49 :: Is double-clicking supported on various components?
Unfortunately, double-clicking is not supported by default. If you wish to add this functionality
to, say, a List or DataGrid component, you will have to add the following ActionScript 2.0 code to
your application:
var someTimestamp:Number;
public function doubleClickHandler( evt:Object ):Void {
var now = getTimer();
// we got a double-click
if( ( now - someTimestamp ) < sometimestamp =" now;" style="color: rgb(255, 0, 0);">50 :: Why are there errors with the macromedia.css.LocatorParser class and WebLogic?
WebLogic ships with its own version of the fop.jar, which in turn includes the batik.jar, which is
older and breaks Flex. To resolve this issue, remove the fop.jar from the CLASSPATH in the
startWebLogic.cmd file. This may apply to non-WebLogic servers as well, where batik.jar was
included.
51 :: Sometimes, if I do not move the mouse, "click" and "mouseDown" do not work. Why is that?
This is a focus issue with Flash Player; usually when the UI changes "underneath" the mouse
pointer, as in a ViewStack navigation where the buttons are in the same screen location.
52 :: Why is myTreeNode.label or myTreeNode.attributes.label undefined?
Make sure you use the TreeDataProvider methods to modify a node. Do not rely on the node
being XML. For example, the above should be myTreeNode.getProperty("label") instead.
53 :: When I add or modify an item in my dataProvider, why does not it show up in my DataGrid?
Low-level methods like Array.push() or myArray[0] = "whatever" do not cause the dataProvider's
modelChanged event to fire.
When you work with a dataProvider, it is always best to use the dataProvider API. In the above
example, you might code: myDataProvider.addItem(myItemObject) to add an item or use
editField() to modify a value programmatically.
Alternatively, you can call myDataProvider.modelChanged yourself or reassign dataProvider to
the control, as follows: myDataGrid.dataProvider = myDataProvider;
54 :: myTree appears just fine but why ca not I access the node attributes?
Select a node in your myTree. In ActionScript, you can reference this node by using the
following code: myTree.selectedNode;
To access the attributes of the node, use the tree DataProvider API. These methods will work for
any format dataProvider item, which might be an object, array, or XML node.
The following example might work: myTree.selectedNode.attributes.myAttribute
But the following example is far more reliable:
myTree.selectedNode.getProperty("myAttribute");
55 :: How do I pass parameters to a pop-up window in actionscript?
Three different ways to pass data into a title window.
It uses the initobj to pass in several built-in properties plus two user defined properties.
One is a simple string, the other is a reference to the main application that can be used for
binding. Note the variable that holds the application reference is typed to the name of the
application. this is critical for binding to work correctly.
56 :: How do I run Flex as a service?
Flex is not a server that you deploy and run. It is simply deployed as part of your web
application. So it will work, no matter which web container you are using: Tomcat, JRun 4,
WebLogic, and so forth. To learn how to deploy Tomcat, JRun 4, or any other Java server as a
service, refer to the appropriate documentation for the server you are using.
57 :: How do I get Flex to query my database?
Flex does not have any native database integration functionality. You must have your own
server-side tier that provides the database-access tier and sends the data back to Flex through
one of the following protocols:
• RemoteObjects: This is the fastest. It communicates with server-side EJBs or POJOs using
AMF, a binary compressed format.
• HTTPService: This one uses the HTTP protocol. Sources can be JSP, ASPx, .NET, or any URL
that returns HTTP.
• WebService: This is the slowest. It uses the SOAP protocol. Sources can be .NET or any web
service.
58 :: I am sending my request, and I see the data traffic in the command window, but why is the
result always empty?
You are probably trying to read the result immediately after the send(), right? You're expecting
synchronous behavior?
59 :: How do I make synchronous data calls in actionscript?
You cannot make synchronous calls. You must use the result event. No, you can't use a loop,
setInterval, or even doLater. This paradigm is quite aggravating at first. Take a deep breath,
surrender to the inevitable, resistance is futile.
There is a generic way to handle the asynchronous nature of data service calls, called ACT
(Asynchronous Call Token). Search for this in the Developing Flex Applications LiveDocs for a
full description.
Here it is in a nutshell. This example uses HTTPService but will be similar for RemoteObject and
WebService:
1. Create a function to handle the data return, like onResult().
2. In the HTTPService tag, put this function name in the result property and pass "event" in too.
3. Invoke the call in the script:
//invokes the call to the HTTP data service
var oRequestCallbject = app.mxdsGetData.send(oRequest);
//Next, define a string to identify the call. We will use this string value in the result handler.
oRequestCall.MyQueryId = "WhateverIWanttoUseToIdentifyThisCall" ;
//Yes, you CAN set this AFTER you invoke send()
4. In the result handler, which will be called every time the data service call returns, identify what
the returned data contains, as follows:
var callResponse = oEvent.call; //get the call object
//gets the value of this property you set in the call
var sQueryId = callResponse.MyQueryId; //will be "WhateverIWanttoUseToIdentifyThisCall";
trace(sQueryId);
60 :: When I have only a single record, why does not it appear in my DataGrid?
This is a known issue that is caused by the inability of Flex to differentiate between an object
and an array with a single row. The solution is to always use toArray(), as in the following
examples:
In MXML:
{mx.utils.ArrayUtil.toArray(modelAccidents1.accidents.accident)}
The inline format:
dataProvider={mx.utils.ArrayUtil.toArray(testSrv.result.result.error)}
In ActionScript:
myControl.dataProvider = mx.utils.ArrayUtil.toArray(testSrv.result.result.error)
61 :: Why are the columns in my DataGrid in some strange order?
The order is typically the reverse of the order in which they were added. If you need a specific
order, specify that and many other good things by using DataGridColumn tags.
62 :: Can I embed HTML in my Flex application?
Flex supports a limited subset of HTML in its TextArea and some other text-related classes.
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