Flex Interview Questions - An interviewhelper.org blog

I'm sending my request, and I see the data traffic in the command window, but why is the result always

2009-03-27T05:35:00.059-07:00

Question :I'm sending my request, and I see the data traffic in the command window, but why is the result always
empty?

Answer :You are probably trying to read the result immediately after the send(), right? You're expecting
synchronous behavior?

How do I get Flex to query my database

2009-03-27T05:35:00.058-07:00

Question :How do I get Flex to query my database?
Answer :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.

myTree appears just fine but why can't I access the node attributes

2009-03-27T05:35:00.057-07:00

Question :myTree appears just fine but why can't I access the node attributes?
Answer :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");

When I add or modify an item in my dataProvider, why doesn't it show up in my DataGrid

2009-03-27T05:35:00.056-07:00

Question :When I add or modify an item in my dataProvider, why doesn't it show up in my DataGrid?
Answer :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;

Why is myTreeNode.label or myTreeNode.attributes.label undefined

2009-03-27T05:35:00.055-07:00

Question :Why is myTreeNode.label or myTreeNode.attributes.label undefined?
Answer :Make sure you use the TreeDataProvider methods to modify a node. Don't rely on the node being
XML. For example, the above should be myTreeNode.getProperty("label") instead.

: Sometimes, if I don't move the mouse, "click" and "mouseDown" don't work. Why is that

2009-03-27T05:35:00.054-07:00

Question :Sometimes, if I don't move the mouse, "click" and "mouseDown" don't work. Why is that?
Answer :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.

What does "The URL is not in the Proxy's whitelist" mean

2009-03-27T05:35:00.053-07:00

Question :What does "The URL is not in the Proxy's whitelist" mean?
Answer :The whitelist is a security feature in Flex that requires you to define explicitly which URLs a data
service call can access.
You set this by editing the following file: ...\[flexroot]\WEB-INF\flex\flex-config.xml
There are three sections, one each for WebService, HTTPService, and RemoteObject. Be sure you
edit the correct section! Each has a subsection which contains nodes. To enable a URL for access by
a Flex dataService call, enter that URL between the tags.
For development phase only, you can allow global access with the wildcard rows. The flex-config
file is heavily commented. Open it up and you will see more detailed instructions there.

Why are there errors with the macromedia.css.LocatorParser class and WebLogic

2009-03-27T05:35:00.052-07:00

Question :Why are there errors with the macromedia.css.LocatorParser class and WebLogic?
Answer :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.

Is double-clicking supported on various components

2009-03-27T05:35:00.051-07:00

Question :Is double-clicking supported on various components?
Answer :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 ) < 500 ) {
// do something here ...
}
someTimestamp = now;
}

Can I resize the Internet Explorer browser window from Flex

2009-03-27T05:35:00.050-07:00

Question :Can I resize the Internet Explorer browser window from Flex?
Answer :Use getURL() to communicate with JavaScript in the HTML wrapper:
getURL('javascript:window.resizeTo(1050,900)');

How do I get access to the J2EE session from my RemoteObjects

2009-03-27T05:35:00.049-07:00

Question :How do I get access to the J2EE session from my RemoteObjects?
Answer :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();

Why do strongly typed objects appear as "undefined" in the NetConnection Debugger

2009-03-27T05:35:00.048-07:00

Question :Why do strongly typed objects appear as "undefined" in the NetConnection Debugger?
Answer :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.

Why are my ValueObject member variables undefined in the results from my RemoteObject requests

2009-03-27T05:35:00.047-07:00

Question :Why are my ValueObject member variables undefined in the results from my RemoteObject requests?
Answer :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.

: When I set visible="false", the component still takes up space and appears in the tab order. Why is

2009-03-27T05:35:00.046-07:00

Question :: When I set visible="false", the component still takes up space and appears in the tab order. Why is
that?

Answer :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.

Can I load CSS style sheets dynamically at runtime

2009-03-27T05:35:00.045-07:00

Question :Can I load CSS style sheets dynamically at runtime?
Answer :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.

Can I dynamically instantiate a WebService or HTTPService in ActionScript

2009-03-27T05:35:00.044-07:00

Question :Can I dynamically instantiate a WebService or HTTPService in ActionScript?
Answer :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.

What is state what is the difference between states and ViewStack

2009-03-27T05:35:00.043-07:00

Question :What is state? what is the difference between states and ViewStack?
Answer :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.
Login/Registration/Forgot password is the best example for using States as each page will either add
or remove to the already existing one.

How do you use a repeater

2009-03-27T05:35:00.042-07:00

Question :How do you use a repeater?
Answer :: The Repeater class is the runtime object that corresponds to the tag. It creates
multiple instances of its subcomponents based on its dataProvider. The repeated components can be
any standard or custom controls or containers.
You can use the tag anywhere a control or container tag is allowed, with the
exception of the container tag. To repeat a user interface component, you place
its tag in the tag. You can use more than one tag in an MXML
document. You can also nest tags.
You cannot use the tag for objects that do not extend the UIComponent class.
MXML Syntax Hide MXML Syntax
The class has the following properties:
recycleChildren="false|true" startingIndex="0"
Events
repeat="No default" repeatEnd="No default" repeatStart="No default" >

How do you call javascript from Flex

2009-03-27T05:35:00.041-07:00

Question :How do you call javascript from Flex?
Answer :The ExternalInterface class is the External API, an application programming interface that enables
straightforward communication between ActionScript and the Flash Player container– for example,
an HTML page with JavaScript. Adobe recommends using ExternalInterface for all JavaScript-
ActionScript communication.
You can call an ActionScript function in Flash Player, using JavaScript in the HTML page. The
ActionScript function can return a value, and JavaScript receives it immediately as the return value
of the call.
This functionality replaces the fscommand() method.
The ExternalInterface class requires the user's web browser to support either ActiveX® or the
NPRuntime API that is exposed by some browsers for plug-in scripting. Even if a browser and
operating system combination are not listed above, they should support the ExternalInterface class if
they support the NPRuntime API. See http://www.mozilla.org/projects/plugins/npruntime.html.
Note: When embedding SWF files within an HTML page, make sure that the id and name attributes
of the object and embed tags do not include the following characters: . - + * / \
From ActionScript, you can do the following on the HTML page:
•Call any JavaScript function.
•Pass any number of arguments, with any names.
•Pass various data types (Boolean, Number, String, and so on).
•Receive a return value from the JavaScript function.
From JavaScript on the HTML page, you can:
•Call an ActionScript function.
•Pass arguments using standard function call notation.
•Return a value to the JavaScript function.
Flash Player does not currently support SWF files embedded within HTML forms.

What is a drag manager

2009-03-27T05:35:00.040-07:00

Question :What is a drag manager?
Answer :The DragManager class manages drag and drop operations, which let you move data from one place
to another in a Flex application. For example, you can 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.
All methods and properties of the DragManager are static, so you do not need to create an instance of
it.
All Flex components support drag and drop operations. Flex provides additional support for drag and
drop to the List, Tree, and DataGrid controls.
When the user selects an item with the mouse, the selected component is called the drag initiator. The
image displayed during the drag operation is called the drag proxy.
When the user moves the drag proxy over another component, the dragEnter event is sent to that
component. If the component accepts the drag, it becomes the drop target and receives dragOver,
dragExit, and dragDrop events.
When the drag is complete, a dragComplete event is sent to the drag initiator.

What are the methods called when a UI component is intialized

2009-03-27T05:35:00.039-07:00

Question :What are the methods called when a UI component is intialized?
Answer :createChildren()

: How do you generate random numbers within a given limit with actionscript

2009-03-27T05:35:00.038-07:00

Question :: How do you generate random numbers within a given limit with actionscript?
Answer :public function randRange(min:Number, max:Number):Number {
var randomNum:Number = Math.floor(Math.random() * (max - min + 1)) + min;
return randomNum;
}

What is the difference between httpService and Data Service

2009-03-27T05:35:00.037-07:00

Question :What is the difference between httpService and Data Service?
Answer :The Flex presentation layer communicates with the business layer by using Flex
data services, which are objects you insert in a Flex file. Specifically, you can use Flex data services
to interact with the following:
* Web services
* HTTP services
* Remote objects
A Flex data service is an object you insert in an MXML file to communicate with the business layer
of a multi-tier application. You use data services to send and receive data from web services, HTTP
URLs, and remote objects such as server-based Java objects.
An HTTP service is nothing more than an HTTP request to a URL. The primary purpose of HTTP
services is to retrieve XML data from an external source.

Differences between defining bindings in MXML and ActionScript

2009-03-27T05:35:00.036-07:00

Question :Differences between defining bindings in MXML and ActionScript?
Answer :: 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.

How do you identify a component created in a repeater

2009-03-27T05:35:00.035-07:00

Question :How do you identify a component created in a repeater?
Answer :: 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.

Explain the difference between creating an effect and setting the target as opposed to adding an

2009-03-27T05:35:00.034-07:00

Question :Explain the difference between creating an effect and setting the target as opposed to adding an
effectListener

Answer :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.

paddingLeft="10" paddingRight="10" autoLayout="false" left="41" top="24" right="42">
mouseDownEffect="{shrink}" mouseUpEffect="{revert}"/>

What is the problem with calling setStyle()

2009-03-27T05:35:00.033-07:00

Question :What is the problem with calling setStyle()?
Answer :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.

What does calling preventDefault() on an event do How is this enforced

2009-03-27T05:35:00.032-07:00

Question :What does calling preventDefault() on an event do? How is this enforced?
Answer :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.

How do you add event listeners in mxml components. Now AS3 components

2009-03-27T05:35:00.031-07:00

Question :How do you add event listeners in mxml components. Now AS3 components?
Answer :1) addEventListener(type:String, listener:Function, useCapture:Boolean = false, priority:int = 0,
useWeakReference:Boolean = false):void
2) removeEventListener(type:String, listener:Function, useCapture:Boolean = false):void
3) dispatchEvent(event:Event):Boolean
4) hasEventListener(type:String):Boolean
5) willTrigger(type:String):Boolean

Why would you want to keep a reference to a ChangeWatcher and call unwatch()

2009-03-27T05:35:00.030-07:00

Question :Why would you want to keep a reference to a ChangeWatcher and call unwatch()?
Answer :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

What’s the difference between ChangeWatcher.watch, and BindingUtils.bindProperty

2009-03-27T05:35:00.029-07:00

Question :What’s the difference between ChangeWatcher.watch, and BindingUtils.bindProperty?
Answer :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.

Explain how binding works in mxml components.

2009-03-27T05:35:00.028-07:00

Question :Explain how binding works in mxml components.
Answer :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.

What design patterns have you used in Actionscript and java

2009-03-27T05:35:00.027-07:00

Question :What design patterns have you used? in Actionscript and java?
Answer :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

What keyword allows you to implement abstraction better

2009-03-27T05:35:00.026-07:00

Question :What keyword allows you to implement abstraction better?
Answer :Flex does not support abstart class directly.

What is cairnghorm ? how do you use it Have you worked with Cairnghorn

2009-03-27T05:35:00.025-07:00

Question :What is cairnghorm ? how do you use it?Have you worked with Cairnghorn?
Answer :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 bestpractices
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

What are runtime shared libraries

2009-03-27T05:35:00.024-07:00

Question :What are runtime shared libraries?
Answer :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.

What are sealed classes

2009-03-27T05:35:00.023-07:00

Question :What are sealed classes ?
Answer :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.

What is dynamic keyword used for

2009-03-27T05:35:00.022-07:00

Question :What is dynamic keyword used for?
Answer :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

How do you overload functions in actionscript

2009-03-27T05:35:00.021-07:00

Question :How do you overload functions in actionscript?
Answer :Method overloading using namespaces.

How polymorphism works on actionscript

2009-03-27T05:35:00.020-07:00

Question :How polymorphism works on actionscript?
Answer :class UnpaidIntern extends Employee {
override public function receivePayment():Number {
return 0;
}
}
class Manager extends Employee {
override public function receivePayment():Number {
return baseSalary*3;
}
}
class Engineer extends Employee {
override public function receivePayment():Number {
return this.baseSalary*2;
}
}
class Employee {
internal var baseSalary:Number = 1000;
public function receivePayment():Number {
return this.baseSalary;
}
}

What keyword allows you to refer to private variables of a class

2009-03-27T05:35:00.019-07:00

Question :What keyword allows you to refer to private variables of a class?
Answer :private keyword , this keyworld

How does item renderer work How do I add item renderer at runtime

2009-03-27T05:35:00.018-07:00

Question : How does item renderer work? How do I add item renderer at runtime?
Answer :: 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.

What is state what is the difference between states and ViewStack

2009-03-27T05:35:00.017-07:00

Question :What is state? what is the difference between states and ViewStack?
Answer :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.
Diff :
1) View Stack is to handle different MXML file eg TAB control and states is the transition within
single MXML file.
2) 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.
3) 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

What is MVC and how do you relate it to flex apps

2009-03-27T05:35:00.016-07:00

Question :What is MVC and how do you relate it to flex apps?
Answer :: (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.

What is the difference between sealed class and dynamic classes

2009-03-27T05:35:00.015-07:00

Question :What is the difference between sealed class and dynamic classes?
Answer :Classes are sealed by default, i.e. properties cannot be added dynamically at runtime.
1) Dynamic classes can add additional dynamic properties at runtime; sealed classes cannot.
2) Sealed classes conserve memory because no internal hash table is needed to store dynamic
properties, and the compiler can provide better error feedback.

How do you use css styles in flex

2009-03-27T05:35:00.014-07:00

Question :How do you use css styles in flex?
Answer :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 tag, as follows:

.myclass { background-color: xFF0000 }
TextInput { font-family: Helvetica; font-size: 12pt }

Inline styles are defined in an MXML tag and can only be used in that tag. Inline styles are defined
as follows:

What are three ways to skin a component in flex

2009-03-27T05:35:00.013-07:00

Question :What are three ways to skin a component in flex?
Answer :: 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).

How do you use a repeater

2009-03-27T05:35:00.012-07:00

Question :How do you use a repeater?
Answer :

[Bindable]
public var myArray:Array=[1,2,3,4];
]]>

paddingRight="10" paddingTop="10">

How do you call javascript from Flex

2009-03-27T05:35:00.011-07:00

Question :How do you call javascript from Flex?
Answer :: 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

What is a drag manager

2009-03-27T05:35:00.010-07:00

Question :What is a drag manager?
Answer :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.

Can you write to the file system from flex

2009-03-27T05:35:00.009-07:00

Question :Can you write to the file system from flex?
Answer :Yes .
import flash.filesystem.*;
private var stream:FileStream;
private function saveFile():void{
var file:File = File.desktopDirectory.resolvePath("HelloWorld.txt");
var stream:FileStream = new FileStream()
stream.open(file, FileMode.WRITE);
var str:String = "Congratulations on your 1st file, Rich Tretola - EverythingFlex.com";
stream.writeUTFBytes(str);
stream.close();
mx.controls.Alert.show("File has been saved to \n" + file.nativePath, "Notice");

What are the methods called when a UI component is intialized

2009-03-27T05:35:00.008-07:00

Question :What are the methods called when a UI component is intialized?
Answer :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).

How do you implement push with flex data services

2009-03-27T05:35:00.007-07:00

Question :How do you implement push with flex data services?
Answer :Using Blaze DS Server & LCDS

What is the dynamic keyword used for

2009-03-27T05:35:00.006-07:00

Question :What is the dynamic keyword used for?
Answer :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.

What are the similarities between java and flex

2009-03-27T05:35:00.005-07:00

Question :What are the similarities between java and flex?
Answer :
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).

What is a resource Manager

2009-03-27T05:35:00.004-07:00

Question :What is a resource Manager??
Answer :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.

I am going to add images into a tag. How will it resize itself

2009-03-27T05:35:00.003-07:00

Question :I am going to add images into a tag. How will it resize itself?
Answer :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.

I am going to add images into a tag. How will it resize itself

2009-03-27T05:35:00.002-07:00

How do you implement push on a flex applications

2009-03-27T05:35:00.001-07:00

Question :How do you implement push on a flex applications?
Answer :Using BlazeDS Server, LiveCycle Data Services,

Have you built any components with actionscript? If so explain how you did it

2009-03-27T05:34:00.001-07:00

Question :Have you built any components with actionscript? If so explain how you did it?
Answer :CountryComboBox.as
package components
{ import mx.controls.ComboBox;
public class CountryComboBox extends ComboBox
{ public function CountryComboBox()
{ dataProvider = [ "United States", "United Kingdom" ];
}
}
}

xmlns:mx="http://www.adobe.com/2006/mxml"
xmlns:custom="components.*"
width="220" height="115"
>

How do you generate random numbers within a given limit with actionscript

2009-03-27T05:33:00.000-07:00

Question :How do you generate random numbers within a given limit with actionscript?
Answer :Math.round(Math.random() * (high - low)) + low

What is the difference between httpService and Data Service

2009-03-27T05:31:00.000-07:00

Question :What is the difference between httpService and Data Service?
Answer :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.

I need to load an image from flickr into my application. Do I need a crossdomain.xml file on flickr

2009-03-27T05:30:00.000-07:00

Question :I need to load an image from flickr into my application. Do I need a crossdomain.xml file on flickr?
Answer :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.

Is it possible to make httpService Requests synchronous

2009-03-27T05:20:00.000-07:00

Question :Is it possible to make httpService Requests synchronous?
Answer :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.
For example: 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.