Differences in mobile, desktop, and browser application development

Use Flex to develop applications for the following deployment environments:

Deploy the application as a SWF file for use in Flash Player running in a browser.

Deploy a standalone AIR application for a desktop computer, such as a Windows computer or Macintosh.

Deploy a standalone AIR application for a mobile device, such as a phone or a tablet.

The Flash Player and AIR runtimes are similar. You can perform most of the same operations in either runtime. Besides allowing you to deploy standalone applications outside a browser, AIR provides close integration with the host platform. This integration enables such features as access to the file system of the device, the ability to create and work with local SQL databases, and more.

Considerations in designing and developing mobile applications

Applications for mobile touchscreen devices differ from desktop and browser applications in several ways:

  • To allow for easy manipulation by touch input, mobile components generally have larger hit areas than they do in desktop or browser applications.

  • The interaction patterns for actions like scrolling are different on touchscreen devices.

  • Because of the limited screen area, mobile applications are typically designed with only a small amount of the user interface visible on the screen at one time.

  • User interface designs must take into account differences in screen resolution across devices.

  • CPU and GPU performance is more limited on phones and tablets than on desktop devices.

  • Owing to the limited memory available on mobile devices, applications must be careful to conserve memory.

  • Mobile applications can be quit and restarted at any time, such as when the device receives a call or text message.

Therefore, building an application for a mobile device is not just a matter of scaling down a desktop application to a different screen size. Flex lets you create separate user interfaces appropriate for each form factor, while sharing underlying model and data access code among mobile, browser, and desktop projects.

Restrictions on using Spark and MX components in a mobile application

Use the Spark component set when creating mobile applications in Flex. The Spark components are defined in the spark.components.* packages. However, for performance reasons or because not all Spark components have skins for the Mobile theme, mobile applications do not support the entire Spark component set.

Except for the MX charting controls and the MX Spacer control, mobile applications do not support the MX component set defined in the mx.* packages.

The following table lists the components that you can use, that you cannot use, or that require care to use in a mobile application:



Use in mobile?


Spark ActionBar

Spark BusyIndicator

Spark Callout

Spark CalloutButton

Spark DateSpinner

Spark SpinnerList

Spark SpinnerListContainer

Spark TabbedViewNavigator

Spark TabbedViewNavigatorApplication

Spark ToggleSwitch

Spark View

Spark ViewMenu

Spark ViewNavigator

Spark ViewNavigatorApplication


These new components support mobile applications.

Spark Button

Spark CheckBox

Spark DataGroup

Spark Group/HGroup/VGroup/TileGroup

Spark Image/BitmapImage

Spark Label

Spark List

Spark RadioButton/RadioButtonGroup

Spark SkinnableContainer

Spark Scroller

Spark TextArea

Spark TextInput


Most of these components have skins for the Mobile theme. Label, Image, and BitmapImage can be used even though they do not have a mobile skin.

Some Spark layout containers, such as Group and its subclasses, do not have skins. Therefore, you can use them in a mobile application.

Other Spark skinnable components



Skinnable Spark components other than the ones listed above are discouraged because they do not have a skin for the Mobile theme. If the component does not have a skin for the Mobile theme, you can create one for your application.

Spark DataGrid

Spark RichEditableText

Spark RichText


These components are discouraged for performance reasons. While you can use them in a mobile application, doing so can affect performance.

For the DataGrid control, performance is based on the amount of data that you render. For the RichEditableText and RichText controls, performance is based on the amount of text, and the number of controls in the application.

MX components other than Spacer and charts



Mobile applications do not support MX components, such as the MX Button, CheckBox, List, or DataGrid. These components correspond to the Flex 3 components in the mx.controls.* and mx.containers.* packages.

MX Spacer



Spacer does not use a skin, so it can be used in a mobile application.

MX chart components


Yes, but with performance implications

You can use the MX chart controls, such as the AreaChart and BarChart, in a mobile application. The MX chart controls are in the mx.charts.* packages.

However, performance on a mobile device can be less than optimal depending on the size and type of charting data.

By default, Flash Builder does not include the MX components in the library path of mobile projects. To use the MX charting components in an application, add the mx.swc and charts.swc to your library path.

The following Flex features are not supported in mobile applications:

  • No support for drag-and-drop operations

  • No support for the ToolTip control

  • No support for RSLs

Performance considerations with mobile applications

Owing to the performance constraints of mobile devices, some aspects of mobile application development differ from development for browser and desktop applications. Some performance considerations include the following:

  • Write item renderers in ActionScript

    For mobile applications, you want list scrolling to have the highest performance possible. Write item renderers in ActionScript to achieve the highest performance. While you can write item renderers in MXML, your application performance can suffer.

    Flex provides two item renderers that are optimized for use in a mobile application: spark.components.LabelItemRenderer and spark.components.IconItemRenderer. For more information on these item renderers, see Using a mobile item renderer with a Spark list-based control.

    For more information on creating custom item renderers in ActionScript, see Custom Spark item renderers. For more information on the differences between mobile and desktop item renderers, see Differences between mobile and desktop item renderers.

  • Use ActionScript and compiled FXG graphics or bitmaps to develop custom skins

    The mobile skins shipped with Flex are written in ActionScript with compiled FXG graphics to provide the highest performance. You can write skins in MXML, but your application performance can suffer depending on the number of components that use MXML skins. For the highest performance, write skins in ActionScript and use compiled FXG graphics. For more information, see Spark Skinning and FXG and MXML graphics.

  • Use text input components that use StageText

    When adding text input components such as TextInput and TextArea, use the defaults. These controls use StageText as the underlying mechanism for text input, which hooks into the native text input classes. This gives you better performance and access to native features such as auto-correction, auto-capitalization, text restriction, and custom soft keyboards.

    There are some drawbacks to using StageText including not being able to scroll the view that the controls are in. In addition, you can’t use embedded fonts or use custom sizing for the StageText-based controls. If these are necessary, you can use text input controls based on the TextField class.

    For more information, see Use text in a mobile application.

  • Take care when using MX chart components in a mobile application

    You can use the MX chart controls, such as the AreaChart and BarChart controls, in a mobile application. However, they can affect performance depending on the size and type of charting data.