MediaTraitBase  - AS3 OSMF

套件	org.osmf.traits
類別	public class MediaTraitBase
繼承	MediaTraitBase EventDispatcher Object
子類別	AlternativeAudioTrait, AudioTrait, BufferTrait, DisplayObjectTrait, DRMTrait, DVRTrait, DynamicStreamTrait, LoadTrait, PlayTrait, SeekTrait, TimeTrait

語言版本:

ActionScript 3.0

產品版本:

OSMF 1.0

執行階段版本:

Flash Player 10, AIR 1.5

A MediaTraitBase is the encapsulation of a trait or capability that's inherent to a MediaElement. The sum of all traits on a media element define the overall capabilities of the media element.

Media traits are first-class members of the object model for a number of reasons:

• Traits allow us to isolate common aspects of different media types into reusable building blocks. For example, music and video may share a common implementation for audio. An "audio" trait can encapsulate that common implementation in such a way that it can be used for both media types, while still providing a uniform interface to these different media types.
• Different media elements may have their capabilities change dynamically over time, and traits allow us to isolate these capabilities in such a way that we can clearly express that dynamism. For example, a video player might not initially be "viewable", due to its need to be loaded before playback can begin. Rather than express this dynamism through changes to a set of methods on a monolithic media class, we can express it through the presence or absence of a trait instance on a lighter weight media class.
• Traits make compositioning scalable. (Compositioning is the ability to temporally and spatially composite collections of media.) If traits represent the overall vocabulary of the media framework, then we can implement compositioning primarily in terms of the traits, rather than in terms of the media that aggregate those traits. This approach allows developers to create new media implementations that can easily integrate with the compositioning parts of the framework without requiring changes to that framework. Our working assumption, of course, is that most (if not all) media will generally share the same vocabulary, which can be expressed through a core set of media traits.
• Traits allow for uniform, media-agnostic client classes. For example, if a client class is capable of rendering the "display object" trait, then it's capable of rendering any and all media that host that trait.

It's important to be aware of the relationship between a media trait and a media element. Some media trait implementations will be tightly coupled to a specific type of media element, while others will be generic enough to work with any media element. For example, an implementation of a "play" trait that works with video is typically going to be specific to one class of media elements, namely the class that plays video, since the playback operations will be specific to the underlying implementation of video (i.e. NetStream). On the other hand, an implementation of a "display object" trait might be able to work with any media element, since DisplayObjectTrait will use the same underlying media implementation (DisplayObject) for any media element.

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