Handling metadata and cue points in Flash video(AsyncErrorEvent text=Error #2095 flash.net.NetStream)

Handling metadata and cue points in Flash video(AsyncErrorEvent text=Error #2095 flash.net.NetStream)
2011年04月13日
　　This Quick Start article illustrates several techniques for handling the DE>onMetaDataDE> and DE>onCuePointDE> callback methods when using the NetConnection and NetStream classes to load Flash videos (FLVs). You'll discover how you can use the DE>asyncErrorDE> event (DE>AsyncErrorEvent.ASYNC_ERRORDE>) or DE>clientDE> property in the NetStream class to handle or ignore the meta data or cue points. The next sections describe the most popular and useful ways to use the DE>asyncErrorDE> and DE>clientDE> property when working with loading videos. There are many cases where you may prefer to create your own custom video player to play videos instead of using an existing component. For example, you may be trying to build a certain feature into your custom video player, or perhaps you're trying to make a video player with a very small file size. When building your own code, it is important to understand how the DE>onMetaDataDE> and DE>onCuePointDE> event handlers are used so you can handle them accordingly. The following example creates a new NetConnection, NetStream, and Video object to dynamically load an FLV file and display it in an SWF file. Since the specified FLV contains metadata and three cue points and there are no handlers defined for the DE>onMetaDataDE> and DE>onCuePointDE> event handlers, the DE>asyncErrorDE> is dispatched and informs you that the NetStream class was unable to invoke the callback DE>onMetaDataDE> and DE>onCuePointDE>:  DE>var nc:NetConnection = new NetConnection(); nc.connect(null); var ns:NetStream = new NetStream(nc); ns.play("http://www.helpexamples.com/flash/video/c uepoints.flv"); var myVideo:Video = new Video(); myVideo.attachNetStream(ns); addChild(myVideo); DE> Result
　　The previous example loads a Flash video file and begins video playback. Once the video's metadata or cue points are encountered an DE>asyncErrorDE> is dispatched. If you're running this code in the Flash authoring environment, you'll see that four errors are displayed in the Output panel with error messages similar to the following: DE>Error #2044: Unhandled AsyncErrorEvent:. text=Error #2095: flash.net.NetStream was unable to invoke callback onMetaData. error=ReferenceError: Error #1069: Property onMetaData not found on flash.net.NetStream and there is no default value. at asyncErrorExample_fla::MainTimeline/asyncErrorExam ple_fla::frame1() Error #2044: Unhandled AsyncErrorEvent:. text=Error #2095: flash.net.NetStream was unable to invoke callback onCuePoint. error=ReferenceError: Error #1069: Property onCuePoint not found on flash.net.NetStream and there is no default value. at asyncErrorExample_fla::MainTimeline/asyncErrorExam ple_fla::frame1() Error #2044: Unhandled AsyncErrorEvent:. text=Error #2095: flash.net.NetStream was unable to invoke callback onCuePoint. error=ReferenceError: Error #1069: Property onCuePoint not found on flash.net.NetStream and there is no default value. at asyncErrorExample_fla::MainTimeline/asyncErrorExam ple_fla::frame1() Error #2044: Unhandled AsyncErrorEvent:. text=Error #2095: flash.net.NetStream was unable to invoke callback onCuePoint. error=ReferenceError: Error #1069: Property onCuePoint not found on flash.net.NetStream and there is no default value. at asyncErrorExample_fla::MainTimeline/asyncErrorExam ple_fla::frame1() DE>
　　If you were looking at this SWF online in a web browser, you'd see the following errors instead: To prevent these errors, you have two primary solutions: Add an event listener for the DE>asyncErrorDE> event. 
　　Set a value for the NetStream object's DE>clientDE> property. 
　　To get the source files for this example, including Flash Professional CS5 versions of the files, download example01.zip at the top of this page. One of the easiest ways to handle the DE>asyncErrorDE> event dispatched by the NetStream object is to listen for the event using the DE>addEventListener()DE> method. This allows you to either handle or ignore the event. Example
　　The following example loads an FLV and traces the DE>asyncErrorDE> event's DE>textDE> property whenever the DE>asyncErrorDE> is dispatched: DE>var nc:NetConnection = new NetConnection(); nc.connect(null); var ns:NetStream = new NetStream(nc); ns.addEventListener(AsyncErrorEvent.ASYNC_ERROR, asyncErrorHandler); ns.play("http://www.helpexamples.com/flash/video/c uepoints.flv"); var myVideo:Video = new Video(); myVideo.attachNetStream(ns); addChild(myVideo); function asyncErrorHandler(event:AsyncErrorEvent):void { trace(event.text); } DE>
　　The second way to handle the DE>asyncErrorDE> event is to use the DE>clientDE> property of the NetStream class. The DE>clientDE> property specifies the object on which callback methods are invoked. The default object is the NetStream object being created. If you set the DE>clientDE> property to another object, callback methods will be invoked on that other object. Example
　　The following example creates a NetStream object and sets its DE>clientDE> property to an empty object, which prevents the DE>asyncErrorDE> from being dispatched: DE>var customClient:Object = new Object(); customClient.onMetaData = metaDataHandler; var nc:NetConnection = new NetConnection(); nc.connect(null); var ns:NetStream = new NetStream(nc); ns.client = customClient; ns.play("http://www.helpexamples.com/flash/video/c uepoints.flv"); var myVideo:Video = new Video(); myVideo.attachNetStream(ns); addChild(myVideo); function metaDataHandler(infoObject:Object):void { myVideo.width = infoObject.width; myVideo.height = infoObject.height; } DE>
　　The previous example defines a handler method for the DE>onMetaDataDE> handler which resizes the Video object on the Stage to match the dimensions of the FLV document, as reported by the metadata. Tip: You can also use the following shorthand notation for creating an object and specifying a handler:
　　DE>var customClient:Object = {onMetaData:metaDataHandler};DE> This examples will display like this: To get the source files for this example, including Flash Professional CS5 versions of the files, download example03.zip at the top of this page. Note: All of the following examples will display just like the example shown above. However some of the following examples will show additional trace information in the Flash concole window when they are run within the Flash CS3 authoring tool. One of the easiest ways to handle the DE>asyncErrorDE> event dispatched by the NetStream object is to listen for the event using the DE>addEventListener()DE> method. This allows you to either handle or ignore the event. Example
　　The following example sets the NetStream object's DE>clientDE> property to a custom class, CustomClient, which defines handlers for the callback methods: Note: The CustomClient class defines a handler for the DE>onMetaDataDE> callback handler. If a cue point was encountered and the DE>onCuePointDE> callback handler was called, an DE>asyncErrorDE> event would be dispatched saying "flash.net.NetStream was unable to invoke callback onCuePoint." To prevent this error, you would either need to define an DE>onCuePointDE> callback method in your CustomClient class, or define an event handler for the DE>asyncErrorDE> event. To get the source files for this example, including Flash Professional CS5 versions of the files, download example04.zip at the top of this page. DE>package { import flash.net.NetConnection; import flash.net.NetStream; public class CustomNetStream extends NetStream { public function CustomNetStream(nc:NetConnection) { super(nc); } public function onMetaData(infoObject:Object):void { trace("metadata"); } public function onCuePoint(infoObject:Object):void { trace("cue point"); } } } DE>
　　DE>package { import flash.net.NetConnection; import flash.net.NetStream; public class CustomNetStream extends NetStream { public var onMetaData:Function; public var onCuePoint:Function; public function CustomNetStream(nc:NetConnection) { onMetaData = metaDataHandler; onCuePoint = cuePointHandler; super(nc); } private function metaDataHandler(infoObject:Object):void { trace("metadata"); } private function cuePointHandler(infoObject:Object):void { trace("cue point"); } } DE>
　　Even with no handlers for the DE>onMetaDataDE> and DE>onCuePointDE> callback handlers, no errors are thrown since the DynamicCustomNetStream class is dynamic. If you want to define methods for the DE>onMetaDataDE> and DE>onCuePointDE> callback handlers, you could use the following code: DE>var nc:NetConnection = new NetConnection(); nc.connect(null); var ns:DynamicCustomNetStream = new DynamicCustomNetStream(nc); ns.onMetaData = metaDataHandler; ns.onCuePoint = cuePointHandler; ns.play("http://www.helpexamples.com/flash/video/c uepoints.flv"); var vid:Video = new Video(); vid.attachNetStream(ns); addChild(vid); function metaDataHandler(infoObject:Object):void { trace("metadata"); } function cuePointHandler(infoObject:Object):void { trace("cue point"); } DE>
　　To get the source files for this example, including Flash Professional CS5 versions of the files, download example07.zip at the top of this page. For more information
　　For more information about this topic, see "Using the Adobe Flash CS3 Video Encoder". For more information about this topic, see the NetStream class in the ActionScript 3.0 Reference for the Adobe Flash Platform.