即使您的主mxml仅包含可点击的图像，也应指定Application的宽度和高度！
如果您希望页面具有width: 400px和height: 100px的Flex图像（按钮？），则您的Application标记必须如下所示：
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" width="400" height="100">
尽管如此，在您的HTML中，您应该同时拥有object和embed标签具有相同的width和height，并且您还应该为embed标签的align属性指定一个值，例如：align="middle"。
您的object标签应该类似于
<object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000"
width="400" height="100" id="myMovieName"
codebase="http://fpdownload.macromedia.com/get/flashplayer/current/swflash.cab">
<param name="movie" value="/media/players/testsound.swf"/>
<param name="soundurl" value="/media/players/music.mp3"/>
<param name="quality" value="high"/>
<param name="bgcolor" value="#FFFFFF"/>
<embed width="400" height="100"
src="/media/players/testsound.swf"
flashvars="soundUrl=/media/players/music.mp3"
quality="high" bgcolor="#FFFFFF"
name="myMovieName" loop="false" align="middle"
type="application/x-shockwave-flash"
pluginspage="http://www.adobe.com/go/getflashplayer">
</embed>
</object>
其他
你的sndClass在哪里声明？如果你已经嵌入了那个mp3文件，你的脚本标签应该包含：
<mx:Script>
<![CDATA[
import mx.core.SoundAsset;
[Embed('/media/players/music.mp3')]
private var _sound:Class;
public var snd:SoundAsset = new _sound() as SoundAsset;
public var sndChannel:SoundChannel;
public function playSound():void {
sndChannel=snd.play();
}
]]>
</mx:Script>
如果您想从HTML指定mp3的路径，可以参考此帖子。
更新2
为了根据您的Flex按钮大小设置HTML object的宽度和高度，您应该按照以下方式更新应用程序MXML代码：
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute"
width="1" height="1" backgroundColor="#bee3f6"
horizontalScrollPolicy="off" verticalScrollPolicy="off"
creationComplete="onCreationComplete()" viewSourceURL="srcview/index.html">
<mx:Script>
<![CDATA[
import mx.events.FlexEvent;
//This method will change the button's label ==> width.
public function sayWhat():void {
var _date:Date = new Date();
extButton.label = "It's " + (_date.getHours() + 1) + ":" + _date.getMinutes() +
((_date.getMilliseconds() % 2) == 0 ? ". nice." : ". very tired.");
}
public function onCreationComplete():void {
// binds this.sayWhat to the external interface, so when from
// javascript is called the compiled swf object's sayWhat function,
// it will be transferred to this.sayWhat.
ExternalInterface.addCallback("sayWhat", sayWhat);
// set the flash application's size to be exact the button's size.
this.width = extButton.width;
this.height = extButton.height;
try
{
// The js function: onFlashAppInited(width, height);
// The next line tells the external interface (the parent application:
// browser window), that this application has finished loading, its
// ready to be used.
// We're passing the button's width and height as parameters
// In js there has to be a global method with this name.
ExternalInterface.call("onFlashAppInited", extButton.width, extButton.height);
}
catch (e:Error)
{
trace(e.message + "\n" + e.getStackTrace(), e.name);
}
}
protected function onButtonUpdateComplete(event:FlexEvent):void
{
// if the button's size has changed, we notify the javascript to set the
// correct size to the object tag too.
if ((this.width != extButton.width) || (this.height != extButton.height))
{
// set the application size
this.width = extButton.width;
this.height = extButton.height;
// notify the js about the change
ExternalInterface.call("onFlashAppSizeChanged", this.width, this.height);
}
}
]]>
</mx:Script>
<mx:Button id="extButton" label="Do something!" updateComplete="onButtonUpdateComplete(event)" />
</mx:Application>
请注意，初始时此应用程序仅为1x1像素（如果小于此值，则不会初始化！）。在
onCreationComplete处理程序中，它的大小将更改以匹配按钮的大小。
这些值（宽度和高度）将传递给javascript函数
onFlashAppInited，您也应该更新此函数：
function onFlashAppInited(width, height) {
alert("Flash app inited!");
appInited = true;
onFlashAppSizeChanged(width,height);
document.body.removeChild(document.getElementById("tmp"));
}
function onFlashAppSizeChanged(width, height) {
flashApp.width = width + "px";
flashApp.height = height + "px";
}
