Flex播放器(实现播放、缓冲进度条和音频曲线显示)

mx:ProgressBar实现加载歌曲缓冲进度条

ProgressBar有三大mode模式，分别为event、manual、polled，event为基于事件驱动模式，可设置source对象自动显示加载进程；manual为手动模式，需要调用ProgressBar.setProgress()方法设置滚动条进度；polled为轮询模式，本例使用的manual模式，Sound加载load请求歌曲添加一个ProgressEvent.PROGRESS处理中监听事件，然后根据Sound已加载的bytes和bytesTotal数，设置setProgress进度。这里需要注意在切换歌曲的时候先要移除ProgressEvent.PROGRESS事件，否则之前播放歌曲还未加载完又切换load新歌曲时回出现ProgressBar触发多个PROGRESS事件被设置进度出现来回滚动的问题。

mx:HSlide调节滑秆

这个控件在本例中2处使用，实现对播放进度和声音大小的控制。最一开始调整播放进度的问题难倒了我很久，因为在歌曲播放过程中HSlide要自动滑动当前播放位置，同时又需要能手动拖动播放位置，HSlide本来有一个很好的change事件用来侦听改变，但是我使用定时器设置HSlide的value的时竟然也给我触发change事件，参考了Adobe哥官网的帮助文档，说是Slider 组件的值因鼠标或键盘交互操作而改变时调度，如果 liveDragging 属性是 true，则在用户移动滑块时持续调度该事件。 如果 liveDragging 是 false，则在用户释放滑块时调度该事件。但是无论我怎么设置，在代码里改变了HSlide的value值怎会触发change事件，不是说在用户交互操作而改变时调度吗？无赖啊，后来只能折中采取监听thumbDrag滑秆拖动时事件，这个事件Adobe哥的解释是当按下滑块并随后随鼠标移动时调度，这样会有一个小问题，就是需要拖动滑秆按下时才会触发，点击无效。

SoundMixer.computeSpectrum()分析音频曲线

本例你看到显示的音频曲线其实是右64个绘制成条状的Canvas控件排列而成，然后使用定时器每间隔100毫秒重新设置他们的scaleY位置以呈现出变幻曲线的效果，代码只有三行很简单，具体可参见我下面源码给出的timerTick事件。这里为什么要用定时器呢？在网上看别人是监听Event.ENTER_FRAME事件重绘音频曲线的，不想搞那么麻烦就直接用定时器了，随便根据bytesTotal和bytesLoaded计算下歌曲播放时间，使用100毫秒的定时器也并好耗站资源，CPU没有涨很高。

mxml代码如下：

<?xml version="1.0" encoding="utf-8"?><mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" verticalGap="0" scroll="false" backgroundAlpha="0"     horizontalScrollPolicy="off" verticalScrollPolicy="off" verticalAlign="middle" horizontalAlign="center"     initialize="init(event)" layout="vertical" fontSize="14" paddingLeft="0" paddingTop="0" paddingRight="0" paddingBottom="0" >    <mx:Script>        <![CDATA[            import mx.formatters.DateFormatter;                    import mx.effects.SoundEffect;            import mx.events.SliderEvent;            import mx.core.SoundAsset;                    import mx.controls.Alert;            import mx.managers.CursorManager;            import flash.media.*;                        import flash.utils.Timer;                        [Embed(source="images/cursor.gif")]             private var cursorHand : Class;//图标                        private var xml:XML;             private var xmlPath:String = "/flex/bin-debug/song.xml";            private var currIndex : Number = 0;                         private var song :Sound;            private var channel :SoundChannel;            private var position : Number = 0;            // 保存 512 个声音波形的快照            private var bytes:ByteArray = new ByteArray();            // SoundBar 的个数            private var barNum:uint = 64;            // 保存所有 SoundBar 的引用            private var soundBars:Array = new Array();                        //定时器            private var timer : Timer;                        //Application的initialize初试化事件            private function init(event:Event):void            {                var loader:URLLoader = new URLLoader();                 loader.load(new URLRequest(xmlPath));                 loader.addEventListener(Event.COMPLETE,Xml_Complete);                                timer = new Timer(100);                timer.addEventListener(TimerEvent.TIMER,timerTick);                                var barWidth:Number = boxSoundBar.width*1.00/barNum;                // 初始化Canvas为音频条，放入舞台并加入数组                for (var i:uint = 0; i < barNum; i++)  {                   var soundBar:Canvas = new Canvas();                   soundBar.width = barWidth;                   soundBar.height = boxSoundBar.height;                   soundBar.x = i * barWidth;                      soundBar.y =  0;                   var g:Graphics = soundBar.graphics;                   g.lineStyle(1,0x6688AA,1);                   g.beginGradientFill(GradientType.RADIAL,[0x33cc00,0x456628],[1,1],[0,255],null,SpreadMethod.REFLECT,InterpolationMethod.RGB,0);                   g.drawRect(0,0,soundBar.width,soundBar.height);                   g.endFill();                   boxSoundBar.addChild(soundBar);                   soundBars.push(soundBar);                }                // 隐藏一些内建的鼠标右键菜单项                this.contextMenu.hideBuiltInItems();                 var contextMenuItem : ContextMenuItem = new ContextMenuItem("Powered By: Jonllen");                contextMenuItem.enabled = false;                contextMenu.customItems.push(contextMenuItem);                this.contextMenu.customItems.push(contextMenuItem);                                //更改鼠标图标                CursorManager.setCursor(cursorHand);            }                        //读取XML文件完成事件            private function Xml_Complete(event:Event):void             {                xml = new XML(event.target.data);                if(xml.item.length()>=1)                {                    listSong.dataProvider= xml.item.name;                    listSong.selectedIndex = 0;                    //手动触发List的Change事件                    listSong.dispatchEvent(new mx.events.ListEvent(Event.CHANGE, true, false));                }            }                        //List选择歌曲改变事件            private function Xml_Change(event:Event):void            {                currIndex = event.target.selectedIndex;                                timer.stop();                                //停止声音文件的加载                if( song!=null )                {                    //移除之前加载PROGRESS事件对songProgress进度条的控制                    song.removeEventListener(ProgressEvent.PROGRESS,songProgress_Change);                    if( song.isBuffering )                        song.close();                }                                song = new Sound();                var url : String = xml.item[currIndex].url;                var source:URLRequest = new URLRequest(url);                song.load(source);                song.addEventListener(ProgressEvent.PROGRESS, songProgress_Change);                song.addEventListener(IOErrorEvent.IO_ERROR, songProgress_Error);                                position = 0;                songStart();            }                        //歌曲播放完成            private function songProgress_Complete(e:Event):void {                if(currIndex == xml.item.length()-1) {                    currIndex = 0;                }else {                    currIndex++;                }                listSong.selectedIndex = currIndex;                listSong.dispatchEvent(new mx.events.ListEvent(Event.CHANGE, true, false));            }                        //加载歌曲失败            private function songProgress_Error(e:IOErrorEvent):void {                Alert.show("文件不存在！","系统提示");            }                        //开始播放歌曲            private function songStart():void {                                if ( channel != null ){                    channel.stop();                }                                lblName.text = xml.item[currIndex].name;                channel = song.play(position,int.MAX_VALUE);                                var length :Number = song.length*song.bytesTotal/song.bytesLoaded;                var date : Date = new Date();                date.time = length;                                var dt : DateFormatter = new DateFormatter();                dt.formatString="NN:SS";                var totalTime : String = dt.format(date);                                date.time = channel.position;                lblTime.text = dt.format(date) + " | " + totalTime;                lblStatus.text = "播放";                                var soundcontrol : SoundTransform = channel.soundTransform;                soundcontrol.volume = volumeSlider.value;                channel.soundTransform= soundcontrol;                                timer.start();                boxSoundBar.visible = true;            }                        //停止歌曲播放            private function songStop():void {                timer.stop();                position = 0;                boxSoundBar.visible = false;                lblTime.text = "00:00 |"+lblTime.text.split("|")[1];                lblStatus.text = "停止";                songSlider.value = songSlider.minimum;                songProgress.setProgress(songProgress.minimum,songProgress.maximum);                if ( channel != null )                {                    channel.stop();                }            }                        //暂停歌曲播放            private function songPause():void {                if ( channel != null ){                    timer.stop();                    position = channel.position;                    channel.stop();                    lblStatus.text = "暂停";                }            }                        //加载歌曲进度条显示            private function songProgress_Change(e:ProgressEvent):void {                var percent:int = Math.round(e.bytesLoaded * 100 / e.bytesTotal);                songProgress.setProgress(e.bytesLoaded,e.bytesTotal);            }                        //定时器方法            private function timerTick( e:TimerEvent):void {                                if( channel!=null) {                                        var length :Number = song.length*song.bytesTotal/song.bytesLoaded;                    var date : Date = new Date();                    date.time = length;                                    var dt : DateFormatter = new DateFormatter();                    dt.formatString="NN:SS";                    var totalTime : String = dt.format(date);                                        date.time = channel.position;                    lblTime.text = dt.format(date) + " | " + totalTime;                                        songSlider.value=100*channel.position/length;                    if( songSlider.value>=songSlider.maximum){                        timer.stop();                        songProgress_Complete(null);                        return;                    }                                        SoundMixer.computeSpectrum(bytes, false, 0);                    for (var i:uint = 0; i < barNum; i++)  {                       soundBars[i].scaleY = bytes.readFloat();                    }                                    }            }                        //歌曲进度调整事件            internal function songSlider_Change(e:SliderEvent):void{                timer.stop();                if ( channel != null ){                    var length :Number = song.length*song.bytesTotal/song.bytesLoaded;                    position = e.value*length/100;                    songStart();                }            }                        //声音大小调整事件            internal function changeVolume(evt:SliderEvent):void{                if ( channel != null ){                    var soundcontrol : SoundTransform = channel.soundTransform;                    soundcontrol.volume = evt.value;                    channel.soundTransform= soundcontrol;                }            }                        //设置歌曲播放时间和总时间            private function setTimeStatus():void {                var length :Number = song.length*song.bytesTotal/song.bytesLoaded;                var date : Date = new Date();                date.time = length;                                var dt : DateFormatter = new DateFormatter();                dt.formatString="NN:SS";                var totalTime : String = dt.format(date);                                date.time = channel.position;                lblTime.text = dt.format(date) + " | " + totalTime;            }                    ]]>    </mx:Script>    <mx:HBox width="100%" verticalGap="0" verticalAlign="middle" horizontalAlign="center">        <mx:Canvas width="440" borderColor="#CCCCCC" borderStyle="solid" height="171">            <mx:Label id="lblName" x="5" fontSize="18" y="10" text=""/>            <mx:HBox id="boxSoundBar" horizontalGap="0" verticalAlign="middle"                 width="192" height="50" x="5" y="39" visible="false"></mx:HBox>            <mx:ProgressBar id="songProgress" label=""                 width="290" height="3" mode="manual" textAlign="left"                 labelPlacement="center" fontSize="3" x="10" y="97"                 minimum="0" maximum="100" barColor="yellow"                trackColors="[white, haloSilver]"/>            <mx:HSlider id="songSlider" styleName="song" value="0"                 showTrackHighlight="true" x="5" y="85" thumbDrag="songSlider_Change(event)"                 width="300" height="22" minimum="0" maximum="100"                  liveDragging="false" snapInterval="1"  toolTip="拖动调整播放进度">            </mx:HSlider>            <mx:Label id="lblStatus" x="243" y="41" text=""/>            <mx:Label id="lblTime" x="205" y="66" text="00:00 | 5:23"/>            <mx:Button x="10" y="124" label="Play" click="songStart()"/>            <mx:Button x="74" y="124" label="Pause" click="songPause()"/>            <mx:Button x="152" y="124" label="Stop" click="songStop()"/>            <mx:HSlider id="volumeSlider" styleName="volume" change="changeVolume(event)"                 showTrackHighlight="true" value="0.5" x="222" y="133"                  width="81" minimum="0" maximum="10" liveDragging="true"                   snapInterval="0.1" toolTip="音量调节" />            <mx:Label x="308" fontSize="18" y="10" text="歌曲列表"/>            <mx:List id="listSong" alpha="0.25" x="308" y="43" height="116"                 change="Xml_Change(event)" width="130" toolTip="点击选择歌曲"></mx:List>        </mx:Canvas>    </mx:HBox></mx:Application>