//显示帧速的类

/*
usage:
import fb.fps.FPS 
var t=new FPS() 
this.addChild(t) 
*/
package fb.fps { 
   
   
  import flash.events.*; 
  import flash.display.*; 
  import flash.utils.*; 
  import flash.text.*; 
   
  public class FPS extends Sprite 
   
  { 
    var numFrames:Number = 0; 
    var interval:Number = 10 
    var startTime:Number; 
    var fpsText; 
    function FPS() 
    {   
   
      startTime = getTimer(); 
       
      // 文本实例的样式 
      my_fmt = new TextFormat(); 
      my_fmt.bold = true; 
      my_fmt.font = "Arial"; 
      my_fmt.size = 12; 
      my_fmt.color = 0xFF0000; 
       
      fpsText = new TextField(); 
      fpsText.autoSize = "left"; 
      fpsText.text = "loading"; 
      addChild(fpsText); 
   
      fpsText.defaultTextFormat = my_fmt; 
      fpsText.selectable = false       
   
      this.addEventListener(Event.ADDED, onAdded); 
    } 
   
    function onAdded(event:Event) 
    { 
      this.stage.addEventListener(Event.ENTER_FRAME, update, false, 0); 
    } 
    function update(event:Event) 
    { 
      if (++numFrames == interval) { 
        var now:Number = getTimer(); 
        var elapsedSeconds:Number = (now - startTime) / 1000; 
        var actualFPS:Number = numFrames / elapsedSeconds;         
                fpsText.text = (actualFPS.toFixed(2)); 
        startTime = now; 
        numFrames = 0; 
      } 
    } 
     
     
  } 
}