Air for Android开发中使用Back键弹出是否退出对话框

用Flash cs5做测试的时候试了很久都没有找到方法，按照官方的说明，“请注意：当按下“返回”键时，可调用事件 preventDefault() 方法以避免出现返回至上一应用程序的“返回”键默认行为。“菜单”和“搜索”键无默认行为。”，试了一遍又一遍，最终发现在使用event.preventDefault()方法时，如果侦听的是KeyUp事件的话，是无法阻止默认行为的，所以想要成功阻止返回，请侦听KeyDown事件。

 

 

以下是一个用于测试的文档类：

 

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//code package { import flash.display.Sprite; import flash.events.KeyboardEvent; import flash.events.MouseEvent; import flash.ui.Keyboard; import flash.desktop.NativeApplication; import flash.text.TextField; import flash.events.Event; import flash.text.TextFieldAutoSize; import flash.text.TextFormat;   /** * 描述： 测试阻止Air For Android 默认BACK按键事件 * 作者： Frozensun * 创建日期： 2010-12-14 21:03 */ public class Main extends Sprite { private var _menuBar:Sprite; private var _txtLogger:TextField;   public function Main() { fCreateLogger(); fCreateMenuBar();   output("试试按下menu和返回键吧!");   NativeApplication.nativeApplication.addEventListener(KeyboardEvent.KEY_DOWN, eMenuBarHandler); }   //创建logger显示文本 private function fCreateLogger():void { _txtLogger = new TextField(); _txtLogger.width = stage.stageWidth; _txtLogger.height = stage.stageHeight; _txtLogger.defaultTextFormat = new TextFormat(null, 20, 0xCCCCCC); _txtLogger.multiline = true; _txtLogger.selectable = false; _txtLogger.background = true; _txtLogger.backgroundColor = 0x333333; addChild(_txtLogger); }   //创建菜单 private function fCreateMenuBar():void { var __W:Number = stage.stageWidth / 1.5; var __H:Number = __W / 2; _menuBar = new Sprite(); _menuBar.graphics.beginFill(0xCCCCCC, 0.75); _menuBar.graphics.drawRoundRect(-__W / 2, -__H / 2, __W, __H, __H / 4, __H / 4); _menuBar.graphics.beginFill(0x666666, 0.8); _menuBar.graphics.drawCircle(0, 0, __H / 2 / 1.5); _menuBar.graphics.endFill(); _menuBar.x = stage.stageWidth / 2; _menuBar.y = stage.stageHeight / 2;   var __txtClose:TextField = new TextField(); __txtClose.autoSize = TextFieldAutoSize.CENTER; __txtClose.defaultTextFormat = new TextFormat(null, 60, 0xCCCCCC, true); __txtClose.selectable = false; __txtClose.text = "X"; __txtClose.x = -__txtClose.width / 2; __txtClose.y = -__txtClose.height / 2; _menuBar.addChild(__txtClose); }   //键盘事件 private function eMenuBarHandler(e:KeyboardEvent):void { switch (e.keyCode) { case Keyboard.MENU : checkMenuBar(); break;   case Keyboard.BACK : e.preventDefault(); checkMenuBar(); break; }   output("keyCode:", e.keyCode, " isDefaultPrevented:", e.isDefaultPrevented()); }   //检测menuBar的显隐 private function checkMenuBar():void { if (! this.contains(_menuBar)) { this.addChild(_menuBar); _menuBar.addEventListener(MouseEvent.CLICK, eExitAppHandler); } else { this.removeChild(_menuBar); _menuBar.removeEventListener(MouseEvent.CLICK, eExitAppHandler); } }   //按下_menuBar时退出 private function eExitAppHandler(e:MouseEvent):void { NativeApplication.nativeApplication.exit(); }   //显示调试文本 private function output(...rest):void { var __log:String = ""; for each (var i:* in rest) { __log += String(i) + " "; } __log += "/n";   _txtLogger.appendText(__log); _txtLogger.scrollV = _txtLogger.maxScrollV; }   }   }