两个小时精通Android开发之按键映射篇

作者：孙东风 2010-01-07（转载务必注明出处）

笔者的上篇文章《两个小时精通Android开发》中讲解了利用Android的接口规范开发J2ME的Wrap包，从而解决了J2ME程序无法运行在Android平台上的技术难题，但是Android平台和J2ME另一个重要的不同点就是按键响应接口，如何让J2ME程序的按键响应可以无缝的移植到Android上呢？答案也是Wrap包。

笔者这里通过按键映射把Android平台的键盘码转换成J2ME平台的键盘码，或者把Android平台的触摸事件通过代理传递给J2ME中相应的接口。

首先，需要在Android平台的GameCanvas里进行如下定义：

public class GameCanvas extends Screen {

     public static final int UP = 1;

     public static final int DOWN = 6;

     public static final int LEFT = 2;

     public static final int RIGHT = 5;

     public static final int FIRE = 8;

     public static final int GAME_A = 9;

     public static final int GAME_B = 10;

     public static final int GAME_C = 11;

     public static final int GAME_D = 12;

     public static final int KEY_NUM0 = 48;

     public static final int KEY_NUM1 = 49;

     public static final int KEY_NUM2 = 50;

     public static final int KEY_NUM3 = 51;

     public static final int KEY_NUM4 = 52;

     public static final int KEY_NUM5 = 53;

     public static final int KEY_NUM6 = 54;

     public static final int KEY_NUM7 = 55;

     public static final int KEY_NUM8 = 56;

     public static final int KEY_NUM9 = 57;

     public static final int KEY_STAR = 42;

     public static final int KEY_POUND = 35;

}

当然，为了适配J2ME里的接口笔者还定义如下的接口：

     protected abstract void keyRepeated(int keyCode);

     protected abstract void keyPressed(int keyCode);

     protected abstract void keyReleased(int keyCode);

     protected abstract void pointerPressed(int x, int y);

     protected abstract void pointerReleased(int x, int y)

     protected abstract void pointerDragged(int x, int y);

笔者在上面定义的都是J2ME的视图类Canvas里的按键响应接口，这里需要做的工作就是把Android里的按键进行映射转换成J2ME里的标准键值后传递给这些接口，并由继承自GameCanvas的界面类进行实现，完全和J2ME里一样了，基本不用修改任何代码。

键值映射的代码如下：

     public int keyActual = 0;

     public int keyAction = 0;

     public void keyPreparse(int keyCode,KeyEvent e)

     {

         if(keyCode == KeyEvent.KEYCODE_0)

         {

              keyActual = GameCanvas.KEY_NUM0;

         }else if(keyCode == KeyEvent.KEYCODE_1)

         {

              keyActual = GameCanvas.KEY_NUM1;

         }else if(keyCode == KeyEvent.KEYCODE_2)

         {

              keyActual = GameCanvas.KEY_N