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_NUM2;

}else if(keyCode == KeyEvent.KEYCODE_3)

{

keyActual = GameCanvas.KEY_NUM3;

}else if(keyCode == KeyEvent.KEYCODE_4)

{

keyActual = GameCanvas.KEY_NUM4;

}else if(keyCode == KeyEvent.KEYCODE_5)

{

keyActual = GameCanvas.KEY_NUM5;

}else if(keyCode == KeyEvent.KEYCODE_6)

{

keyActual = GameCanvas.KEY_NUM6;

}else if(keyCode == KeyEvent.KEYCODE_7)

{

keyActual = GameCanvas.KEY_NUM7;

}else if(keyCode == KeyEvent.KEYCODE_8)

{

keyActual = GameCanvas.KEY_NUM8;

}else if(keyCode == KeyEvent.KEYCODE_9)

{

keyActual = GameCanvas.KEY_NUM9;

}else if(keyCode == KeyEvent.KEYCODE_POUND)

{

keyActual = GameCanvas.KEY_POUND;

}else if(keyCode == KeyEvent.KEYCODE_STAR)

{

keyActual = GameCanvas.KEY_STAR;

}else if(keyCode == KeyEvent.KEYCODE_DPAD_UP)

{

keyActual = GameCanvas.UP;

keyAction = GameCanvas.UP;

}else if(keyCode == KeyEvent.KEYCODE_DPAD_DOWN)

{

keyActual = GameCanvas.DOWN;

keyAction = GameCanvas.DOWN;

}else if(keyCode == KeyEvent.KEYCODE_DPAD_LEFT)

{

keyActual = GameCanvas.LEFT;

keyAction = GameCanvas.LEFT;

}else if(keyCode == KeyEvent.KEYCODE_DPAD_RIGHT)

{

keyActual = GameCanvas.RIGHT;

keyAction = GameCanvas.RIGHT;

}else if(keyCode == KeyEvent.KEYCODE_DPAD_CENTER)

{

keyActual = GameCanvas.FIRE;

keyAction = GameCanvas.FIRE;

}

else if(keyCode == KeyEvent.KEYCODE_SOFT_LEFT)

{

keyActual = Globe.softKeyLeft;

}

else if(keyCode == KeyEvent.KEYCODE_SOFT_RIGHT)

{

keyActual = Globe.softKeyRight;

}

笔者对Android里常用的键1~9以及*、#、上下左右、确定键进行了映射，映射后为标准J2ME下的键值，接下来只需要把这些键值传递给原来J2ME里的接口即可，如下：

public boolean onTouchUp(MotionEvent e) {

if (isEvent) {

return isEvent;

}

pointerReleased((int)(e.getX()),(int)(e.getY()));

return isEvent;

}

public boolean onTouchDown(MotionEvent e) {

if (isEvent) {

return isEvent;

}

pointerPressed((int)(e.getX()),(int)(e.getY()));

return isEvent;

}

public boolean onKeyDown(int keyCode, KeyEvent e) {

keyPreparse(keyCode,e);

keyPressed(keyActual);

return true;

}

public boolean onKeyUp(int keyCode, KeyEvent e) {

keyPreparse(keyCode,e);

keyReleased(keyActual);

return true;

}

前面是对触摸事件进行的映射处理，后面是对按键事件进行的处理，当然，如果有需要还可以实现getGameAction()接口，如下：

public int getKeyStates()

{

return keyActual;

}

public int getGameAction(int keyCode)

{

return keyAction;

}

到这里，读者原来的J2ME程序基本不需要修改任何代码就可以运行在Android平台上并进行按键响应了：）

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