本文转载自：http://blog.csdn.net/u013308744/article/details/49274069
首先看touchscreen的kl文件
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key 158 BACK VIRTUAL WAKE
key 102 HOME VIRTUAL WAKE
key 580 APP_SWITCH VIRTUAL WAKE
key 116 GESTURE_DOUBLE_CLICK VIRTUAL
WAKE
key 46 GESTURE_C VIRTUAL WAKE
key 18 GESTURE_E VIRTUAL WAKE
key 31 GESTURE_S VIRTUAL WAKE
key 47 GESTURE_V VIRTUAL WAKE
key 17 GESTURE_W VIRTUAL WAKE
key 44 GESTURE_Z VIRTUAL WAKE
那么这个kl有啥用呢，众所周知，android kernel和framework是不同的两层，也就是说，kernel里认识的
key值是158之类的这种数字，这个158是scankode，它往framework上报的时候也只会报这样的数字，但是framework不认识这个数字是什么，所以framework需要先解析kl文件，map起来，这样kernel传值上来的时候才会知道到底是什么key，也就是说转换scancode 158变成KeyCodeLabel也就是BACK，然后back再转换成4这个keycode
首先
key 580 APP_SWITCH VIRTUAL WAKE
这里的580是scancode，转换撑了APP_SWITCH这个keycodelabel
InputEventLabels.h里的
DEFINE_KEYCODE(APP_SWITCH),
#define DEFINE_KEYCODE(key) { #key, AKEYCODE_##key }
这里拼接了AKEYCODE_APP_SWITCH
Keycodes.h (nativeincludeandroid): AKEYCODE_APP_SWITCH = 187,
KeyEvent.java (basecorejavaandroidview): public static final int KEYCODE_APP_SWITCH = 187;
然后就变成了keycode 187