android 物理键盘 关键因素

参考PhoneWindowManager.java的adjustConfigurationLw()方法，可以找出以下关键因素：

config_lidKeyboardAccessibility：在frameworks/base/core/res/res/values/config.xml中定义，含义如下：

Indicate whether the lid state impacts the accessibility of the physical keyboard.

0 means it doesn't,

1 means it is accessible when the lid is open,

2 means it is accessible when the lid is closed.

The default is 1.

意为物理键盘是否受滑盖影响，0表示不受滑盖影响，1表示当滑盖打开时物理键盘可用，2表示滑盖关闭时物理键盘可用。

另外PhoneWindowManager.java还有个常量也对物理键盘的状态有影响：

// Debugging: set this to have the system act like there is no hard keyboard.
static final boolean KEYBOARD_ALWAYS_HIDDEN = false;

InputMethodService.java: 判断是否显示软键盘的代码：

onShowInputRequested() {

if (!onEvaluateInputViewShown()) {
return false;
}
......................

}

public boolean onEvaluateInputViewShown() {
Configuration config = getResources().getConfiguration();
return config.keyboard == Configuration.KEYBOARD_NOKEYS
|| config.hardKeyboardHidden == Configuration.KEYBOARDHIDDEN_YES;
}

其中两项config.hardKeyboardHidden就是framworks中config.xml的config_lidKeyboardAccessibility取值

物理键盘映射过程：
手机/system/usr/keylayout/*.kl ：内核将keyCode映射成有含义的字符串
KeycodeLabels.h ： framework 将字符串映射成keyEvent的keyCode
frameworks/.../res/values/attrs.xml