Android L 判断是否有NavigationBar的方式

Android L中，如何得知是否有虚拟按键呢。查看了下PhoneWindowManager中的代码，这会在这整理处如下方法：
获取是否存在NavigationBar：
private static boolean checkDeviceHasNavigationBar(Context context) {
boolean hasNavigationBar = false;
Resources rs = context.getResources();
int id = rs.getIdentifier("config_showNavigationBar", "bool", "android");
if (id > 0) {
hasNavigationBar = rs.getBoolean(id);
}
try {
Class systemPropertiesClass = Class.forName("android.os.SystemProperties");
Method m = systemPropertiesClass.getMethod("get", String.class);
String navBarOverride = (String) m.invoke(systemPropertiesClass, "qemu.hw.mainkeys");
if ("1".equals(navBarOverride)) {
hasNavigationBar = false;
} else if ("0".equals(navBarOverride)) {
hasNavigationBar = true;
}
} catch (Exception e) {
Log.w(TAG, e);
}

return hasNavigationBar;

}
获取NavigationBar的高度：
private static int getNavigationBarHeight(Context context) {
int navigationBarHeight = 0;
Resources rs = context.getResources();
int id = rs.getIdentifier("navigation_bar_height", "dimen", "android");
if (id > 0 && checkDeviceHasNavigationBar(context)) {
navigationBarHeight = rs.getDimensionPixelSize(id);
}
return navigationBarHeight;
}