Android一些设备都有上下两条bar，我们可以获取这些bar的信息。
原文地址：http://www.cnblogs.com/rossoneri/p/4142962.html

获取顶部status bar 高度

private int getStatusBarHeight() {
    Resources resources = mActivity.getResources();
    int resourceId = resources.getIdentifier("status_bar_height", "dimen","android");
    int height = resources.getDimensionPixelSize(resourceId);
    Log.v("dbw", "Status height:" + height);
    return height;
}

获取底部 navigation bar 高度

private int getNavigationBarHeight() {
    Resources resources = mActivity.getResources();
    int resourceId = resources.getIdentifier("navigation_bar_height","dimen", "android");
    int height = resources.getDimensionPixelSize(resourceId);
    Log.v("dbw", "Navi height:" + height);
    return height;
}