@TargetApi(11)
    public void setNavigationBarAlpha(float alpha) {
        if (mNavBarAvailable && Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
            mNavBarTintView.setAlpha(alpha);
        }
    }
Apply the specified alpha to the system navigation bar.

@param alpha The alpha to use
app/src/main/java/com/zhao/myreader/util/SystemBarTintManager.java