MTK WIFI底部加入返回按钮

wifi设置页面的源码是WiFiSettings.java 类，该类实际就是一个PreferenceFragment的子类，下面是源码，工作原理在注释中说明

FrameLayout.LayoutParams returnLayoutparams = new FrameLayout.
                LayoutParams(LayoutParams.MATCH_PARENT, );
        returnLayoutparams.gravity = Gravity.BOTTOM|Gravity.RIGHT;
        RelativeLayout returnLayout = new RelativeLayout(getActivity());
        returnLayout.setPadding(, , , );
        returnLayout.setBackgroundResource(android.R.color.transparent);