在Activity A的布局外加一層CoordinatorLayout，并設置android:fitsSystemWindows="true"，如下所示

<?xml version="1.0" encoding="utf-8"?><android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:fitsSystemWindows="true" >    <LinearLayout         android:orientation="vertical"        android:layout_width="match_parent"        android:layout_height="match_parent">        <android.support.v7.widget.Toolbar            style="@style/ToolbarTheme">            <RelativeLayout                android:layout_width="match_parent"                android:layout_height="match_parent">                    <TextView                    android:id="@+id/go_back"                    style="@style/ToolbarGoBackTextStyle" />                    <TextView                    style="@style/ToolBarTitleTheme"                    android:text="@string/live"                    />            </RelativeLayout>        </android.support.v7.widget.Toolbar>        <android.support.v7.widget.RecyclerView            android:id="@+id/live_list"            android:layout_width="match_parent"            android:layout_height="match_parent"/>        </LinearLayout>    </android.support.design.widget.CoordinatorLayout>