在Activity A的佈局外加一層CoordinatorLayout，並設定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>