在最外层使用
RelativeLayout作为根节点，同时设置
android:fitsSystemWindows="true"
问题解决．
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/white"
android:fitsSystemWindows="true">
<android.support.design.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<!--标题栏 Toolbar-->
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:minHeight="48dp"
android:layout_height="48dp"
android:background="?attr/colorPrimary"
app:popupTheme="@style/AppTheme" />
</android.support.design.widget.AppBarLayout>
