步骤：

    1.将需要悬浮的layout放到CollapsingToolbarLayout之外，AppBarLayout之内
    2.将CollapsingToolbarLayout的app:layout_scrollFlags设置为scroll
    3.给NestedScroolView设置app:layout_behavior="@String/appbar_scrolling_view_behavior"就大功告成了(根布局一定要是CoordinatorLayout)

xml文件

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
  >

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <android.support.design.widget.CollapsingToolbarLayout
            android:layout_width="match_parent"
            android:layout_height="220dp"
            app:contentScrim="#000000"
            app:layout_scrollFlags="scroll">

            <TextView
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:background="#00ff00"
                android:gravity="center"
                android:text="banner"
                android:textColor="#ffffff" />
        </android.support.design.widget.CollapsingToolbarLayout>

        <TextView
            android:layout_width="match_parent"
            android:layout_height="30dp"
            android:gravity="center"
            android:text="suspension part" />
    </android.support.design.widget.AppBarLayout>

    <android.support.v4.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior">

        <ListView
            android:id="@+id/lv"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </android.support.v4.widget.NestedScrollView>
</android.support.design.widget.CoordinatorLayout>

java代码

public class ThirdActivity extends AppCompatActivity {
    private ListView lv;
    private List<String> list;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_third);

        lv = (ListView) findViewById(R.id.lv);
        list = new ArrayList<>();
        for (int i = 0; i < 100; i++) {
            list.add("第" + (i + 1) + "项数据！");
        }
        ArrayAdapter adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, list);
        lv.setAdapter(adapter);
    }
}