Android - CollapsingToolbarLayout仅在顶部显示菜单项

Question

当CollapsingToolbarLayout打开时，我尝试隐藏菜单项。

我这样做：XML

<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"
tools:context="com.compafone.app.ViewNews">

<android.support.design.widget.AppBarLayout android:id="@+id/app_bar"
    android:fitsSystemWindows="true" android:layout_height="@dimen/app_bar_height"
    android:layout_width="match_parent" android:theme="@style/AppTheme.AppBarOverlay">

    <android.support.design.widget.CollapsingToolbarLayout android:id="@+id/toolbar_layout"
        android:fitsSystemWindows="true" android:layout_width="match_parent"
        android:scaleType="centerCrop" android:layout_centerInParent="true"
        android:adjustViewBounds="true"
        android:layout_height="match_parent" app:layout_scrollFlags="scroll|exitUntilCollapsed"
        app:contentScrim="?attr/colorPrimary">

        <android.support.v7.widget.Toolbar android:id="@+id/toolbar"
            android:layout_height="?attr/actionBarSize" android:layout_width="match_parent"
            app:layout_collapseMode="pin" app:popupTheme="@style/AppTheme.PopupOverlay" />

    </android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>

<include layout="@layout/content_view_news" />

<android.support.design.widget.FloatingActionButton android:id="@+id/fab"
    android:layout_width="wrap_content" android:layout_height="wrap_content"
    android:layout_margin="@dimen/fab_margin" app:layout_anchor="@id/app_bar"
    app:layout_anchorGravity="bottom|end" android:src="@drawable/chatboxes" />

这是XML菜单：

<menu 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" tools:context="com.compafone.app.ViewNews">

<item
    android:id="@+id/action_comments"
    android:title="Comments"
    android:orderInCategory="200"
    android:icon="@drawable/chatboxes"
    app:showAsAction="ifRoom" />

<item
    android:id="@+id/menu_item_share"
    android:title="Partager"
    android:icon="@android:drawable/ic_menu_share"
    android:orderInCategory="100"
    app:showAsAction="ifRoom"/>

然后，这是Java活动：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_view_news);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    toolbar.setNavigationIcon(R.drawable.arrowleft);

    fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });

    //On récupère l'intent
    Intent i = getIntent();
    id = i.getStringExtra("ID");

    collapsingToolbarLayout = (CollapsingToolbarLayout) findViewById(R.id.toolbar_layout);
    collapsingToolbarLayout.setExpandedTitleColor(getResources().getColor(android.R.color.transparent));
    collapsingToolbarLayout.setTitle("Compafone");
    appbar = (AppBarLayout) findViewById(R.id.app_bar);

    new NewsListActivityLoad().execute();


    title = (TextView) findViewById(R.id.news_title);
    content = (TextView) findViewById(R.id.news_content);

}



@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu resource
    getMenuInflater().inflate(R.menu.menu_view_news, menu);
    MenuItem menuItem = menu.findItem(R.id.menu_item_share);
    //mShareActionProvider = (ShareActionProvider) MenuItemCompat.getActionProvider(menuItem);
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case android.R.id.home:
            // app icon in action bar clicked; goto parent activity.
            this.finish();
            this.overridePendingTransition(0, R.anim.abc_fade_out);
            return true;
        case R.id.action_comments:
            Intent intent = getIntent();
            //Intent intent3 = new Intent(this, comments.class);
            try {
                //intent3.putExtra(Intent_ID, intent.getStringExtra(EXTRA_PROJET));
                //intent3.putExtra(Intent_SUCCES, "null");
                //startActivity(intent3);
            } catch (Exception e) {
                Log.i("notFoundProject", "Le projet n'existe pas");
            }
            return true;
        case R.id.menu_item_share:
            //doShare(shareintent);
            return true;
        default:
            return super.onOptionsItemSelected(item);
    }
}

因此，我希望仅在用户向下滚动时隐藏菜单中的项目并显示项目（当工具栏处于正常大小时，因此在工具栏中显示工具栏标题时同时显示项目。）

抱歉英语不好，提前谢谢。