我有一个活动 CoordinatorLayout ， AppBarLayout ， Col​​lapsingToolbarLayout 和工具栏。所以，基本上，滚动时崩溃景色的 RecyclerView 。

I have an activity with a CoordinatorLayout, AppBarLayout, CollapsingToolbarLayout and Toolbar. So, basically, a view that collapses when scrolling a RecyclerView.

我需要做的是显示时的展开布局视图是隐藏的，由于倒塌的自定义视图。

What I need to do is to show a custom view when the view of the expanded layout is hidden due to collapsing.

这是我的布局：

<android.support.design.widget.CoordinatorLayout 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:fitsSystemWindows="true">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="192dp"
        android:fitsSystemWindows="true"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collapsing_toolbar"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fitsSystemWindows="true"
            app:contentScrim="#2196F3"
            app:expandedTitleMarginBottom="32dp"
            app:expandedTitleMarginEnd="64dp"
            app:expandedTitleMarginStart="48dp"
            app:layout_scrollFlags="scroll|exitUntilCollapsed">

            <include
                android:id="@+id/header"
                layout="@layout/header_big_first_screen"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:fitsSystemWindows="true"
                android:scaleType="centerCrop"
                app:layout_collapseMode="parallax"/>

            <android.support.v7.widget.CollapsingToolbarLayout
                android:id="@+id/anim_toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:layout_collapseMode="pin"
                app:popupTheme="@style/ThemeOverlay.AppCompat.Light">

                <TextView

                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:text="Hello!"/>


            </android.support.v7.widget.CollapsingToolbarLayout>


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

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

    <android.support.v7.widget.RecyclerView
        android:id="@+id/categories_recyclerview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"/>


</android.support.design.widget.CoordinatorLayout>

在结束时，当工具栏膨胀装有元件的视图被示出。当它被折叠它没有。当它消失的的TextView 在工具栏应显示。目前，它显示了所有的时间。

In the end, when the toolbar is expanded the view loaded with the element is shown. When it is collapsed it doesn't . When it disappears the TextView inside Toolbarshould be shown. Currently it shows all the time.

我一直在寻找的 Col​​lapsingToolbarLayout 的事件添加一个监听器，当它改变大小，这样我可以检查是否是比价值更小，表明这一观点。

I've been looking in the events of CollapsingToolbarLayout to add a listener when it changes size so I can check if that is smaller than a value and show that view.

这可能是有点棘手的解释，但我相信我自己清楚。我一直在Google上搜寻四周，找不到任何人试图做同样的。

This can be kind of tricky to explain but I believe I made myself clear. I've been googling around and cannot find anyone trying to do the same.

推荐答案

纵观该 Col​​lapsingToolbarLayout 源，内容麻布动画通过触发 OnOffsetChangedListener 在 AppBarLayout 。所以，你可以添加另一个触发阿尔法动画上的文字来看：

Taking a look at the CollapsingToolbarLayout source, the content scrim animations are triggered via an OnOffsetChangedListener on the AppBarLayout. So you could add another one to trigger alpha animations on your text view:

mListener = new AppBarLayout.OnOffsetChangedListener() {
    @Override
    public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
        if(collapsingToolbar.getHeight() + verticalOffset < 2 * ViewCompat.getMinimumHeight(collapsingToolbar)) {
            hello.animate().alpha(1).setDuration(600);
        } else {
            hello.animate().alpha(0).setDuration(600);
        }
    }
};

appBar.addOnOffsetChangedListener(mListener);