当 RecyclerView 在 SwipeRefreshLayout 内时，如何使用 Behavior 滚动 RecyclerView 时显示/隐藏 FloatingActionButton？答案

【问题标题】：How can I show/hide FloatingActionButton when scrolling RecyclerView using Behavior when RecyclerView is inside SwipeRefreshLayout?当 RecyclerView 在 SwipeRefreshLayout 内时，如何使用 Behavior 滚动 RecyclerView 时显示/隐藏 FloatingActionButton？
【发布时间】：2016-06-17 08:03:18
【问题描述】：

当RecyclerView 在SwipeRefreshLayout 内时，我如何在使用Behavior 滚动RecyclerView 时显示/隐藏FloatingActionButton？我正在使用 22.2.0 版本的支持设计库。

我正在附加我的布局：

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

    <android.support.v4.widget.SwipeRefreshLayout
        android:id="@+id/swipe_refresh_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <android.support.v7.widget.RecyclerView
            android:id="@+id/recycler_view"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:clipToPadding="false"
            android:paddingBottom="@dimen/list_padding_bottom"
            android:paddingTop="@dimen/list_padding_top"
            android:scrollbars="vertical"/>

    </android.support.v4.widget.SwipeRefreshLayout>

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|right"
        android:layout_margin="@dimen/fab_margin"
        android:src="@drawable/ic_bookmark"/>

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

【问题讨论】：

标签： android android-recyclerview android-coordinatorlayout floating-action-button

【解决方案1】：

我使用的是过时版本的支持设计库。将其更新到 23.2.0 版解决了我的问题。

自定义 FAB Behavior（来自文章How to hide/show Toolbar when list is scrolling (part 3)）：

public class ScrollingFABBehavior extends FloatingActionButton.Behavior {
    private int toolbarHeight;

    public ScrollingFABBehavior(Context context, AttributeSet attrs) {
        super();
        this.toolbarHeight = Utils.getToolbarHeight(context);
    }

    @Override
    public boolean layoutDependsOn(CoordinatorLayout parent, FloatingActionButton fab, View dependency) {
        return super.layoutDependsOn(parent, fab, dependency) || (dependency instanceof AppBarLayout);
    }

    @Override
    public boolean onDependentViewChanged(CoordinatorLayout parent, FloatingActionButton fab, View dependency) {
        boolean returnValue = super.onDependentViewChanged(parent, fab, dependency);
        if (dependency instanceof AppBarLayout) {
                CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams) fab.getLayoutParams();
                int fabBottomMargin = lp.bottomMargin;
                int distanceToScroll = fab.getHeight() + fabBottomMargin;
                float ratio = (float)dependency.getY()/(float)toolbarHeight;
                fab.setTranslationY(-distanceToScroll * ratio);
        }
        return returnValue;
    }
}

布局：

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
    android:id="@+id/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.support.design.widget.AppBarLayout
        android:id="@+id/appBarLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|enterAlways"/>

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

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

        <android.support.v7.widget.RecyclerView
            android:id="@+id/recyclerView"
            xmlns:android="http://schemas.android.com/apk/res/android"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>

    </android.support.v4.widget.SwipeRefreshLayout>

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fabButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="end|bottom"
        android:layout_margin="@dimen/fab_margin"
        android:src="@drawable/ic_favorite_outline_white_24dp"
        app:borderWidth="0dp"
        app:layout_behavior="...ScrollingFABBehavior"/>

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

【讨论】：