swiperefreshlayout 内的我的 recyclerview 中没有出现过度滚动效果

Question

我有一个包含 SwipeRefreshLayour 和 RecyclerView 的片段。

此 recyclerView 不显示过度滚动效果。我尝试了很多这样的东西：

 android:isScrollContainer="true"
 android:overScrollMode="always"

通过样式自定义颜色不起作用

fadingEdge、fadingEdgeLengh、需要FadingEdge...

滑动刷新正在工作，它显示如下：

我不明白：

Answer 1

我只是通过覆盖 SwipeRefreshLayout 并使用它而不是默认实现来解决它：

import android.content.Context
import android.util.AttributeSet
import android.view.View
import androidx.swiperefreshlayout.widget.SwipeRefreshLayout

class SwipeRefreshLayoutWithRecyclerViewOverscroll : SwipeRefreshLayout {

    constructor(context: Context) : super(context)
    constructor(context: Context, attrs: AttributeSet) : super(context, attrs)

    override fun onStartNestedScroll(child: View, target: View, nestedScrollAxes: Int): Boolean =
        (child.canScrollVertically(1) && super.onStartNestedScroll(child, target, nestedScrollAxes))

}

我正在使用一个 RecyclerView，它是一个线性垂直列表，child.canScrollVertically(1) 检查此列表当前是否位于最底部。如果在列表底部，onStartNestedScroll 返回 false，允许 RecyclerView 处理用户的上拉动作，从而显示过度滚动效果。

注意：这仅显示底部边缘过度滚动而不是顶部边缘，因为我不想看到下拉刷新动画与顶部过度滚动边缘。

Answer 2

在我实现这个功能时，（过度滚动在顶部和底部都起作用），我的布局是这样的：

<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">

<...<custom view>...SwipeRefreshWrapper
    android:id="@+id/swiperefresh_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <RecyclerView
            android:id="@+id/video_recyclerview"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>

        <include layout="@layout/include_video_list_empty_view"/>
        <include layout="@layout/include_watchlist_empty_view"/>

    </FrameLayout>
<SwipeRefreshWrapper>

而我的 SwipeRefreshWrapper 实现如下：

/**
* This Class ensures that a SwipeRefreshLayout will only refresh if the
* list it wraps cannot scroll up anymore, (that it is at the top). Otherwise
* when the user attempts to scroll up from the middle of the list, the refresh
* will trigger. This is necessary for custom List implementations, (or
* RecyclerViews), only.
*/
public class SwipeRefreshWrapper extends SwipeRefreshLayout {
     private ScrollResolver mScrollResolver;

     public SwipeRefreshWrapper(Context context) {
         super(context);
     }

     public SwipeRefreshWrapper(Context context, AttributeSet attrs) {
         super(context, attrs);
     }

     public void setScrollResolver(ScrollResolver scrollResolver) {
         mScrollResolver = scrollResolver;
     }

     @Override
     public boolean canChildScrollUp() {
         if(mScrollResolver != null){
             return mScrollResolver.canScrollUp();
         } else {
             return super.canChildScrollUp();
         }
     }

     public static interface ScrollResolver{
         public boolean canScrollUp();
     }
}

然后在我的 Fragment 中设置 SwipeRefreshLayout：

 /**
 * Initializes PullToRefresh handler
 */
private void initPullToRefresh() {
    mSwipeRefreshLayout = (SwipeRefreshWrapper) mView.findViewById(R.id.swiperefresh_layout);
    mSwipeRefreshLayout.setColorSchemeResources(R.color.colorPrimary, R.color.colorAccent);

    mSwipeRefreshLayout.setScrollResolver(new SwipeRefreshWrapper.ScrollResolver() {
        @Override
        public boolean canScrollUp() {
            return mVideoRecycler.canScrollVertically(-1);
        }
    });

    mSwipeRefreshLayout.setOnRefreshListener(...)
}