android – 当NestedScrollView为空时,停止AppBarLayout滚出屏幕

我有一个相当典型的List功能,使用CoordinatorLayout,AppBarLayout,SwipeRefreshLayout和RecyclerView –

当RecyclerView有足够的内容滚动时,页面似乎很好.当RecyclerView为空或者没有足够的内容可以滚动时,行为是AppBarLayout子应用程序：layout_scrollFlags =“scroll | enterAlwaysCollapsed”将继续滚动 – 这看起来很奇怪.

当NestedScrollView为空时,有没有办法阻止AppBarLayout子项滚动？

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
    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.CoordinatorLayout
        android:id="@+id/coordinatorLayout"
        android:background="@android:color/transparent"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <android.support.design.widget.AppBarLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@android:color/transparent"
            android:elevation="4dp">

            <LinearLayout
                android:id="@+id/eventHeader"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:padding="16dp"
                android:background="@color/green"
                android:orientation="horizontal"
                app:layout_scrollFlags="scroll|enterAlwaysCollapsed">

                <View
                    android:layout_width="0dp"
                    android:layout_height="0dp"
                    android:layout_weight="1"/>

                <TextView
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="scroll|enterAlwaysCollapsed"
                    android:textColor="@color/white"
                    android:textSize="15sp"/>

                <View
                    android:layout_width="0dp"
                    android:layout_height="0dp"
                    android:layout_weight="1"/>

            </LinearLayout>

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

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

            <android.support.v7.widget.RecyclerView
                android:id="@+id/recyclerView"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:background="@android:color/transparent"
                android:dividerHeight="0dp"
                android:layout_gravity="fill_vertical"
                android:drawSelectorOnTop="true"
                android:listSelector="@drawable/selector_ripple_grey_transparent"
                android:scrollbars="vertical"/>

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

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

    <TextView
        android:id="@+id/noData"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:padding="16dp"
        android:text="@string/no_data_available"
        android:textSize="17sp"/>

</FrameLayout>

解决方法:

不知道这是多么优雅的解决方案但是,我覆盖onStartNestedScroll()事件,只有在NestedScrollView可滚动时才触发(在本例中为RecyclerView)

在onCreate()中：

CoordinatorLayout.LayoutParams layoutParams = (CoordinatorLayout.LayoutParams) mAppBarLayout.getLayoutParams();
layoutParams.setBehavior(new AppBarLayoutNoEmptyScrollBehavior(mAppBarLayout, mRecyclerView));

行为：

public class AppBarLayoutNoEmptyScrollBehavior extends AppBarLayout.Behavior {

    AppBarLayout mAppBarLayout;
    RecyclerView mRecyclerView;
    public AppBarLayoutNoEmptyScrollBehavior(AppBarLayout appBarLayout, RecyclerView recyclerView) {
        mAppBarLayout = appBarLayout;
        mRecyclerView = recyclerView;
    }

    public boolean isRecylerViewScrollable(RecyclerView recyclerView) {
        int recyclerViewHeight = recyclerView.getHeight(); // Height includes RecyclerView plus AppBarLayout at same level
        int appCompatHeight    = mAppBarLayout != null ? mAppBarLayout.getHeight() : 0;
        recyclerViewHeight -= appCompatHeight;

        return recyclerView.computeVerticalScrollRange() > recyclerViewHeight;
    }

    @Override
    public boolean onStartNestedScroll(CoordinatorLayout parent, AppBarLayout child, View directTargetChild, View target, int nestedScrollAxes) {
        if (isRecylerViewScrollable(mRecyclerView)) {
            return super.onStartNestedScroll(parent, child, directTargetChild, target, nestedScrollAxes);
        }
        return false;
    }

}

编辑

作为RecyclerView编辑的解决方案将高度显示为可见的RecyclerView高度和AppBarLayout高度(这是CoordinatorLayout高度).

但是,如果滚动手势在可见的AppBarLayout区域上开始,则仍会发生滚动,即使您将此行为添加到AppBarLayout也是如此.因此,这个答案不是解决问题的方法.

标签：android-appbarlayout,android,android-recyclerview
来源： https://codeday.me/bug/20191005/1855588.html