Question

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，页面看起来很好。当RecyclerView为空或者没有足够的内容可以滚动时，行为是具有app:layout_scrollFlags="scroll|enterAlwaysCollapsed"的AppBarLayout子项将继续滚动 - 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>

Answer 1

不确定解决方案有多优雅但是，如果NestedScrollView可滚动（在这种情况下是RecyclerView），我会覆盖onStartNestedScroll()事件以仅触发

onCreate（）中的

：

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;
    }

}

修改

编辑的解决方案为RecyclerView，高度为可见 RecyclerView高度和AppBarLayout高度（这是CoordinatorLayout高度）。

但是，如果您的滚动手势在可见的AppBarLayout区域开始，即使您将此行为也添加到AppBarLayout，滚动仍会仍然。因此，这个答案不能解决问题。

Answer 2

（基于：Reference）

（1）创建此类。

public class AppBarLayoutBehaviorForEmptyRecyclerView extends AppBarLayout.Behavior
{
    private boolean canRecyclerViewBeScrolled = false;

    public AppBarLayoutBehaviorForEmptyRecyclerView()
    {
    }

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

    @Override
    public boolean onInterceptTouchEvent(CoordinatorLayout parent, AppBarLayout child, MotionEvent ev)
    {
        return canRecyclerViewBeScrolled && super.onInterceptTouchEvent(parent, child, ev);
    }

    @Override
    public boolean onStartNestedScroll(CoordinatorLayout parent, AppBarLayout child, View directTargetChild, View target, int nestedScrollAxes)
    {
        updateScrollable(target);
        return canRecyclerViewBeScrolled && super.onStartNestedScroll(parent, child, directTargetChild, target, nestedScrollAxes);
    }

    @Override
    public boolean onNestedFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY, boolean consumed)
    {
        return canRecyclerViewBeScrolled && super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
    }

    private void updateScrollable(View targetChild)
    {
        if(targetChild instanceof RecyclerView)
        {
            RecyclerView.Adapter adapter = ((RecyclerView) targetChild).getAdapter();

            canRecyclerViewBeScrolled = adapter != null && adapter.getItemCount() > 0;
        }
        else
        {
            canRecyclerViewBeScrolled = true;
        }
    }
}

（2）向您的AppBarLayout XML元素添加以下属性：

app:layout_behavior="com.xxxx.xxxxxx.AppBarLayoutBehaviorForEmptyRecyclerView"

Answer 3

Graeme答案还可以，但我也在构造函数

中添加了

public AppBarLayoutOnEmptyRecyclerViewScrollBehavior(@NonNull AppBarLayout appBarLayout, @NonNull RecyclerView recyclerView) {
    this.appBarLayout = checkNotNull(appBarLayout);
    this.recyclerView = checkNotNull(recyclerView);

    setDragCallback(new DragCallback() {
        @Override
        public boolean canDrag(@NonNull AppBarLayout appBarLayout) {
            return isRecylerViewScrollable(recyclerView);
        }
    });
}

所以当RecyclerView为空时，我也会停用AppBarLayout

的拖动

Answer 4

将数据加载到RecyclerView后，如果它是空的，只需手动取消滚动标记：

AppBarLayout.LayoutParams toolbarLayoutParams = (AppBarLayout.LayoutParams) mEventHeader.getLayoutParams();
toolbarLayoutParams.setScrollFlags(0);
mEventHeader.setLayoutParams(toolbarLayoutParams);

如果不为空，请设置滚动标记：

AppBarLayout.LayoutParams toolbarLayoutParams = (AppBarLayout.LayoutParams) mEventHeader.getLayoutParams();
toolbarLayoutParams.setScrollFlags(AppBarLayout.LayoutParams.SCROLL_FLAG_SCROLL | AppBarLayout.LayoutParams.SCROLL_FLAG_ENTER_ALWAYS);
mEventHeader.setLayoutParams(toolbarLayoutParams);

当NestedScrollView为空时，停止AppBarLayout滚动屏幕

4 个答案: