RecyclerView 滚动不适用于 NestedScrollView

Question

我有一个布局，其中有一个 NestedScrollView，其中包含一个图像、多个按钮和一个 RecycleView。

当我说 recycleView.smoothScrollToPosition 或 recycleView.scrollToPosition() 时，它现在什么也没做。拒绝滚动甚至一个像素。如果我删除 NestedScrollView 它可以正常工作，但以防我失去对周围区域的滚动效果。

你们中有人遇到过这个问题吗？

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout   xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context="world.the.rule.com.testtollbarstuff.ScrollingActivity">

<android.support.design.widget.AppBarLayout
    android:id="@+id/app_bar"
    android:layout_width="match_parent"
    android:layout_height="@dimen/app_bar_height"
    android:fitsSystemWindows="true"
    android:orientation="vertical"
    android:theme="@style/AppTheme.AppBarOverlay">


    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        app:layout_collapseMode="none"
        app:popupTheme="@style/AppTheme.PopupOverlay" />


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

<android.support.design.widget.CollapsingToolbarLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:fitsSystemWindows="true"
    app:contentScrim="?attr/colorPrimary"
    app:layout_scrollFlags="scroll">

    <android.support.v4.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            app:layout_collapseMode="parallax">

            <ImageView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:adjustViewBounds="true"
                android:clickable="true"
                android:src="@drawable/mock_image" />

            <include layout="@layout/content_scrolling" />

        </LinearLayout>
    </android.support.v4.widget.NestedScrollView>
</android.support.design.widget.CollapsingToolbarLayout>

Answer 1

如果您只想要平滑滚动，则不需要我之前在其他线程中提到的自定义滚动。

当你想开始平滑滚动时添加如下行

appBarLayout.setExpanded(false, /*true if animation required else false*/true);
recyclerView.smoothScrollToPosition(position);

其他信息

此外，我在您的布局中没有看到任何RecyclerView，您很可能将它保存在LinearLayout 中，这又是CollapsingToolbarLayout 的一部分。我完全不知道你为什么将RecyclerView 保留为CollapsingToolbarLayout 的一部分。我将给出我正在使用的布局（简化版）。

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <android.support.design.widget.AppBarLayout
            android:id="@+id/app_bar_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:expanded="true"
            app:layout_behavior="com.company.app.custom.CustomRecyclerScrollBehavior">

            <android.support.design.widget.CollapsingToolbarLayout
                android:id="@+id/collapsing_toolbar"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                app:contentScrim="?attr/colorPrimary"
                app:expandedTitleMarginEnd="64dp"
                app:expandedTitleMarginStart="48dp"
                app:layout_scrollFlags="scroll|exitUntilCollapsed">

                <FrameLayout
                    android:id="@+id/header_frame"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    app:layout_collapseMode="parallax"
                    app:layout_collapseParallaxMultiplier="0.8">

                    <com.company.app.custom.CustomViewPager
                        android:id="@+id/view_pager"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        app:calculation="height"
                        app:height_ratio="@integer/product_listitem_img_width_ratio"
                        app:width_ratio="@integer/product_listitem_img_height_ratio" />

                    <com.company.app.custom.CustomImageView
                        android:id="@+id/img_stock_layer"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:adjustViewBounds="true"
                        android:scaleType="fitXY"
                        android:src="@color/transparent_app_black"
                        android:visibility="gone"
                        app:calculation_type="height"
                        app:ratio_height="@integer/product_listitem_img_width_ratio"
                        app:ratio_width="@integer/product_listitem_img_height_ratio" />

                    <com.inneex.www.customfonts.FontTextView
                        android:id="@+id/lbl_out_of_stock"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_gravity="center"
                        android:text="@string/out_of_stock"
                        android:textColor="?android:attr/textColorPrimaryInverse"
                        android:textSize="13sp"
                        android:visibility="gone"
                        app:customFont="@string/font_ss_semibold" />

                    <LinearLayout
                        android:id="@+id/ll_page"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_gravity="bottom|center_horizontal"
                        android:orientation="horizontal"
                        android:paddingBottom="@dimen/inspire_detail_oval_margin_bottom" />

                </FrameLayout>

                <android.support.v7.widget.Toolbar
                    android:id="@+id/main_toolbar"
                    android:layout_width="match_parent"
                    android:layout_height="@dimen/toolbar_height"
                    android:background="?attr/colorPrimary"
                    app:layout_anchor="@id/header_frame"
                    app:layout_collapseMode="pin"
                    app:title="">

                    <LinearLayout
                        android:layout_width="wrap_content"
                        android:layout_height="match_parent"
                        android:orientation="horizontal">

                        <com.inneex.www.customfonts.FontTextView
                            android:id="@+id/lbl_toolbar_product_name"
                            android:layout_width="0dp"
                            android:layout_height="wrap_content"
                            android:layout_gravity="center"
                            android:layout_weight="1"
                            android:ellipsize="end"
                            android:lines="1"
                            android:maxLines="1"
                            android:minLines="1"
                            android:textColor="?android:attr/textColorPrimary"
                            android:textSize="18sp"
                            app:customFont="@string/font_ss_semibold" />

                    </LinearLayout>
                </android.support.v7.widget.Toolbar>
            </android.support.design.widget.CollapsingToolbarLayout>

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

        <ImageView
            android:id="@+id/img_back"
            android:layout_width="@dimen/toolbar_height"
            android:layout_height="@dimen/toolbar_height"
            android:layout_gravity="top|start"
            android:scaleType="fitXY"
            android:src="@drawable/back"
            app:layout_collapseMode="parallax" />

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

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

    <include
        layout="@layout/listitem_product_detail_buy_cheap"
        android:layout_width="match_parent"
        android:layout_height="@dimen/product_detail_button_buy_cheap_height"
        android:layout_alignParentBottom="true"
        android:layout_gravity="bottom" />

</RelativeLayout>

FrameLayout id header_frame 负责大工具栏，它会在滚动时折叠。 Toolbar id main_toolbar 负责工具栏的折叠视图。 RecyclerView 是下面的AppBarLayout。 ImageView 用于返回按钮，一旦显示Toolbar，就会显示该按钮。

作为参考，为了使滚动流畅，我添加了CustomRecyclerScrollBehavior，我之前与您交谈过。原来是这样的

import android.content.Context;
import android.support.design.widget.AppBarLayout;
import android.support.design.widget.CoordinatorLayout;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.view.View;

import java.lang.ref.WeakReference;
import java.util.HashMap;
import java.util.Map;

/**
 * Created by jimitpatel on 13/12/16.
 */

public class CustomRecyclerScrollBehavior extends AppBarLayout.Behavior {

    private Map<RecyclerView, RecyclerViewScrollListener> scrollListenerMap = new HashMap<>(); //keep scroll listener map, the custom scroll listener also keep the current scroll Y position.


    public CustomRecyclerScrollBehavior() {
    }

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

    /**
     *
     * @param coordinatorLayout
     * @param child The child that attached the behavior (AppBarLayout)
     * @param target The scrolling target e.g. a recyclerView or NestedScrollView
     * @param velocityX
     * @param velocityY
     * @param consumed The fling should be consumed by the scrolling target or not
     * @return
     */
    @Override
    public boolean onNestedFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY, boolean consumed) {
        if (target instanceof RecyclerView) {
            final RecyclerView recyclerView = (RecyclerView) target;
            if (scrollListenerMap.get(recyclerView) == null) {
                RecyclerViewScrollListener recyclerViewScrollListener = new RecyclerViewScrollListener(coordinatorLayout, child, this);
                scrollListenerMap.put(recyclerView, recyclerViewScrollListener);
                recyclerView.addOnScrollListener(recyclerViewScrollListener);
            }
            scrollListenerMap.get(recyclerView).setVelocity(velocityY);
            consumed = scrollListenerMap.get(recyclerView).getScrolledY() > 0; //recyclerView only consume the fling when it's not scrolled to the top
        }
        return super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
    }

    private static class RecyclerViewScrollListener extends RecyclerView.OnScrollListener {
        private int scrolledY;
        private boolean dragging;
        private float velocity;
        private WeakReference<CoordinatorLayout> coordinatorLayoutRef;
        private WeakReference<AppBarLayout> childRef;
        private WeakReference<CustomRecyclerScrollBehavior> behaviorWeakReference;

        public RecyclerViewScrollListener(CoordinatorLayout coordinatorLayout, AppBarLayout child, CustomRecyclerScrollBehavior barBehavior) {
            coordinatorLayoutRef = new WeakReference<>(coordinatorLayout);
            childRef = new WeakReference<>(child);
            behaviorWeakReference = new WeakReference<>(barBehavior);
        }

        @Override
        public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
            dragging = newState == RecyclerView.SCROLL_STATE_DRAGGING;
        }

        public void setVelocity(float velocity) {
            this.velocity = velocity;
        }

        public int getScrolledY() {
            return scrolledY;
        }

        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            scrolledY += dy;

            if (scrolledY <= 0 && !dragging && childRef.get() != null && coordinatorLayoutRef.get() != null && behaviorWeakReference.get() != null) {
                //manually trigger the fling when it's scrolled at the top
                behaviorWeakReference.get().onNestedFling(coordinatorLayoutRef.get(), childRef.get(), recyclerView, 0, velocity, false);
            }
        }
    }
}

此类用于在嵌套滚动中保持RecyclerView 的滚动速度。这里的fling已经改变了

希望这对你有用！

Answer 2

这样做

recycleView.smoothScrollToPosition(80);

稍后，不在 onCreate 方法内部，要么使用延迟线程，要么在另一个覆盖方法中。

示例：

     new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {
              recycleView.smoothScrollToPosition(80);
        }
     }, 150);

Answer 3

给recyclerview一个固定的高度，而不是match_parent或wrap_content。因为当recyclerview在scrollview里面时，它的高度就是它的items的总高度，所以这会禁用recyclerview的滚动，只启用nestedscrollview。