使用RecyclerView + AppBarLayout

Question

我正在使用带有AppBarLayout和CollapsingToolbarLayout的新CoordinatorLayout。在AppBarLayout下面，我有一个包含内容列表的RecyclerView。

我已经验证了当我在列表中上下滚动时，滚动滚动在RecyclerView上工作。但是，我还希望AppBarLayout在扩展期间顺利滚动。

向上滚动以展开CollaspingToolbarLayout时，一旦将手指从屏幕上抬起，滚动会立即停止。如果向上快速向上滚动，有时CollapsingToolbarLayout也会重新折叠。与使用NestedScrollView时，RecyclerView的这种行为似乎有很大不同。

我试图在recyclerview上设置不同的滚动属性，但我还没有想到这一点。

这是一段显示某些滚动问题的视频。 https://youtu.be/xMLKoJOsTAM

以下示例显示了RecyclerView（CheeseDetailActivity）的问题。 https://github.com/tylerjroach/cheesesquare

以下是使用Chris Banes的NestedScrollView的原始示例。 https://github.com/chrisbanes/cheesesquare

Answer 1

Kirill Boyarshinov的答案几乎是正确的。

主要问题是RecyclerView有时会给出不正确的fling方向，所以如果你将以下代码添加到他的答案中它可以正常工作：

public final class FlingBehavior extends AppBarLayout.Behavior {
    private static final int TOP_CHILD_FLING_THRESHOLD = 3;
    private boolean isPositive;

    public FlingBehavior() {
    }

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

    @Override
    public boolean onNestedFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY, boolean consumed) {
        if (velocityY > 0 && !isPositive || velocityY < 0 && isPositive) {
            velocityY = velocityY * -1;
        }
        if (target instanceof RecyclerView && velocityY < 0) {
            final RecyclerView recyclerView = (RecyclerView) target;
            final View firstChild = recyclerView.getChildAt(0);
            final int childAdapterPosition = recyclerView.getChildAdapterPosition(firstChild);
            consumed = childAdapterPosition > TOP_CHILD_FLING_THRESHOLD;
        }
        return super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
    }

    @Override
    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, int dx, int dy, int[] consumed) {
        super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed);
        isPositive = dy > 0;
    }
}

我希望这会有所帮助。

Answer 2

我通过将OnScrollingListener应用于recyclerView找到了修复程序。现在它运作得很好。问题是recyclerview提供了错误的消费价值，并且行为不知道何时将Recyclerview滚动到顶部。

package com.singmak.uitechniques.util.coordinatorlayout;

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 maksing on 26/3/2016.
 */
public final class RecyclerViewAppBarBehavior 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 RecyclerViewAppBarBehavior() {
    }

    public RecyclerViewAppBarBehavior(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<RecyclerViewAppBarBehavior> behaviorWeakReference;

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

Answer 3

自支持设计26.0.0以来，它已得到修复。

compile 'com.android.support:design:26.0.0'

Answer 4

这是Google支持设计AppBarLayout的流畅版本。如果你正在使用AppBarLayout，你会知道它有一个问题。

compile "me.henrytao:smooth-app-bar-layout:<latest-version>"

请在此处查看图书馆。https://github.com/henrytao-me/smooth-app-bar-layout

Answer 5

这是一个回收者视图错误。它应该在v23.1.0中修复。

看https://code.google.com/p/android/issues/detail?id=177729

Answer 6

这是我的布局和滚动它正常工作。

private final AsyncCallback<IssuesResponse> callback;

public IssuesGetter(AsyncCallback<IssuesResponse> callback) {
    this.callback = callback;
}

@Override
protected String doInBackground(String... strings) {
    HttpURLConnection c = null;
    try {
        c = (HttpURLConnection) new URL(strings[0]).openConnection();
    } catch (IOException e) {
        e.printStackTrace();
    }
    c.setUseCaches(false);
    try {
        c.setRequestMethod("GET");
    } catch (ProtocolException e) {
        e.printStackTrace();
    }
    c.setRequestProperty("Accept", "application/json");
    c.setRequestProperty("Authorization", UserManager.getInstance().getUserPass());
    int responseCode = 0;
    try {
        responseCode = c.getResponseCode();
    } catch (IOException e) {
        e.printStackTrace();
    }
    if(responseCode == 200) {
        try {
            c.connect();
        } catch (IOException e) {
            e.printStackTrace();
        }
        BufferedReader br = null;
        try {
            br = new BufferedReader(new InputStreamReader((c.getInputStream())));
        } catch (IOException e) {
            e.printStackTrace();
        }
        StringBuilder sb = new StringBuilder();
        String output;
        try {
            while ((output = br.readLine()) != null) {
                sb.append(output);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

        return sb.toString();
    }
    else {
        return null;
    }
}

@Override
protected void onPostExecute(String result) {
    super.onPostExecute(result);
    if(result == null) {
        callback.onError();
    }
    else {
        IssuesResponse issues = new Gson().fromJson(result, IssuesResponse.class);
        callback.onSuccess(issues);
    }
}
}

Answer 7

到目前为止，我的解决方案基于Mak Sing和Manolo Garcia答案。

这并不完美。现在我不知道如何重新计算valide速度以避免奇怪的效果：appbar可以比滚动速度更快地扩展。 但是无法访问具有扩展的appbar和滚动回收器视图的状态。

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
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;

public class FlingAppBarLayoutBehavior
        extends AppBarLayout.Behavior {

    // The minimum I have seen for a dy, after the recycler view stopped.
    private static final int MINIMUM_DELTA_Y = -4;

    @Nullable
    RecyclerViewScrollListener mScrollListener;

    private boolean isPositive;

    public FlingAppBarLayoutBehavior() {
    }

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

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

    @Override
    public boolean onNestedFling(
            CoordinatorLayout coordinatorLayout,
            AppBarLayout child,
            View target,
            float velocityX,
            float velocityY,
            boolean consumed) {

        if (velocityY > 0 && !isPositive || velocityY < 0 && isPositive) {
            velocityY = velocityY * -1;
        }

        if (target instanceof RecyclerView) {
            RecyclerView recyclerView = (RecyclerView) target;

            if (mScrollListener == null) {
                mScrollListener = new RecyclerViewScrollListener(
                        coordinatorLayout,
                        child,
                        this
                );
                recyclerView.addOnScrollListener(mScrollListener);
            }

            mScrollListener.setVelocity(velocityY);
        }

        return super.onNestedFling(
                coordinatorLayout,
                child,
                target,
                velocityX,
                velocityY,
                consumed
        );
    }

    @Override
    public void onNestedPreScroll(
            CoordinatorLayout coordinatorLayout,
            AppBarLayout child,
            View target,
            int dx,
            int dy,
            int[] consumed) {
        super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed);
        isPositive = dy > 0;
    }

    private static class RecyclerViewScrollListener
            extends RecyclerView.OnScrollListener {

        @NonNull
        private final WeakReference<AppBarLayout> mAppBarLayoutWeakReference;

        @NonNull
        private final WeakReference<FlingAppBarLayoutBehavior> mBehaviorWeakReference;

        @NonNull
        private final WeakReference<CoordinatorLayout> mCoordinatorLayoutWeakReference;

        private int mDy;

        private float mVelocity;

        public RecyclerViewScrollListener(
                @NonNull CoordinatorLayout coordinatorLayout,
                @NonNull AppBarLayout child,
                @NonNull FlingAppBarLayoutBehavior barBehavior) {
            mCoordinatorLayoutWeakReference = new WeakReference<>(coordinatorLayout);
            mAppBarLayoutWeakReference = new WeakReference<>(child);
            mBehaviorWeakReference = new WeakReference<>(barBehavior);
        }

        @Override
        public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
            if (newState == RecyclerView.SCROLL_STATE_IDLE) {
                if (mDy < MINIMUM_DELTA_Y
                        && mAppBarLayoutWeakReference.get() != null
                        && mCoordinatorLayoutWeakReference.get() != null
                        && mBehaviorWeakReference.get() != null) {

                    // manually trigger the fling when it's scrolled at the top
                    mBehaviorWeakReference.get()
                            .callSuperOnNestedFling(
                                    mCoordinatorLayoutWeakReference.get(),
                                    mAppBarLayoutWeakReference.get(),
                                    recyclerView,
                                    0,
                                    mVelocity, // TODO find a way to recalculate a correct velocity.
                                    false
                            );

                }
            }
        }

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

        public void setVelocity(float velocity) {
            mVelocity = velocity;
        }

    }

}

Answer 8

在我的情况下，我遇到的问题是RecyclerView投掷不会顺利滚动它，使其卡住。

这是因为，出于某种原因，我忘记了我已将RecyclerView放入NestedScrollView 。

这是一个愚蠢的错误，但我花了一段时间来搞清楚......

Answer 9

接受的答案对我没有用，因为我在RecyclerView和SwipeRefreshLayout内有ViewPager。这是在层次结构中寻找RecyclerView并且应该适用于任何布局的改进版本：

public final class FlingBehavior extends AppBarLayout.Behavior {
    private static final int TOP_CHILD_FLING_THRESHOLD = 3;
    private boolean isPositive;

    public FlingBehavior() {
    }

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

    @Override
    public boolean onNestedFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY, boolean consumed) {
        if (velocityY > 0 && !isPositive || velocityY < 0 && isPositive) {
            velocityY = velocityY * -1;
        }
        if (!(target instanceof RecyclerView) && velocityY < 0) {
            RecyclerView recycler = findRecycler((ViewGroup) target);
            if (recycler != null){
                target = recycler;
            }
        }
        if (target instanceof RecyclerView && velocityY < 0) {
            final RecyclerView recyclerView = (RecyclerView) target;
            final View firstChild = recyclerView.getChildAt(0);
            final int childAdapterPosition = recyclerView.getChildAdapterPosition(firstChild);
            consumed = childAdapterPosition > TOP_CHILD_FLING_THRESHOLD;
        }
        return super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
    }

    @Override
    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, int dx, int dy, int[] consumed) {
        super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed);
        isPositive = dy > 0;
    }

    @Nullable
    private RecyclerView findRecycler(ViewGroup container){
        for (int i = 0; i < container.getChildCount(); i++) {
            View childAt = container.getChildAt(i);
            if (childAt instanceof RecyclerView){
                return (RecyclerView) childAt;
            }
            if (childAt instanceof ViewGroup){
                return findRecycler((ViewGroup) childAt);
            }
        }
        return null;
    }
}

Answer 10

答案：已修复支持库v26

但是v26在投掷方面存在一些问题。有时，即使投掷不是太难，AppBar也会反弹。

How do I remove the bouncing effect on appbar?

如果您在更新支持v26时遇到同样的问题，请参阅此answer的摘要。

  

解决方案：扩展AppBar的默认行为并阻止其通话   AppBar时AppBar.Behavior的onNestedPreScroll（）和onNestedScroll（）   在NestedScroll尚未停止时触及。

Answer 11

我在AppBarLayout中添加了一个1dp高度的视图，然后它运行得更好。这是我的布局。

  <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:background="@android:color/white"
tools:context="com.spof.spof.app.UserBeachesActivity">

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

    <android.support.v7.widget.Toolbar
        android:id="@+id/user_beaches_toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:layout_alignParentTop="true"
        android:background="?attr/colorPrimary"
        android:minHeight="?attr/actionBarSize"
        android:theme="@style/WhiteTextToolBar"
        app:layout_scrollFlags="scroll|enterAlways" />

    <View
        android:layout_width="match_parent"
        android:layout_height="1dp" />
</android.support.design.widget.AppBarLayout>


<android.support.v7.widget.RecyclerView
    android:id="@+id/user_beaches_rv"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:layout_behavior="@string/appbar_scrolling_view_behavior" />

Answer 12

这里已经有一些非常受欢迎的解决方案，但在玩完它们后，我想出了一个相当简单的解决方案，对我来说效果很好。我的解决方案还确保AppBarLayout仅在可滚动内容到达顶部时展开，这是其他解决方案的优势。

private int mScrolled;
private int mPreviousDy;
private AppBarLayout mAppBar;

myRecyclerView.addOnScrollListener(new OnScrollListener() {
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);
            mScrolled += dy;
            // scrolled to the top with a little more velocity than a slow scroll e.g. flick/fling.
            // Adjust 10 (vertical change of event) as you feel fit for you requirement
            if(mScrolled == 0 && dy < -10 && mPrevDy < 0) {
                mAppBar.setExpanded(true, true);
            }
            mPreviousDy = dy;
    });

Answer 13

在这里添加另一个答案，因为上面的答案要么完全没有满足我的需要，要么不能很好地工作。这个部分基于这里传播的想法。

那么这个人做了什么？

情景下降： 如果AppBarLayout被折叠，它会让RecyclerView自行投掷而不做任何事情。否则，它会折叠AppBarLayout并阻止RecyclerView执行其操作。一旦它崩溃（直到达到给定的速度要求）并且如果剩下速度，则RecyclerView会以原始速度减去App​​BarLayout刚刚消耗掉的速度而被抛弃。

情景向上投掷： 如果RecyclerView的滚动偏移不为零，则会以原始速度抛出。一旦完成并且仍然存在速度（即RecyclerView滚动到位置0），AppBarLayout就会扩展到原始速度减去刚刚消耗的需求的程度。 否则，AppBarLayout会扩展到原始速度要求的程度。

AFAIK，这是一种侵犯行为。

涉及很多反思，而且非常习惯。但是没有发现任何问题。 它也写在Kotlin中，但理解它应该没问题。 您可以使用IntelliJ Kotlin插件将其编译为字节码 - ＆gt;并将其反编译回Java。 要使用它，请将其放在android.support.v7.widget包中，并将其设置为AppBarLayout的CoordinatorLayout.LayoutParams＆＃39;代码中的行为（或添加xml适用的构造函数）

/*
 * Copyright 2017 Julian Ostarek
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.support.v7.widget

import android.support.design.widget.AppBarLayout
import android.support.design.widget.CoordinatorLayout
import android.support.v4.widget.ScrollerCompat
import android.view.View
import android.widget.OverScroller

class SmoothScrollBehavior(recyclerView: RecyclerView) : AppBarLayout.Behavior() {
    // We're using this SplineOverScroller from deep inside the RecyclerView to calculate the fling distances
    private val splineOverScroller: Any
    private var isPositive = false

    init {
        val scrollerCompat = RecyclerView.ViewFlinger::class.java.getDeclaredField("mScroller").apply {
            isAccessible = true
        }.get(recyclerView.mViewFlinger)
        val overScroller = ScrollerCompat::class.java.getDeclaredField("mScroller").apply {
            isAccessible = true
        }.get(scrollerCompat)
        splineOverScroller = OverScroller::class.java.getDeclaredField("mScrollerY").apply {
            isAccessible = true
        }.get(overScroller)
    }

    override fun onNestedFling(coordinatorLayout: CoordinatorLayout?, child: AppBarLayout, target: View?, velocityX: Float, givenVelocity: Float, consumed: Boolean): Boolean {
        // Making sure the velocity has the correct sign (seems to be an issue)
        var velocityY: Float
        if (isPositive != givenVelocity > 0) {
            velocityY = givenVelocity * - 1
        } else velocityY = givenVelocity

        if (velocityY < 0) {
            // Decrement the velocity to the maximum velocity if necessary (in a negative sense)
            velocityY = Math.max(velocityY, - (target as RecyclerView).maxFlingVelocity.toFloat())

            val currentOffset = (target as RecyclerView).computeVerticalScrollOffset()
            if (currentOffset == 0) {
                super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, false)
                return true
            } else {
                val distance = getFlingDistance(velocityY.toInt()).toFloat()
                val remainingVelocity = - (distance - currentOffset) * (- velocityY / distance)
                if (remainingVelocity < 0) {
                    (target as RecyclerView).addOnScrollListener(object : RecyclerView.OnScrollListener() {
                        override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
                            if (newState == RecyclerView.SCROLL_STATE_IDLE) {
                                recyclerView.post { recyclerView.removeOnScrollListener(this) }
                                if (recyclerView.computeVerticalScrollOffset() == 0) {
                                    super@SmoothScrollBehavior.onNestedFling(coordinatorLayout, child, target, velocityX, remainingVelocity, false)
                                }
                            }
                        }
                    })
                }
                return false
            }
        }
        // We're not getting here anyway, flings with positive velocity are handled in onNestedPreFling
        return false
    }

    override fun onNestedPreFling(coordinatorLayout: CoordinatorLayout?, child: AppBarLayout, target: View?, velocityX: Float, givenVelocity: Float): Boolean {
        // Making sure the velocity has the correct sign (seems to be an issue)
        var velocityY: Float
        if (isPositive != givenVelocity > 0) {
            velocityY = givenVelocity * - 1
        } else velocityY = givenVelocity

        if (velocityY > 0) {
            // Decrement to the maximum velocity if necessary
            velocityY = Math.min(velocityY, (target as RecyclerView).maxFlingVelocity.toFloat())

            val topBottomOffsetForScrollingSibling = AppBarLayout.Behavior::class.java.getDeclaredMethod("getTopBottomOffsetForScrollingSibling").apply {
                isAccessible = true
            }.invoke(this) as Int
            val isCollapsed = topBottomOffsetForScrollingSibling == - child.totalScrollRange

            // The AppBarlayout is collapsed, we'll let the RecyclerView handle the fling on its own
            if (isCollapsed)
                return false

            // The AppbarLayout is not collapsed, we'll calculate the remaining velocity, trigger the appbar to collapse and fling the RecyclerView manually (if necessary) as soon as that is done
            val distance = getFlingDistance(velocityY.toInt())
            val remainingVelocity = (distance - (child.totalScrollRange + topBottomOffsetForScrollingSibling)) * (velocityY / distance)

            if (remainingVelocity > 0) {
                (child as AppBarLayout).addOnOffsetChangedListener(object : AppBarLayout.OnOffsetChangedListener {
                    override fun onOffsetChanged(appBarLayout: AppBarLayout, verticalOffset: Int) {
                        // The AppBarLayout is now collapsed
                        if (verticalOffset == - appBarLayout.totalScrollRange) {
                            (target as RecyclerView).mViewFlinger.fling(velocityX.toInt(), remainingVelocity.toInt())
                            appBarLayout.post { appBarLayout.removeOnOffsetChangedListener(this) }
                        }
                    }
                })
            }

            // Trigger the expansion of the AppBarLayout
            super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, false)
            // We don't let the RecyclerView fling already
            return true
        } else return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY)
    }

    override fun onNestedPreScroll(coordinatorLayout: CoordinatorLayout?, child: AppBarLayout?, target: View?, dx: Int, dy: Int, consumed: IntArray?) {
        super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed)
        isPositive = dy > 0
    }

    private fun getFlingDistance(velocity: Int): Double {
        return splineOverScroller::class.java.getDeclaredMethod("getSplineFlingDistance", Int::class.javaPrimitiveType).apply {
            isAccessible = true
        }.invoke(splineOverScroller, velocity) as Double
    }

}

Answer 14

Julian Os是对的。

如果recyclerview低于阈值并滚动，则

Manolo Garcia's answer不起作用。您必须比较Recyclerview的offset和velocity to the distance，而不是项目位置。

我通过参考朱利安的kotlin代码并减去反射来制作java版本。

public final class FlingBehavior extends AppBarLayout.Behavior {

    private boolean isPositive;

    private float mFlingFriction = ViewConfiguration.getScrollFriction();

    private float DECELERATION_RATE = (float) (Math.log(0.78) / Math.log(0.9));
    private final float INFLEXION = 0.35f;
    private float mPhysicalCoeff;

    public FlingBehavior(){
        init();
    }

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

    private void init(){
        final float ppi = BaseApplication.getInstance().getResources().getDisplayMetrics().density * 160.0f;
        mPhysicalCoeff = SensorManager.GRAVITY_EARTH // g (m/s^2)
                * 39.37f // inch/meter
                * ppi
                * 0.84f; // look and feel tuning
    }

    @Override
    public boolean onNestedFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY, boolean consumed) {

        if (velocityY > 0 && !isPositive || velocityY < 0 && isPositive) {
            velocityY = velocityY * -1;
        }
        if (target instanceof RecyclerView && velocityY < 0) {
            RecyclerView recyclerView = (RecyclerView) target;

            double distance = getFlingDistance((int) velocityY);
            if (distance < recyclerView.computeVerticalScrollOffset()) {
                consumed = true;
            } else {
                consumed = false;
            }
        }
        return super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
    }

    @Override
    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, int dx, int dy, int[] consumed) {
        super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed);
        isPositive = dy > 0;
    }

    public double getFlingDistance(int velocity){
        final double l = getSplineDeceleration(velocity);
        final double decelMinusOne = DECELERATION_RATE - 1.0;
        return mFlingFriction * mPhysicalCoeff * Math.exp(DECELERATION_RATE / decelMinusOne * l);
    }

    private double getSplineDeceleration(int velocity) {
        return Math.log(INFLEXION * Math.abs(velocity) / (mFlingFriction * mPhysicalCoeff));
    }

}

Answer 15

我通过 Eniz Bilgin https://stackoverflow.com/a/45090239/7639018

找到了解决方法

此存储库中的库已解决了该问题。

（https://developer.android.com/topic/libraries/support-library/setup.html）

allprojects {
    repositories {
        jcenter()
        maven {
            url "https://maven.google.com"
        }
    }
}

Answer 16

参考Google issue tracker，已修复Android 26.0.0-beta2版支持库

请更新 Android支持库版本26.0.0-beta2。

如果问题仍然存在，请在Google issue tracker报告，然后重新审核。

Answer 17

这是我项目的解决方案。
在获取Action_Down时停止mScroller

的xml：

    <android.support.design.widget.AppBarLayout
        android:id="@+id/smooth_app_bar_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/white"
        app:elevation="0dp"
        app:layout_behavior="com.sogou.groupwenwen.view.topic.FixAppBarLayoutBehavior">

FixAppBarLayoutBehavior.java：

    public boolean onInterceptTouchEvent(CoordinatorLayout parent, AppBarLayout child, MotionEvent ev) {
        if (ev.getAction() == ACTION_DOWN) {
            Object scroller = getSuperSuperField(this, "mScroller");
            if (scroller != null && scroller instanceof OverScroller) {
                OverScroller overScroller = (OverScroller) scroller;
                overScroller.abortAnimation();
            }
        }

        return super.onInterceptTouchEvent(parent, child, ev);
    }

    private Object getSuperSuperField(Object paramClass, String paramString) {
        Field field = null;
        Object object = null;
        try {
            field = paramClass.getClass().getSuperclass().getSuperclass().getDeclaredField(paramString);
            field.setAccessible(true);
            object = field.get(paramClass);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return object;
    }

//or check the raw file:
//https://github.com/shaopx/CoordinatorLayoutExample/blob/master/app/src/main/java/com/spx/coordinatorlayoutexample/util/FixAppBarLayoutBehavior.java

Answer 18

对于androidx，

如果清单文件中包含android：hardwareAccelerated =“ false”行，则将其删除。