android - 当 AppBarLayout 滚动时，RecyclerView fling 会导致延迟

Question

我有如下布局

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">


    <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_behavior=".AppBarFlingBehavior">

        <android.support.design.widget.CollapsingToolbarLayout
            android:layout_width="match_parent"
            android:layout_height="300dp"
            app:layout_scrollFlags="scroll|enterAlwaysCollapsed">


            <ImageView
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                app:layout_collapseMode="parallax"
                android:background="#ff99"/>


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


        <TextView
            android:layout_width="match_parent"
            android:layout_height="200dp"
            app:layout_scrollFlags="scroll|enterAlwaysCollapsed"
            android:text="aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"/>


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


    <android.support.v7.widget.RecyclerView
        android:id="@+id/rv_sample"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="android.support.design.widget.AppBarLayout$ScrollingViewBehavior"/>


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

我的问题是当我向下滑动我的AppBarLayout时，内容正在向下滚动，突然，我向上滑动我的RecyclerView，整个布局有点滞后然后按照 RecyclerView (UP) 的滑动方向向上滚动，如您在此 video 中所见.我已经尝试了很多来自许多来源的解决方案(自定义行为)，但到目前为止还没有成功。有什么方法可以解决我的问题，我被困在这个问题上了一个星期。非常感谢您花时间解决我的问题。欣赏它。

Answer 1

我找到了解决方案(归功于 yangchong:https://developpaper.com/coordinator-layout-sliding-jitter-problem/ ):

应用栏行为:

/**
 * <pre>
 *     @author yangchong
 *     blog  : https://github.com/yangchong211
 *     time  : 2019/03/13
 * desc: Custom Behavior
 * Revision: Solving Some Problems of AppbarLayout
 * 1) Fast sliding appbarLayout will rebound
 * 2) Fast sliding appbarLayout to fold state, immediately sliding down, there will be the problem of jitter.
 * 3) Slide appbarLayout, unable to stop sliding by pressing it with your finger
*/
public class AppBarLayoutBehavior extends AppBarLayout.Behavior {

    private static final String TAG = "AppbarLayoutBehavior";
    private static final int TYPE_FLING = 1;
    private boolean isFlinging;
    private boolean shouldBlockNestedScroll;

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

    @Override
    public boolean onInterceptTouchEvent(CoordinatorLayout parent, AppBarLayout child, MotionEvent ev) {
        LogUtil.d(TAG, "onInterceptTouchEvent:" + child.getTotalScrollRange());
        shouldBlockNestedScroll = isFlinging;
        switch (ev.getActionMasked()) {
            case MotionEvent.ACTION_DOWN:
                // Stop fling when your finger touches the screen
                stopAppbarLayoutFling(child);
                break;
            default:
                break;
        }
        return super.onInterceptTouchEvent(parent, child, ev);
    }

    /**
     * Reflect to get private flingRunnable attributes, considering the problem of variable name modification after support 28
     * @return Field
     * @throws NoSuchFieldException
     */
    private Field getFlingRunnableField() throws NoSuchFieldException {
        Class<?> superclass = this.getClass().getSuperclass();
        try {
            // Support design 27 and the following version
            Class<?> headerBehaviorType = null;
            if (superclass != null) {
                headerBehaviorType = superclass.getSuperclass();
            }
            if (headerBehaviorType != null) {
                return headerBehaviorType.getDeclaredField("mFlingRunnable");
            }else {
                return null;
            }
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
            // Possibly 28 or more versions
            Class<?> headerBehaviorType = superclass.getSuperclass().getSuperclass();
            if (headerBehaviorType != null) {
                return headerBehaviorType.getDeclaredField("flingRunnable");
            } else {
                return null;
            }
        }
    }

    /**
     * Reflect to get private scroller attributes, considering the problem of variable name modification after support 28
     * @return Field
     * @throws NoSuchFieldException
     */
    private Field getScrollerField() throws NoSuchFieldException {
        Class<?> superclass = this.getClass().getSuperclass();
        try {
            // Support design 27 and the following version
            Class<?> headerBehaviorType = null;
            if (superclass != null) {
                headerBehaviorType = superclass.getSuperclass();
            }
            if (headerBehaviorType != null) {
                return headerBehaviorType.getDeclaredField("mScroller");
            }else {
                return null;
            }
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
            // Possibly 28 or more versions
            Class<?> headerBehaviorType = superclass.getSuperclass().getSuperclass();
            if (headerBehaviorType != null) {
                return headerBehaviorType.getDeclaredField("scroller");
            }else {
                return null;
            }
        }
    }

    /**
     * Stop appbarLayout's fling event
     * @param appBarLayout
     */
    private void stopAppbarLayoutFling(AppBarLayout appBarLayout) {
        // Get the flingRunnable variable in HeaderBehavior by reflection
        try {
            Field flingRunnableField = getFlingRunnableField();
            Field scrollerField = getScrollerField();
            if (flingRunnableField != null) {
                flingRunnableField.setAccessible(true);
            }
            if (scrollerField != null) {
                scrollerField.setAccessible(true);
            }
            Runnable flingRunnable = null;
            if (flingRunnableField != null) {
                flingRunnable = (Runnable) flingRunnableField.get(this);
            }
            OverScroller overScroller = (OverScroller) scrollerField.get(this);
            if (flingRunnable != null) {
                LogUtil.d (TAG,'Flying Runnable');
                appBarLayout.removeCallbacks(flingRunnable);
                flingRunnableField.set(this, null);
            }
            if (overScroller != null && !overScroller.isFinished()) {
                overScroller.abortAnimation();
            }
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
    }

    @Override
    public boolean onStartNestedScroll(CoordinatorLayout parent, AppBarLayout child,
                                       View directTargetChild, View target,
                                       int nestedScrollAxes, int type) {
        LogUtil.d(TAG, "onStartNestedScroll");
        stopAppbarLayoutFling(child);
        return super.onStartNestedScroll(parent, child, directTargetChild, target,
                nestedScrollAxes, type);
    }

    @Override
    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout,
                                  AppBarLayout child, View target,
                                  int dx, int dy, int[] consumed, int type) {
        LogUtil.d(TAG, "onNestedPreScroll:" + child.getTotalScrollRange()
                + " ,dx:" + dx + " ,dy:" + dy + " ,type:" + type);
        // When type returns to 1, it indicates that the current target is in a non-touch sliding.
        // The bug is caused by the sliding of the NestedScrolling Child2 interface in Coordinator Layout when the AppBar is sliding
        // The subclass has not ended its own fling
        // So here we listen for non-touch sliding of subclasses, and then block the sliding event to AppBarLayout
        if (type == TYPE_FLING) {
            isFlinging = true;
        }
        if (!shouldBlockNestedScroll) {
            super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed, type);
        }
    }

    @Override
    public void onNestedScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child,
                               View target, int dxConsumed, int dyConsumed, int
            dxUnconsumed, int dyUnconsumed, int type) {
        LogUtil.d(TAG, "onNestedScroll: target:" + target.getClass() + " ,"
                + child.getTotalScrollRange() + " ,dxConsumed:"
                + dxConsumed + " ,dyConsumed:" + dyConsumed + " " + ",type:" + type);
        if (!shouldBlockNestedScroll) {
            super.onNestedScroll(coordinatorLayout, child, target, dxConsumed,
                    dyConsumed, dxUnconsumed, dyUnconsumed, type);
        }
    }

    @Override
    public void onStopNestedScroll(CoordinatorLayout coordinatorLayout, AppBarLayout abl,
                                   View target, int type) {
        LogUtil.d(TAG, "onStopNestedScroll");
        super.onStopNestedScroll(coordinatorLayout, abl, target, type);
        isFlinging = false;
        shouldBlockNestedScroll = false;
    }

    private static class LogUtil{
        static void d(String tag, String string){
            Log.d(tag,string);
        }
    }

}