CollapsingToolbarLayout无法识别滚动

我创建了一个简单的CollapsingToolbarLayout，它的工作原理很像。我的问题是，如果我尝试在nestedscrollview上使用浮动滚动，则在松开手指时滚动将停止。正常的滚动工作应该像它应该的那样。

我的活动代码未更改=>自动生成的空活动。（我只是单击了在android studio中创建新的空活动并编辑了XML）。

我在这里读到，imageview上的滚动手势本身是错误的，但不是，滚动本身是错误的：请参见此处。

我尝试通过Java代码激活“平滑滚动”。似乎如果我滚动到足够远以至于图像视图不再可见，则可以识别出挥动手势。

TLDR：为什么只要可见图像视图，挥动手势就不起作用？我的XML代码如下所示：

    <android.support.design.widget.CoordinatorLayout
    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:fitsSystemWindows="true">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/profile_app_bar_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        android:fitsSystemWindows="true">

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

            <ImageView
                android:id="@+id/image"
                android:layout_width="match_parent"
                android:layout_height="420dp"
                android:scaleType="centerCrop"
                android:fitsSystemWindows="true"
                android:src="@drawable/headerbg"
                android:maxHeight="192dp"

                app:layout_collapseMode="parallax"/>

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
                app:layout_collapseMode="pin" />

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

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

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        app:layout_anchor="@id/profile_app_bar_layout"
        app:layout_anchorGravity="bottom|right|end"
        android:layout_height="@dimen/fab_size_normal"
        android:layout_width="@dimen/fab_size_normal"
        app:elevation="2dp"
        app:pressedTranslationZ="12dp"
        android:layout_marginRight="8dp"
        android:layout_marginEnd="8dp"/>

    <android.support.v4.widget.NestedScrollView
        android:id="@+id/profile_content_scroll"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:clipToPadding="false"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"
        android:layout_gravity="fill_vertical"
        android:minHeight="192dp"
        android:overScrollMode="ifContentScrolls"
        >

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">

            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="@string/LoremIpsum"/>

        </RelativeLayout>

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

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

我在CollapsingToolbarLayout里面有ImageView和NestedScrollView时遇到了完全相同的问题。松开手指时，滚动滚动停止。

但是，我注意到了一些奇怪的事情。如果您从用OnClickListener（例如Button）的视图开始用手指滚动，则滑动滚动会完美工作。

因此，我用一个奇怪的解决方案将其修复。设置OnClickListener（什么都不做）上的直接孩子NestedScrollView。然后，它完美地工作！

<android.support.v4.widget.NestedScrollView 
   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"
   app:layout_behavior="@string/appbar_scrolling_view_behavior">

  <LinearLayout
      android:id="@+id/content_container"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:orientation="vertical">

    <!-- Page Content -->

  </LinearLayout>

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

给直接子级（LinearLayout）一个ID，并在Activity中设置OnClickListener

ViewGroup mContentContainer = (ViewGroup) findViewById(R.id.content_container);    
mContentContainer.setOnClickListener(this);

@Override
public void onClick(View view) {
    int viewId = view.getId();
}

笔记：

使用支持设计库25.0.1测试

具有scrollFlags =“ scroll | enterAlwaysCollapsed”的CollapsingToolbarLayout“

我知道这个问题是一年多以前提出的，但支持/设计库中似乎仍未解决该问题。您可以为这个问题加注星标，以使其在优先级队列中更进一步。

也就是说，我尝试了大多数已发布的解决方案，包括patrick-iv的解决方案，但均未成功。我上班的唯一办法是模拟猛击，如果在程序中检测到一定条件，则以程序方式调用它onPreNestedScroll()。在调试的几个小时中，我注意到onNestedFling()从未被要求向上（向下滚动）猛冲，并且似乎被过早消耗掉了。我不能100％肯定地说这将适用于100％的实现，但是对于我的使用来说已经足够好了，所以我最终为此解决了，即使它很笨拙，而且绝对不是我想做的。

public class NestedScrollViewBehavior extends AppBarLayout.Behavior {

    // Lower value means fling action is more easily triggered
    static final int MIN_DY_DELTA = 4;
    // Lower values mean less velocity, higher means higher velocity
    static final int FLING_FACTOR = 20;

    int mTotalDy;
    int mPreviousDy;
    WeakReference<AppBarLayout> mPreScrollChildRef;

    @Override
    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child,
                                  View target, int dx, int dy, int[] consumed) {
        super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed);
        // Reset the total fling delta distance if the user starts scrolling back up
        if(dy < 0) {
            mTotalDy = 0;
        }
        // Only track move distance if the movement is positive (since the bug is only present
        // in upward flings), equal to the consumed value and the move distance is greater
        // than the minimum difference value
        if(dy > 0 && consumed[1] == dy && MIN_DY_DELTA < Math.abs(mPreviousDy - dy)) {
            mPreScrollChildRef = new WeakReference<>(child);
            mTotalDy += dy * FLING_FACTOR;
        }
        mPreviousDy = dy;
    }

    @Override
    public boolean onStartNestedScroll(CoordinatorLayout parent, AppBarLayout child,
                                       View directTargetChild, View target, int nestedScrollAxes) {
        // Stop any previous fling animations that may be running
        onNestedFling(parent, child, target, 0, 0, false);
        return super.onStartNestedScroll(parent, child, directTargetChild, target, nestedScrollAxes);
    }

    @Override
    public void onStopNestedScroll(CoordinatorLayout parent, AppBarLayout abl, View target) {
        if(mTotalDy > 0 && mPreScrollChildRef != null && mPreScrollChildRef.get() != null) {
            // Programmatically trigger fling if all conditions are met
            onNestedFling(parent, mPreScrollChildRef.get(), target, 0, mTotalDy, false);
            mTotalDy = 0;
            mPreviousDy = 0;
            mPreScrollChildRef = null;
        }
        super.onStopNestedScroll(parent, abl, target);
    }
}

并将其应用于AppBar

AppBarLayout scrollView = (AppBarLayout)findViewById(R.id.appbar);
CoordinatorLayout.LayoutParams params = (CoordinatorLayout.LayoutParams)scrollView.getLayoutParams();
params.setBehavior(new NestedScrollViewBehavior());

CheeseSquare演示： 之前 之后

我尝试了Floofer的解决方案，但对我来说仍然不够好。所以我想出了他的行为的一个更好的版本。AppBarLayout现在在猛扑时可以平滑地展开和折叠。

注意：我使用反射来解决这个问题，因此它可能不适用于版本25.0.0以外的Android Design库。

public class SmoothScrollBehavior extends AppBarLayout.Behavior {
    private static final String TAG = "SmoothScrollBehavior";
    //The higher this value is, the faster the user must scroll for the AppBarLayout to collapse by itself
    private static final int SCROLL_SENSIBILITY = 5;
    //The real fling velocity calculation seems complex, in this case it is simplified with a multiplier
    private static final int FLING_VELOCITY_MULTIPLIER = 60;

    private boolean alreadyFlung = false;
    private boolean request = false;
    private boolean expand = false;
    private int velocity = 0;
    private int nestedScrollViewId;

    public SmoothScrollBehavior(int nestedScrollViewId) {
        this.nestedScrollViewId = nestedScrollViewId;
    }

    @Override
    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child,
                                  View target, int dx, int dy, int[] consumed) {
        super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed);
        if(Math.abs(dy) >= SCROLL_SENSIBILITY) {
            request = true;
            expand = dy < 0;
            velocity = dy * FLING_VELOCITY_MULTIPLIER;
        } else {
            request = false;
        }
    }

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

    @Override
    public void onStopNestedScroll(CoordinatorLayout coordinatorLayout, AppBarLayout appBarLayout, View target) {
        if(request) {
            NestedScrollView nestedScrollView = (NestedScrollView) coordinatorLayout.findViewById(nestedScrollViewId);
            if (expand) {
                //No need to force expand if it is already ready expanding
                if (nestedScrollView.getScrollY() > 0) {
                    int finalY = getPredictedScrollY(nestedScrollView);
                    if (finalY <= 0) {
                        //since onNestedFling does not work to expand the AppBarLayout, we need to manually expand it
                        expandAppBarLayoutWithVelocity(coordinatorLayout, appBarLayout, velocity);
                    }
                }
            } else {
                //onNestedFling will collapse the AppBarLayout with an animation time relative to the velocity
                onNestedFling(coordinatorLayout, appBarLayout, target, 0, velocity, true);

                if(!alreadyFlung) {
                    //TODO wait for AppBarLayout to be collapsed before scrolling for even smoother visual
                    nestedScrollView.fling(velocity);
                }
            }
        }
        alreadyFlung = false;
        super.onStopNestedScroll(coordinatorLayout, appBarLayout, target);
    }

    private int getPredictedScrollY(NestedScrollView nestedScrollView) {
        int finalY = 0;
        try {
            //With reflection, we can get the ScrollerCompat from the NestedScrollView to predict where the scroll will end
            Field scrollerField = nestedScrollView.getClass().getDeclaredField("mScroller");
            scrollerField.setAccessible(true);
            Object object = scrollerField.get(nestedScrollView);
            ScrollerCompat scrollerCompat = (ScrollerCompat) object;
            finalY = scrollerCompat.getFinalY();
        } catch (Exception e ) {
            e.printStackTrace();
            //If the reflection fails, it will return 0, which means the scroll has reached top
            Log.e(TAG, "Failed to get mScroller field from NestedScrollView through reflection. Will assume that the scroll reached the top.");
        }
        return finalY;
    }

    private void expandAppBarLayoutWithVelocity(CoordinatorLayout coordinatorLayout, AppBarLayout appBarLayout, float velocity) {
        try {
            //With reflection, we can call the private method of Behavior that expands the AppBarLayout with specified velocity
            Method animateOffsetTo = getClass().getSuperclass().getDeclaredMethod("animateOffsetTo", CoordinatorLayout.class, AppBarLayout.class, int.class, float.class);
            animateOffsetTo.setAccessible(true);
            animateOffsetTo.invoke(this, coordinatorLayout, appBarLayout, 0, velocity);
        } catch (Exception e) {
            e.printStackTrace();
            //If the reflection fails, we fall back to the public method setExpanded that expands the AppBarLayout with a fixed velocity
            Log.e(TAG, "Failed to get animateOffsetTo method from AppBarLayout.Behavior through reflection. Falling back to setExpanded.");
            appBarLayout.setExpanded(true, true);
        }
    }

    @Override
    public boolean onNestedPreFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY) {
        alreadyFlung = true;
        return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY);
    }
}

要使用它，请为您的AppBarLayout设置一个新的Behavior。

AppBarLayout appBarLayout = (AppBarLayout) findViewById(R.id.app_bar);
CoordinatorLayout.LayoutParams params = (CoordinatorLayout.LayoutParams) appBarLayout.getLayoutParams();
params.setBehavior(new SmoothScrollBehavior(R.id.nested_scroll_view));

这个答案为我解决了这个问题。创建一个AppBarLayout.Behavior这样的自定义：

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;
    }
}

并添加到AppBarLayout这样的：

<android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        ...
        app:layout_behavior="com.example.test.FlingBehavior">

我只是在这里发布，以便其他人不会在评论中错过它。通过回答Jinang工作很漂亮，但荣誉给AntPachon您指出了同样的一个简单得多的方法。替代OnClick以Child of the NestedScrollView编程方式实现方法的一种更好的方法是clickable=true在子级xml中进行设置。

（使用与Jinang相同的示例）

<android.support.v4.widget.NestedScrollView 
   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"
   app:layout_behavior="@string/appbar_scrolling_view_behavior">

  <LinearLayout
      android:id="@+id/content_container"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:orientation="vertical"
      android:clickable="true" >                  <!-- new -->

    <!-- Page Content -->

  </LinearLayout>

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

在代码中：https : //android.googlesource.com/platform/frameworks/support/+/master/core-ui/java/android/support/v4/widget/NestedScrollView.java#834

       case MotionEvent.ACTION_UP:
            if (mIsBeingDragged) {
                final VelocityTracker velocityTracker = mVelocityTracker;
                velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
                int initialVelocity = (int) VelocityTrackerCompat.getYVelocity(velocityTracker,
                        mActivePointerId);
                if ((Math.abs(initialVelocity) > mMinimumVelocity)) {
                    flingWithNestedDispatch(-initialVelocity);
                } else if (mScroller.springBack(getScrollX(), getScrollY(), 0, 0, 0,
                        getScrollRange())) {
                    ViewCompat.postInvalidateOnAnimation(this);
                }
            }
            mActivePointerId = INVALID_POINTER;
            endDrag();
            break;

当我在NestedScrollView上使用fling滚动时，有时会出现“ mIsBeingDragged = false”，因此NestedScrollView不会调度fling事件。

当我删除if (mIsBeingDragged)声明时。

 case MotionEvent.ACTION_UP:
        //if (mIsBeingDragged) {
            final VelocityTracker velocityTracker = mVelocityTracker;
            velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
            int initialVelocity = (int) VelocityTrackerCompat.getYVelocity(velocityTracker,
                    mActivePointerId);
            if ((Math.abs(initialVelocity) > mMinimumVelocity)) {
                flingWithNestedDispatch(-initialVelocity);
            } else if (mScroller.springBack(getScrollX(), getScrollY(), 0, 0, 0,
                    getScrollRange())) {
                ViewCompat.postInvalidateOnAnimation(this);
            }
        //}
        mActivePointerId = INVALID_POINTER;
        endDrag();
        break;

不会有问题。但我不知道还会导致什么其他严重问题