Android：CoordinatorLayout中RecyclerView滚动与高度限制异常问题

1. 修复LinearLayoutWithVariableHeight刷新后高度为0的问题 #

问题原因：RecyclerView数据刷新后，父布局未触发重测量，或onMeasure逻辑未正确计算子View实际高度。
解决方案：

• 在自定义LinearLayout中，确保onMeasure正确计算所有子View的高度；
• 监听RecyclerView的Adapter数据变化，主动触发父布局重测量。

代码示例：

public class LinearLayoutWithVariableHeight extends LinearLayout {
    private int maxHeight;
    private int minHeight;
    private RecyclerView mBoundRecyclerView;

    public LinearLayoutWithVariableHeight(Context context) {
        super(context);
        init();
    }

    // 省略其他构造方法

    private void init() {
        // 初始化max/min高度逻辑
    }

    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();
        // 遍历子View找到RecyclerView并监听数据变化
        for (int i = 0; i < getChildCount(); i++) {
            View child = getChildAt(i);
            if (child instanceof RecyclerView) {
                mBoundRecyclerView = (RecyclerView) child;
                mBoundRecyclerView.getAdapter().registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
                    @Override
                    public void onChanged() {
                        requestLayout(); // 数据变化时触发重测量
                    }
                });
                break;
            }
        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int measuredHeight = getMeasuredHeight();
        // 限制高度在min和max区间内
        int finalHeight = Math.max(minHeight, Math.min(measuredHeight, maxHeight));
        setMeasuredDimension(getMeasuredWidth(), finalHeight);
    }
}

2. 修复RecyclerViewWithMaxHeight无法滚动的问题 #

问题原因：自定义RecyclerView时，onMeasure错误设置了固定高度测量模式，未保留可滚动的AT_MOST模式。
解决方案：在onMeasure中，将高度测量模式设为AT_MOST，限制最大高度的同时允许内容超出时滚动。

代码示例：

public class RecyclerViewWithMaxHeight extends RecyclerView {
    private int maxHeight;

    public RecyclerViewWithMaxHeight(Context context) {
        super(context);
    }

    // 省略其他构造方法

    public void setMaxHeight(int maxHeight) {
        this.maxHeight = maxHeight;
        requestLayout();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        if (maxHeight > 0) {
            // 设置高度测量模式为AT_MOST，最大高度限制为maxHeight
            heightMeasureSpec = MeasureSpec.makeMeasureSpec(maxHeight, MeasureSpec.AT_MOST);
        }
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }
}

3. 修复BottomSheet中RecyclerView触摸事件异常（仅边界可滚动） #

问题原因：BottomSheetBehavior默认仅识别第一个可滚动子View，后续RecyclerView的触摸事件被拦截。
解决方案：自定义Behavior时，重写canScrollVertically/canScrollHorizontally方法，判断当前触摸的View是否为可滚动RecyclerView，返回对应滚动状态。

4. 修复自定义Behavior后RecyclerView滚到顶部且无惯性的问题 #

问题原因：自定义Behavior错误拦截了触摸事件，未传递惯性滚动的MotionEvent，或重置了RecyclerView的滚动状态。
解决方案：

• 在onInterceptTouchEvent中，仅当触摸对象不是RecyclerView时才拦截事件；
• 重写onStartNestedScroll和onNestedScroll方法，不干扰RecyclerView自身的滚动逻辑。

代码示例：

public class MultiScrollRecyclerViewBottomSheetBehavior<V extends View> extends BottomSheetBehavior<V> {
    private RecyclerView mCurrentTouchRecyclerView;

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

    @Override
    public boolean onInterceptTouchEvent(@NonNull CoordinatorLayout parent, @NonNull V child, @NonNull MotionEvent event) {
        // 定位当前触摸点下的RecyclerView
        mCurrentTouchRecyclerView = findRecyclerViewUnder(child, event.getX(), event.getY());
        // 触摸RecyclerView时不拦截事件，让其自行处理
        if (mCurrentTouchRecyclerView != null) {
            return false;
        }
        return super.onInterceptTouchEvent(parent, child, event);
    }

    @Override
    public boolean canScrollVertically(@NonNull CoordinatorLayout coordinatorLayout, @NonNull V child, @NonNull View target, int direction) {
        // 允许纵向RecyclerView滚动
        if (target instanceof RecyclerView && ((RecyclerView) target).getLayoutManager().canScrollVertically()) {
            return true;
        }
        return super.canScrollVertically(coordinatorLayout, child, target, direction);
    }

    @Override
    public boolean canScrollHorizontally(@NonNull CoordinatorLayout coordinatorLayout, @NonNull V child, @NonNull View target, int direction) {
        // 允许横向RecyclerView滚动
        if (target instanceof RecyclerView && ((RecyclerView) target).getLayoutManager().canScrollHorizontally()) {
            return true;
        }
        return super.canScrollHorizontally(coordinatorLayout, child, target, direction);
    }

    // 递归查找触摸点下的RecyclerView
    private RecyclerView findRecyclerViewUnder(View root, float x, float y) {
        if (root instanceof RecyclerView) {
            Rect rect = new Rect();
            root.getHitRect(rect);
            if (rect.contains((int) x, (int) y)) {
                return (RecyclerView) root;
            }
        } else if (root instanceof ViewGroup) {
            ViewGroup group = (ViewGroup) root;
            for (int i = 0; i < group.getChildCount(); i++) {
                RecyclerView recyclerView = findRecyclerViewUnder(group.getChildAt(i), x - group.getScrollX(), y - group.getScrollY());
                if (recyclerView != null) {
                    return recyclerView;
                }
            }
        }
        return null;
    }
}

内容的提问来源于stack exchange，提问作者Martin