解决Scrollview 嵌套recyclerview不能显示，高度不正常的问题

我们先看一个效果，问题说的就是中间的Grid效果在Scrollview 嵌套recyclerview显示问题，在Android Api 24是好的，不过在5,1,1版本（api 22）缺出现了问题

最近项目中，有一个商品详情页面，页面有好几个网格页面，大家说，我们大可以用GridView去做，但是需要方的要求是，我们的网格的中间的线怎么做呢，对于GridView，我们知道我们可以这是一个背景，然后用verticalSpacing来做，这也算一个方法吧，但是对于Line线的计算是一个问题，有很多的计算逻辑，这样对代码的美观就造成了破坏，且看一段之前的代码：

private void computeCompanyGridViewHeight(int size) {
		S.p("computeCompanyGridViewHeight size:" + size);
		if (size > 9) {
			size = 9;
		}
		int len = 3;
		if (size % 3 == 0) {
			len = size / 3 - 1;
		} else {
			len = size / 3;
		}
		int height = (len + 1) * Utils.dip2px(getActivity(), 58);
		ship_mid_companys.getLayoutParams().height = height;
	}

我们这里采用RecycleView来实现。以前在ScrollView中嵌套嵌套ListView，无法正确的计算ListView的大小，现在我们在ScrollView中嵌套嵌套RecycleView的时候，也出现了计算不出高度的问题，于是有人想到我们是不是可以自己实现一个重写一个继承自RecycleView的类，重写OmMeasure，呵呵，但是实际上这是不行的，RecycleView是具体的一个控件，不相同与我们的ListView，这里参照之前网上的解决方案，我们可以继承自GridManager，然后对OnMeasure重写，其他的列表效果如此，

public class WrappingGridLayoutManager extends GridLayoutManager {

        private int mwidth = 0;
        private int mheight = 0;

        public WrappingGridLayoutManager(Context context, int spanCount) {
            super(context, spanCount);
        }

        public WrappingGridLayoutManager(Context context, int spanCount, int orientation, boolean reverseLayout) {
            super(context, spanCount, orientation, reverseLayout);
        }

        private int[] mMeasuredDimension = new int[2];

        public int getMwidth() {
            return mwidth;
        }

        public void setMwidth(int mwidth) {
            this.mwidth = mwidth;
        }

        public int getMheight() {
            return mheight;
        }

        public void setMheight(int mheight) {
            this.mheight = mheight;
        }

        @Override
        public void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state, int widthSpec, int heightSpec) {
            final int widthMode = View.MeasureSpec.getMode(widthSpec);
            final int heightMode = View.MeasureSpec.getMode(heightSpec);
            final int widthSize = View.MeasureSpec.getSize(widthSpec);
            final int heightSize = View.MeasureSpec.getSize(heightSpec);

            int width = 0;
            int height = 0;
            int count = getItemCount();
            int span = getSpanCount();
            for (int i = 0; i < count; i++) {
                measureScrapChild(recycler, i,
                        View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),
                        View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),
                        mMeasuredDimension);

                if (getOrientation() == HORIZONTAL) {
                    if (i % span == 0) {
                        width = width + mMeasuredDimension[0];
                    }
                    if (i == 0) {
                        height = mMeasuredDimension[1];
                    }
                } else {
                    if (i % span == 0) {
                        height = height + mMeasuredDimension[1];
                    }
                    if (i == 0) {
                        width = mMeasuredDimension[0];
                    }
                }
            }

            switch (widthMode) {
                case View.MeasureSpec.EXACTLY:
                    width = widthSize;
                case View.MeasureSpec.AT_MOST:
                case View.MeasureSpec.UNSPECIFIED:
            }

            switch (heightMode) {
                case View.MeasureSpec.EXACTLY:
                    height = heightSize;
                case View.MeasureSpec.AT_MOST:
                case View.MeasureSpec.UNSPECIFIED:
            }
            setMheight(height);
            setMwidth(width);
            setMeasuredDimension(width, height);
        }

        private void measureScrapChild(RecyclerView.Recycler recycler, int position, int widthSpec,
                                       int heightSpec, int[] measuredDimension) {
            if (position < getItemCount()) {
                try {
                    View view = recycler.getViewForPosition(0);//fix 动态添加时报IndexOutOfBoundsException
                    if (view != null) {
                        RecyclerView.LayoutParams p = (RecyclerView.LayoutParams) view.getLayoutParams();
                        int childWidthSpec = ViewGroup.getChildMeasureSpec(widthSpec,
                                getPaddingLeft() + getPaddingRight(), p.width);
                        int childHeightSpec = ViewGroup.getChildMeasureSpec(heightSpec,
                                getPaddingTop() + getPaddingBottom(), p.height);
                        view.measure(childWidthSpec, childHeightSpec);
                        measuredDimension[0] = view.getMeasuredWidth() + p.leftMargin + p.rightMargin;
                        measuredDimension[1] = view.getMeasuredHeight() + p.bottomMargin + p.topMargin;
                        recycler.recycleView(view);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
    }
}

 private void measureScrapChild(RecyclerView.Recycler recycler, int position, int widthSpec,
                                       int heightSpec, int[] measuredDimension) {
            if (position < getItemCount()) {
                try {
                    View view = recycler.getViewForPosition(0);//fix 动态添加时报IndexOutOfBoundsException
                    if (view != null) {
                        RecyclerView.LayoutParams p = (RecyclerView.LayoutParams) view.getLayoutParams();
                        int childWidthSpec = ViewGroup.getChildMeasureSpec(widthSpec,
                                getPaddingLeft() + getPaddingRight(), p.width);
                        int childHeightSpec = ViewGroup.getChildMeasureSpec(heightSpec,
                                getPaddingTop() + getPaddingBottom(), p.height);
                        view.measure(childWidthSpec, childHeightSpec);
                        measuredDimension[0] = view.getMeasuredWidth() + p.leftMargin + p.rightMargin;
                        measuredDimension[1] = view.getMeasuredHeight() + p.bottomMargin + p.topMargin;
                        recycler.recycleView(view);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
    }

至于划线，我们需要另一个类实现，这用到了Recycle的一个方法

recyclerView.addItemDecoration(new SupportGridItemLine(this));

Line线计算类：

public class SupportGridItemLine extends RecyclerView.ItemDecoration {

    private static final int[] ATTRS = new int[]{android.R.attr.listDivider};
    private Drawable mDivider;

    public SupportGridItemLine(Context context) {
        final TypedArray a = context.obtainStyledAttributes(ATTRS);
        mDivider = a.getDrawable(0);
        a.recycle();
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {

        drawHorizontal(c, parent);
        drawVertical(c, parent);

    }

    private int getSpanCount(RecyclerView parent) {
        // 列数
        int spanCount = -1;
        RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        if (layoutManager instanceof GridLayoutManager) {

            spanCount = ((GridLayoutManager) layoutManager).getSpanCount();
        } else if (layoutManager instanceof StaggeredGridLayoutManager) {
            spanCount = ((StaggeredGridLayoutManager) layoutManager)
                    .getSpanCount();
        }
        return spanCount;
    }

    public void drawHorizontal(Canvas c, RecyclerView parent) {
        int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                    .getLayoutParams();
            final int left = child.getLeft() - params.leftMargin;
            final int right = child.getRight() + params.rightMargin
                    + mDivider.getIntrinsicWidth();
            final int top = child.getBottom() + params.bottomMargin;
            final int bottom = top + mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }

    public void drawVertical(Canvas c, RecyclerView parent) {
        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);

            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                    .getLayoutParams();
            final int top = child.getTop() - params.topMargin;
            final int bottom = child.getBottom() + params.bottomMargin;
            final int left = child.getRight() + params.rightMargin;
            final int right = left + mDivider.getIntrinsicWidth();

            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }

    private boolean isLastColum(RecyclerView parent, int pos, int spanCount,
                                int childCount) {
        RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        if (layoutManager instanceof GridLayoutManager) {
            if ((pos + 1) % spanCount == 0)// 如果是最后一列，则不需要绘制右边
            {
                return true;
            }
        } else if (layoutManager instanceof StaggeredGridLayoutManager) {
            int orientation = ((StaggeredGridLayoutManager) layoutManager)
                    .getOrientation();
            if (orientation == StaggeredGridLayoutManager.VERTICAL) {
                if ((pos + 1) % spanCount == 0)// 如果是最后一列，则不需要绘制右边
                {
                    return true;
                }
            } else {
                childCount = childCount - childCount % spanCount;
                if (pos >= childCount)// 如果是最后一列，则不需要绘制右边
                    return true;
            }
        }
        return false;
    }

    private boolean isLastRaw(RecyclerView parent, int pos, int spanCount,
                              int childCount) {
        RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        if (layoutManager instanceof GridLayoutManager) {
            childCount = childCount - childCount % spanCount;
            if (pos >= childCount)// 如果是最后一行，则不需要绘制底部
                return true;
        } else if (layoutManager instanceof StaggeredGridLayoutManager) {
            int orientation = ((StaggeredGridLayoutManager) layoutManager)
                    .getOrientation();
            // StaggeredGridLayoutManager 且纵向滚动
            if (orientation == StaggeredGridLayoutManager.VERTICAL) {
                childCount = childCount - childCount % spanCount;
                // 如果是最后一行，则不需要绘制底部
                if (pos >= childCount)
                    return true;
            } else
            // StaggeredGridLayoutManager 且横向滚动
            {
                // 如果是最后一行，则不需要绘制底部
                if ((pos + 1) % spanCount == 0) {
                    return true;
                }
            }
        }
        return false;
    }

    @Override
    public void getItemOffsets(Rect outRect, int itemPosition,
                               RecyclerView parent) {
        int spanCount = getSpanCount(parent);
        int childCount = parent.getAdapter().getItemCount();
        if (isLastRaw(parent, itemPosition, spanCount, childCount))// 如果是最后一行，则不需要绘制底部
        {
            outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
        } else if (isLastColum(parent, itemPosition, spanCount, childCount))// 如果是最后一列，则不需要绘制右边
        {
            outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
        } else {
            outRect.set(0, 0, mDivider.getIntrinsicWidth(),
                    mDivider.getIntrinsicHeight());
        }
    }
}

好了，最后我们在使用的时候，先对RecycleView初始化相关的属性参数：

 WrappingGridLayoutManager manager = new WrappingGridLayoutManager(getActivity(), 2);//2表示2个单元格
        manager.setOrientation(GridLayoutManager.VERTICAL);
        manager.setSmoothScrollbarEnabled(true);
        recyclerView.setLayoutManager(manager);
        recyclerView.setHasFixedSize(true);
        recyclerView.setNestedScrollingEnabled(false);
        recyclerView.addItemDecoration(new SupportGridItemLine(getActivity()));

至于网上有人说的，在RecycleView外加一个布局，不知道什么原因，我这里还是没有解决。

 <RelativeLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:descendantFocusability="blocksDescendants">
                <android.support.v7.widget.RecyclerView
                    android:id="@+id/menuRv"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_marginLeft="@dimen/margin_16"
                    android:layout_marginRight="@dimen/margin_16">

                </android.support.v7.widget.RecyclerView>
                </RelativeLayout>

好了，姑且记下，帮助后来人，有疑问请加群：278792776