public interface OnItemTouchListener {
    //是否讓RecyclerView攔截事件
    boolean onInterceptTouchEvent(@NonNull RecyclerView rv, @NonNull MotionEvent e);
    //攔截之后處理RecyclerView的事件
    void onTouchEvent(@NonNull RecyclerView rv, @NonNull MotionEvent e);
    //監(jiān)聽(tīng)禁止攔截事件的請(qǐng)求結(jié)果
    void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept);
}

class ItemTouchUIUtilImpl implements ItemTouchUIUtil {
    static final ItemTouchUIUtil INSTANCE =  new ItemTouchUIUtilImpl();

    @Override
    public void onDraw(Canvas c, RecyclerView recyclerView, View view, float dX, float dY,
            int actionState, boolean isCurrentlyActive) {
        if (Build.VERSION.SDK_INT >= 21) {
            if (isCurrentlyActive) {
                Object originalElevation = view.getTag(R.id.item_touch_helper_previous_elevation);
                if (originalElevation == null) {
                    originalElevation = ViewCompat.getElevation(view);
                    float newElevation = 1f + findMaxElevation(recyclerView, view);
                    ViewCompat.setElevation(view, newElevation);
                    view.setTag(R.id.item_touch_helper_previous_elevation, originalElevation);
                }
            }
        }

        view.setTranslationX(dX);
        view.setTranslationY(dY);
    }
     //省略一些有關(guān)或者無(wú)關(guān)的代碼
}

View#getChildDrawingOrder

private void addChildDrawingOrderCallback() {
    if (Build.VERSION.SDK_INT >= 21) {
        return; // we use elevation on Lollipop
    }
    if (mChildDrawingOrderCallback == null) {
        mChildDrawingOrderCallback = new RecyclerView.ChildDrawingOrderCallback() {
            @Override
            public int onGetChildDrawingOrder(int childCount, int i) {
                if (mOverdrawChild == null) {
                    return i;
                }
                int childPosition = mOverdrawChildPosition;
                if (childPosition == -1) {
                    childPosition = mRecyclerView.indexOfChild(mOverdrawChild);
                    mOverdrawChildPosition = childPosition;
                }
                if (i == childCount - 1) {
                    return childPosition;
                }
                return i < childPosition ? i : i + 1;
            }
        };
    }
    mRecyclerView.setChildDrawingOrderCallback(mChildDrawingOrderCallback);
}

@Override
public boolean onItemMove(int fromPosition, int toPosition) {
    Collections.swap(mDataList, fromPosition, toPosition);
    notifyItemMoved(fromPosition, toPosition);
    return true;
}

@Override
public void clearView(View view) {
    if (Build.VERSION.SDK_INT >= 21) {
        final Object tag = view.getTag(R.id.item_touch_helper_previous_elevation);
        if (tag instanceof Float) {
            ViewCompat.setElevation(view, (Float) tag);
        }
        view.setTag(R.id.item_touch_helper_previous_elevation, null);
    }

    view.setTranslationX(0f);
    view.setTranslationY(0f);
}

Bitmap srcInputBitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.image_4);
Bitmap source = Bitmap.createScaledBitmap(srcInputBitmap, width, height, true);
srcInputBitmap.recycle();

int colCount = spanCount;
int rowCount = 6;

int spanImageWidthSize = source.getWidth() / colCount;
int spanImageHeightSize = (source.getHeight() - rowCount * padding/2) / rowCount;

Bitmap[] bitmaps = new Bitmap[rowCount * colCount];
for (int i = 0; i < rowCount; i++) {
    for (int j = 0; j < colCount; j++) {
        int y = i * spanImageHeightSize;
        int x = j * spanImageWidthSize;
        Bitmap bitmap = Bitmap.createBitmap(source, x, y, spanImageWidthSize, spanImageHeightSize);
        bitmaps[i * colCount + j] = bitmap;
    }
}

public class SimpleItemDecoration extends RecyclerView.ItemDecoration {

    public int delta;
    public SimpleItemDecoration(int padding) {
        delta = padding;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view,
                               RecyclerView parent, RecyclerView.State state) {
        int position = parent.getChildAdapterPosition(view);
        RecyclerView.Adapter adapter = parent.getAdapter();
        int viewType = adapter.getItemViewType(position);
        if(viewType== Bean.TYPE_GROUP){
            return;
        }
        GridLayoutManager layoutManager = (GridLayoutManager) parent.getLayoutManager();
         //列數(shù)量
        int cols = layoutManager.getSpanCount(); 
        //position轉(zhuǎn)為在第幾列
        int current =  layoutManager.getSpanSizeLookup().getSpanIndex(position,cols); 
        //可有可無(wú)
        int currentCol = current % cols;


        int bottomPadding = delta / 2;

        if (currentCol == 0) {  //第0列左側(cè)貼邊
            outRect.left = 0;
            outRect.right = delta / 4;
            outRect.bottom = bottomPadding;
        } else if (currentCol == cols - 1) {
            outRect.left = delta / 4;
            outRect.right = 0;
            outRect.bottom = bottomPadding;
             //最后一列右側(cè)貼邊
        } else {
            outRect.left = delta / 4;
            outRect.right = delta / 4;
            outRect.bottom = bottomPadding;
        }
    }
}

mLinearLayoutManager = new GridLayoutManager(this, spanCount, LinearLayoutManager.VERTICAL, false);
mLinearLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup(){
    @Override
    public int getSpanSize(int position) {
        if(mAdapter.getItemViewType(position) == Bean.TYPE_GROUP){
            return spanCount;
        }
        return 1;
    }
});
mAdapter = new RecyclerViewAdapter();
mRecyclerView.setAdapter(mAdapter);
mRecyclerView.setLayoutManager(mLinearLayoutManager);
mRecyclerView.addItemDecoration(new SimpleItemDecoration(padding));
ItemTouchHelper itemTouchHelper = new ItemTouchHelper(new GridItemTouchCallback(mAdapter));
itemTouchHelper.attachToRecyclerView(mRecyclerView);

public class GridItemTouchCallback extends ItemTouchHelper.Callback {
    private final ItemTouchCallback mItemTouchCallback;
    public GridItemTouchCallback(ItemTouchCallback itemTouchCallback) {
        mItemTouchCallback = itemTouchCallback;
    }
    @Override
    public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
        // 上下左右拖動(dòng)，但允許觸發(fā)刪除
        int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN | ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT;
        return makeMovementFlags(dragFlags, 0);
    }

    @Override
    public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
        // 通知Adapter移動(dòng)View
        return mItemTouchCallback.onItemMove(viewHolder.getAdapterPosition(), target.getAdapterPosition());
    }
    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
        // 通知Adapter刪除View
        mItemTouchCallback.onItemRemove(viewHolder.getAdapterPosition());
    }

    @Override
    public void onChildDraw(@NonNull Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
        super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
    }
    @Override
    public void onChildDrawOver(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
        Log.d("GridItemTouch","dx="+dX+", dy="+dY);
        super.onChildDrawOver(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
    }
}

public static int makeMovementFlags(int dragFlags, int swipeFlags) {
    return makeFlag(ACTION_STATE_IDLE, swipeFlags | dragFlags)
            | makeFlag(ACTION_STATE_SWIPE, swipeFlags)
            | makeFlag(ACTION_STATE_DRAG, dragFlags);
}