【Android -- UI 开发】Recyclerview 的通用分隔线

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简介

ItemDecoration 是 RecyclerView 的一个抽象静态内部类，负责装饰 Item 视图，例如添加间距、高亮或者分组边界等。

LinearLayoutManager 添加分割线

1. 效果图

2. 源码

public class DividerItemDecoration extends RecyclerView.ItemDecoration{private Context mContext;private Drawable mDivider;private int mOrientation;public static final int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL;public static final int VERTICAL_LIST = LinearLayoutManager.VERTICAL;//我们通过获取系统属性中的listDivider来添加，在系统中的AppTheme中设置public static final int[] ATRRS  = new int[]{android.R.attr.listDivider};public DividerItemDecoration(Context context, int orientation) {this.mContext = context;final TypedArray ta = context.obtainStyledAttributes(ATRRS);this.mDivider = ta.getDrawable(0);ta.recycle();setOrientation(orientation);}//设置屏幕的方向public void setOrientation(int orientation){if (orientation != HORIZONTAL_LIST && orientation != VERTICAL_LIST){throw new IllegalArgumentException("invalid orientation");}mOrientation = orientation;}@Overridepublic void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {if (mOrientation == HORIZONTAL_LIST){drawVerticalLine(c, parent, state);}else {drawHorizontalLine(c, parent, state);}}//画横线, 这里的parent其实是显示在屏幕显示的这部分public void drawHorizontalLine(Canvas c, RecyclerView parent, RecyclerView.State state){int left = parent.getPaddingLeft();int right = parent.getWidth() - parent.getPaddingRight();final int childCount = parent.getChildCount();for (int i = 0; i < childCount; i++){final View child = parent.getChildAt(i);//获得child的布局信息final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)child.getLayoutParams();final int top = child.getBottom() + params.bottomMargin;final int bottom = top + mDivider.getIntrinsicHeight();mDivider.setBounds(left, top, right, bottom);mDivider.draw(c);//Log.d("wnw", left + " " + top + " "+right+"   "+bottom+" "+i);}}//画竖线public void drawVerticalLine(Canvas c, RecyclerView parent, RecyclerView.State state){int top = parent.getPaddingTop();int bottom = parent.getHeight() - parent.getPaddingBottom();final int childCount = parent.getChildCount();for (int i = 0; i < childCount; i++){final View child = parent.getChildAt(i);//获得child的布局信息final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)child.getLayoutParams();final int left = child.getRight() + params.rightMargin;final int right = left + mDivider.getIntrinsicWidth();mDivider.setBounds(left, top, right, bottom);mDivider.draw(c);}}//由于Divider也有长宽高，每一个Item需要向下或者向右偏移@Overridepublic void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {if(mOrientation == HORIZONTAL_LIST){//画横线，就是往下偏移一个分割线的高度outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());}else {//画竖线，就是往右偏移一个分割线的宽度outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);}}
}

3. 使用方法

		LinearLayoutManager manager = new LinearLayoutManager(this);mRecyclerView.setLayoutManager(manager);mRecyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL_LIST));mRecyclerView.setAdapter(mAdapter);

GridLayoutManager 添加分割线

1. 效果图

2. 源码

public class GridDividerItemDecoration extends RecyclerView.ItemDecoration {private Context mContext;private int mFirstAndLastColumnW;          //您所需指定的间隔宽度，主要为第一列和最后一列与父控件的间隔；行间距，列间距将动态分配private int mFirstRowTopMargin = 0; //第一行顶部是否需要间隔private int mLastRowBottomMargin = 0;private int mSpanCount = 0;private int mScreenW = 0;private int mItemDistance;/*** @param firstAndLastColumnW 间隔宽度* @param firstRowTopMargin   第一行顶部是否需要间隔*/public GridDividerItemDecoration(Context context, int firstAndLastColumnW, int firstRowTopMargin, int lastRowBottomMargin) {mContext = context;mFirstAndLastColumnW = firstAndLastColumnW;mFirstRowTopMargin = firstRowTopMargin;mLastRowBottomMargin = lastRowBottomMargin;}public void setFirstRowTopMargin(int firstRowTopMargin) {mFirstRowTopMargin = firstRowTopMargin;}public void setLastRowBottomMargin(int lastRowBottomMargin) {mLastRowBottomMargin = lastRowBottomMargin;}public void setItemDistance(int itemDistance) {mItemDistance = itemDistance;}@Overridepublic void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {super.getItemOffsets(outRect, view, parent, state);int top = 0;int left;int right;int bottom;int itemPosition = ((RecyclerView.LayoutParams) view.getLayoutParams()).getViewLayoutPosition();mSpanCount = getSpanCount(parent);int childCount = parent.getAdapter().getItemCount();// 屏幕宽度-View的宽度*spanCount 得到屏幕剩余空间int maxDividerWidth = getMaxDividerWidth(view);int spaceWidth = mFirstAndLastColumnW;//首尾两列与父布局之间的间隔// 除去首尾两列，item与item之间的距离int eachItemWidth = maxDividerWidth / mSpanCount;int dividerItemWidth = (maxDividerWidth - 2 * spaceWidth) / (mSpanCount - 1);//item与item之间的距离left = itemPosition % mSpanCount * (dividerItemWidth - eachItemWidth) + spaceWidth;right = eachItemWidth - left;bottom = dividerItemWidth;// 首行if (mFirstRowTopMargin > 0 && isFirstRow(parent, itemPosition, mSpanCount, childCount)) {top = mFirstRowTopMargin;}//最后一行if (isLastRow(parent, itemPosition, mSpanCount, childCount)) {if (mLastRowBottomMargin < 0) {bottom = 0;} else {bottom = mLastRowBottomMargin;}}outRect.set(left, top, right, bottom);}/*** 获取Item View的大小，若无则自动分配空间* 并根据 屏ge幕宽度-View的宽度*spanCount 得到屏幕剩余空间** @param view* @return*/private int getMaxDividerWidth(View view) {int itemWidth = view.getLayoutParams().width;int itemHeight = view.getLayoutParams().height;int screenWidth = getScreenWidth();int maxDividerWidth = screenWidth - itemWidth * mSpanCount;if (itemHeight < 0 || itemWidth < 0 || maxDividerWidth <= (mSpanCount - 1) * mFirstAndLastColumnW) {view.getLayoutParams().width = getAttachCloumnWidth();view.getLayoutParams().height = getAttachCloumnWidth();maxDividerWidth = screenWidth - view.getLayoutParams().width * mSpanCount;}return maxDividerWidth;}private int getScreenWidth() {if (mScreenW > 0) {return mScreenW;}mScreenW = mContext.getResources().getDisplayMetrics().widthPixels > mContext.getResources().getDisplayMetrics().heightPixels? mContext.getResources().getDisplayMetrics().heightPixels : mContext.getResources().getDisplayMetrics().widthPixels;return mScreenW;}/*** 根据屏幕宽度和item数量分配 item View的width和height** @return*/private int getAttachCloumnWidth() {int itemWidth = 0;int spaceWidth = 0;try {int width = getScreenWidth();spaceWidth = 2 * mFirstAndLastColumnW;itemWidth = (width - spaceWidth) / mSpanCount - 40;} catch (Exception e) {e.printStackTrace();}return itemWidth;}/*** 判读是否是第一列** @param parent* @param pos* @param spanCount* @return*/private boolean isFirstColumn(RecyclerView parent, int pos, int spanCount) {RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();if (layoutManager instanceof GridLayoutManager) {if (pos % spanCount == 0) {return true;}} else if (layoutManager instanceof StaggeredGridLayoutManager) {int orientation = ((StaggeredGridLayoutManager) layoutManager).getOrientation();if (orientation == StaggeredGridLayoutManager.VERTICAL) {if (pos % spanCount == 0) {// 第一列return true;}} else {}}return false;}/*** 判断是否是最后一列** @param parent* @param pos* @param spanCount* @return*/private boolean isLastColumn(RecyclerView parent, int pos, int spanCount) {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) {// 最后一列return true;}} else {}}return false;}/*** 判读是否是最后一行** @param parent* @param pos* @param spanCount* @param childCount* @return*/private boolean isLastRow(RecyclerView parent, int pos, int spanCount, int childCount) {RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();if (layoutManager instanceof GridLayoutManager) {int lines = childCount % spanCount == 0 ? childCount / spanCount : childCount / spanCount + 1;return lines == pos / spanCount + 1;}return false;}/*** 判断是否是第一行** @param parent* @param pos* @param spanCount* @param childCount* @return*/private boolean isFirstRow(RecyclerView parent, int pos, int spanCount, int childCount) {RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();if (layoutManager instanceof GridLayoutManager) {if ((pos / spanCount + 1) == 1) {return true;} else {return false;}}return false;}/*** 获取列数** @param parent* @return*/private int getSpanCount(RecyclerView parent) {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;}
}

3. 使用方法

		int firstAndLastColumnW = DensityUtil.dip2px(this, 20);int firstRowTopMargin = DensityUtil.dip2px(this, 20);GridDividerItemDecoration gridDividerItemDecoration =new GridDividerItemDecoration(this, firstAndLastColumnW, firstRowTopMargin, firstRowTopMargin);gridDividerItemDecoration.setFirstRowTopMargin(firstRowTopMargin);gridDividerItemDecoration.setLastRowBottomMargin(firstRowTopMargin);mRecyclerView.addItemDecoration(gridDividerItemDecoration);GridLayoutManager layoutManager = new GridLayoutManager(this, 3);mRecyclerView.setLayoutManager(layoutManager);mRecyclerView.setAdapter(mAdapter);