了解RecyclerView的分割线

效果

实现思路

核心方法
绘制分割线的核心方法onDraw();
定位分割线位置（也可以说是与其他组件之间的空隙）方法getItemOffsets()；
计算
每条分割线的长度都是根据每一个ItemVIew的长度计算，位置同样根据ItemView的位置来确定，详细的计算在drawTop()、drawLeft()、drawRight()、drawBottom()、四个方法中！

灵魂图解

完整代码

/*** 万能分割线* <p>* 横向列表分割线 {@link #HORIZONTAL_DIV}* 纵向列表分割线 {@link #VERTICAL_DIV}* 表格列表分割线 {@link #GRID_DIV}* </P>*/
public class ItemDecorationPowerful extends RecyclerView.ItemDecoration {private static final String TAG = "ItemDecorationPowerful";//横向布局分割线public static final int HORIZONTAL_DIV = 0;//纵向布局分割线public static final int VERTICAL_DIV = 1;//表格布局分割线public static final int GRID_DIV = 2;private int mOrientation;private int mDividerWidth = 0;private Paint mPaint;/*** 默认纵向布分割线*/public ItemDecorationPowerful() {this(VERTICAL_DIV);}/*** @param orientation 方向类型*/public ItemDecorationPowerful(int orientation) {this(orientation, Color.parseColor("#808080"), 2);}/*** @param orientation 方向类型* @param color       分割线颜色* @param divWidth    分割线宽度*/public ItemDecorationPowerful(int orientation, int color, int divWidth) {this.setOrientation(orientation);mDividerWidth = divWidth;mPaint = new Paint();mPaint.setAntiAlias(true);mPaint.setColor(color);mPaint.setStyle(Paint.Style.FILL);}@Overridepublic void onDraw(@NonNull Canvas c, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {switch (mOrientation) {case HORIZONTAL_DIV://横向布局分割线drawHorizontal(c, parent);break;case VERTICAL_DIV://纵向布局分割线drawVertical(c, parent);break;case GRID_DIV://表格格局分割线drawGrid(c, parent);break;default://纵向布局分割线drawVertical(c, parent);break;}}@Overridepublic void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {int itemPosition = parent.getChildAdapterPosition(view);RecyclerView.Adapter mAdapter = parent.getAdapter();if (mAdapter != null) {int mChildCount = mAdapter.getItemCount();switch (mOrientation) {case HORIZONTAL_DIV:/*** 横向布局分割线* <p>*     如果是第一个Item，则不需要分割线* </p>*/if (itemPosition != 0) {outRect.set(mDividerWidth, 0, 0, 0);}break;case VERTICAL_DIV:/*** 纵向布局分割线* <p>*     如果是第一个Item，则不需要分割线* </p>*/if (itemPosition != 0) {outRect.set(0, mDividerWidth, 0, 0);}break;case GRID_DIV:/*** 表格格局分割线* <p>*      1：当是第一个Item的时候，四周全部需要分割线*      2：当是第一行Item的时候，需要额外添加顶部的分割线*      3：当是第一列Item的时候，需要额外添加左侧的分割线*      4：默认情况全部添加底部和右侧的分割线* </p>*/RecyclerView.LayoutManager mLayoutManager = parent.getLayoutManager();if (mLayoutManager instanceof GridLayoutManager) {GridLayoutManager mGridLayoutManager = (GridLayoutManager) mLayoutManager;int mSpanCount = mGridLayoutManager.getSpanCount();if (itemPosition == 0) {//1outRect.set(mDividerWidth, mDividerWidth, mDividerWidth, mDividerWidth);} else if ((itemPosition + 1) <= mSpanCount) {//2outRect.set(0, mDividerWidth, mDividerWidth, mDividerWidth);} else if (((itemPosition + mSpanCount) % mSpanCount) == 0) {//3outRect.set(mDividerWidth, 0, mDividerWidth, mDividerWidth);} else {//4outRect.set(0, 0, mDividerWidth, mDividerWidth);}}break;default://纵向布局分割线if (itemPosition != (mChildCount - 1)) {outRect.set(0, 0, 0, mDividerWidth);}break;}}}/*** 绘制横向列表分割线** @param c      绘制容器* @param parent RecyclerView*/private void drawHorizontal(Canvas c, RecyclerView parent) {int mChildCount = parent.getChildCount();for (int i = 0; i < mChildCount; i++) {View mChild = parent.getChildAt(i);drawLeft(c, mChild, parent);}}/*** 绘制纵向列表分割线** @param c      绘制容器* @param parent RecyclerView*/private void drawVertical(Canvas c, RecyclerView parent) {int mChildCount = parent.getChildCount();for (int i = 0; i < mChildCount; i++) {View mChild = parent.getChildAt(i);drawTop(c, mChild, parent);}}/*** 绘制表格类型分割线** @param c      绘制容器* @param parent RecyclerView*/private void drawGrid(Canvas c, RecyclerView parent) {int mChildCount = parent.getChildCount();for (int i = 0; i < mChildCount; i++) {View mChild = parent.getChildAt(i);RecyclerView.LayoutManager mLayoutManager = parent.getLayoutManager();if (mLayoutManager instanceof GridLayoutManager) {GridLayoutManager mGridLayoutManager = (GridLayoutManager) mLayoutManager;int mSpanCount = mGridLayoutManager.getSpanCount();if (i == 0) {drawTop(c, mChild, parent);drawLeft(c, mChild, parent);}if ((i + 1) <= mSpanCount) {drawTop(c, mChild, parent);}if (((i + mSpanCount) % mSpanCount) == 0) {drawLeft(c, mChild, parent);}drawRight(c, mChild, parent);drawBottom(c, mChild, parent);}}}/*** 绘制右边分割线** @param c            绘制容器* @param mChild       对应ItemView* @param recyclerView RecyclerView*/private void drawLeft(Canvas c, View mChild, RecyclerView recyclerView) {RecyclerView.LayoutParams mChildLayoutParams = (RecyclerView.LayoutParams) mChild.getLayoutParams();int left = mChild.getLeft() - mDividerWidth - mChildLayoutParams.leftMargin;int top = mChild.getTop() - mChildLayoutParams.topMargin;int right = mChild.getLeft() - mChildLayoutParams.leftMargin;int bottom;if (isGridLayoutManager(recyclerView)) {bottom = mChild.getBottom() + mChildLayoutParams.bottomMargin + mDividerWidth;} else {bottom = mChild.getBottom() + mChildLayoutParams.bottomMargin;}c.drawRect(left, top, right, bottom, mPaint);}/*** 绘制顶部分割线** @param c            绘制容器* @param mChild       对应ItemView* @param recyclerView RecyclerView*/private void drawTop(Canvas c, View mChild, RecyclerView recyclerView) {RecyclerView.LayoutParams mChildLayoutParams = (RecyclerView.LayoutParams) mChild.getLayoutParams();int left;int top = mChild.getTop() - mChildLayoutParams.topMargin - mDividerWidth;int right = mChild.getRight() + mChildLayoutParams.rightMargin;int bottom = mChild.getTop() - mChildLayoutParams.topMargin;if (isGridLayoutManager(recyclerView)) {left = mChild.getLeft() - mChildLayoutParams.leftMargin - mDividerWidth;} else {left = mChild.getLeft() - mChildLayoutParams.leftMargin;}c.drawRect(left, top, right, bottom, mPaint);}/*** 绘制右边分割线** @param c            绘制容器* @param mChild       对应ItemView* @param recyclerView RecyclerView*/private void drawRight(Canvas c, View mChild, RecyclerView recyclerView) {RecyclerView.LayoutParams mChildLayoutParams = (RecyclerView.LayoutParams) mChild.getLayoutParams();int left = mChild.getRight() + mChildLayoutParams.rightMargin;int top;int right = left + mDividerWidth;int bottom = mChild.getBottom() + mChildLayoutParams.bottomMargin;if (isGridLayoutManager(recyclerView)) {top = mChild.getTop() - mChildLayoutParams.topMargin - mDividerWidth;} else {top = mChild.getTop() - mChildLayoutParams.topMargin;}c.drawRect(left, top, right, bottom, mPaint);}/*** 绘制底部分割线** @param c            绘制容器* @param mChild       对应ItemView* @param recyclerView RecyclerView*/private void drawBottom(Canvas c, View mChild, RecyclerView recyclerView) {RecyclerView.LayoutParams mChildLayoutParams = (RecyclerView.LayoutParams) mChild.getLayoutParams();int left = mChild.getLeft() - mChildLayoutParams.leftMargin;int top = mChild.getBottom() + mChildLayoutParams.bottomMargin;int bottom = top + mDividerWidth;int right;if (isGridLayoutManager(recyclerView)) {right = mChild.getRight() + mChildLayoutParams.rightMargin + mDividerWidth;} else {right = mChild.getRight() + mChildLayoutParams.rightMargin;}c.drawRect(left, top, right, bottom, mPaint);}/*** 判断RecyclerView所加载LayoutManager是否为GridLayoutManager** @param recyclerView RecyclerView* @return 是GridLayoutManager返回true，否则返回false*/private boolean isGridLayoutManager(RecyclerView recyclerView) {RecyclerView.LayoutManager mLayoutManager = recyclerView.getLayoutManager();return (mLayoutManager instanceof GridLayoutManager);}/*** 初始化分割线类型** @param orientation 分割线类型*/public void setOrientation(int orientation) {if (mOrientation != HORIZONTAL_DIV && mOrientation != VERTICAL_DIV && mOrientation != GRID_DIV) {throw new IllegalArgumentException("ItemDecorationPowerful：分割线类型设置异常");} else {this.mOrientation = orientation;}}
}

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了解RecyclerView的分割线

效果

实现思路

灵魂图解

完整代码

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