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);
}
@Override
public 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;
}
}
@Override
public 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) {//1
outRect.set(mDividerWidth, mDividerWidth, mDividerWidth, mDividerWidth);
} else if ((itemPosition + 1) <= mSpanCount) {//2
outRect.set(0, mDividerWidth, mDividerWidth, mDividerWidth);
} else if (((itemPosition + mSpanCount) % mSpanCount) == 0) {//3
outRect.set(mDividerWidth, 0, mDividerWidth, mDividerWidth);
} else {//4
outRect.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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